tilapia Bibliography based on merger of WOS with a Medline search of titles for 'tilapia' as of Jan.15, 2000

Abel, P. D., and Papoutsoglou, S. E. (1986). Lethal toxicity of cadmium to Cyprinus carpio and Tilapia aurea. Bull Environ Contam Toxicol 37, 382-6.

Abo Hegab, S., and Hanke, W. (1984). The significance of cortisol for osmoregulation in carp (Cyprinus carpio) and tilapia (Sarotherodon mossambicus). Gen Comp Endocrinol 54, 409-17.
Changes in plasma cortisol and glucose concentration were studied in carp during acclimation from fresh water (FW) to 1.5% salt water and vice versa. There was an increase in cortisol and glucose concentration during acclimation from FW to salt water which lasted for several days. Reacclimation to FW did not cause clear changes in cortisol and glucose levels. One single injection of cortisol (0.2 mg/100 g or 1 mg/100 g) and additional transfer to salt water (1.5% for carp and 2.7% for tilapia) altered the changes caused by acclimation alone of cortisol, glucose, Na+ concentration, and the osmolality in plasma. Gill Na-K- ATPase activity was also influenced. The effects of cortisol on electrolyte concentrations during acclimation and on Na+-K+-ATPase activity differed in both types of fish. Cortisol clearly lowered the increase in plasma Na+ concentration of the stenohaline carp and increased the ATPase activity. The changes in plasma Na+ concentration of the euryhaline tilapia was not clearly altered and the enzyme activity was inhibited. The significance of these cortisol effects is discussed.

Agnese, J. F., Adepo-Gourene, B., Abban, E. K., and Fermon, Y. (1997). Genetic differentiation among natural populations of the Nile tilapia Oreochromis niloticus (Teleostei, cichlidae). Heredity 79, 88-96.
We analysed the genetic differentiation among 17 natural populations of the Nile tilapia Oreochromis niloticus (Linnaeus, 1758) using allozymes and restriction fragment length polymorphism (RFLP) of mitochondrial DNA (mtDNA). The populations studied, from the River Senegal to Lake Tana and from Lake Manzalla to Lake Baringo, represent all subspecies which have been previously described. Sixteen variable nuclear loci showed that these populations can be clustered in three groups: (1) West African populations (Senegal, Niger, Volta and Chad drainages), (2) Ethiopian Rift Valley populations (Lakes Awasa, Ziway, Koka and the Awash River) and (3) Nile drainage (Manzalla, Cairo, Lake Edward) and Kenyan Rift Valley populations (Lakes Turkana, Baringo and River Suguta). Nine different mtDNA haplotypes were found in the RFLP analysis of a 1 kb portion of the D-loop region. The network obtained showed that there are three geographically distinct groups; all West African populations and O. aureus are clustered, the two Ethiopian Rift Valley populations are distinct and between these two groups are the Kenyan and Ugandan Rift Valley populations. Nile populations show affinities both with West African populations and with specimens from Lakes Tana and Turkana. Taxonomic and biogeographical implications of these results are discussed.

Agnese, J. F., Adepo-Gourene, B., Owino, J., Pouyaud, L., and Aman, R. (1999). Genetic characterization of a pure relict population of Oreochromis esculentus, an endangered tilapia. Journal of Fish Biology 54, 1119-1123.
Genetic variation of the Oreochromis esculentus population from Lake Kanyaboli was studied using 24 allozyme loci and three microsatellite loci and compared with four populations of O. niloticus. Results strongly suggest that this population can be considered as pure. (C) 1999 The Fisheries Society of the British Isles.

Al Hafedh, Y. S. (1999). Effects of dietary protein on growth and body composition of Nile tilapia, Oreochromis niloticus L. Aquaculture Research 30, 385-393.
The effects of dietary protein (25%, 30%, 35%, 40% and 45%) on growth, survival, feed conversion ratio (FCR), protein efficiency ratio (PER) and body composition were investigated for four sizes (0.51, 45, 96 and 264 g) of Nile tilapia, Oreochromis niloticus L. In all four experiments, there was a progressive increase in growth with increasing dietary protein. In fry (0.51 g), significantly higher growth, survival and feed conversion were recorded for fish fed 40-45% rather than 25-35% protein diets. Similar trends for growth and FCR were also noted in 45 g fish. For larger (96 and 264 g) tilapia, significant differences in growth and FCR were found only between fish fed 25% and 30-45% protein diets. FCR and PER decreased with increasing weight of fish, and both were found to be negatively correlated with dietary protein level. Whole- body composition of the smallest fish was significantly influenced by dietary protein content. Percentage body protein of the fish fed 40-45% protein was higher than that of fish fed 25-35% protein diets, whereas lipid content decreased with increasing dietary protein level. In 45 g fish, both protein and lipid contents were higher in fish fed 25% and 30% protein diets than in those fed 35-45% protein diets. In larger tilapia, no significant influence of dietary protein level on body protein content was found. Percentage lipid decreased with increasing dietary protein level, and no definite trends in ash content were found. The results of these studies indicate that O. niloticus fry (0.51 g) should be reared on a practical diet containing 40% protein, and larger tilapia (96-264 g) on a diet containing 30% protein.

Alam, M. S., Lavender, F. L., Iyengar, A., Rahman, M. A., Ayad, H. H., Lathe, R., Morley, S. D., and Maclean, N. (1996). Comparison of the activity of carp and rat beta-actin gene regulatory sequences in tilapia and rainbow trout embryos. Mol Reprod Dev 45, 117-22.
A comparative study on the level of expression of lacZ reporter constructs driven by equivalent carp and rat beta-actin regulatory sequences was carried out in embryos of tilapia and rainbow trout. DNA was microinjected into fertilised tilapia and rainbow trout eggs and the embryos/fry were assayed at various developmental stages for beta- galactosidase expression. We provide evidence to demonstrate that the carp beta-actin promoter/ lacZ reporter gene is expressed at higher levels than the equivalent rat beta-actin construct in both species.

Allen, P. (1994). Distribution of mercury in the soft tissues of the blue tilapia Oreochromis aureus (Steindachner) after acute exposure to mercury (II) chloride. Bull Environ Contam Toxicol 53, 675-83.

Allen, P. (1995). Soft-tissue accumulation of lead in the blue tilapia, Oreochromis aureus (Steindachner), and the modifying effects of cadmium and mercury. Biol Trace Elem Res 50, 193-208.
The interaction of mercury and cadmium with lead was investigated by exposing Oreochromis aureus to two heavy metals simultaneously. The chronic accumulation profile of lead was determined by analyzing the liver, brain, gill filaments, intestine, caudal muscle, spleen, trunk kidney, and gonads following exposure to lead alone and in mixtures with mercury and cadmium. Nominal exposure concentrations of lead were 0.05, 0.10, 0.50, and 1.00 mg/L. Mixtures of lead (0.50 or 0.05 mg/L) with cadmium (0.05 mg/L) and lead (0.50 or 0.05 mg/L) with mercury (0.05 mg/L) were also used. Following 140 d of exposure to lead, the highest concentrations of lead consistently accumulated in the trunk kidney. The concentration of lead in the kidney was decreased by coexposure to mercury or cadmium, but increased in the muscle and liver. Under all exposure regimes, the median concentration of lead in the muscle exceeded safety levels recommended for human consumption. In a food fish, such as O. aureus, a knowledge of toxic metal accumulation patterns is of great importance.

Alsop, D. H., Kieffer, J. D., and Wood, C. M. (1999). The effects of temperature and swimming speed on instantaneous fuel use and nitrogenous waste excretion of the Nile tilapia. Physiol Biochem Zool 72, 474-83.
The effects of acclimation temperature (30 degrees, 20 degrees, and 15 degrees C) and swimming speed on the aerobic fuel use of the Nile tilapia (Oreochromis niloticus; 8-10 g, 8-9-cm fork length) were investigated using a respirometric approach. As acclimation temperature was decreased from 30 degrees C to 15 degrees C, resting oxygen consumption (MO2) and carbon dioxide excretion (MCO2+) decreased approximately twofold, while nitrogenous waste excretion (ammonia-N plus urea-N) decreased approximately fourfold. Instantaneous aerobic fuel usage was calculated from respiratory gas exchange. At 30 degrees C, resting MO2 was fueled by 42% lipids, 27% carbohydrates, and 31% protein. At 15 degrees C, lipid use decreased to 21%, carbohydrate use increased greatly to 63%, and protein use decreased to 16%. These patterns at 30 degrees C and 15 degrees C in tilapia paralleled fuel use previously reported in rainbow trout acclimated to 15 degrees C and 5 degrees C, respectively. Temperature also had a pronounced effect on critical swimming speed (UCrit). Tilapia acclimated to 30 degrees C had a UCrit of 5.63+/-0. 06 body lengths/s (BL/s), while, at 20 degrees C, UCrit was significantly lower at 4.21+/-0.14 BL/s. Tilapia acclimated to 15 degrees C were unable or unwilling to swim. As tilapia swam at greater speeds, MO2 increased exponentially; MO2min and MO2max were 5.8+/-0.6 and 21.2+/-1.5 micromol O2/g/h, respectively. Nitrogenous waste excretion increased to a lesser extent with swimming speed. At 30 degrees C, instantaneous protein use while swimming at 15 cm/s ( approximately 1.7 BL/s) was 23%, and at UCrit (5.6 BL/s), protein use dropped slightly to 17%. During a 48-h swim at 25 cm/s (2.7 BL/s, approximately 50% UCrit), MO2 and urea excretion remained unchanged, while ammonia excretion more than doubled by 24 h and remained elevated 24 h later. These results revealed a shift to greater reliance on protein as an aerobic fuel during prolonged swimming.

Alvarenga, C. M., and Volpato, G. L. (1995). Agonistic profile and metabolism in alevins of the Nile tilapia. Physiol Behav 57, 75-80.
Metabolic differences derived from social stress usually show data with high variance that may hinder the finding of important differences. Since such high variance may be caused by agonistic variability occurring during social interactions, this work tested whether metabolism is associated with agonistic profile in the cichlid fish Nile tilapia, Oreochromis niloticus (L.). Metabolism was inferred from oxygen consumption, resistance to progressive hypoxia and ventilatory rate. Fifteen pairs of alevins were used for each metabolic and behavioral series. An ethogram based on 8 types of agonistic interactions was employed. Agonistic profiles were determined and associated with the physiological parameters later on. The test of canonical correlation showed significant association between some agonistic profiles and metabolism. Ventral nipping and lateral fight appeared as the two most important in promoting association with metabolism.

Alves, M. M., Leme Dos Santos, H. S., Lopes, R. A., Petenusci, S. O., and Haiyashi, C. (1983). Rhythm of development in the oocyte of the tilapia Oreochromis niloticus L. (Pisces: Cichlidae); a morphometric and histochemical study. Gegenbaurs Morphol Jahrb 129, 575-92.
The ovary of the tilapia Oreochromis niloticus was studied morphologically and morphometrically; the zonas granulosa and radiata, the ooplasm and the yolk globules were studied histochemically. The ovary is of typical teleostean type consisting of a wall and developing oocytes. The development of oocytes has been divided into 10 cytological stages. Histochemically the zona radiata and yolk globules contain glycoprotein (neutral mucopolysaccharides and protein radicals alpha-amino groups, cystine, cystein, tyrosin, tryptophane, and arginine. The zona granulosa and ooplasm contain neutral and carboxylate acid mucopolysaccharides and protein radicals alpha-amino group, cystein, cystine, tyrosin, arginine, and tryptophane.

Amin, N. E., Abdallah, I. S., Faisal, M., Easa, M. e.-S., Alaway, T., and Alyan, S. A. (1988). Columnaris infection among cultured Nile tilapia Oreochromis niloticus. Antonie Van Leeuwenhoek 54, 509-20.
Flexibacter columnaris was isolated from 13 cultured Oreochromis niloticus showing respiratory disorders. The isolates developed typical swarming rhizoid colonies on Cytophaga agar medium. Antibiotic sensitivity test revealed the susceptibility of F. columnaris isolated to oxytetracycline, chloramphenicol and erythromycin. A marked difference in the pathogenicity of seven tested isolates was observed: two were highly virulent, one was moderately virulent and four were avirulent. No experimental infection could be induced with the highly virulent isolates except after injuring one of the natural barriers of the fish body. The severity of the disease and the increased median death time shortened by keeping infected fishes with injured gills in water containing ammonia. In naturally infected O. niloticus, the disease became chronic as indicated by the presence of excessive proliferative and necrotic changes. On the other hand, severe dilatation of branchial blood vessel, oedema and round cell infiltration proved that, the disease among experimentally infected tilapias was acute.

Ananthakrishnan, K. R., and Kutty, M. N. (1974). Mortality & breathing rate at high ambient temperatures in the cichlid fish, Tilapia mossambica Peters. Indian J Exp Biol 12, 55-9.

Anderson, J., Capper, B. S., and Bromage, N. R. (1991). Measurement and prediction of digestible energy values in feedstuffs for the herbivorous fish tilapia (Oreochromis niloticus Linn.). Br J Nutr 66, 37-48.
Digestible energy (DE) values were measured in a selection of feedstuffs for the tilapia (Oreochromis niloticus Linn.) and used to develop equations for predicting DE values of a wider range of feedstuffs from chemical analyses. Preliminary work examined the influences of substitution level in a reference diet and adaptation over time on DE values for soya-bean meal. Length of adaptation period significantly affected DE values (P less than 0.01), but substitution level, over the range 200-600 g soya-bean meal/kg reference diet, did not. The DE values of sixteen feedstuffs, thirteen derived from plant sources and three animal by-products, were subsequently determined. DE values for plant-derived feedstuffs were found to be higher than those quoted in the literature for trout (Oncorhynchus mykiss) and catfish (Ictalurus punctatus), whereas DE values for animal-derived feedstuffs were lower than those for trout and pigs. It was concluded that energy values quoted in tables of feed composition for other species are inaccurate when used as proxy values for tilapia. Regression equations were therefore computed using data from the present study to provide a rapid means of predicting DE values of feedstuffs for tilapia. Equations using neutral-detergent fibre as an independent variable were found to predict DE values of plant-derived feedstuffs reliably. Where fibre values were not used as independent variables, available carbohydrate and crude protein (nitrogen x 6.25) were found to be useful predictors of DE values. These equations offer the possibility of reducing the need for time-consuming digestibility trials with tilapia when formulating least-cost production diets for this species.

Andrade, R. M. d., and Antunes, C. M. (1969). [Biological control: Tilapia melanopleura Dumeril versus Biomphalaria glabrata (Say), under laboratory conditions]. Rev Bras Malariol Doencas Trop 21, 49-58.

Anjum, F., and Qadri, S. S. (1986). In vivo metabolism of fenitrothion (0,0-dimethyl-0-(4-nitro-m-tolyl) phosphorothioate) in fresh water teleost (Tilapia mossambica). Bull Environ Contam Toxicol 36, 140-5.

Annett, C. A., Pierotti, R., and Baylis, J. R. (1999). Male and female parental roles in the monogamous cichlid, Tilapia mariae, introduced in Florida. Environmental Biology of Fishes 54, 283-293.
We documented male and female parental roles of a monogamous fish, the spotted tilapia, Tilapia mariae, in channelized rivers in southern Florida, where this species dominated the fish fauna within 10 years of their introduction. Clearly differentiated parental roles existed between males and females, with females performing nearly all tending of embryos and most tending of free embryos. After young became free- swimming and left the nest, however, males took over primary tending of the school of young while the female patrolled the perimeter of the school and performed nearly all chases directed at predators. Male and female T. marine also traded off vigilance and feeding, and showed a high degree of intrapair coordination. Experimental removal of one or both parents had major effects on parental behavior and brood survival and integrity. Solitary females took on a parental role intermediate between that of the male and female of a pair. Untended broods were attacked by predators and scattered into aquatic vegetation, and were not observed to reform. Under dense nesting conditions we observed adoption of broods, group rearing of free-swimming young and the presence of non-breeder 'satellites' sharing and defending a territory with breeders. This highly complex parental care may have allowed T. mariae to invade fish communities dominated by uniparental centrarchids, as well as allowing them to use disturbed habitats such as channelized rivers that are of poor quality for nesting and rearing offspring.

Apfelbach, R. (1969). Correlation analyses of behaviour patterns in Tilapia (Pisces, Cichlidae). Naturwissenschaften 56, 335.

Arnold, M., Kriesten, K., and Peters, H. M. (1968). [The prehensile organs of Tilapia larvae (Cichlidae, Teleostei). Histochemical and electron microscopic studies]. Z Zellforsch Mikrosk Anat 91, 248-60.

Auperin, B., Rentier-Delrue, F., Martial, J. A., and Prunet, P. (1994). Characterization of a single prolactin (PRL) receptor in tilapia (Oreochromis niloticus) which binds both PRLI and PRLII. J Mol Endocrinol 13, 241-51.
In tilapia, there are two forms of prolactin (PRL) whose effects on sodium and chloride movements differ and depend on the living environment of the fish. To see whether different receptors or the same receptor mediates these different effects, we have characterized the specific binding of both forms of tilapia (ti)PRL in two osmoregulatory organs, the gill and kidney. Two recombinant tiPRLs were used for this analysis. The recombinant hormones had the same properties as the native hormones in a tilapia gill radioreceptor assay. Specific binding to gill and kidney membranes was increased by optimizing the quality of the tissue preparations (physiological state of fish, membrane preparation) and the incubation conditions (pH, salt concentrations, temperature, time). Under these optimized conditions, we detected only one class of high affinity PRL receptor in gill and kidney. Its binding affinity was higher for tiPRLI than for tiPRLII in both gill and kidney (for tiPRLI the respective affinity values were 2.9 and 2.3 x 10(10) per M, for tiPRLII they were 1.9 and 0.5 x 10(10) per M). In competition studies, tiPRLI was more potent, followed by tiPRLII and ovine (o)PRL. tiGH and oGH did not significantly displace either tiPRL. The receptor we have characterized thus recognizes quite specifically both tiPRLs.

Auperin, B., Rentier-Delrue, F., Martial, J. A., and Prunet, P. (1994). Evidence that two tilapia (Oreochromis niloticus) prolactins have different osmoregulatory functions during adaptation to a hyperosmotic environment. J Mol Endocrinol 12, 13-24.
Two forms of prolactin (tiPRLI and tiPRLII), with only 69% sequence identity, have been previously described in the cichlid fish tilapia (Oreochromis species). In the present study we have attempted to investigate the biological activity of these two prolactin forms during adaptation to a hyperosmotic environment. For this purpose, we have developed two highly sensitive (sensitivity: 0.05 ng/ml) and specific (cross-reactivity 0.04%) radioimmunoassays for tiPRLI and tiPRLII, using recombinant hormones. When fish were directly transferred from fresh to brackish water, the measured levels of plasma tiPRLI and tiPRLII dropped abruptly until 12 h after transfer. Thereafter, plasma tiPRLII remained stable (around 0.5 ng/ml) until the end of the experiment, whereas plasma tiPRLI continued to decrease to undetectable levels. These different patterns of change are reflected in the calculated ratio of plasma tiPRLII to tiPRLI, which increased from 2-3 in fresh water-adapted fish to over 10 in fish which had spent 3 days or more in brackish water. The pituitary contents of tiPRLI and tiPRLII varied in a qualitatively similar fashion after transfer to brackish water. The tiPRLI content dropped continuously after 12 h, reaching one- twelfth of its initial level after 2 weeks. The pituitary tiPRLII content, on the other hand, did not decrease significantly until day 7, and after a 2-week exposure to brackish water it had only decreased by 50%. When injected into tilapia adapted to brackish water, both ovine prolactin and recombinant tiPRLI induced a clear dose-dependent ion- retaining effect. In contrast, the effect induced by tiPRLII treatment was markedly smaller and not dose-dependent. Northern blot analysis of tiPRL mRNAs using either a tiPRLI or a tiPRLII cDNA probe indicated the presence of two mRNAs differing in size: a 1.7 kb mRNA coding for tiPRLI and a 1.3 kb mRNA coding for tiPRLII. After transfer to brackish water, levels of the two mRNAs decreased similarly. The present study indicates that, in O. niloticus, the two forms of prolactin have different osmoregulatory roles during adaptation to brackish water. Accordingly, their synthesis are differentially regulated after transfer to a hyperosmotic environment, presumably at a post- transcriptional level.

Auperin, B., Rentier-Delrue, F., Martial, J. A., and Prunet, P. (1995). Regulation of gill prolactin receptors in tilapia (Oreochromis niloticus) after a change in salinity or hypophysectomy. J Endocrinol 145, 213-20.
Prolactin (PRL) receptors in gill tissue have been analyzed in tilapia (Oreochromis niloticus) after transfer from fresh water (FW) to brackish water (BW). This study has indicated the presence of only one class of tilapia PRL (tiPRL) receptor whatever the salinity. After transfer, however, the percentage of specific binding of the two forms of tiPRL (tiPRLI and tiPRLII) increased significantly. Scatchard analysis of tiPRLI binding indicated an increase in receptor affinity, an effect which was not accompanied by any change in receptor specificity. Transfer to BW also caused the number of tiPRL receptors to increase rapidly, remaining high in fish adapted to BW for 28 days. Based on the sharp reduction in plasma tiPRLI and tiPRLII levels after transfer to BW, one possible explanation may be that tiPRL itself is an important factor regulating the number of free receptors. This hypothesis finds support in the fact that the number of tiPRL receptors also increased in hypophysectomized fish reared in FW. However, the absence of change in receptor affinity after hypophysectomy suggested that yet other factors are involved in tiPRL receptor regulation during the transfer from FW to BW. The paradoxically high numbers of tiPRL receptors in the gills of BW-adapted tilapia, even though PRL is known to be a FW-adapting hormone, is discussed with regard to the environment in which tilapia live.

Auperin, B., Leguen, I., Rentier-Delrue, F., Smal, J., and Prunet, P. (1995). Absence of a tiGH effect on adaptability to brackish water in tilapia (Oreochromis niloticus). Gen Comp Endocrinol 97, 145-59.
The aim of this study was to investigate the possible role of growth hormone in the adaptation of tilapia (Oreochromis niloticus) to brackish water and to analyze its interactions with prolactin in this process. Plasma levels of growth hormone do not change upon transfer to brackish water. Treatment of intact tilapia in fresh water with growth hormone prior to transfer did not enable the fish to preadapt to brackish water: the duration of the hydromineral imbalance after transfer was the same in treated animals and controls. The major osmoregulatory role of prolactin in fresh water led us to test the hypothesis that prolactin might antagonize the effect of growth hormone on adaptation to brackish water. Growth-hormone-treated hypophysectomized animals, however, exhibited no increased osmoregulatory capacity as compared to hypophysectomized controls, confirming the absence of a growth-hormone-related osmoregulatory effect. When prolactin and growth hormone were coinjected, growth hormone also proved unable to oppose the Na+ retaining effect of prolactin, in both brackish and fresh water. Surprisingly, hypophysectomized animals adapt better to brackish water than do sham- operated animals. This result is discussed in light of the effects of prolactin and cortisol on osmoregulation in brackish water and we suggest that an important event which allows O. niloticus to adapt to hyperosmotic environment is the reduction of plasma PRL upon transfer to brackish water.

Auperin, B., Baroiller, J. F., Ricordel, M. J., Fostier, A., and Prunet, P. (1997). Effect of confinement stress on circulating levels of growth hormone and two prolactins in freshwater-adapted tilapia (Oreochromis niloticus). Gen Comp Endocrinol 108, 35-44.
The aim of the present study was to assess a potential link between confinement stress and prolactin (PRL), the hormone responsible for adaptation to a hypoosmotic environment in freshwater-adapted tilapia (Oreochromis niloticus). The effect of stress on plasma levels of the two tilapia PRL forms, tiPRLI (or tiPRL188) and tiPRLII (or tiPRL177), was examined along with the effects on plasma levels of cortisol and growth hormone (GH). In a preliminary study, various sampling protocols (immediate sampling; sampling one by one; anesthesia at 0.5, 1, 2 ml/liter phenoxyethanol) were tested for their ability to modify basal plasma PRL and cortisol. In fish sampled within 1 min of capture (immediate sampling), no changes in the plasma levels of these hormones were observed, whereas when fish were sampled one at a time, PRL levels did not change but cortisol levels were modified. The immediate sampling protocol was used to study the effects of 1 hr confinement stress, which induced a large increase in plasma cortisol levels as well as increases tiPRLI and tiPRLII levels with kinetics similar to those of cortisol. In contrast, plasma tiGH levels significantly decreased after 1 hr confinement. When this stress situation was removed, plasma cortisol and tiPRL levels decreased and plasma GH levels increased. Two and one-half hours later, values were not significantly different from those measured in control fish. In tilapia exposed to 24 hr confinement stress, similar changes in hormone levels were observed. However, after 24 hr confinement, only cortisol levels were significantly different from those measured in control fish. None of these stress conditions significantly changed plasma chloride levels. Together, these results indicate that both PRL and GH have important roles in the adaptive response of freshwater-adapted tilapia to confinement stress. Copyright 1997 Academic Press.

Ay, O., Kalay, M., Tamer, L., and Canli, M. (1999). Copper and lead accumulation in tissues of a freshwater fish Tilapia zillii and its effects on the branchial Na,K-ATPase activity. Bull Environ Contam Toxicol 62, 160-8.

Ayson, F. G., Kaneko, T., Tagawa, M., Hasegawa, S., Grau, E. G., Nishioka, R. S., King, D. S., Bern, H. A., and Hirano, T. (1993). Effects of acclimation to hypertonic environment on plasma and pituitary levels of two prolactins and growth hormone in two species of tilapia, Oreochromis mossambicus and Oreochromis niloticus. Gen Comp Endocrinol 89, 138-48.
Specific radioimmunoassays (RIAs) for the pair of tilapia prolactins (tPRLs) and growth hormone (tGH) were developed using antisera raised in rabbits. Anti-tPRL177 did not cross-react with tPRL188 and tGH. Anti- tPRL188 did not cross-react with tPRL177 and showed slight cross- reaction (3.1%) with tGH. Anti-tGH showed negligible cross-reactions with tPRL177 (0.4%) and tPRL188 (1.6%). Pituitary homogenates and plasma from Oreochromis niloticus exhibited displacement curves parallel to the standards in the three RIAs. Plasma from hypophysectomized O. niloticus showed no cross-reaction in any of the three RIAs. Plasma and pituitary levels of the two PRLs in O. mossambicus in freshwater did not differ significantly from each other, whereas in O. niloticus, the levels of PRL177 were significantly greater than those of PRL188 in both plasma and pituitary. After acclimation for 3-4 weeks in seawater (O. mossambicus) or 50% seawater (O. niloticus), the levels of both PRLs decreased significantly compared to their levels in freshwater. Acclimation to a hypertonic environment did not affect plasma and pituitary GH levels in either species. Immunocytochemical staining of the pituitary of O. niloticus revealed colocalization of both PRLs in rostral pars distalis. Our findings suggest that the synthesis and secretion of the two tPRLs could be independently regulated in the same cells.

Ayson, F. G., Kaneko, T., Hasegawa, S., and Hirano, T. (1994). Differential expression of two prolactin and growth hormone genes during early development of tilapia (Oreochromis mossambicus) in fresh water and seawater: implications for possible involvement in osmoregulation during early life stages. Gen Comp Endocrinol 95, 143-52.
The possible involvement of prolactin (PRL) and growth hormone (GH) in osmoregulation during early life stages of the tilapia (Oreochromis mossambicus) was examined by in situ hybridization and immunocytochemistry using synthetic oligonucleotide probes and homologous antisera to two tilapia PRLs (PRL188 and PRL177) and GH. Hybridization signals for PRL188 mRNA were detected for the first time in newly hatched larvae (5 days after fertilization), and were significantly greater in larvae in fresh water (FW) than those in seawater (SW) until 10 days after hatching. PRL177 mRNA was detected in the pituitary of embryos 1 day before hatching. Although PRL177 gene expression in the embryo and newly hatched larvae in FW was not significantly different from those in SW, the expression was significantly greater in FW than in SW from Day 2 until Day 10. Hybridization signals for GH mRNA were first detected in newly hatched larvae. No significant differences in GH mRNA expression were observed between larvae in FW and those in SW. A stronger immunoreaction, a significantly larger PRL cell size, and a pituitary area containing PRL cells were observed in larvae hatched and maintained in FW, in those transferred from SW to FW, compared to larvae hatched and maintained in SW, and in those transferred from FW to SW. No significant difference was observed in the activity of GH cells between larvae in FW and those in SW. These results suggest that both PRLs are involved importantly in FW adaptation, whereas GH does not seem to play a critical role in osmoregulation during early stages of tilapia.

Baker, D. A., and Smitherman, R. O. (1983). Immune response of Tilapia aurea exposed to Salmonella typhimurium. Appl Environ Microbiol 46, 28-31.
Tilapia aurea showed a specific immune response to Salmonella typhimurium. S. typhimurium was introduced into the gut of T. aurea by force-feeding. S. typhimurium was isolated from the fish viscera after 15 days, but at 30 days viable cells were not detected. T. aurea had an antibody titer to S. typhimurium after 30 days which was fivefold greater than the natural background antibody titer. An elevated antibody titer was not indicative of active bacterial infection.

Baker, D. A., Smitherman, R. O., and McCaskey, T. A. (1983). Longevity of Salmonella typhimurium in Tilapia aurea and water from pools fertilized with swine waste. Appl Environ Microbiol 45, 1548-54.
Salmonella typhimurium declined rapidly when inoculated into Tilapia aurea culture pools fertilized with fresh swine waste. Within the water column, a 95% decline of viable cells occurred during the first 6 h. Isolation of viable salmonellae was possible at 16 days post- inoculation, but not at 32 days. Similarly, salmonellae could be detected in the viscera and epithelium of T. aurea at 16 days, although not at 32 days. Salmonellae were not isolated from the fish flesh, nor was there evidence of septicemic infection.

Balavenkatasubbaiah, M., Rani, A. U., Geethanjali, K., Purushotham, K. R., and Ramamurthi, R. (1984). Effect of cupric chloride on oxidative metabolism in the freshwater teleost, Tilapia mossambica. Ecotoxicol Environ Saf 8, 289-93.
The freshwater teleost Tilapia mossambica was subjected to lethal (6.0 mg X liter-1 = LC50/48 hr) and sublethal (1.5 mg X liter-1 copper treatment for 1, 7, and 14 days. The whole animal oxygen consumption and the activity levels of succinate dehydrogenase and lactate dehydrogenase in liver and muscle were studied. The decrease in oxygen consumption and succinate dehydrogenase activity and significant increase in lactate dehydrogenase activity suggest that the stressed fish is meeting its energy requirements through anaerobic oxidation and these enzymes can be used as indicators in monitoring metal-induced toxicity in fish.

Balm, P. H., Groneveld, D., Lamers, A. E., and Wendelaar Bonga, S. E. (1993). Multiple actions of melanotropic peptides in the teleost Oreochromis mossambicus (tilapia). Ann N Y Acad Sci 680, 448-50.

Balm, P. H., Pepels, P., Helfrich, S., Hovens, M. L., and Bonga, S. E. (1994). Adrenocorticotropic hormone in relation to interrenal function during stress in tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 96, 347-60.
This study examines ACTH-like immunoreactivity in the pituitary pars distalis and pars intermedia of the freshwater teleost Oreochromis mossambicus (tilapia). Two products (tACTHA and tACTHB) were present in both lobes. These two products also accounted for the majority of the ACTH i.r. when in vitro pars distalis incubation medium was analyzed by HPLC. In a homologous bioassay the two tilapia ACTH-like molecules and human ACTH1-39 possessed similar corticotropic potency. The peptides were quantified using a newly validated radioimmunoassay, which was also used to measure ACTH in plasma of unstressed and stressed fish. Short-term ( 12 min) stress rapidly increased plasma cortisol, reaching levels of around 300 ng/ml in 5 min. Surprisingly, this initial elevation was not accompanied by a rise in plasma ACTH levels. A more prolonged (3 hr) confinement in pairs resulted in high plasma cortisol and ACTH levels in one fish of every pair. The second fish had control ACTH levels and only marginally elevated cortisol levels. Therefore, in this species social interactions seem to influence the reaction of the pituitary-interrenal axis to stress. The short-term cortisol response to disturbance could be abolished completely by pretreating fish in vivo with cortisol for 48 hr. This treatment did not alter circulating ACTH levels. It is concluded that tilapia did not rely on circulating ACTH for a rapid elevation of plasma cortisol levels. Both neuronal mechanisms and cortisol feedback may regulate the pituitary-interrenal axis at the level of the interrenal.

Balm, P. H., Hovens, M. L., and Wendelaar Bonga, S. E. (1995). Endorphin and MSH in concert form the corticotropic principle released by tilapia (Oreochromis mossambicus; Teleostei) melanotropes. Peptides 16, 463-9.
HPLC characterization of tilapia pituitary endorphins using an antibody specific for N-terminally acetylated endorphins yielded three major peaks in the neurointermediate lobe, but none in the pars distalis. The melanotropes secreted two of the immunoreactive products in vitro, one of which coeluted with Xenopus laevis N-ac-beta-END(1-8). This immunoreactive fraction also coeluted with diacetyl-alpha-MSH. Evidence is presented that the noteworthy corticotropic potency of this HPLC fraction, previously attributed to diacetyl-alpha-MSH, results from END and MSH acting in a coordinated fashion. Confinement stress had no effect on plasma N-ac-beta-END immunoreactivity, but led to a decrease in plasma alpha-MSH levels. Therefore, it seems unlikely that the corticotropic action of the peptides regulates the elevation of cortisol production that takes place during confinement, but it may play a role during other forms of stress that are known to activate the melanotropes.

Balm, P. H., van Lieshout, E., Lokate, J., and Wendelaar Bonga, S. E. (1995). Bacterial lipopolysaccharide (LPS) and interleukin 1 (IL-1) exert multiple physiological effects in the tilapia Oreochromis mossambicus (Teleostei). J Comp Physiol [B] 165, 85-92.
To gain insight in immuno-endocrine communication in teleosts the physiological effects of interleukin 1 and bacterial lipopolysaccharide in teleosts were investigated. Tilapia (Oreochromis mossambicus) were treated with murine interleukin 1 and E. coli lipopolysaccharide in vivo, and lipopolysaccharide was administered to pituitary lobes and head kidneys in vitro. The integument of the fish appeared to be a sensitive target for the preparations tested, since proliferation of chloride cells and of epidermal mucous cells was observed as well as an increase in epidermal thickness. These effects may relate to an acute phase-like reaction caused by the treatments. Lipopolysaccharide administration furthermore resulted in an increase in plasma free fatty acids levels. Lipopolysaccharide, but not interleukin 1, stimulated the interrenal axis of the fish, as judged by the increase in cortisol production measured in superfusion of head kidneys. In addition to these in vivo effects, lipopolysaccharide also displayed several effects in vitro. Pituitary adrenocorticotropic hormone, as well as alpha-melanocyte stimulating hormone, release was inhibited, and the head kidney responsiveness to adrenocorticotropic hormone was inhibited after pretreatment of the tissue with the E. coli product. This latter effect coincided with the release of an unidentified alpha-melanocyte stimulating hormone immunoreactive fraction by the head kidneys which could be stimulated by lipopolysaccharide. The data strongly support the notion that the immune system is involved in adaptive regulations in teleosts, and that immunoendocrine interactions are phylogenetically old mechanisms.

Balthazart, J. (1974). [Non-stationary and functional aspects of the agonistic behavior in Tilapia macrochir (Boulanger 1912) (Piscer: Cichlidae)]. Acta Zool Pathol Antverp 58, 29-40.

Banerjee, S. K., Dastidar, G., Mukhopadhyay, P. K., and Dehadrai, P. V. (1978). Toxicity of cadmium: a comparative study in the air-breathing fish, Clarias batrachus (Linn.) & in the non air-breathing one, Tilapia mossumbica (Peters). Indian J Exp Biol 16, 1274-7.

Barash, D. P. (1975). Behavioral individuality in the cichlid fish, Tilapia mossambica. Behav Biol 13, 197-202.

Barcellos, L. J. G., Nicolaiewsky, S., de Souza, S. M. G., and Lulhier, F. (1999). Plasmatic levels of cortisol in the response to acute stress in Nile tilapia, Oreochromis niloticus (L.), previously exposed to chronic stress. Aquaculture Research 30, 437-444.
Many studies have been made about the physiological effects of isolated chronic or acute stress. However, few studies have been made to assess the combination of both responses. The fish submitted to chronic stress may be subjected to an additional acute stressor. The aim of the present work was to evaluate the acute stress response in Nile tilapia Oreochromis niloticus (L.) previously subjected to chronic stress. For this, two experiments were performed. In the first experiment, the fish were subjected to chronic stress followed by an additional acute stress, In the second experiment, the fish were submitted only to an acute stress, The data showed that Nile tilapia fingerlings can adapt to chronic stress situations, and this decreases, but does not eliminate, their capacity to respond to an additional acute stressor, In both experiments, plasma cortisol levers reached a peak 1 h after administration of the acute stressor. In fish previously submitted to chronic stress, the highest concentration of plasma cortisol measured was 196 ng mL(-1). This value was significantly different from the cortisol concentration obtained in the second experiment (267 ng mL(-1)) with non-chronically stressed fish, The data also suggest that the chronic stress response can provoke a reduction in performance and growth rates compared with non- stressed fish.

Bardakci, F., and Skibinski, D. O. (1994). Application of the RAPD technique in tilapia fish: species and subspecies identification. Heredity 73, 117-23.
Random Amplified Polymorphic DNA (RAPD) analysis was applied to three species of the tilapia genus Oreochromis and four subspecies of O. niloticus. Thirteen random 10-mer primers were used to assay polymorphisms within and between populations. Different RAPD fragment patterns were observed for different species, although not always for different subspecies. Evidence is presented that RAPD markers might be useful for systemic investigation at the level of species and subspecies.

Bardakci, F., and Skibinski, D. O. (1999). A polymorphic SCAR-RAPD marker between species of tilapia (Pisces: Cichlidae). Anim Genet 30, 78-9.

Basha, S. M., Prasada Rao, K. S., Sambasiva Rao, K. R., and Ramana Rao, K. V. (1983). Differential toxicity of malathion, BHC, and carbaryl to the freshwater fish, Tilapia mossambica (Peters). Bull Environ Contam Toxicol 31, 543-6.

Basha, S. M., Rao, K. S., Rao, K. R., and Rao, K. V. (1984). Respiratory potentials of the fish (Tilapia mossambica) under malathion, carbaryl and lindane intoxication. Bull Environ Contam Toxicol 32, 570-4.

Basiao, Z. U., and Doyle, R. W. (1999). Test of size-specific mass selection for Nile tilapia, Oreochromis niloticus L., cage farming in the Philippines. Aquaculture Research 30, 373-378.
One generation of mass selection based on the collimation procedure (early culling of large fry) was applied on Nile tilapia, Oreochromis niloticus L., in net cages set in Laguna de Bay, Philippines. The objective was to test the effectiveness of a low-cost, small-scale broodstock improvement procedure in this culture environment. Directional selection was performed in two steps after initial removal of large fry at 21 days. Selection of parents and testing of the offspring were also conducted in hapa net cages set up in Laguna de Bay. The selection resulted in a significant positive response of 3% relative to the control, which represents a projected 34% gain over 5 years in Laguna cage culture. The realized heritability is approximate to 16%.

Basu, J., Nandi, J., and Bern, H. A. (1965). The homolog of the pituitary-adrenocortical axis in the teleost fish Tilapia mossambica. J Exp Zool 159, 347-55.

Belal, I. E. H., and Al-Dosari, M. (1999). Replacement of fish meal with Salicornia meal in feeds for Nile tilapia Oreochromis niloticus. Journal of the World Aquaculture Society 30, 285-289.
We investigated the use of the halophyte salicornia Salicornia bigelovii as a replacement for fish meal in feeds containing 35% crude protein for Nile tilapia Oreochromis niloticus. Five isocaloric, isonitrogenous diets were formulated with salicornia meal to replace 0%, 20%, 40%, 60%, and 80% of the fish meal in the feed. Another diet was formulated entirely from salicornia meal. Diets were fed to three replicate groups of tilapia fingerlings (mean initial weight = 0.5 g/fish) for 6 wk in 40-L aquaria supplied with 22 C well water. Tilapia growth did not differ (P < 0.05) for fish fed diets in which 0%, 20%, or 40% of the fish meal in the diet was replaced with salicornia meal. Weight gain was reduced when fish were fed diets with higher levels of salicornia meal, and growth was slowest for fish fed diets formulated entirely from salicornia meal. Body fat was reduced and body moisture content was increased (P < 0.05) for fish fed diets in which more than 80% of the fish meal was replaced with salicornia meal. We conclude that saIicornia meal can replace up to 40% of the fish meal in O. niloticus feeds without affecting growth or body composition.

Belal, I. E. H. (1999). Replacing dietary corn with barley seeds in Nile tilapia, Oreochromis niloticus (L.), feed. Aquaculture Research 30, 265-269.
Four isocaloric-isonitrogenous rations containing 0%, 15%, 30% and 51% of ground barley seeds as a replacement for dietary corn were fed to three replicate groups of Oreochromis niloticus (Linnaeus) fingerlings with a mean initial weight of 3.5 g. The randomly selected fish were tested for 9 weeks in 60 L circular tanks. Each tank was considered as an experimental unit. The tanks were put together in a water recirculating system using filtered and aerated ground well water (24 +/- 3 degrees C). Tilapia weight gain, feed conversion, specific growth rate and protein efficiency ratio were similar in fish fed diets containing 15% and 30% barley and were superior to those fed diets containing 0% control and 51% barley, There were no differences between tilapia fed diets containing 0% and 51% barley. Body moisture, crude fat, crude protein and total ash did not change as the level of barley in the feeds was increased.

Ber, R., and Daniel, V. (1992). Structure and sequence of the growth hormone-encoding gene from Tilapia nilotica. Gene 113, 245-50.
We report here the nucleotide (nt) sequence of the growth hormone (GH)- encoding gene (GH) of the tilapia fish (Tilapia nilotica). The T. nilotica GH gene, similar to that of the salmonidae fish, Atlantic salmon and rainbow trout, contains six exons and five introns. However, despite the presence of an additional intron (intron V), the size of the primary transcript of T. nilotica GH (1666 nt) is significantly shorter than that of all other currently characterized fish GH genes. Comparison of sequences upstream from the transcription start point of the tilapia, carp, rainbow trout and Atlantic salmon GH genes shows a region of high homology preceding the typical TATA box. This homology does not seem to extend to the regions further upstream of the compared fish GH genes and is not observed to be present in the corresponding region of the mammalian GH genes. A sequences search for putative DNA- binding domains for transcription factors shows the presence of short nt stretches similar to those considered to be involved in the tissue- specific expression of mammalian GH genes.

Ber, R., and Daniel, V. (1993). Sequence analysis suggests a recent duplication of the growth hormone- encoding gene in Tilapia nilotica. Gene 125, 143-50.
The sequence of two growth hormone(GH)-encoding genes from tilapia fish (Tilapia nilotica) is reported. Our data indicate that the presence of two GH in the tilapia genome is a consequence of a relatively recent duplication event. The two genes are highly homologous, having a similar intron (five)/exon (six) arrangement, and both encode an identical polypeptide. Sequence similarity extends up to bp -628 upstream to the transcription start point, after which the sequences of the two genes are not related to each other. The presence of two GH in the tilapia genome is supported both by the nucleotide sequence and by genomic DNA blot hybridization analysis. Tilapias, like salmonids, contain an extra intron compared with the mammalian GH structure. We suggest that within the superorder Teleostei, the insertion of intron 5 into GH took place after the evolutionary separation of Cyprinoidea, but before Isospondyli (salmonids) and Acanthopterygii (tilapias) were separated. Thus, the additional intron which is probably present in many teleost fish GH may provide an excellent natural marker for evolution and classification studies.

Bhaskar, M., and Govindappa, S. (1985). Tissue compensatory metabolic profiles in Tilapia mossambica (Peters) on acclimation to sublethal acidic and alkaline media. Gill glycogen metabolism. Arch Int Physiol Biochim 93, 59-63.
Freshwater Fish, Tilapia mossambica (Peters) was acclimated to sublethal acidic and alkaline media and branchial tissue glycogen metabolism was studied. In acidic media, the glycogenolysis is elevated in the tissues and glycolysis is suppressed. In contrast, in alkaline media, the tissue glycolytic pathway is accelerated with accumulation of organic acids. In both the cases tissue had elevated G-6-PDH activity indicating stress conditions on the tissue metabolism. The tissue compensatory changes provided survival value to the fish under altered pH media.

Bhaskar, M., and Govindappa, S. (1986). Acclimation to sublethal acidic and alkaline media of Tilapia mossambica (Peters): changes in glycogen metabolism of red muscle. Bull Environ Contam Toxicol 37, 113-9.

Bhattacharyya, A., Sarkar, S. K., Basu, S. K., and Ganguly, S. (1989). Lactate dehydrogenase as genetic marker enzyme in fish Tilapia mossambica. Indian J Exp Biol 27, 913-4.

Bhujel, R. C. (2000). A review of strategies for the management of Nile tilapia (Oreochromis niloticus) broodfish in seed production systems, especially hapa-based systems. Aquaculture 181, 37-59.
Low egg production per spawning and lack of spawning synchrony are the major problems of mass seed production in mouthbrooding tilapias. Collection of eggs or fry from the mouths of incubating females reared in large hapas suspended in fertilized ponds and incubating them artificially has been found to be commercially viable. However, fouling of the hapa is a major problem causing inconsistent performance of broodfish. In addition, other factors influencing with the tilapia seed output in hapa within pond systems are age and the size of the broodfish, feeding and feed management, environmental factors and management techniques. However, information on the factors affecting tilapia seed output is limited and scattered; therefore, this paper discusses the various aspects of management strategies based on the present state of knowledge and explores areas for the future research. (C) 2000 Elsevier Science B.V. All rights reserved.

Bijvelds, M., Kolar, Z., Bonga, S., and Flik, G. (1997). Mg2+ transport in plasma membrane vesicles of renal epithelium of the Mozambique tilapia (Oreochromis mossambicus). J Exp Biol 200, 1931-9.
To elucidate the mechanisms involved in Mg2+ transport at the apical and basolateral poles of the renal tubular epithelium, apical and basolateral plasma membrane vesicle preparations were derived from kidney tissue of freshwater- and seawater-adapted Mozambique tilapia Oreochromis mossambicus. Brush-border preparations were enriched 15.8- fold in alkaline phosphatase activity and consisted almost exclusively of right-side-out membrane vesicles. Basolateral membrane preparations were enriched 7.5-fold in Na+/K+-ATPase activity and contained resealed vesicles and leaky membrane fragments. Mg2+ association with brush- border and basolateral plasma membranes, traced using radioactive 27Mg, occurred in an osmotically active space. In all instances, Mg2+ binding to the vesicular membrane was low compared with the vesicular uptake. Mg2+ equilibration across the vesicular membrane of brush-border preparations was rapid and sensitive to the presence of extravesicular Ca2+, suggesting that the apical membrane of the renal epithelium contains a transport pathway for divalent cations. Application of various ionic gradients did not affect vesicular Mg2+ transport in apical and basolateral membrane preparations, suggesting the presence of an ion-coupled transport mechanism. ATP or ATP--S did not stimulate Mg2+ fluxes, indicating that Mg2+ transport does not proceed via an ATP- driven or activated transporter. In these aspects, vesicular Mg2+ transport was similar in seawater and freshwater preparations. These results suggest that the apical membrane of renal epithelial cells lacks an active secretory Mg2+ transport mechanism. We propose that the Mg2+ conductivity of the apical membrane reflects a route for downhill Mg2+ entry and is involved in renal Mg2+ reabsorption.

Bocci, M. (1999). Modelling the growth of Nile Tilapia (Oreochromis niloticus) feeding on natural resources in enclosures in Laguna de Bay (Philippines). Ecological Modelling 119, 135-148.
Laguna de Bay (Philippines), one of the largest freshwater bodies in the Southeast Asia, is located near Metro Manila. The lake is an important resource for the local population because of fish production: fishing and aquaculture are relevant activities for the economy of the area. Nile Tilapia (Oreochromis niloticus) is one of the cultured species and it is grown within net cages in the lake. In this paper, a model is proposed to describe the growth of Nile Tilapia under natural conditions; food sources have been considered to be phytoplankton, zooplankton and suspended organic matter (detritus), without additional feed supply. The metabolic approach has been adopted to describe fish growth. The parameters characterising fish metabolism have been estimated for O. niloticus or similar species, according to literature information. The model has been applied to twelve growing conditions representative of increasing stocking densities and of different growing periods. Model results have been successfully compared with the experimental data reported in literature. This model has been used to estimate the amount of natural food (phytoplankton) exploited by the culture of O. niloticus with the final aim to quantitatively relate lake's water quality with fish growth and production. (C) 1999 Elsevier Science B.V. All rights reserved.

Bonga, S. E., and van der Meij, J. C. (1980). The effect of ambient calcium on prolactin cell activity and plasma electrolytes in Sarotherodon mossambicus (Tilapia mossambica). Gen Comp Endocrinol 40, 391-401.

Borski, R. J., Yoshikawa, J. S., Madsen, S. S., Nishioka, R. S., Zabetian, C., Bern, H. A., and Grau, E. G. (1994). Effects of environmental salinity on pituitary growth hormone content and cell activity in the euryhaline tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 95, 483-94.
Studies were undertaken to determine whether several indicators of growth hormone (GH) cell activity, namely GH content, fine structure, and volume of the GH region, differ in the pituitaries of freshwater (FW) and seawater (SW) tilapia, Oreochromis mossambicus. Tilapia raised from the stage of yolk-sac absorption for 7 months in SW contain significantly more GH in their pituitaries than in those of fish reared in FW. Pituitary growth hormone content in tilapia raised in FW for 7 months and transferred to SW for 49 days is greater than that in sibling tilapia retained in FW. Conversely, GH content is significantly lower in the pituitaries of SW-reared tilapia transferred to FW for 49 days than that in the pituitaries from fish retained in SW. Likewise, the volume of the GH region and activity of the GH cells are enhanced in pituitaries from SW-reared tilapia over that seen in pituitaries from FW fish. Taken together, all data indicate heightened GH cell activity in SW-raised tilapia and suggest that GH may play a causal role in the greater growth rates observed in SW tilapia compared to FW fish and/or that GH may be involved in SW osmoregulation. The latter suggestion is supported, in part, by our observation that in vivo oGH treatment (2 micrograms/g body wt) stimulated gill Na+,K(+)-ATPase activity.

Bury, N., Flik, G., Eddy, F., and Codd, G. (1996). The effects of cyanobacteria and the cyanobacterial toxin microcystin- LR on Ca2+ transport and Na+/K+-ATPase in tilapia gills. J Exp Biol 199, 1319-26.
The effects of cytotoxic substances from cyanobacteria on ionic transport processes in tilapia (Oreochromis mossambicus) were examined. Inhibitory effects on ionic transport including whole-body Ca2+ fluxes and P-type ATPases of the gill were found. The compounds tested were (1) purified microcystin-LR (MC-LR), a heptapeptide hepatotoxin produced by the cyanobacterium Microcystis aeruginosa, (2) extracts from M. aeruginosa strain PCC 7820, a strain producing MC-LR and other microcystin variants, and (3) extracts of M. aeruginosa CYA 43, a strain producing toxins including small quantities of MC-LR. Whole-body Ca2+ influx was inhibited by a 24 h exposure to extracts of M. aeruginosa CYA 43 and 7820, but not by exposure to an equivalent amount (90 mg l-1) of purified MC-LR. Shorter exposure times (4 h) were ineffective. Fish exposed to extracts from M. aeruginosa CYA 43 showed significant plasma hypocalcaemia. Both strains of M. aeruginosa inhibited Ca2+ uptake by basolateral plasma membrane vesicles (BLMVs), endoplasmic reticulum (ER) and mitochondria, as well as BLMV K+- dependent p-nitrophenol phosphatase (pNPPase) activity. The hydrophobic fractions of the cyanobacterial extracts were the most potent, inhibiting BLMV, ER and mitochondrial Ca2+ uptake by up to 99 %, but they were less inhibitory of BLMV K+-dependent pNPPase activity. Purified MC-LR was without effect on these preparations. In conclusion, cytotoxic substances from cyanobacteria have the potential to disrupt normal physiological processes dependent upon Ca2+ transport processes in tilapia gills.

Byamungu, N., Corneillie, S., Mol, K., Darras, V., and Kuhn, E. R. (1990). Stimulation of thyroid function by several pituitary hormones results in an increase in plasma thyroxine and reverse triiodothyronine in tilapia (Tilapia nilotica). Gen Comp Endocrinol 80, 33-40.
In this study, intravenous injection of several doses of porcine follicle stimulating hormone (pFSH: 0.002, 0.01, 0.05, and 0.5 micrograms/g body wt), bovine TSH (bTSH: 0.5 micrograms/g body wt), and ovine growth hormone (oGH: 0.04, 0.02, and 0.4 microgram/g body wt) stimulated an increase in plasma thyroxine (T4) and reverse triiodothyronine (rT3) in tilapia. This effect occurred in a dose- dependent manner. pFSH was the most potent in stimulating thyroid function. The dose of 0.002 microgram pFSH/g body wt increased plasma levels of T4 over control levels (2.59 +/- 0.16 ng/ml) about 2.5-fold within 4 hr, whereas a concentration of 0.5 micrograms/g body wt caused a great and prolonged increase of T4 and rT3 levels. Control levels (2.59 +/- 0.16 ng/ml for T4 and 40.37 +/- 8.60 pg/ml for rT3) were increased 19- and 22-fold respectively, over 24 hr. An increase of T4 and rT3 levels occurred also after injection of total hypophyseal extract and Con A II glycoprotein fraction of a tilapia pituitary homogenate, whereas the protein fraction failed to alter plasma concentrations of T4 and rT3. rT3 levels were also significantly increased at 2 hr, but not at 1 hr, after injection of T4. Basal T3 levels (1.90 +/- 0.22 ng/ml) were reduced by half over 24 hr in all experiments. These results suggest the existence, in tilapia, of a 5-D pathway deiodination of T4 which is pituitary independent. Stimulation of T4 release is always followed by an increase in plasma rT3 levels.

Byamungu, N., Darras, V. M., and Kuhn, E. R. (1991). Purification of tilapia thyrotropin from a crude pituitary homogenate by immunoaffinity chromatography using a matrix of antibodies against porcine follicle-stimulating hormone. Gen Comp Endocrinol 84, 183-91.
An immunoadsorbent matrix using antibodies against porcine follicle- stimulating hormone (pFSH), a high heterothyrotropic stimulant in tilapia, was used to purify tilapia thyrotropic hormone (t-TSH) from crude pituitary extracts. A homologous bioassay monitored TSH bioactivity during the purification. Thyroid hormones (thyroxine, T4; triiodothyronine, T3; and reverse triiodothyronine, rT3) and testosterone were measured in vivo in Tilapia nilotica. TSH activity eluted as one major peak at pH 2.8 using a PBS-glycine buffer. The TSH fraction increased plasma T4 and plasma rT3. The potency of tTSH was comparable to that of pituitary extract or its Con A II fraction; however, pFSH was a stronger thyroid stimulant. tTSH had no effect on plasma T3 levels and was free of gonadotropic activity, as indicated by its failure to alter plasma testosterone concentrations. Chromatographic and electrophoretic analyses demonstrated a high degree of purity. Like other vertebrate TSHs, the tTSH appeared to have a subunit structure with a possible microgeneity in one subunit.

Byamungu, N., Mol, K., and Kuhn, E. R. (1991). Somatostatin increases plasma T3 concentrations in Tilapia nilotica in the presence of increased plasma T4 levels. Gen Comp Endocrinol 82, 401-6.
An injection of ovine growth hormone, porcine follicle stimulating hormone, and bovine thyrotropin stimulating hormone increased in Tilapia nilotica plasma concentrations of thyroxine (T4) and reverse triiodothyronine (rT3) after 4 and 8 hr, whereas plasma concentrations of T3 were unaffected. An injection of somatostatin (SRIF) alone did not influence thyroid hormone levels. If, however, SRIF was injected together with these hormones, which raised plasma T4, or together with T4 itself, an increase in plasma concentrations of T3 could be observed, whereas the increase in rT3 was less pronounced. It is concluded that SRIF may change the normal 5-deiodinase (5-D) activity and increased rT3 during hyperthyroxinemia into a 5'-D activity and a rise in T3, respectively, in T. nilotica.

Callard, G. V., Specker, J. L., Knapp, J., Nishioka, R. S., and Bern, H. A. (1988). Aromatase is concentrated in the proximal pars distalis of tilapia pituitary. Gen Comp Endocrinol 71, 70-9.
Aromatase has been identified in the telostean, avian, and mammalian pituitaries, although its cellular location(s) is not yet certain. To address this question, experiments were performed in tilapia (Oreochromis mossambicus), a species which has been well characterized with respect to the intraglandular distribution of the different pituitary cell types. To estimate aromatase, glands were microdissected into rostral pars distalis (RPD), proximal pars distalis (PPD), and neurointermediate lobe (NIL) and organs were cultured in the presence of [3H]androstenedione for 16-24 hr. [3H]Estrogen products were isolated and quantified after ether extraction, hydrolysis with glucuronidase-sulfatase, thin-layer chromatography, and phenolic partition. Authentic estrone or estradiol-17 beta were produced by all pituitary regions and also by the urophyseal region of the spinal cord. Aromatase was two to five times higher in PPD than in RPD or NIL and similar to activity in adjacent hypothalamus-preoptic area (HPOA). Much lower estrogen yields were obtained in cultures of cerebellum, urophysis, and other cord regions. Since the PPD contains most of the somatotropes, these data are consistent with earlier studies implicating GH3/GH4 cell strains as an enriched enzyme source, although its presence in other cell types cannot be ruled out. The unusually high and localized aromatase in tilapia pituitary renders this species a useful model for studying the targets and functional importance of estrogen as a parahormone in the pituitary.

Camargo, L. d. A., and Belda Neto, F. M. (1969). [Chemical and nutritional aspects of "Tilapia Melanopleura, Dumeril, 1859"]. Rev Fac Farm Odontol Araraquara 3, 259-65.

Carrasco, L. A. P., Penman, D. J., and Bromage, N. (1999). Evidence for the presence of sex chromosomes in the Nile tilapia (Oreochromis niloticus) from synaptonemal complex analysis of XX, XY and YY genotypes. Aquaculture 173, 207-218.
A cytogenetic analysis of chromosome synapsis was carried out during the first meiotic prophase of the Nile tilapia, Oreochromis niloticus. Three different genotypes were studied: XX sex-reversed males, 'wild-type' (XY) males and YY 'supermales'. TEM analysis of synaptonemal complex (SC) spreads revealed the presence of 22 fully paired bivalents during pachytene in both homogametic genotypes. In the heterogametic genotype, an incompletely paired segment was frequently observed during the process of meiotic synapsis in the terminal region of the longest bivalent. The presence of this unpaired segment, together with several features characteristic of sex- chromosome behaviour during meiosis, suggests the existence of a non-homologous region in this chromosomal pair in the heterogametic genotype, and provides cytological evidence for the chromosomal basis of sex determination in O. niloticus. The usefulness of SC analysis for the understanding of sex determination and its relevance in the management of species of aquacultural importance are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

Carrieri, M. P., and Volpato, G. L. (1991). Does snatching frequency really indicate food ingestion in the Nile tilapia? Physiol Behav 50, 489-92.
The fitness of the snatching frequency as an indicator of food intake in Nile tilapia fingerlings, Oreochromis niloticus (L), was studied. Five groups of four individuals each were used after a two-day starvation period. The hierarchical rank among individuals in the same group was registered. Food in the form of tiny pellets (ranging from 1.30 to 1.95 mm in diameter) was offered, and the individual snatching frequency was observed during a 20-min period. The animals were then sacrificed for evaluation of stomach contents. It was concluded that snatching frequency is not a good parameter to indicate individual food intake in this species when fed as a group with pellets crushed into tiny particles. This raises a problem for investigations that require evaluation of the cumulative effect of competition on food intake, such as growth or conversion efficiency studies. Furthermore, a very low correlation between snatching frequency and food intake was shown in the third hierarchical rank. It is suggested that the linearity assumed in such hierarchies should be reconsidered.

Caruso, D., and Lazard, J. (1999). Subordination stress in Nile tilapia and its effect on plasma lysozyme activity. Journal of Fish Biology 55, 451-454.
Dominant Nile tilapia had significantly higher lysozyme activity than did subordinate fishes (alpha = 0.05). Plasma lysozyme level was not correlated with sex, parental origin, rearing length, weight, condition factor or rearing density. (C) 1999 The Fisheries Society of the British Isles.

Chan, K. M. (1994). PCR-cloning of goldfish and tilapia metallothionein complementary DNAs. Biochem Biophys Res Commun 205, 368-74.
Metallothionein (MT) is believed to be a sensitive and effective "biomarker" for monitoring metal contamination in fish. Comparison of amino acid sequences between flounder MT and trout MT revealed that there is a conserved region at their N-terminals. Using oligonucleotides derived from this conserved region, reverse transcription- polymerase chain reaction (RT-PCR) was performed to obtain MT complementary DNAs (cDNAs) from goldfish, Carassius auratus, and tilapia, Tilapia mossambica. These cDNA probes would be useful in developing sensitive PCR-based methods to detect MT gene expression for monitoring metal pollution in local waters.

Chan, W. L., Chan, C. H., and Chan, T. Y. (1999). Vibrio vulnificus septicaemia and necrotizing fasciitis after a prick from the dorsal fin of a tilapia. Trans R Soc Trop Med Hyg 93, 174.

Chan, W. L., Chan, C. H. S., and Chan, T. Y. K. (1999). Vibrio vulnificus septicaemia and necrotizing fasciitis after a prick from the dorsal fin of a tilapia. Transactions of the Royal Society of Tropical Medicine and Hygiene 93, 174-174.

Chang, C. U., and Liao, C. F. (1994). Characterization of beta-adrenoceptors of tilapia erythrocytes with hydrophobic and hydrophilic radioligands. Chin J Physiol 37, 153-9.
Tilapia are widely used for to investigate stress physiology, and beta- adrenoceptors in fish erythrocytes play important roles in response to hypoxia and other environmental stresses. As the beta-adrenoceptor in tilapia erythrocytes has never been investigated, we characterized beta- adrenoceptors in intact red blood cells of a tilapia (Oreochromis mossambicus) in this study by radioligand binding assay with a hydrophobic beta-adrenoceptor antagonist, 1-[4,6-propyl- 3H]dihydroalprenolol ([3H]DHA), and a hydrophilic ligand (-)-4-(3-t- butylamino-2-hydroxypropoxy)-[5,7-3H] benzimidazol-2-one ([3H]CGP- 12177). The equilibrium dissociation constant (KD) for [3H]CGP-12177 calculated from kinetic experiments (KD = 5.8 +/- 4.8 nM) was comparable to that obtained from Scatchard analysis (KD = 1.22 +/- 0.18 nM). However, the KD for [3H]DHA obtained from kinetic studies (KD = 0.41 +/- 0.12 nM) was much smaller than that from a Scatchard plot (KD = 7.8 +/- 1.6 nM). The hydrophobic [3H]DHA bound to two sites (KD = 7.8 nM, Bmax = 12,500 sites/cell and KD = 77.4 nM, Bmax = 70,550 sites/cell), whereas the hydrophilic [3H]CGP-12177 bound to one site (KD = 1.2 nM, Bmax = 1,900 sites/cell). The results indicate that high- affinity beta-adrenoceptors are located both on the surface of and inside tilapia erythrocytes, and low-affinity receptors exist only inside erythrocytes.

Chang, C. F., and Lin, S. J. (1995). Immersion in bovine insulin stimulates growth of tilapia. Reprod Nutr Dev 35, 95-103.
The objective of this study was to investigate the effects of bovine insulin on growth responses in tilapia. Juvenile hybrid male tilapia (Oreochromis niloticus x O aurea; n = 135) were subjected to 1 of 3 treatments. Each treatment was subdivided into 3 replicates of 15 fish each. The fish were immersed into 1 of 2 doses (10 and 100 micrograms/100 ml water) of insulin or no hormone for 15 min per week for 8 weeks. Body weight, growth and feed conversion efficiency were significantly higher as a result of the first 4 weeks of insulin treatment as compared to control fish. The lower dose of insulin had a better stimulation effect than that of the higher doses. Insulin also stimulated feed consumption. Liver protein and protein/DNA ratio were higher in both insulin-treated groups than in the control group. Muscle proximate composition and hepatosomatic index were similar in the insulin-treated and control groups. The experimental findings suggest that insulin administered by immersion can enhance growth, feed consumption, food utilization and liver cell size in tilapia.

Chang, X. T., Kobayashi, T., Kajiura, H., Nakamura, M., and Nagahama, Y. (1997). Isolation and characterization of the cDNA encoding the tilapia (Oreochromis niloticus) cytochrome P450 aromatase (P450arom): changes in P450arom mRNA, protein and enzyme activity in ovarian follicles during oogenesis. J Mol Endocrinol 18, 57-66.
A cDNA clone encoding the complete tilapia (a teleost fish, Oreochromis niloticus) cytochrome P450 aromatase (P450arom) was isolated from an ovarian follicle cDNA library. The deduced amino acid sequence (522 amino acid residues) had 72.2% and 59.5% homology with rainbow trout and catfish P450arom respectively, and about 50% homology with mammalian and avian P450arom. Expression of this cDNA in COS-7 cells produced a protein that converted exogenous testosterone to estrogens. Northern blots using a tilapia P450arom cDNA fragment and Western blots using an antiserum against a tilapia P450arom polypeptide fragment revealed a single P450arom mRNA (2.6 kb) and a single protein (59 kDa) in tilapia ovarian tissue respectively. These analyses also revealed that the levels of both P450arom mRNA and protein were low in early vitellogenic follicles, increased in midvitellogenic follicles, and declined to non-detectable levels in post-vitellogenic follicles. Changes in the ability of follicles to convert exogenous testosterone to estrogens (aromatase activity) were similar to those of P450arom mRNA and protein. These observations indicated that the capacity of tilapia ovarian follicles to synthesize estradiol-17 beta is closely related to the contents of P450arom mRNA and protein within them.

Chang, M. H., Lin, H. C., and Hwang, P. P. (1998). Ca2+ uptake and Cd2+ accumulation in larval tilapia (Oreochromis mossambicus) acclimated to waterborne Cd2+. Am J Physiol 274, R1570-7.
The present study compares the rates of Ca2+ uptake and Cd2+ accumulation in tilapia (Oreochromis mossambicus) between larvae preexposed to Cd2+ and naive larvae. Preexposure to Cd2+ induces some form of adaptation that attenuates the effects of Cd2+ later on. Exposure to Cd2+ decreased the uptake of Ca2+ but did not suppress the accumulation rate of Cd2+. A 12-fold increase in 96-h half-maximal lethal concentration was found in tilapia larvae preexposed to 0.45 microM Cd2+ from hatching for 3 days in comparison with naive 3-day-old larvae. The effects of Cd2+ on Ca2+ influx kinetics in larvae preexposed to 0.18 microM Cd2+ for 3 days were examined. The Michaelis constant for Ca2+ in the 0.18 microM Cd2+ preexposed larvae did not change significantly in the presence of Cd2+, whereas maximal velocity increased by approximately 23%. An enhanced Ca2+ uptake efficiency ( approximately 18%) was found in these Cd2+-acclimated larvae. The criterion that determines the survival of tilapia larvae encountering Cd2+ challenge is the degree of interference with Ca2+ homeostasis instead of the absolute amount of Cd2+ accumulated.

Chang, X. T., Kobayashi, T., Todo, T., Ikeuchi, T., Yoshiura, M., Kajiura-Kobayashi, H., Morrey, C., and Nagahama, Y. (1999). Molecular cloning of estrogen receptors alpha and beta in the ovary of a teleost fish, the Tilapia (Oreochromis niloticus). Zoological Science 16, 653-658.
Estrogen receptors (ER) in mammals have recently been shown to be encoded by two distinct genes, ER alpha and ER beta. In this study, cDNAs encoding two tilapia ER subtypes, tER5.1 and tER4.3, were cloned from an ovarian cDNA library of a teleost fish, the tilapia Oreochromis niloticus. The tER5.1 and tER4.3 contain complete open reading frames encoding 585 and 557 amino acid residues, respectively. The two receptors share about 12% homology in the A/B domain, 96% in the DNA binding domain (C domain), 12% in the D domain, 57% in the ligand binding domain (E damain), and 20% in the F domain. Phylogenetic analysis of ER proteins from various vertebrate species indicated that vertebrate ERs consist of two major groups (ER alpha and ER beta); tER5.1 and tER4.3 belong to ER alpha and ER beta subtypes, respectively. Thus, we consider tER5.1 and tER4.3 to be the tilapia homologs of ER alpha (tER alpha) and ER beta (tER beta), respectively. In transient transfection assays using mammalian COS-7 cells, both tER alpha and tER beta showed estradiol-17 beta dependent activation of transcription from the estrogen-responsive ERE-Luc promoter. This is the first report of the presence of ER alpha and ER beta within a single non-mammalian vertebrate species.

Change, X. T. (1999). Molecular cloning of estrogen receptors alpha and beta in the ovary of a teleost fish, the Tilapia (Oreochromis niloticus) (vol 16, pg 653, 1999). Zoological Science 16, 853-853.

Chen, J. D., Yew, F. H., and Li, G. C. (1988). Thermal adaptation and heat shock response of Tilapia ovary cells. J Cell Physiol 134, 189-99.
The growth of tissue culture TO-2 cells derived from the warm water fish Tilapia, the induction of thermotolerance, and protein synthesis profiles of these cells in response to temperature changes were examined. TO-2 cells can grow between 15 to 34 degrees, with an optimal growth temperature of 31 degrees. There is no apparent killing of the cells when the temperature is lowered to 4 degrees for up to 3 days. Survival of TO-2 cells at 43 degrees was studied after various preheat treatments: 1) acute heating at 40 degrees for 15 min followed by 31 degrees incubation, 2) chronic exposure at 37 degrees for several hr, or 3) long-term thermal adaptation at 34 degrees. The cells acquire thermotolerance from pre-exposure to 37 degrees for as short as 6 hr. Preheating at 40 degrees followed by incubation at 31 degrees also induces thermotolerance against a subsequent 43 degrees heat challenge. In addition, 34 degrees thermal adapted cells are resistant to 43 degrees heating. One- and two-dimensional gel electrophoresis of proteins after heat treatments show that three major heat shock proteins with molecular weights around 87, 70, and 27 kD are preferentially synthesized. The synthesis of two additional proteins with an isoelectric point of 6.9 and molecular weights of 60 and 44 kD are significantly enhanced in 34 degrees thermal-adapted and 37 degrees chronic heated cells, but not in cells subjected to an acute heat shock at either 40 degrees or 43 degrees. On the other hand, the 27 kD heat shock proteins are mainly present in the 43 degrees, 40 degrees, and 37 degrees heat-shocked cells, but not in the 34 degrees thermal-adapted cells.

Chen, J. D., and Yew, F. H. (1988). DNA replication and repair of Tilapia cells. II. Effects of temperature on DNA replication and ultraviolet repair in Tilapia ovary cells. J Cell Sci 89, 263-72.
TO-2 is a fish cell line derived from the Tilapia ovary. It grows over a wide range of temperature (15-34 degrees C). While most fish cells lack DNA excision repair and are hypersensitive to ultraviolet light (u.v.), Tilapia cells are more u.v.-resistant than mammalian cells. In this paper we report the effects of temperature on DNA replication and u.v. repair in TO-2 cells. When the cells were moved from 31 degrees C to the sublethal high temperature of 37 degrees C, the rate of DNA synthesis first decreased to 60%, then speedy recovery soon set in, and after 8 h at 37 degrees C the rate of DNA synthesis overshot the 31 degrees C control level by 180%. When moved to low temperature (18 degrees C) Tilapia cells also showed an initial suppression of DNA synthesis before settling at 30% of the control level. u.v. reduced but could not block DNA synthesis completely. The inhibition was overcome in 3 h at 37, 31 and 25 degrees C, but not at 18 degrees C. Initiation of nascent DNA synthesis was blocked at 4 J m-2 in TO-2 cells compared with less than or equal to 1 J m-2 in mammalian cells. After 9 J m-2 u.v. irradiation, low molecular weight DNA replication intermediates started to accumulate, and they could be chased into high molecular weight DNA with little delay. TO-2 cells showed low levels of u.v.- induced excision repair; but this was prominent compared with other fish cells. The u.v.-induced incision rate has been measured at various temperatures, and the activation energy of incision estimated to be 13 kcal mol-1 (1 cal approximately equal to 4.184 J).

Chen, J. Y., Chang, C. Y., Chen, J. C., Shen, S. C., and Wu, J. L. (1997). Production of biologically active recombinant tilapia insulin-like growth factor-II polypeptides in Escherichia coli cells and characterization of the genomic structure of the coding region. DNA Cell Biol 16, 883-92.
Insulin-like growth factor-II (IGF-II) is a fetal growth factor in humans, but has not been clearly identified in fish up to now. For a detailed understanding of the physiological response of fish IGF-II, the first step was to clone tilapia IGF-II cDNA from the brain cDNA library, coding the region of genomic DNA, and also expressing tilapia IGF-II polypeptides from Escherichia coli. Tilapia cDNA sequences total 1,977 bp, and predicted nucleotide sequences and amino acid sequences of tilapia share 77.9% and 90.7% homology identity with rainbow trout IGF-II, respectively. The genomic structure of the tilapia prepro-IGF- II coding region is very difficult to sequence in mammals and birds. The cloned tilapia IGF-II gene coding region appears much more complex than in other vertebrates. In tilapia IGF-II, the first coding exon I encoding part of the signal peptide sequence is 25 amino acids shorter than the first coding exon of mammals and birds. The other 23 amino acids of the signal peptide, and the first amino acids of the B domain and C domain are encoded by tilapia coding exon 2. The C, A, and D domains, and the first 20 amino acids of the E peptide are encoded by tilapia coding exon 3. The other E peptides and the 3' untranslated region (UTR) region are encoded by tilapia coding exon 4. These data show that the IGF-II genes have significantly differing structures in vertebrate evolution, and there are differences of interrupting introns in the IGF-I genomic structure compared with mammals. To obtain recombinant biologically active polypeptides, tilapia IGF-II B-C-A-D domains were amplified using the polymerase chain reaction (PCR), then ligated with glutathione S-transferase (GST, pGEX-2T vector). Tilapia recombinant IGF-II protein was purified and characterized in E. coli. The fusion protein was also digested with thrombin and appeared as a recombinant IGF-II polypeptide single band with a molecular mass of 7 kD. The recombinant tilapia IGF-II protein biological function was measured by stimulation of [3H]thymidine incorporation. The assay concentration was set up from 0 to 120 nM to stimulate tilapia ovary cell line (TO-2) significantly to uptake thymidine. The results suggest that the recombinant IGF-II protein was dose dependent.

Chen, J. Y., Tsai, H. L., Chang, C. Y., Wang, J. I., Shen, S. C., and Wu, J. L. (1998). Isolation and characterization of tilapia (Oreochromis mossambicus) insulin-like growth factors gene and proximal promoter region. DNA Cell Biol 17, 359-76.
To understand the molecular mechanism which controls the transcription of the insulin-like growth factors (IGFs) gene, we have cloned and sequenced the cDNA for the proximal promoter region of the tilapia IGFs gene and have characterized its activity by chloramphenicol acetyltransferase (CAT) transient transfected expression assays. Tilapia (Oreochromis mossambicus) IGF-I cDNA (549 bp) was amplified by PCR from single-stranded cDNA of growth hormone (GH)-induced liver RNA using a pair of oligonucleotides specific for fish IGF-I as amplification primers. Tilapia IGF-I and IGF-II 5' termini were analyzed by rapid amplification of cDNA 5' ends (5'RACE). Analysis of the 5'RACE results revealed two transcription start sites in IGF-I and one transcription start site in IGF-II. Different fragments of the 5' flanking region were transfected into human lung adenocarcinoma cells. In the cell line, maximum promoter activity was located in the distal 657 basepairs of the IGF-I 5' flanking region and in the distal 450 basepairs of the IGF-II 5' flanking region. The in vivo actions of the IGFs promoter on developmental stage expression were investigated further in transgenic zebrafish in which an IGFs promoter-driven green fluorescent protein (GFP) encoding the cDNA transgene was microinjected into embryos. Morphologic and RT-PCR studies of the transgenic zebrafish indicated that IGF-I promoter-driven GFP transcripts appeared for the first time in the 1-K-cell stage and the IGF-II promoter-driven GFP transcripts appeared for the first time in the 32-cell stage. Fluorescent (GFP) distribution was apparent within 48 h in IGF-II- transgenic zebrafish embryos, especially in eye, muscle, corpuscle, floor plate, horizontal myoseptum, yolk sac extension, and yolk sac. These results indicate that the IGF-I and IGF-II promoters are active in tissue and in a development-specific manner. Our findings also indicate that the IGF-II promoter influences the growth of fish embryos earlier than does IGF-I, and IGF-II has higher levels of expression than does IGF-I. These results suggest that the IGF-II promoter plays a growth factor role in teleost embryo development.

Chiayvareesajja, J., Roed, K. H., Eknath, A. E., Danting, J. C., De Vera, M. P., and Bentsen, H. B. (1999). Genetic variation in lytic activities of blood serum from Nile tilapia and genetic associations with survival and body weight. Aquaculture 175, 49-62.
A study was carried out on lysozyme activity and spontaneous haemolytic (SH) activity of blood serum from 388 individuals of Nile tilapia (Oreochromis niloticus) coming from 42 full-sib groups within 21 paternal half-sib groups. The lysozyme activity was measured at both 15 degrees C and 30 degrees C incubation temperatures, whereas SH activity was measured at 30 degrees C incubation temperature, Significant variation in lysozyme activity was detected between half-sib groups at 30 degrees C incubation temperature, but not at 15 degrees C incubation temperature and not for SH activity. Significant variation was found between full-sib groups for all parameters. The estimated heritabilities of lysozyme activity were relatively high (0.6-0.7) at 30 degrees C incubation temperature and intermediate (about 0.3) at 15 degrees C incubation temperature. The heritability estimate of SH activity was zero according to estimates based both on the sire component of variance and on variance components from an individual animal model, whereas the estimate based on the dam component of variance was about 0.7 and highly significant, Survival and growth were recorded after a grow-out period of 120 days in individuals from a parallel set of samples from the same sib families. Significant negative correlations were found between least-squares means in the parallel sib groups for lysozyme activity and survival rates for both half-sib groups (r = -0.53; P = 0.01) and full-sib groups (r = -0.32; P = 0.04). No significant correlations were found between SH activity and survival rate nor between lytic activities and body weight at harvest. (C) 1999 Elsevier Science B.V. All rights reserved.

Chimbari, M. J., Ndamba, J., and Madsen, H. (1996). Food selection behaviour of potential biological agents to control intermediate host snails of schistosomiasis: Sargochromis codringtoni and Tilapia rendalli. Acta Trop 61, 191-9.
The food selection behaviour of two fish species indigenous to Zimbabwe (Tilapia rendalli and Sargochromis codringtoni) was studied under laboratory conditions with a view to considering them as biological agents for snail control. Six glass aquaria were set up and divided into two sets each with two aquaria. One S. codringtoni was introduced into each aquarium of the first set while one T. rendalli was introduced into each aquarium of the other set. In one of the aquaria of each set the fish were supplied with snails and trout food. Snails and weeds were provided, but trout food was excluded in the second aquarium of each set while the third aquarium for each set was provided with trout food, snails and weeds. A fourth aquarium with weeds and snails but no fish was set up as a control. Data collected over 9 weeks showed that T. rendalli was primarily herbivorous while S. codringtoni was shown to be malacophagous. Presence of trout food made no difference in the snail-eating habit of S. codringtoni or the weed- eating behaviour of T. rendalli. However, trout food seemed to be a good protein supplement to T. rendalli as the fish with access to trout food gained more weight and length.

Chistova, M. N. (1971). [Hormonal effects on vitellogenesis and fertility rates in tilapian fish, Tilapia mossambica Peters]. Dokl Akad Nauk SSSR 200, 1479-82.

Chmilevskii, D. A., and Ivoilov, A. A. (1978). [Effect of irradiation on early gametogenesis in Tilapia]. Tsitologiia 20, 1264-8.
The 10 day old fries of Tilapia mossambica Peters were irradiated with 350 R dose. Dynamics of germ cells in control and after irradiation was studied. In 10 day old fry primordial germ cells and gonial cells were observed; in 15 days--mainly gonial cells were seen; in 20 days part of gonial cells move in the early prophase of meiosis; in 25 days gonial cells and oocytes of early prophase of meiosis are seen; in 30 days oogonial cells, oocytes of early prophase of meiosis and of previtellogenesis are observed. After irradiation of 13--14 day old fries some anomalies of mitosis were observed. But mass destruction of germ cells took place during the pachytene stage in 25 day old fries. The causes of the destruction of germ cells are discussed.

Chmilevskii, D. A., and Mel'nikova, I. V. (1988). [Effect of X-rays on the oogenesis of tilapia (Oreochromis mossambicus Peters.). IV. Irradiation of fish at the age of 30 and 60 days]. Ontogenez 19, l56-64.

Chou, B. S., and Shiau, S. Y. (1999). Both n-6 and n-3 fatty acids are required for maximal growth of juvenile hybrid tilapia. North American Journal of Aquaculture 61, 13-20.
An 8-week feeding experiment was conducted to provide preliminary information on essential fatty acid requirements of hybrid tilapia (female Nile tilapia Oreochromis niloticus x male blue tilapia O. aureus). Seven semipurified diets containing 30% crude protein from casein with 3.2 kcal available energy/g were supplemented with 5% of either lard (L), corn oil (C), cod liver oil (F), lard and corn oil (1:1, L-C), lard and cod liver oil (1:1, L-F), corn oil and cod liver oil (1:1, C-F), or lard, corn oil, and cod liver oil(1:1:1, L- C-F). Each diet was fed to three replicate groups of fish initially weighing 0.84 +/- 0.02 g (mean +/- SD) in 60-L aquaria connected as a closed recirculating-water system containing freshwater at 25 +/- 1 degrees C. Results indicate that significantly (P < 0.05) higher weight gain, feed efficiency (FE), protein efficiency ratio (PER), and protein deposition (PD) were associated with fish fed the diet supplemented with F. Among groups fed diets containing F, weight gain was significantly higher in fish fed L-C-F than in fish fed L-F and F. Fish fed L-C-F had significantly higher FE and PER values than those fed F, LF or C-E Protein deposition was significantly better in fish fed GC-F than in fish fed L-E Fatty acid compositions of liver and muscle in fish generally reflected the composition of the diet. These data suggest that n-3 highly unsaturated fatty acid as well as n-6 fatty acid are essential for maximum growth of juvenile hybrid tilapia.

Chrappa, V., and Sabo, V. (1999). Feeding meals of housefly larvae and pupae to the Nile tilapia (Oreochromis niloticus). Czech Journal of Animal Science 44, 81-85.
Two trials were conducted to study the feeding of meals made of housefly larvae and pul,ne to the Nile tilapia (Oreochromis niloticus) as a fifty-percent and full replacement of fish meal in granular isoprotein feed mixtures. Formulations of these feeds ate shown in Tabs. I and II. Trial No. I (started on 28th May 1996) involved 25 tilapias in a group of average live weight of 46.7 g and body length 105 nm. The trial lasted 28 weeks. Trial No. ? (started on 18th July 1996), lasting 46 weeks. involved fish with initial live weight of 16.6 g and body length 60 mm. The group comprised 30 individuals. Each group was kept in a 200-liter aquarium. Water temperature ranged from 23 to 25 degrees C. The aquaria were filled with new water. in about 10-day intervals. The feeding of both types of meals at both replacements did not significantly influence the live weight and body length of Fish (P > 0.05); a trend of higher live weight was observed in experimental groups (Figs. 1 and 7). Feed conversion was lower in the meal of housefly larvae (by 12.0 and 4.7%) and higher iii that of housefly pupae (by 28.6 and 21.1%). Fish mortality was not influenced by feeding these meals. Caress analyses showed that gill weight significantly (P < 0.05) decreased as a result of feeding the meal of housefly larvae (by 21.9 and 13.7%) while the weight of inedible viscera increased (P < 0.05) after applications of both meals: by 16.9 and 22.0% in trial 1 and by 55 and 26.7% in trial 2.

Clarke, W. C. (1973). Sodium-retaining bioassay of prolactin in the intact teleost Tilapia mossambica acclimated to sea water. Gen Comp Endocrinol 21, 498-512.

Clarke, W. C. (1973). Disc-electrophoretic identification of prolactin in the cichlid teleosts Tilapia and Cichlasoma and densitometric measurement of its concentration in Tilapia pituitaries during salinity transfer experiments. Can J Zool 51, 687-95.

Clarke, W. C., Farmer, S. W., and Hartwell, K. M. (1977). Effect of teleost pituitary growth hormone on growth of Tilapia mossambica and on growth and seawater adaptation of sockeye salmon (Oncorhynchus nerka). Gen Comp Endocrinol 33, 174-8.

Cockson, A. (1970). Some polysaccharides in the mucus-cells in the gills of Tilapia shirana chilwae Trewavas Pisces, Cichlidae). Cellule 68, 205-10.

Colombo, L., Bern, H. A., Pieprzyk, J., and Johnson, D. W. (1972). Corticosteroidogenesis in vitro by the head kidney of Tilapia mossambica (Cichlidae, Teleostei). Endocrinology 91, 450-62.

Cuvin-Aralar, M. L., and Aralar, E. V. (1993). Effects of long-term exposure to a mixture of cadmium, zinc, and inorganic mercury on two strains of tilapia Oreochromis niloticus (L.). Bull Environ Contam Toxicol 50, 891-7.

Dadzie, S., and Hyder, M. (1976). Compensatory hypertrophy of the remaining ovary and the effects of methallibure in the unilaterally ovariectomized Tilapia aurea. Gen Comp Endocrinol 29, 433-40.

Dange, A. D. (1986). Branchial Na+ -K+ -ATPase activity in freshwater or saltwater acclimated tilapia, Oreochromis (Sarotherodon) mossambicus: effects of cortisol and thyroxine. Gen Comp Endocrinol 62, 341-3.
The ability of cortisol to stimulate branchial Na+ -K+ -ATPase activity in tilapia was further augmented by thyroxine. The effects of hormonal treatments were greater in the saltwater acclimated fish than in the freshwater acclimated ones.

Dauder, S., Young, G., and Bern, H. A. (1990). Effect of hypophysectomy, replacement therapy with ovine prolactin, and cortisol and triiodothyronine treatment on prolactin receptors of the tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 77, 378-85.
The effects of hypophysectomy and subsequent replacement therapy with ovine prolactin (oPRL) on specific binding of 125I-oPRL to gill, kidney, and liver membranes of male tilapia were examined. The possible control of prolactin receptors by cortisol (F) and triiodothyronine (T3) was also studied using intact animals. In gill and kidney, hypophysectomy resulted in a significant decrease in specific binding that was partially restored (threefold increase) by three injections of oPRL, suggesting a role of the pituitary in the control of prolactin receptors. However, removal of the pituitary and replacement therapy with oPRL had no effect on binding by liver membranes. Cortisol and T3 treatment, alone or in combination, did not significantly affect prolactin binding by any of the tissues tested.

Dauder, S., Young, G., Hass, L., and Bern, H. A. (1990). Prolactin receptors in liver, kidney, and gill of the tilapia (Oreochromis mossambicus): characterization and effect of salinity on specific binding of iodinated ovine prolactin. Gen Comp Endocrinol 77, 368-77.
Specific binding of 125I-ovine prolactin (oPRL) to microsomal fractions from gill, kidney, and liver of adult tilapia was determined. Specific binding varied among tissues, the highest values being displayed by kidney membranes. In the liver, the binding of oPRL was not strongly displaced by tilapia prolactins (tPRL177 and tPRL188), although tPRL177 was six times more potent than tPRL188. On the other hand, in kidney and gill membranes, the two tPRLs were equipotent. Tilapia PRLs showed low potency in competing for oPRL-binding sites when pregnant rat liver membranes were utilized. Tilapia growth hormone (tGH) and human growth hormone (hGH) displaced 125I-oPRL from liver as well as did tPRL177 but were not recognized well by renal or branchial receptors. Two 125I-oPRL- binding sites were detected in every tissue tested. These binding sites are subject to physiological regulation since adaptation to seawater resulted in a significant decrease in specific binding.

Davies, W., and Jackson, H. (1977). Chemosterilant action of niridazole on Tilapia mossambica (Sarotherodon mossambicus). Gen Pharmacol 8, 31-5.

de la Fuente, J., Guillen, I., Martinez, R., and Estrada, M. P. (1999). Growth regulation and enhancement in tilapia: basic research findings and their applications [In Process Citation]. Genet Anal 15, 85-90.
Growth manipulation in fish is one of the targets of gene transfer experiments. The aim is to produce strains with improved growth performance. The transfer of growth hormone transgenes has been successful in many fish species. Now detailed knowledge of the molecular events that control growth in fish is necessary in order to efficiently manipulate this process. We have selected tilapia for our studies because these species are suitable for basic research as well as for the development of improved strains for aquaculture. Here we review the results of basic and applied research in the field of growth control and manipulation in tilapia. Our experiments produced new scientific results on growth control in tilapia. These results were used to develop a new aquacultured line with improved growth performance. Many of these results are probably applicable to other teleosts.

de la Fuente, J., Guillen, I., Martinez, R., and Estrada, M. P. (1999). Growth regulation and enhancement in tilapia: basic research findings and their applications. Genetic Analysis-Biomolecular Engineering 15, 85-90.
Growth manipulation in fish is one of the targets of gene transfer experiments. The aim is to produce strains with improved growth performance. The transfer of growth hormone transgenes has been successful in many fish species. Now detailed knowledge of the molecular events that control growth in fish is necessary in order to efficiently manipulate this process. We have selected tilapia for our studies because these species are suitable for basic research as well as for the development of improved strains for aquaculture. Here we review the results of basic and applied research in the field of growth control and manipulation in tilapia. Our experiments produced new scientific results on growth control in tilapia. These results were used to develop a new aquacultured line with improved growth performance. Many of these results are probably applicable to other teleosts. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

de Vera, M. P., and Pocsidio, G. N. (1998). Potential protective effect of calcium carbonate as liming agent against copper toxicity in the African tilapia Oreochromis mossambicus. Sci Total Environ 214, 193-202.
The lipid peroxidative effects of copper sulfate singly (4 mg/l CuSO4.5H2O) and in combination with calcium carbonate (4 mg/l CuSO4.5H2O + 50 mg/l CaCO3) were determined in the liver of the African tilapia Oreochromis mossambicus following exposures of the fish to the chemicals for 24, 48, 72, 96 and 168 h. Lipid peroxidative effects of the treatment with calcium carbonate (50 mg/l CaCO3) and with a known hepatotoxicant, carbon tetrachloride (0.25 ml/l CCl4) were also determined. Fish not exposed to any chemical served as negative controls. The extent of lipid peroxidation was based on hepatic malondialdehyde (MDA) levels as assayed using the thiobarbituric acid reaction test. Results suggested the lipid peroxidative property of the copper salt which was associated with the toxic nature of the heavy metal, although, this effect was not as potent as that of CCl4. Findings also indicated a measure of protection against copper hepatotoxicity provided by the addition of calcium carbonate as a liming agent in the water.

Delicio, H. C., and Vicentini-Paulino, M. L. (1993). 2-deoxyglucose-induced food intake by Nile tilapia, Oreochromis niloticus (L.). Braz J Med Biol Res 26, 327-31.
The alimentary and glycemic responses to cytoglycopenia were studied in thirty-one Nile tilapia alevins of indeterminate sex and age, measuring on average 10.67 +/- 0.82 cm. The cytoglycopenia was provoked by ip injection of 60 mg/kg 2-deoxy-D-glucose (2-DG, N = 16). The control group (N = 15) was submitted to ip injection of 0.2 ml saline. Blood samples for glucose determination were obtained before and three hours after drug administration by cardiac puncture. Food was then offered ad libitum. One hour later the animals were sacrificed and their stomachs removed. The difference in wet weight between full and empty stomach was utilized to quantify the food intake. Median food intake was 0.3877 g for the fish treated with 2-DG and 0.107 g for the animals injected with saline. This difference was statistically significant by the Mann- Whitney test (P 0.05). The median values of blood glucose levels before drug injection were 46.19 mg/100 ml in the 2-DG-treated fish and 44.54 mg/100 ml in the control group. Three hours after drug administration, the values were 48.64 mg/100 ml in the experimental group and 56.90 mg/100 ml in the control group. The difference between the values of blood glucose before and after the drug was not significant for either group. We conclude that glucoprivation provokes food intake in fish and that the same glucoprivation was not sufficient to provoke hyperglycemia.

Desai, A. K., Joshi, U. M., and Ambadkar, P. M. (1984). Histological observations on the liver of Tilapia mossambica after exposure to monocrotophos, an organophosphorus insecticide. Toxicol Lett 21, 325-31.
The histological changes in the liver of Tilapia mossambica were observed after exposure to a sublethal level (2.5 ppm) of monocrotophos. The changes observed after 2 days of exposure were characterized by necrosis and vacuolation of hepatocytes. Fatty degeneration was observed after 10 days of exposure. However, normalization of histological picture was evident after 15 days of treatment, though some patches of degenerating zones were also found to exist concomitantly. A wave of secondary intensively degenerative changes was observed from 30 days up to 45 days of experimentation. The possible significance of histological lesions and adaptation to exposure after sublethal doses as well as continuous exposure are discussed.

Dharmamba, M., Handin, R. I., Nandi, J., and Bern, H. A. (1967). Effect of prolactin on freshwater survival and on plasma osmotic pressure of hypophysectomized Tilapia mossambica. Gen Comp Endocrinol 9, 295-302.

Dharmamba, M., and Nishioka, R. S. (1968). Response of "prolactin-secreting" cells of Tilapia mossambica to environmental salinity. Gen Comp Endocrinol 1, 409-20.

Dharmamba, M. (1970). Studies of the effects of hypophysectomy and prolactin on plasma osmolarity and plasma sodium in Tilapia mossambica. Gen Comp Endocrinol 14, 256-69.

Dharmamba, M., and Maetz, J. (1972). Effects of hypophysectomy and prolactin on the sodium balance of Tilapia mossambica in fresh water. Gen Comp Endocrinol 19, 175-83.

Dharmamba, M., Mayer-Gostan, N., Maetz, J., and Bern, H. A. (1973). Effect of prolactin on sodium movement in Tilapia mossambica adapted to sea water. Gen Comp Endocrinol 21, 179-87.

Dharmamba, M., Bornancin, M., and Maetz, J. (1975). Environmental salinity and sodium and chloride exchanges across the gill of Tilapia mossambica. J Physiol (Paris) 70, 627-35.
10 Freshwater-(FW)-adapted, one-third seawater (1/3 SW)-adapted and seawater (SW) adapted Tilapia mossambica were compared for their branchial Na+ influx and efflux as well as Cl- efflux. Na+ and Cl- effluxes were identical. Rates of effluxes were in 1/3 SW- and in SW- adapted fish 10 times and 200 times higher respectively than in FW specimens. 20 Shock due to handling and transfer to small experimental chambers induced, within 20 to 45 min., a considerable increase in Na+ efflux and a more discrete augmentation of the Na+ influx. 30 Branchial Mg++-and Na+-K+ activated ATPase activities increased significantly upon adaptation from FW to 1/3 SW. No significant increase was apparent upon adaptation from 1/3 SW to SW. 40 The trans-branchial potential observed in SW Tilapia resembled the pattern previously described in other species of teleosts.

Dharmamba, M., and Maetz, J. (1976). Branchial sodium exchange in seawater-adapted Tilapia mossambica: effects of prolactin and hypophysectomy. J Endocrinol 70, 293-9.
The effects of exogenous prolactin and hypophysectomy were tested on Na exchange across the gills of Tilapia mossambica adapted to sea-water. Exogenous prolactin produced a 75% decrease of both total Na influx and Na efflux. Total Na influx was measured simultaneously with the drinking rate. Water ingestion stopped almost completely in prolactin- treated fish. Thus branchial net excretion flux of Na was reduced 75% by prolactin. Hypophysectomy produced a 50% inhibition of Na efflux across the gill.

Dickson, B. C., Yang, H., Pohajdak, B., and Wright, J. R., Jr. (1998). Quantification of tilapia islets: a direct relationship between islet cell number and body mass. Transplant Proc 30, 621-2.

Ding, J. L., Hee, P. L., and Lam, T. J. (1989). Differential susceptibility of a fish, tilapia Oreochromis mossambicus (Teleostei, Cichlidae) to hepatocarcinogenesis by diethylnitrosamine and methylazoxymethanol acetate. Carcinogenesis 10, 493-9.
Oreochromis mossambicus, commonly known as tilapia, is a freshwater teleost with a wide tolerance to environmental conditions. Multiple focal lesions in the liver were observed 2 months after cessation of a one-month long treatment with 100 p.p.m. diethylnitrosamine. Cells were small and compact and arranged in sheets. Ultrastructurally, these cells have abundant endoplasmic reticulum, round mitochondria, less conspicuous golgi apparatus and fat droplets. Other organs like the intestines, spleen, kidneys, ovaries and pituitary appeared normal. Two liver inducible enzymes, gamma-glutamyl transferase and tyrosine aminotransferase were elevated by 5- and 3-fold respectively. Aggressive migration of hepatocytes was observed in tumorigenic liver explants. Vitellogenesis and early embryological development appeared unaffected as the female fish spawned during hepatocarcinogenesis. However, their fry were stunted and short-lived. To compare the susceptibility of tilapia to another hepatocarcinogen, the fish were also treated with methylazoxymethanol acetate at 10 p.p.m. for 0.5-1 h. However, methylazoxymethanol acetate was too toxic and 75% of the fish succumbed 1 day after treatment. Moreover, after 2 months post- treatment, neither tumors nor change in enzyme activities were observed in any organ. These results suggest that tilapia could be a useful model for screening and differentiating carcinogens since they could develop liver tumors within only 2 months after treatment with diethylnitrosamine.

DiStefano, J. J., 3rd, Ron, B., Nguyen, T. T., Weber, G. M., and Grau, E. G. (1998). 3,5,3'-Triiodothyronine (T3) clearance and T3-glucuronide (T3G) appearance kinetics in plasma of freshwater-reared male tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 111, 123-40.
Distribution and metabolism of the thyroid hormone 3,5, 3'-l- triiodothyronine (T3) were studied in several ways to gain insights into these processes in the warm water fish tilapia Oreochromis mossambicus. Trace doses of 125I-labeled T3 (T*3)1 were injected intraarterially, extraarterially, or intraperitoneally in freshwater- reared male tilapia to explore plasma clearance kinetic responses to these different input modalities. Multicompartmental analysis of the plasma clearance data indicated a kinetic distribution of T*3 much like that reported for the rat and human, with about 2% of total body T*3 in plasma, 5% in rapidly exchanging tissues such as kidney and liver, and 93% in slowly exchanging tissues such as muscle. However, plasma clearance rates (PCR, 5.37 mL/h . 100 g body wt) and plasma appearance rates (PAR3 = PCR x [T3] plasma = 36.3 ng/h . 100 g body wt) were quite different than these indices in rat and human and 5 to 50 times larger than values reported for rainbow trout. On a whole-body basis, normalized for body weight, the tilapia we studied produced and accumulated much more T3 than rat, human, or rainbow trout. Enzymatic and chromatographic analyses of the plasma clearance data samples indicated substantial production of labeled glucuronide, but not sulfate, conjugates of iodothyronines (TiG) of unknown origin appearing in plasma. The TiG appeared beginning a few hours postinjection, peaked at 6 hours, and yielded a predicted steady-state TiG level of 8.3% of the T3 level in plasma. In contrast, in published studies, no conjugates were detected in rainbow trout plasma from 2 to 24 h after iv injection of T*3, T*4, or reverse-T*3, although conjugates of all were present in bile. To our knowledge, although T3 and T4 sulfate conjugates are present in the sera of several mammals, this is the first quantification of iodothyronine glucuronides reported in blood of any species under normal conditions. This might have physiological significance for the tilapia, with T3G providing a reversible storage form of T3 in blood, as has been suggested for sulfate conjugates of T3 and T4 in blood of several mammals. Copyright 1998 Academic Press.

Drakenberg, K., Sara, V. R., Lindahl, K. I., and Kewish, B. (1989). The study of insulin-like growth factors in Tilapia, Oreochromus mossambicus. Gen Comp Endocrinol 74, 173-80.
Whole and acid-separated serum samples from fed, starved, and refed Tilapia were analyzed for insulin-like growth factors 1 (IGF-1) and 2 (IGF-2) using human fetal brain radioreceptorassay (RRA-IGF-1), rat liver membrane radioreceptorassay (RRA-IGF-2), and radioimmunoassay (RIA-IGF-1). Triidothyronine (T3) and thyroxine (T4) levels were measured by commercial kits for RIA. For serum separation, acid Sephadex G-50 and G-100 and neutral Sephadex G-200 columns were used. Whole serum and separated serum cross-reacted in RRA-IGF-1, but only slightly in RRA-IGF-2. IGF activity eluted in two peaks after acid G-50 chromatography. Peak I eluted at the void volume, and peak II eluted with an apparent molecular weight of approximately 7 kDa. The 7 kDa activity did not cross-react in RIA-IGF-1 excluding identity with human intact or truncated IGF-1, but did suggest the presence of an IGF-1 variant form. Whole serum was separated over a neutral G-200 column, and all activity eluted at the void volume indicated an apparent molecular weight equal to or greater than 250 kDa. No IGF-binding activity was displayed by either whole serum or peak I after acid G-50 chromatography. Despite significant changes in body weight, an influence of starvation and refeeding on serum IGF activity could not be established. No correlation was seen between serum IGF and T3 and T4 levels.

du Preez, H. H., and van Vuren, J. H. (1992). Bioconcentration of atrazine in the banded tilapia, Tilapia sparrmanii. Comp Biochem Physiol C 101, 651-5.
1. The bioconcentration of atrazine was determined in the liver, muscle, heart, gonads and brain of Tilapia sparrmanii exposed to high concentrations of atrazine. 2. The highest concentrations were recorded in the ovaries (50.6 micrograms/g) and in the liver (40.1 +/- 5.5 micrograms/g). This may be attributed to the higher lipid content of these organs, while the liver also accumulates atrazine as a result of its detoxification function. 3. The bioaccumulation factors for atrazine in the liver, muscle, heart, gonads and brain ranged from 0.9 to 20.0. Bioconcentration of atrazine in banded tilapia was found to be low, even after exposure to external atrazine concentration much higher than detected in natural surface water.

du Preez, H. H., van Rensburg, E., and van Vuren, J. H. (1993). Preliminary laboratory investigation of the bioconcentration of zinc and iron in selected tissues of the banded tilapia, Tilapia sparrmanii (Cichlidae). Bull Environ Contam Toxicol 50, 674-81.

Duponchelle, F., Cecchi, P., Corbin, D., Nunez, J., and Legendre, M. (1999). Spawning season variations of female Nile Tilapia, Oreochromis niloticus, from man-made lakes of Cote D'Ivoire. Environmental Biology of Fishes 56, 375-387.
The spawning season of Oreochromis niloticus females was studied over two annual cycles in 6 small agropastoral and 2 large hydroelectric reservoirs of Cote d'Ivoire (Ayame and Kossou), situated between 5 and 10 degrees N of latitude. Reproduction occurred during a marked season in the agropastoral reservoirs and in Lake Ayame, whereas it was continuous in Lake Kossou. Spawning season differed between reservoirs and among years within the same reservoir. Seasonal changes in temperature, rainfall, day length, chlorophyll a concentration and water level often corresponded with changes in the annual spawning cycle. However, annual periodicity of O. niloticus reproduction was more likely influenced by the ephemerides cycle.

Eckstein, B. (1970). Metabolic pathways of steroid biosynthesis in ovarian tissue of a teleost, Tilapia aurea. Gen Comp Endocrinol 14, 303-12.

Eckstein, B., and Katz, Y. (1971). Steroidogenesis in post- and pre-spawned ovaries of a cichlid fish, Tilapia aurea. Comp Biochem Physiol A 38, 329-38.

Edery, M., Young, G., Bern, H. A., and Steiny, S. (1984). Prolactin receptors in tilapia (Sarotherodon mossambicus) tissues: binding studies using 125I-labeled ovine prolactin. Gen Comp Endocrinol 56, 19-23.
The binding of 125I-labeled ovine prolactin (oPRL) to membrane preparations of tissue from freshwater-adapted tilapia (Sarotherodon mossambicus) was examined. Liver, ovary, and testis showed a relatively high specific binding (5-10%). A lower specific binding occurred consistently in intestine and gill tissue, and inconsistently in urinary bladder and kidney preparations. Desaturation experiments with MgCl2 indicated that a majority of the PRL receptors were already occupied by endogenous PRL. Scatchard analysis of liver binding gave a dissociation constant of 0.6 X 10(-9) M and a capacity of 207 fmol/mg protein.

El Gamal, A. R. A., Davis, K. B., Jenkins, J. A., and Torrans, E. L. (1999). Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus (L.). Journal of the World Aquaculture Society 30, 269-275.
Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus, was investigated by heat shock, cold shock, hydrostatic pressure, and/or chemicals (cytochalasin A, B, and D). Additionally, efficacy of combined protocols was determined. Heat shock 10 min after fertilization induced triploidy when incubation temperature was 24 C but not when incubation temperature was 31 C. Heat shock of 40-41 C at 4-6 min after fertilization was effective in inducing up to 100% triploidy with hatchability similar to controls. Cold shock at 13 C for 45 min five min after fertilization induced 85-100% triploids. Heat shock and multiple heat shocking were the most effective treatments for the induction of tetraploidy. Two heat treatments of 41 C applied at 65 and 80 min after fertilization for 5 min each produced approximately 80% tetraploidy in hatched fry. Immersion of fertilized eggs in cytochalasin A, B, or D at concentrations up to 10 mu g/L applied at various times and durations was ineffective in inducing triploidy or tetraploidy.

el Safi, S. H., Haridi, A. A., and Rabaa, F. M. (1985). The food of the larvivorous fish Gambusia affinis (Baird and Girard) and Oreochromis (formerly Tilapia) niloticus (Linnaeus) in Gezira irrigation canals. J Trop Med Hyg 88, 169-74.
The food of both Gambusia affinis and Oreochromis niloticus was studied. Organisms eaten by both species of fish are tabulated, together with the amounts eaten during the various months of the year. G. affinis larger than 25 mm are carnivorous and become more so with age. Food selection by G. affinis depends on the availability of food items rather than choice. It showed a marked preference for mosquito larvae. O. niloticus smaller than 150 mm were markedly carnivorous, but this decreased with age. Only small fish of this species are useful for the biological control of mosquitoes. Fish larger than 150 mm showed a marked preference for higher aquatic macrophytes.

el-Bedawey, A. E., el-Sherbiny, A. M., Zaki, M. S., and Khalil, A. H. (1985). The effect of certain antibiotics on the keeping quality of bolti fish (Tilapia nilotica). Nahrung 29, 665-70.
Fresh bolti fish (Tilapia nilotica), caught in the river Nile was immersed in 10 and 20 ppm tetracycline (TC) solutions for 10 and 15 min respectively and in 500 and 1000 R.U. nisin/g fish for 20 and 30 min respectively. Total volatile bases (TVN) showed in both fish treated with TC and nisin a slow increase at the first stage and after that a fast increase. There was an increase in trimethylamine (TMA) during the storage period, but the fish treated with TC and nisin contained less TMA than the control. Starting from 6 h the residual TC decreased gradually till the third day, when it disappeared completely. There is no change in pH values in both control and treated fish. Optical density (OD) of gills extract increased gradually as the storage period progresses. The treated fish showed lower OD values than the controls. The refractive index of muscle fluids and the OD of muscle extract showed no significant differences between the control and treated fish.

el-Bedawey, A. E., Zaki, M. S., el-Sherbiney, A. M., and Khalil, A. H. (1985). The effect of certain antibiotics on bolti fish (Tilapia nilotica) preservation. Nahrung 29, 303-8.
The shelf life of bolti fish (Tilapia nilotica) caught in the river Nile, has been successfully prolonged for about 9 days by dipping in tetracycline (TC) or nisin solution followed by refrigeration, although the initial microbial contamination in the fresh fish was very high. The caught fish were gutted and treated with 10 and 20 ppm TC solutions for 10 and 15 min by dipping, and with 500 and 1000 R.U. nisin/g fish for 20 and 30 min. The treated and control fish samples, were stored and refrigerated at (4 +/- 1) degree C for 12 days. Total bacterial counts, the most probable number of coliform bacteria and lactic acid bacteria in the fish treated with TC or nisin, were lower than those of the control, especially at 20 ppm TC, 15 min dipping, and 1000 R.U. nisin/g, 30 min. Further more TC was more effective against yeasts and moulds. This result suggest that antibiotics would help in transporting chilled fish from the highdam lake in Aswan to Cairo (about 900 km). According to the present results it may be recommended to use the antibiotic TC, with the concentration of 20 ppm for 15 min dipping, for prolonging the shelflife of bolti fish. The presence and increase of coliform bacteria in fish, draw the attention to the necessity of hygienic measures when dealing with such fish until to the consumption.

El-Demerdash, F. M., and Elagamy, E. I. (1999). Biological effects in Tilapia nilotica fish as indicators of pollution by cadmium and mercury. International Journal of Environmental Health Research 9, 173-186.
Fish samples of Tilapia nilotica obtained from Lake Maryout were used to investigate the relationship between heavy metals and biological effects due to the industrial contaminations in the lake. Samples were examined for the activities of acetylcholinesterase, alkaline phosphatase and glutathione S- transferase. Meanwhile, levels of cadmium (Cd) and mercury (Hg) were determined in both fish and water. Also, the electrophoretic patterns of proteins were presented as well as the amino acid composition of fish proteins. Results obtained revealed that the activities of all studied enzymes were markedly inhibited. Maryout samples contained higher concentrations of Hg and Cd than Nozha samples. Marked differences in electrophoretic patterns of proteins prepared from Maryout and Nozha fish samples were found. The nutritional quality of Maryout fish proteins was lower than that of Nozha samples due to the lower content of essential amino acids. Results obtained from field and laboratory exposures can give a useful indication for a proper use of biochemical responses as biomarkers in monitoring heavy metal pollution.

El-Dib, M. A., El-Elaimy, I. A., Kotb, A., and Elowa, S. H. (1996). Activation of in vivo metabolism of malathion in male Tilapia nilotica. Bull Environ Contam Toxicol 57, 667-74.

el-Elaimy, I. A., Sakr, S. A., el-Saadany, M. M., and Gabr, S. A. (1993). Electron microscopic study of the liver of Tilapia nilotica exposed to neopybuthrin. Bull Environ Contam Toxicol 50, 682-8.

el-Gendy, K. S., Aly, N. M., and el-Sebae, A. H. (1998). Effects of edifenphos and glyphosate on the immune response and protein biosynthesis of bolti fish (Tilapia nilotica). J Environ Sci Health B 33, 135-49.
The effects of 1/1000 field recommended concentration of the organophosphorus compounds; edifenphos and glyphosate on the immune response and protein contents were investigated after different time intervals. The cell mediated immune response assessed by proliferative response of splenocytes to mitogens; phytohemagglutinin (PHA) and concanavalin A (Con A) for T cell and lipopolysaccharide (LPS) for B cell decreased significantly in tems of the level of stimulation index in the treated fish and reached maximal depression after 4 weeks. Humoral immunity assessed as splenic antibody plaque forming cells (PFC) measured after 5 days in vitro immunization to sheep erythrocytes (SRBC's) were suppressed in a concentration dependent pattern by the two compounds. The estimated ED50 for the PFC/10(6) cells of edifenphos and glyphosate were 1.48 x 10(-2) uM and 1.65 x 10(-2) uM respectively. The data also showed that serum antibody titres in the treated fish were decreased in a time dependent manner. The total protein content of serum treated with the two pesticides was decreased after different time periods compared with control. The blood serum of treated and untreated Tilapia nilotica were analyzed electrophoretically for protein components and the percentage of proteins in each fraction was determined.

el-Sayed, M. M., Ezzat, A. A., Kandeel, K. M., and Shaban, F. A. (1984). Biochemical studies on the lipid content of Tilapia nilotica and Sparus auratus. Comp Biochem Physiol [B] 79, 589-94.
Seasonal variations of total lipids, free fatty acids, triglycerides, phospholipids and cholesterol content of the freshwater fish Tilapia nilotica and the marine fish Sparus auratus were investigated. Male fish of S. auratus showed higher muscular and hepatic total lipids and hepatic free fatty acids than those of T. nilotica (P less than 0.05). The mean differences in gonadal male lipids of the two species were not significant. Tilapia nilotica female fish showed a significantly higher content of hepatic free fatty acids, phospholipids and cholesterol (P less than 0.01, 0.01, 0.05 respectively) and gonadal total lipids, triglycerides, and cholesterol (P less than 0.05) than those of S. auratus females. In contrast S. auratus females exhibited higher muscular total lipids, triglycerides, phospholipids and cholesterol content (P less than 0.01, 0.05, 0.02, 0.05, respectively) and gonadal phospholipids (P less than 0.05) than those of the T. nilotica females. In general hepatic and gonadal lipids of freshwater fish T. nilotica were higher than those of the marine fish S. auratus, and in contrast the marine fish contained higher muscular lipids than the freshwater fish.

El-Sayed, A. F. M. (1999). Alternative dietary protein sources for farmed tilapia, Oreochromis spp. Aquaculture 179, 149-168.
Tilapia are widely cultured in the tropical and subtropical regions of the world and constitute the third largest group of farmed finfish, only after carps and salmonids, with an annual growth rate of about 11.5%. Global production of farmed tilapia has increased more than three-fold since 1984, from 186,544 m to 659,000 m, representing about 4.48% of total farmed finfish in 1995, with a value of US$925 million. Feeding represents over 50% of the operational costs of aquaculture. The shortage in world production of fish meal (the main conventional protein source), coupled with increased demand for fish meal in feeds for livestock and poultry is likely to reduce the dependence on fish meal as a single protein source in aquafeeds. Therefore, fish nutritionists have made several attempts to partially or totally replace fish meal with less expensive, locally available protein sources. The present review presents alternative dietary protein sources for tilapia, with emphasis on fishery by-products, terrestrial animal by-products, oilseed plants, aquatic plants, single cell proteins, grain legumes, plant protein concentrates and cereal by-products. The nutritive values, inclusion levels, constraints and economic evaluation of these sources are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

El-Sharouny, H. M., and Badran, R. A. (1995). Experimental transmission and pathogenicity of some zoosporic fungi to Tilapia fish. Mycopathologia 132, 95-103.
Seventeen fungal species belong to sex genera were recovered from the four organs of Tilapia fish and the most common were Saprolegnia ferax, S. diclina, Achlya dubia, A. americana, A. racemosa and A. flagellata, Dictyuchus sterile, Pythium undulatum and Aphanomyces sp. Severe infection followed by death of all fish was incited by S. parasitica and S. ferax through experiment I. 30-70% of T. nilotica and T. galileae were killed through experiment II by S. parasitica and S. ferax. T. galileae was more susceptible to fungal infection than T. nilotica.

el-Zanfaly, H. T., and Ibrahim, A. A. (1980). Boulti (Tilapia nilotica Linn.) fish paste. 2. Bacteriological studies of the raw fish and the produced paste. Z Ernahrungswiss 19, 163-5.
Total viable bacterial count reached 10(9) per gram of raw fish. It was decreased to 10(7) in fish paste and increased to 10(8)-10(9) after storage at 2-4 degrees C for 5 weeks. It was observed that fish paste showed higher counts when preserved in polyethylene bags than in aluminum tubes.

El-Zanfaly, H. T., and Ibrahim, A. A. (1982). Occurrence of bacterial pollution indicators in Boulti (Tilapia nilotica Linn.) fish. Z Ernahrungswiss 21, 246-53.
A study was made for the occurrence of coliform and streptococcal groups on the skin surface (32 samples), gills (32 samples), intestinal tract (4 samples) and raw fish flesh (4 samples) and raw fish flesh (4 samples) of Boulti fish (Tilapia nilotica Linn.), a fresh water fish caught from Nasser's Lake in Aswan. Streptococcus group was detected in 13 samples taken from fish surface, 12 samples out of 32 swabs from gills. All intestine samples and raw fish flesh were positive for the streptococcus group. Coliform organisms were detected at nearly 43% of skin or gill samples, 100% of intestine and raw fish flesh samples.

Eldar, A., Shapiro, O., Bejerano, Y., and Bercovier, H. (1995). Vaccination with whole-cell vaccine and bacterial protein extract protects tilapia against Streptococcus difficile meningoencephalitis. Vaccine 13, 867-70.
Formalin-killed Streptococcus difficile strains used as vaccines delivered intraperitoneally were able to protect tilapia against a challenge of 100 LD50. The protection obtained was not strain specific. A vaccine based on an S. difficile extract containing 50% protein conjugated to alum also protected tilapia challenged with a virulent S. difficile strain. Protection in tilapia was correlated with the development of specific agglutinins. Western blot analysis supported the hypothesis that only a few proteins act as protective antigens in both the whole-cell vaccine and the streptococcal extract. The high efficacy of these vaccines make them good candidates for the control of streptococcal fish meningoencephalitis.

Englander, E., and Moav, B. (1989). Cloning and characterization of a histone gene family in Tilapia fish. Biochim Biophys Acta 1007, 277-82.
Genomic organization and expression of a histone gene family in the Tilapia (Cichlidae) fish was determined. A genomic library was prepared; four clones containing the complete set of core histones were analyzed. These clones differed significantly in their restriction maps, although three of them revealed a uniform internal gene arrangement of the core histone genes. Differential expression between two of the cloned clusters was observed when the hybridization pattern of those clusters to various RNA preparations was compared. The copy number of histone genes was estimated to be 100 to 110 for haploid Tilapia genome.

Faisal, M., Popp, W., and Refai, M. (1987). [High mortality of the Nile tilapia Oreochromis niloticus caused by Providencia rettgeri]. Berl Munch Tierarztl Wochenschr 100, 238-40.

Faisal, M., Popp, W., and Refai, M. (1989). [Aeromonas hydrophila-related septicemia in the Nile tilapia Oreochromis niloticus]. Berl Munch Tierarztl Wochenschr 102, 87-93.
From diseased wild and cultured Oreochromis niloticus in Lower Egypt, 17 Aeromonas hydrophila isolates were recovered. The mortality was between 10% and 70% in among cultured fish. The course of the disease ran in an acute manner. For cultured fish, the disease outbreaks were found mainly in winter and for the wild Nile fish, mortalities were observed in late spring and summer. Additionally wild fish were affected with ectoparasites. The LD50 values of the isolates ranged between 10(3) and 10(7). Isolates of high virulence were resistant to 1 hr boiling and to the bactericidal effect of fresh normal guinea pig serum. Moreover, they did not agglutinate in acriflavin. Only the virulent isolates could agglutinate tilapia erythrocytes. The above effects were reversed for avirulent isolates while moderately virulent isolates showed no consistency in their reactions. Tube agglutination test using O and WC antisera prepared against 6 isolates versus O and WC antigens of 17 isolates indicated an antigenic heterogenicity of different isolates. While some isolates were identical, 4 antigens out of 17 did not react with any of the sera.

Falaye, A. E., and Jauncey, K. (1999). Acceptability and digestibility by tilapia Oreochromis niloticus of feeds containing cocoa husk. Aquaculture Nutrition 5, 157-161.
The acceptability, digestibility and nutrient utilization of feeds containing cocoa husk were determined for tilapia Oreochromis niloticus fingerlings reared in a recirculation system. Three semipurified isonitrogenous diets formulated to contain 0, 100 and 200 g kg(-1) of cocoa husk were fed to satiation three times daily. Although the feeds containing cocoa husk were acceptable to the fish, as indicated by their voracious consumption and positive weight gains, there were significant (P < 0.05) reductions in gross feed conversion efficiency with the cocoa husk feeds. Both apparent protein and dry matter digestibility were significantly (P < 0.05) reduced when 100 and 200 g kg(-1) cocoa husk was fed. Specific growth rates of 3.51 and 3.34% per day, resulting from the two cocoa husk feeds, respectively, were significantly (P < 0.05) lower than growth rates of control fish. Apparent net protein utilization was not significantly affected (P > 0.05) by the 100 g kg-L cocoa husk feed treatment. The consumption of the cocoa husk feeds could compensate for their low digestibility under acceptable fish yields and returns.

Falk, T. M., Abban, E. K., and Villwock, W. (1999). Population genetic analysis of the haemoglobins of the black- chinned tilapia. Journal of Fish Biology 55, 233-242.
Three highly heterogeneous haemoglobin phenotypes, each composed of 22 different haemoglobin components, were identified among 17 West African populations of Sarotherodon melanotheron. Natural populations from (1) Senegal, (2) Ivory Coast/Ghana/Togo/Benin, and (3) Congo were distinguished. The heterogeneity and specificity of these respiratory pigments was based on genetic variations at the globin chain coding loci. In total, five different alpha-chains and four different beta- chains were detected by acidic urea polyacrylamide gel electrophoresis (PAGE). Combinations of alpha-chains were characteristic for populations in (1) Senegal, (2) Ivory Coast, (3) Ghana/Togo/Benin, and (4) Congo. Pronounced variations at the beta-globin chain cluster were found by acidic urea triton PAGE. Cladistic analyses of the globin chain characteristics confirmed the validity of the following taxonomic units previously ranked as sub-species: (1) populations from Ivory Coast, Ghana, Togo and Benin belong to the sub-species S. m. melanotheron; (2) populations from Senegal form genetically a separate cluster representing the sub-species S. m. heudelotii; (3) the Congo population, morphologically considered to represent the sub-species S. m. nigripinnis, forms another distinct unit; but there was no evidence of S. m. paludinosus within the samples from Senegal. (C) 1999 The Fisheries Society of the British Isles.

Farghaly, A. M., Ezzat, A. A., and Shabana, M. B. (1973). Effect of temperature and salinity changes on the blood characteristics of Tilapia zilli G. in Egyptian littoral lakes. Comp Biochem Physiol A 46, 183-93.

Farmer, S. W., and Papkoff, H. (1977). A teleost (Tilapia mossambica) gonadotropin that resembles luteinizing hormone. Life Sci 20, 1227-32.

Fasakin, E. A., Balogun, A. M., and Fasuru, B. E. (1999). Use of duckweed, Spirodela polyrrhiza L-Schleiden, as a protein feedstuff in practical diets for tilapia, Oreochromis niloticus L. Aquaculture Research 30, 313-318.
The use of solar-dried duckweed, Spirodela polyrrhiza L. Schleiden, as a dietary protein component for tilapia, Oreochromis niloticus L., reared in glass tanks was evaluated. Six isonitrogenous diets (30% crude protein) were fed to all- male tilapia fingerlings for 56 days. The fish meal protein in the diets was substituted at a rate of 5%, 10%, 20%, 30% and 100% with duckweed. A diet without the duckweed served as a control. Growth performance and nutrient utilization of fish were based on daily weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio and protein productive value. There were no significant differences (P > 0.05) in growth performance and nutrient utilization of fish fed on diets containing up to 20% duckweed inclusion and the control. However, increases in dietary duckweed inclusion resulted in progressively reduced growth performance and nutrient utilization of fish. Diet without fish meal (100% duckweed) gave the poorest result. The most cost-effective diet in terms of cost per unit gain in weight of fish was obtained with 30% duckweed dietary inclusion. The result showed that solar-dried up to 30% duckweed dietary inclusion as a replacement for fishmeal in practical diets supported fish growth and was cost-effective.

Fernandes, M. d. O., and Volpato, G. L. (1993). Heterogeneous growth in the Nile tilapia: social stress and carbohydrate metabolism. Physiol Behav 54, 319-23.
Increase in heterogeneous growth as a result of grouping in the Nile tilapia, Oreochromis niloticus (L.), is presumed to be partially promoted by the social stress imposed by the dominant fish on the subordinates. Such stress may decrease the energy available for growth. In this study, the effect of social stress on carbohydrate metabolism was studied in adult, growing males. All animals were deprived of food during the experimentation period and pairing was imposed for either 2 or 4 days. Glycemia was measured before and after pairing, and muscle and liver glycogen contents were determined only after pairing. Subordinate fish showed the highest consumption of carbohydrate reserves. This response was caused by the social stress imposed which corroborates the idea that metabolic differences promoted by social stress may be involved in the rouping effect on heterogeneous growth in the Nile tilapia.

Flik, G., van der Velden, J. A., Seegers, H. C., Kolar, Z., and Wendelaar Bonga, S. E. (1989). Prolactin cell activity and sodium fluxes in tilapia (Oreochromis mossambicus) after long-term acclimation to acid water. Gen Comp Endocrinol 75, 39-45.
In tilapia exposed for 3 months to water of pH 4.5, prolactin cell activity, as estimated by ultrastructural morphometry and determination of prolactin synthesis in vitro, was significantly higher than in controls from neutral water. Sodium influx from the water was 50% lower than in the controls, indicating impaired branchial sodium uptake mechanisms. In contrast to predictions based on the results of short- term exposure to acid water--which is known to induce an increase of sodium efflux--the sodium efflux rate was reduced to 70% of the control value. It is concluded that tilapia are able to acclimate to acid water by successful control--probably via prolactin--of diffusional sodium losses across the integument, in particular the gill surface. This compensates for the impaired sodium uptake, and enables the fish to reestablish a positive sodium balance in acid water.

Flores-Crespo, J., Flores-Crespo, R., Ibarra-Velarde, F., Vera-Montenegro, Y., and Vasquez-Pelaez, C. (1995). [Evaluation of chemotherapeutic agents against cichlidogyriasis in tilapia (Oreochromis hornorum) in Mexico]. Rev Latinoam Microbiol 37, 179-87.
To evaluate the efficacy of seven compounds against the cichlidogyriasis of tilapia fish (Oreochromis hornorum), two experiments were carried out. In one, 160 naturally infected fish with a mean burden of 33.4 parasites/animal were used. In another, 1600 fish with a burden of 49.9 parasites/fish were used. Fish were randomly divided into eight equal groups and received three treatments as submersion baths: methylene blue, malachite green, potassium permanganate, sodium chloride, formaldehyde, copper sulfate and triclorfon, and a non-treated control. Five days after the last treatment, all fish were killed and dissected to quantify the remaining parasites. All data were submitted to an ANOVA analysis. All groups compared to the control showed statistical difference (P 0.01), with better efficacy at higher doses. Sodium chloride, potassium permanganate and triclorfon are highly efficient in the control of cichlidogyriasis of tilapia fish, but care should be taken with the toxicity of the two first compounds.

Fontainhas-Fernandes, A., Gomes, E., Reis-Henriques, M. A., and Coimbra, J. (1999). Replacement of fish meal by plant proteins in the diet of Nile tilapia: digestibility and growth performance. Aquaculture International 7, 57-67.
Apparent digestibility coefficient (ADC) values for a number of ingredients of plant or animal origin were obtained in order to formulate diets based on such values and to evaluate growth performance of Nile tilapia Oreochromis niloticus fed four experimental diets in which fish meal was gradually replaced by a mixture of other ingredients. The digestibility of various diet components was measured by using an inert marker in the feed and by using the Guelph faeces collecting system. ADC values of the ingredients tested were generally high, especially for fish meal. It was found that extruded pea seed meal (92.6%), defatted soybean meal (94.4%), full-fat toasted soybean (90.0%) and micronized wheat (88.6%) were the best vegetable proteins tested. Lupin seed meal and faba bean meal had similar ADC values for protein and energy. Groups of tilapia, initial mean body weight (SD) 6.7 (0.1) g, were fed experimental diets with the same digestible protein (DP) and digestible energy (DE) containing graded levels of a mixture of vegetable ingredients as partial or total replacement of fish meal protein. A growth trial was conducted over 12 weeks as partial or total replacement of fish meal protein. A growth trial was conducted over 12 weeks at a water temperature of 25 degrees C. Significant differences were observed for weight gain among tilapia fed diets D0, D33, D66 and D100 (containing only animal protein, 33, 66, and 100% of plant protein, respectively). No significant differences were observed for voluntary intake among tilapia fed diets D0, D33 and D66. These values were significantly lower than those observed for tilapia fed plant protein based diet (D100) and suggest the possibility of partial replacement of fish meal by vegetable proteins without negative effects.

Franciscato, S. M., Lajolo, F. M., and Zucas, S. M. [Bromatological study of protein concentrates from Sardinella aurita and Tilapia melanopleura. III. Effects of potassium suplementation on the biological value]. .

Franck, J. P., Wright, J. M., and McAndrew, B. J. (1992). Genetic variability in a family of satellite DNAs from tilapia (Pisces: Cichlidae). Genome 35, 719-25.
We have cloned and sequenced members of a family of satellite DNAs from three genera of the tilapiine tribe of fishes: Oreochromis, Sarotherodon, and Tilapia. The satellite DNAs, visualized as intensely staining bands following electrophoretic separation of EcoRI-digested genomic DNA, consist of three size variants differentially distributed in the various tilapiine species. The sizes of the monomers are approximately 237 bp (type I), 230 bp (type II), and 209 bp (type III). Several cloned monomers were sequenced from Oreochromis niloticus (type III), Oreochromis placidus (types I and II), Sarotherodon galilaeus (type I), Tilapia zillii (type I), and Tilapia rendalli (type I). Comparison of derived consensus sequences for the monomer units of the satellite DNAs revealed sequence identities within and between species that ranged from 89 to 96%. The type II and type III size variants appear to have arisen by deletions of 9 and 29 bp, respectively, within different regions of the type I satellite. Hybridization of a cloned monomer satellite from O. niloticus (type III) to PalI digests of genomic DNA from all three genera detected polymorphic, high molecular weight restriction fragments that produced fingerprint-like patterns. The complexity of these DNA fingerprints varied from one species to another, suggesting a markedly different genomic organization for these polymorphic satellite DNAs.

Fridberg, G., Iwasaki, S., Yagi, K., Bern, H. A., Wilson, D. M., and Nishioka, R. S. (1966). Relation of impulse conduction to electrically induced release of neurosecretory material from the urophysis of the teleost fish Tilapia mossambica. J Exp Zool 161, 137-49.

Fryer, J. N. (1979). Prolactin-binding sites in tilapia (Sarotherodon mossambicus) kidney. Gen Comp Endocrinol 39, 397-403.

Gale, W. L., Fitzpatrick, M. S., Lucero, M., Contreras-Sanchez, W. M., and Schreck, C. B. (1999). Masculinization of Nile tilapia (Oreochromis niloticus) by immersion in androgens. Aquaculture 178, 349-357.
The use of all-male populations increases the efficiency and feasibility of tilapia aquaculture. The objective of this study was to determine the efficacy of a short-term immersion procedure for masculinizing Nile tilapia (Oreochromis niloticus). Two synthetic androgens were evaluated: 17 alpha- methyldihydrotestosterone (MDHT) and 17 alpha- methyltestosterone (MT). Exposure (3 h) on 10 and again on 13 days post-fertilization to MDHT at 500 mu g/l successfully masculinized fry in all experiments, resulting in 100, 94 and 83 +/- 2% males in Experiments 1, 2 and 3, respectively. Immersions in MDHT or MT at 100 mu g/l resulted in significantly skewed sex ratios in Experiments 1 and 3 (MT resulted in 73 and 83 +/- 3% males; and MDHT resulted in 72 and 91 +/- 1% males) but not in Experiment 2. Immersion in MT at 500 mu g/l only caused masculinization in Experiment 3. Although further research and refinement is needed, immersion of Nile tilapia in MDHT may provide a practical alternative to the use of steroid-treated feed. Furthermore, when compared with current techniques for steroid-induced sex inversion of tilapia, short-term immersion reduces the period of time that workers are exposed to anabolic steroids. (C) 1999 Elsevier Science B.V. All rights reserved.

Gall, G. A. E., and Bakar, Y. (1999). Stocking density and tank size in the design of breed improvement programs for body size of tilapia. Aquaculture 173, 197-205.
Various aspects of cultural conditions were investigated in an effort to design an efficient selective breeding scheme for tilapia. High density culture has the potential of reducing confounding environmental effects associated with fish behavior. Body size of fry reared through 56 days was not affected by any of the stocking densities used (10-200 fry/l) with uniform water inflow. However, when water inflow was proportional to fish density, high density culture of fingerlings (18 fish/l) did appear to promote growth and result in improved normality of the distribution of body size relative to fish stocked at lower (2 fish/l) or higher (200 fish/l) densities. Although this could be interpreted as a consequence of diminished social interactions, a definitive conclusion could not be made in the absence of direct observational data on individual fish. Mixed-model methodology was used to estimate genetic parameters for body size. Estimated heritability for body weight was about 0.25 for all ages from 56 to 126 days. Phenotypic and genetic correlations among body weights at various ages were positive and near unity. (C) 1999 Elsevier Science B.V. All rights reserved.

Gargiulo, A. M., Ceccarelli, P., Dall'aglio, C., and Pedini, V. (1997). Ultrastructural study on the stomach of Tilapia spp (Teleostei). Anat Histol Embryol 26, 331-6.
An ultrastructural study has been made of gastric mucosa of a teleostean fish, Tilapia spp. The cytological features of the surface mucous cells, mucous neck cells, glandular cells and endocrine cells are described. The surface mucous cells, identified by their superficial localization, are characterized by apical granules. The mucous neck cells are distinguished by the appearance of their mucous granules and their localization between surface mucous cells and glandular cells. The gastric glands contain only one form of cell whose fine structure is similar to cells that secrete hydrochloric acid. Physiological implications of some ultrastructural features are also discussed.

Gargiulo, A. M., Ceccarelli, P., Dall'Aglio, C., and Pedini, V. (1998). Histology and ultrastructure of the gut of the tilapia (Tilapia spp.), a hybrid teleost. Anat Histol Embryol 27, 89-94.
The morphology of the intestine has been studied in a species of warm water fish, Tilapia spp., a hybrid teleost of notable economic importance. Light and electron microscope results show that the intestine is a relatively undifferentiated muscular tube lined with a simple columnar epithelium interspersed with goblet cells. The proximal region has a greater surface area, manifested by elongated mucosal ridges. The enterocytes are covered apically with uniform microvilli and exhibit the typical ultrastructural features of pinocytosis, namely extensive invaginations of the luminal plasma membrane and massive accumulation of vesicles in the apical cytoplasm. The distal intestine mucosa is thinner and less elaborately folded and consists of columnar cells with shorter and sparser microvilli. Their supranuclear cytoplasm contains abundant clear vacuoles. Numerous endocrine cells can also be seen. Regional cellular ultrastructural features are correlated with digestive functions.

Gerday, C., and Rao, K. S. (1970). Tryptic peptide maps and terminal amino acid residues of low molecular weight proteins from the white muscles of Cyprinus carpio, Gadus callarias and Tilapia macrochir Boul. Comp Biochem Physiol 36, 229-40.

Ghazaly, K. S. (1991). Influences of thiamin on lead intoxication, lead deposition in tissues and lead hematological responses of Tilapia zillii. Comp Biochem Physiol C 100, 417-21.
1. Lead levels in the blood, kidney, liver, brain and muscle of fish receiving only lead were elevated markedly over the values of both controls and thiamin-treated fish. 2. No statistical difference was observed between the lead levels in bone samples of both fish receiving only lead and thiamin-treated fish. 3. In contrast to the fish receiving only lead the fish treated with thiamin appeared to be healthy and had no lead poisoning signs. 4. Over the period of study, hemoglobin content and red blood cell counts of fish receiving only lead showed significant decreases from the values of both controls and fish treated with thiamin. 5. Hematocrit values and white blood cell counts were uninfluenced by either lead exposure or thiamin treatment at all intervals. 6. The data suggest that thiamin can serve as a promising natural chelator to prevent fish mortality, not only in short term, but also in prolonged exposure.

Ghoneum, M., Faisal, M., Peters, G., Ahmed, II, and Cooper, E. L. (1988). Suppression of natural cytotoxic cell activity by social aggressiveness in Tilapia. Dev Comp Immunol 12, 595-602.
Our earlier observations revealed that social stress causes drastic effects on different physiological mechanisms and degenerative changes in leucocytes. In this preliminary work, we analyzed the effect of social aggressiveness on functional activities of leucocytes emphasizing (NCC) activity in Tilapia. At 10 hr post stress induction, fish could be differentiated into three categories: 1) dominants; 2) subordinates; and 3) indeterminants. Results of NCC as indicated by 4 hr. 51Cr-release assay, demonstrated a significant suppression in cytotoxic reactivity in the subordinates and indeterminants compared to dominants. This suppression appears to be due to a decrease in the binding capacity of effector cells to YAC-1 target cells as indicated by the decreased number of conjugate forming cells. This binding process is a key event in activating the fish equivalent of NK cells in mammals. Decreased NCC-activity in stressed fish suggests that aberrations in cell mediated immunity result from social aggressiveness.

Giaquinto, P. C., and Volpato, G. L. (1997). Chemical communication, aggression, and conspecific recognition in the fish Nile tilapia. Physiol Behav 62, 1333-8.
The chemical modulation of agonistic behavior and conspecific recognition were tested in juveniles of the fish Nile tilapia, Oreochromis niloticus (L.). After a 7-day isolation period, the fish were grouped (four individuals per aquarium) for 7 days. Then fish of alpha and beta ranks (previously matched for similar size) were paired in a neutral territory for analysis of their agonistic interaction. Pairs composed of alpha and beta fish were established with either fish from the same group (familiar) or from two different groups (unfamiliar). The pairs were tested in contiguous compartments, either with water exchange between the compartments or in the absence of water exchange. In each condition the fish were separated by a transparent glass partition. Twelve pairs were tested in each experimental condition. Fish behavior was videotaped and the following variables were analyzed: (a) frequency of and time spent in agonistic patterns, (b) latency to start fighting, and (c) duration of swimming. Water exchange between compartments decreased agonistic interactions. This effect, however, was more pronounced in pairs of fish coming from the same group (in this case, subordinate fish spent less time in confrontations than dominant ones). We conclude that chemical communication decreases aggression in this species by (1) inducing an alarm reaction and (2) increasing conspecific recognition (thus stabilizing the dominance hierarchy).

Gogal, R. M., Jr., Smith, B. J., Robertson, J. L., Smith, S. A., and Holladay, S. D. (1999). Tilapia (Oreochromis niloticus) dosed with azathioprine display immune effects similar to those seen in mammals, including apoptosis. Vet Immunol Immunopathol 68, 209-27.
Azathioprine, an anti-neoplastic drug and therapeutic immunosuppressant, was administered intraperitoneally at 10.0 and 50.0 mg/kg to 3-6-month-old tilapia (Oreochromis niloticus). Consistent alterations in immune cellular parameters of the blood, pronephros (hematopoietic kidney) and spleen were observed. Peripheral blood total cellularity decreased as the azathioprine dose increased, to approximately half that of the control. Differential analysis of white blood cells indicated a decline in lymphocyte number, in particular, with increased dosage of azathioprine. Pronephric total cellularity was depressed in fish receiving the 10.0 or 50.0 mg/kg dose. In contrast, both splenic weight and splenic total cellularity increased proportionately with the increase in the drug dosage. Histopathologic examination of the spleens showed normal patterns for both control and 10.0 mg/kg dose groups. At 50.0 mg/kg, spleens were characterized by marked expansion of the white pulp, although lymphocytes were rare. Melanomacrophage centers at the higher dose were also larger and more numerous than in the control group. Evaluation of splenic and pronephric leukocytes with apoptotic markers showed an increase in apoptotic cells in the pronephros with increasing drug dose. These changes in fish are consistent with those seen in humans and laboratory rodents dosed with azathioprine, suggesting that fish may be potentially useful as preliminary models for detecting immunosuppressive compounds.

Golovanova, I. L., Chuiko, G. M., and Pavlov, D. F. (1994). Effects of cadmium, naphthalene, and DDVP on gut carbohydrases activity in bream (Abramis brama L.) and Mozambique tilapia (Oreochromis mossambicus Peters). Bull Environ Contam Toxicol 52, 338-45.

Goude, G., and Edlund, B. (1972). Approach and withdrawal in young of Tilapia mossambica (Cichlidae, Pisces) as a function of age and onset of stimulation. Z Tierpsychol 31, 60-77.

Gras, G., Pelissier, C., and Tack, D. L. (1982). [Effect of temephos on the acetylcholinesterase activity of the brain of Tilapia guineensis. 1: Experimental study at operative doses]. Toxicol Eur Res 4, 301-8.
After having exposed during 10 minutes the Tilapia guineensis to a concentration of 0,05 mg/l of temephos (concentration of a larvicide used for the field test), the authors note a lowering of the acetylcholinesterastic activity of the brain to an order of 25%. The return to a normal activity is achieved within 20 to 25 days. A new exposure, happening one week after the first, provokes a further lowering before the return to a normal value. The authors question themselves on the consequences of these chemical attacks repeated on a weekly basis during antilarval treatments in the struggle against the onchocercose.

Grau, E. G., Nishioka, R. S., and Bern, H. A. (1981). Effects of osmotic pressure and calcium ion on prolactin release in vitro from the rostral pars distalis of the tilapia Sarotherodon mossambicus. Gen Comp Endocrinol 45, 406-8.

Grau, E. G., Nishioka, R. S., and Bern, H. A. (1982). Effects of somatostatin and urotensin II on tilapia pituitary prolactin release and interactions between somatostatin, osmotic pressure Ca++, and adenosine 3',5'-monophosphate in prolactin release in vitro. Endocrinology 110, 910-5.
Both somatostatin (SRIF) and urotensin II, a dodecapeptide from the teleost caudal neurosecretory system, inhibit PRL release from the organ-cultured rostral pars distalis of the tilapia, Sarotherodon mossambicus, in a dose-related manner. The inhibitory action of SRIF on PRL release was completely prevented by the presence of the calcium ionophore A23187. PRL release was also blocked when Ca++ was excluded from the incubation medium, even in the presence of the ionophore. Both dibutyryl cAMP (dbcAMP) and the phosphodiesterase inhibitor 3-isobutyl- 1-methylxanthine, alone or in combination, stimulated PRL release during incubation in high osmotic pressure medium. The effect of dbcAMP appeared to be dose related. Together, dbcAMP and 3-isobutyl-1- methylxanthine were also effective in preventing the inhibition of PRL release by SRIF. These results are consistent with the notion that Ca++, and possibly cAMP, may be important mediators of PRL secretion, and it is likely that SRIF may inhibit PRL release by blocking a Ca++- or cAMP-mediated mechanism.

Grau, E. G., Ford, C. A., Helms, L. M., Shimoda, S. K., and Cooke, I. M. (1987). Somatostatin and altered medium osmotic pressure elicit rapid changes in prolactin release from the rostral pars distalis of the tilapia, Oreochromis mossambicus, in vitro. Gen Comp Endocrinol 65, 12-8.
Prolactin (PRL) cells in the rostral pars distalis of the tilapia Oreochromis mossambicus respond to somatostatin (SRIF) and reduced medium osmotic pressure within 10-20 min of exposure during perifusion incubation. Pieces of rostral pars distalis tissue were removed from freshwater-adapted tilapia and were preincubated in [3H]leucine in static culture (355 m phi smolal) for 48 hr. Following preincubation, they were placed in the perifusion apparatus and baseline release was established for 3 hr in hyperosmotic medium (355 m phi smolal). Exposure to hyposmotic medium (280 m phi smolal) resulted in a rapid and steep rise in the release of [3H]PRL, which remained elevated for more than 2 hr. When SRIF was added simultaneously with hyposmotic medium, the rise in PRL release normally initiated by reduced osmotic pressure was prevented. Somatostatin also quickly reduced release that had been previously elevated by exposure to hyposmotic medium. The time course of these changes suggests that SRIF and altered osmotic pressure act on PRL secretion in at least partial independence of effects which they may have on PRL synthesis in the tilapia pituitary.

Grau, E. G., and Helms, L. M. (1990). The tilapia prolactin cell--twenty-five years of investigation. Prog Clin Biol Res 342, 534-40.

Grobler-van Heerden, E., van Vuren, J. H., and du Preez, H. H. (1991). Bioconcentration of atrazine, zinc and iron in the blood of Tilapia sparrmanii (Cichlidae). Comp Biochem Physiol C 100, 629-33.
1. The bioconcentration of atrazine, zinc and iron in the blood of Tilapia sparrmanii has been determined separately in each of six exposure groups. 2. An increased bioconcentration of atrazine in the blood occurred with an increased exposure concentration. 3. With exposure to zinc, there was a gradual decrease in bioconcentration of zinc in the blood of T. sparrmanii with an increased concentration in the water. 4. A similar tendency was observed during iron exposure, except that the decrease in bioconcentration was not significant.

Groneveld, D., Balm, P. H., Martens, G. J., and Wendelaar Bonga, S. E. (1995). Differential melanin-concentrating hormone gene expression in two hypothalamic nuclei of the teleost tilapia in response to environmental changes. J Neuroendocrinol 7, 527-33.
For some teleosts, a role has been established for melanin- concentrating hormone (MCH) background adaptation and stress response. In teleost fishes, prepro-MCH (ppMCH) mRNA is expressed in the hypothalamus, predominantly in neurons of the nucleus lateralis tuberis (NLT) and in scattered cells of the nucleus recessus lateralis (NRL). The response of mature tilapia to different environmental challenges was studied by assessing ppMCH mRNA levels in these two hypothalamic nuclei by quantitative dot blot analysis. Changes in background colour induced pronounced differences in ppMCH mRNA expression in the NLT, but not in the NRL. The NLT of tilapia adapted to a white background contained 2.5 to 3 times more ppMCH mRNA than the NLT of black-adapted fish. The NLT of fish kept on neutral background contained intermediate levels of ppMCH mRNA, which were significantly lower than the levels in white-adapted fish. Oral administration of dexamethasone lowered plasma cortisol concentrations, but had no effect on ppMCH mRNA levels in white- and black-adapted fish. In tilapia exposed to strongly acidified water (pH 3.5), plasma cortisol and ACThH concentrations were highly elevated, and plasma chloride concentrations considerably lower than in controls. These fish responded with a 70% rise in ppMCH mRNA levels in the NLT, which is most probably associated with a stress response evoked by inadequate osmoregulation. After exposure to a milder acidification (pH 4.0) or to seawater no significant changes in ppMCH mRNA levels occurred in either the NLT or the NRL, nor in plasma chloride, cortisol and ACTH levels. A specific increase of ppMCH mRNA levels in the NRL was observed in repeatedly disturbed tilapia.(ABSTRACT TRUNCATED AT 250 WORDS).

Groneveld, D., Eckhardt, E. R., Coenen, A. J., Martens, G. J., Balm, P. H., and Wendelaar Bonga, S. E. (1995). Expression of tilapia prepro-melanin-concentrating hormone mRNA in hypothalamic and neurohypophysial cells. J Mol Endocrinol 14, 199-207.
Melanin-concentrating hormone (MCH) is a neuropeptide involved in background adaptation in teleost fish, and in multiple regulatory functions in mammals and fish. To study the expression of the MCH preprohormone (ppMCH) in teleosts, we first cloned a hypothalamic cDNA encoding the complete ppMCH of tilapia (Oreochromis mossambicus), and a cRNA probe derived from a 270 bp ppMCH cDNA fragment was used for the expression studies. The level of ppMCH mRNA expression in tilapia hypothalamus, measured by dot blot analysis, was significantly higher in fish adapted to a white background than in black-adapted animals, which is in accordance with the reported MCH plasma and tissue concentrations in fish. Northern blot analysis not only revealed a strong ppMCH mRNA signal in the hypothalamus, but also the presence of ppMCH mRNA in the neurointermediate lobe (NIL) of the pituitary. In situ hybridization and immunocytochemistry showed that ppMCH mRNA as well as MCH immunoreactivity are located in perikarya of two hypothalamic regions, namely in the nucleus lateralis tuberis (NLT) and the nucleus recessus lateralis (NRL). Quantitative analysis by dot blot hybridization revealed about eight times more ppMCH mRNA in the NLT than in the NRL and NIL of mature tilapias. ppMCH mRNA in the NIL could be localized to cell bodies of the neurohypophysis, which were also MCH immunoreactive.

Groneveld, D., Balm, P. H., and Wendelaar Bonga, S. E. (1995). Biphasic effect of MCH on alpha-MSH release from the tilapia (Oreochromis mossambicus) pituitary. Peptides 16, 945-9.
The effect of melanin-concentrating hormone (MCH) on the release of alpha-melanocyte stimulating hormone (alpha-MSH) from the tilapia pituitary gland was studied in vitro. In a superfusion set up, 10 nM to 1 microM synthetic salmon MCH caused a concentration-dependent inhibition of alpha-MSH release from tilapia neurointermediate lobes (NILs). Immunoneutralization of MCH in tilapia NILs further indicated that endogenous MCH has an inhibitory effect on the melanotropes. The release of monoacetylated alpha-MSH release was more strongly inhibited by MCH than that of des-, and diacetylated alpha-MSH, indicating that MCH modulates the secretory signal of the melanotropes in a quantitative and qualitative manner. A high concentration of MCH (10 microM) substantially increased the release of alpha-MSH. Further evidence in support of a stimulatory action of high concentrations of MCH was provided by the observation that the MCH analogue MCH(2-17) at 10 and 35 microM enhanced alpha-MSH release as well. Therefore, we conclude that the response of pituitary melanotropes to MCH is biphasic, as was reported previously for the effects of MCH on other targets in fish and mammals. Under physiological conditions the inhibitory action of MCH on fish melanotropes most likely dominates.

Groneveld, D., Balm, P. H., and Wendelaar Bonga, S. E. (1996). Melanin-concentrating hormone gene-related peptide stimulates ACTH, but not alpha-MSH, release from the tilapia pituitary. J Endocrinol 148, R1-4.
Tilapia (Oreochromis mossambicus; teleostei) melanin-concentrating hormone gene-related peptide (tMgrp) was tested for tropic actions on adenocorticotropin hormone (ACTH) and alpha-melanocyte stimulating hormone (alpha-MSH) producing cells in the tilapia pituitary gland in vitro. Up to 100 microM synthetic tilapia Mgrp (tMgrp) had no effect on alpha-MSH release from tilapia neuro-intermediate lobes in a superfusion set up. However, at concentrations above 1 microM, tMgrp concentration dependently stimulated ACTH release from tilapia anterior lobes. This is the first evidence that Mgrp modulates ACTH release from teleost corticotropes, and this might implicate the peptide in the regulation of the pituitary-interrenal axis of fish.

Grun, G. (1975). Structural basis of the functional development of the retina in the cichlid Tilapia leucosticta (teleostei). J Embryol Exp Morphol 33, 243-57.
The differentiation of retinal cells has been studied with special reference to the formation of functionally important structures. Three phases could be revealed: from day 3 to day 6 retinal cells in the mostly advanced central part show signs of general cell differentiation (formation of ribosomes, endoplasmic reticulum, mitochondria). In the second phase from day 6 to day 9 characteristic nerve cell structures appear (neurites, dendrites, synapses, receptor outer and inner segments). In the last phase from day 9 to day 12 these special structures attain their final, mature appearance, synapses seem ready for function, dendritic invaginations and synaptic ribbons are formed, twin cones become arranged in mosaic patterns. This developmental order conforms to a gradient running from the ganglion cells to the receptors. Neurites and dendrites appear in the ganglion cells on day 3, in the intermediate neuron layer not before day 4. The horizontal cells are the last ones to differentiate out of the intermediate neurons. The inner plexiform layer synapses are structurally mature before those from the outer plexiform layer. The receptor inner and outer segments differentiate from the 5th day up to the time the young fish is able to see (day 13). The last structures to appear are dendritic invaginations and synaptic ribbons in the receptor terminals, and the twin cone mosaic. It is assumed that the ability to see is achieved only when these structures have been formed.

Grun, G. (1980). Developmental dynamic in synaptic ribbons of retinal receptor cells (Tilapia, Xenopus). Cell Tissue Res 207, 331-9.
In the cichlid teleost Tilapia leucosticta, the origin and linear development of synaptic ribbons in retinal receptor cells have been studied. First ribbons are invariably found close to their future synaptic sites between two dendritic invaginations. They are then clearly shorter than at later stages and appear bifurcate, or of bulb or drop shape. From these precursors typical ribbons rapidly develop, and these vary considerably in length. From a shift in length distribution, a main growth phase can be ddetected which takes place at the time when the retina first becomes functional. Similar observations were made in Xenopus. Placing Tilapia larvae in conditions of 24 h continuous light had no effect on ribbon growth, while 24 h of continuous darkness resulted in a prevalence of shorter ribbons. Thus the growth of synaptic ribbons in the course of retinal development appears to be subject to modification by environmental light conditions.

Guiguen, Y., Baroiller, J. F., Ricordel, M. J., Iseki, K., McMeel, O. M., Martin, S. A., and Fostier, A. (1999). Involvement of estrogens in the process of sex differentiation in two fish species: the rainbow trout (Oncorhynchus mykiss) and a tilapia (Oreochromis niloticus). Mol Reprod Dev 54, 154-62.
In order to study the physiological implication of sex steroid hormones in gonadal sex differentiation in fish, we first investigated the potential role of estrogens using two fish models: the rainbow trout (Oncorhynchus mykiss) and a tilapia species (Oreochromis niloticus). All experiments were carried out on genetically all-male (XY) and all- female (XX) populations. In vivo treatments with an aromatase inhibitor (ATD, 1,4,6- androstatriene-3-17-dione) result in 100% masculinization of an all-female population in rainbow trout (dosage 50 mg/kg of food) and 75.3% in tilapia (dosage 150 mg/kg of food). In tilapia, the effectiveness of the aromatase inhibition by ATD is demonstrated by the marked decrease of the gonadal aromatase activity in treated animals versus control. No masculinization is obtained following treatment with an estrogen receptor antagonist (tamoxifen) in both species. Aromatase and estrogen receptor gene expression was studied in rainbow trout by semi-quantitative RT-PCR in gonads sampled before, during and after sex- differentiation. Aromatase mRNA is specifically detected in female gonads, 3 weeks before the first sign of histological sex- differentiation, i.e., first female meiosis. Aromatase expression in male gonads is at least a few hundred times less than in female gonads. Estrogen receptor gene is expressed in both male and female gonads at all stages with no dimorphic expression between sexes. Specific aromatase gene expression before ovarian differentiation was also demonstrated using virtual Northern blot, with no expression detected in male differentiating gonads. From these results it can be concluded that estrogen synthesis is crucial for ovarian differentiation, and transcription of the aromatase gene can be proposed as a key step in that process in fish. Copyright 1999 Wiley-Liss, Inc.

Guiguen, Y., Baroiller, J. F., Ricordel, M. J., Iseki, K., McMeel, O. M., Martin, S. A. M., and Fostier, A. (1999). Involvement of estrogens in the process of sex differentiation in two fish species: The rainbow trout (Oncorhynchus mykiss) and a Tilapia (Oreochromis niloticus). Molecular Reproduction and Development 54, 154-162.
in order to study the physiological implication of sex steroid hormones in gonadal sex differentiation in fish, we first investigated the potential role of estrogens using two fish models: the rainbow trout (Oncorhynchus mykiss) and a tilapia species (Oreochromis niloticus). All experiments were carried out on genetically all-male (XY) and all-female (XX) populations. In vivo treatments with an aromatase inhibitor (ATD, 1,4,6- androstatriene3-17-dione) result in 100% masculinization of an all-female population in rainbow trout (dosage 50 mg/kg of food) and 75.3% in tilapia (dosage 150 mg/kg of food). In tilapia, the effectiveness of the aromatase inhibition by ATD is demonstrated by the marked decrease of the gonadal aromatase activity in treated animals versus control. No masculinization is obtained following treatment with an estrogen receptor antagonist (tamoxifen) in both species. Aromatase and estrogen receptor gene expression was studied in rainbow trout by semi-quantitative RT-PCR in gonads sampled before, during and after sex-differentiation. Aromatase mRNA is specifically detected in female gonads, 3 weeks before the first sign of histological sex-differentiation, i.e., first female meiosis. Aromatase expression in male gonads is at least a few hundred times less than in female gonads. Estrogen receptor gene is expressed in both male and female gonads at all stages with no dimorphic expression between sexes. Specific aromatase gene expression before ovarian differentiation was also demonstrated using virtual Northern blot, with no expression detected in male differentiating gonads. From these results it can be concluded that estrogen synthesis is crucial for ovarian differentiation, and transcription of the aromatase gene can be proposed as a key step in that process in fish. (C) 1999 Wiley-Liss, Inc.

Guill#n, I., Lleonart, R., Agramonte, A., Morales, R., Morales, A., Hern#ndez, C. A., MM, V. z., Diaz, M., Herrera, M. T., Alvarez-Lajonchere, L., Hern#ndez, O., and de la Fuente, J. (1998). Physiological changes in the juvenile euryhaline teleost, the tilapia Oreochromis hornorum, injected with E. coli-derived homologous growth hormone. Journal of Marine Biotechnology 6, 142-51.
Growth is a complex process in fish. This study was designed to test the effect of different levels of recombinant tilapia growth hormone (tiGH) injected intraperitoneally in juvenile hybrid tilapia Oreochromis hornorum. Tilapia GH cDNA was cloned from hybrid O. hornorum tilapia. The mature protein was expressed in E. coli under regulation of the phage T7 promoter. The E. coli-derived tiGH was partially purified to 67% purity and, following renaturation, was shown to be biologically active in in vivo and in vitro assays. Recombinant tiGH stimulated extracellular matrix synthesis as shown by 35S-sulfate uptake in ceratobranchial cartilage explants. Zero, 0.1, 0.5 and 2.5 #g tiGH/g body weight (gbw) were injected in tilapia, and the effects on the growth-promoting action, hepatosomatic index (HSI), and mRNA insulin-like growth factor (IGF) induction were measured. A significant increase in the body weight (P 0.05) and length (P 0.01) was observed in tilapia receiving 0.5 #g tiGH/gbw. However, tilapia receiving 0.1 and 2.5 #g tiGH/gbw did not show an increase in body weight and length with respect to the control group receiving BSA injections. Binding sites for the recombinant tiGH were identified in the liver. Consistent with its somatotropic actions, the IGF mRNA induction was observed in the groups injected with 0.1 and 0.5 #g tiGH/gbw (P 0.05). No significant increase in the HSI was detected in the injected groups when compared to the control group. These results demonstrated that the injection of biologically active E. coli-derived tiGH produces physiological changes in juvenile tilapia that ultimately resulted in a growth-promoting action only at a dose of 0.5 #g tiGH/gbw.

Guillen, I., Berlanga, J., Valenzuela, C. M., Morales, A., Toledo, J., Estrada, M. P., Puentes, P., Hayes, O., and de la Fuente, J. (1999). Safety evaluation of transgenic Tilapia with accelerated growth. Marine Biotechnology 1, 2-14.
Recent advances in modern marine biotechnology have permitted the generation of new strains of economically important fish species through the transfer of growth hormone genes. These transgenic fish strains show improved growth performance and therefore constitute a better alternative for aquaculture programs. Recently, we have obtained a transgenic tilapia line with accelerated growth However, before introducing this line into Cuban aquaculture, environmental and food safety assessment was required by national authorities. Experiments were performed to evaluate the behavior of transgenic tilapia in comparison to wild tilapia as a way to assess the environmental impact of introducing transgenic tilapia into Cuban aquaculture. Studies were also conducted to evaluate, according to the principle of substantial equivalence, the Safety of consuming transgenic tilapia as food. Behavior studies showed that transgenic tilapia had a lower feeding motivation and dominance status than controls. Food safety assessment indicated that tilapia growth hormone has no biological activity when administered to nonhuman primates. Furthermore, no effects were detected in human healthy volunteers after the consumption of transgenic tilapia. These results showed, at least under the conditions found in Cuba, no environmental implications for the introduction of this transgenic tilapia line and the safety in the consumption of tiGH-transgenic tilapia as an alternative feeding source for humans. These results: support the culture and consumption of these transgenic tilapia.

Hamilton, L. C., and Wright, J. M. (1999). Isolation of complementary DNAs coding for a receptor for activated C kinase (RACK) from zebrafish (Danio rerio) and Tilapia (Oreochromis niloticus): Constitutive developmental and tissue expression. Marine Biotechnology 1, 279-285.
We have cloned and sequenced complementary DNAs coding for a receptor for activated C kinase (RACK) from two species of teleost fishes, zebrafish (Danio rerio) and tilapia (Oreochromis niloticus). The tilapia clone is 1063 nucleotides long, and the zebrafish clone is 1069 nucleotides long. Both clones contain an open reading frame coding for the complete RACK protein of 317 amino acids. Northern hybridization analysis using these clones as probes detected a 1.2-kb band, indicating that these are nearly full-length cDNA clones. In tilapia, RACK messenger RNA was expressed in all tissues examined. In situ hybridization detected the presence of mRNA for this RACK sequence in unfertilized eggs and embryos (development up to 24 hours) from zebrafish.

Haralson, J. V., and Clement, J. J. (1968). Reserpine and the partial reinforcement effect in the fish Tilapia H. macrocephala. Psychol Rep 22, 1057-64.

Hazineh, A., Shin, S. H., Reifel, C., Pang, S. C., and Van der Kraak, G. J. (1997). Dopamine causes ultrastructural changes in prolactin cells of tilapia (Oreochromis niloticus). Cell Mol Life Sci 53, 452-8.
This study was undertaken to examine ultrastructural changes induced by dopamine in fish prolactin cells. Tilapia adenohypophyses were incubated with dopamine and evaluated by electron microscopy. The quantities of rough endoplasmic reticulum (RER) in prolactin cells increased and the number of secretory granules were decreased by dopamine (10(-6) mol/l) treatment. Another set of adenohypophysial tissues was placed back into control medium for 10 min following a 3 h incubation period with dopamine (10(-6) mol/l) (RE10 min group). This group had significantly less RER than the 3 h dopamine-treated tissue, and the shape of many granules in the RE10 min group changed from spherical to rod-like. In addition, some of the granule content appeared to diffuse out of granules since some were not fully surrounded by membrane. It was therefore hypothesized that the rod- shaped granules might be the result of prolactin secretion by diffusion.

Heijden, A., Verbost, P., Eygensteyn, J., Li, J., Bonga, S., and Flik, G. (1997). Mitochondria-rich cells in gills of tilapia (Oreochromis mossambicus) adapted to fresh water or sea water: quantification by confocal laser scanning microscopy. J Exp Biol 200, 55-64.
We used confocal laser scanning microscopy to validate a new and fast co-labelling method to study the distribution of mitochondria-rich (MR) cells in gill filaments and to differentiate between MR cells that are in contact with the water (cells labelled with both DASPMI and Concanavalin-A) and those that are not (DASPMI-positive only). This method was used to describe differences in MR cell density that occur in the gills of tilapia Oreochromis mossambicus adapted to fresh water or sea water. In fresh water, the total MR cell density was 6233 cells mm-2 and the density of the subpopulation of MR cells that are in contact with the water was 3458 mm-2. After seawater adaptation, cell density decreased to 3061 cells mm-2 for all MR cells of which 2445 cells mm-2 were in contact with water. The percentage of double- labelled MR cells in the total MR cell population had increased from 55 to 80 %. MR cell size (measured as the maximal cross-sectional area) increased from 87 &micro;m2 in fresh water to 217 &micro;m2 in sea water. Biochemical determination of specific and total Na+/K+-ATPase activity in gill homogenates showed no difference between freshwater- and seawater-adapted fish. Quantification of 'mature' chloride cell density in fixed gill filaments using scanning electron microscopy resulted in an overestimate of chloride cell density due to shrinkage of the sample.

Heinrich, W. (1967). [Studies on the sexual behavior in the species Tilapia (Chichlidae, Teleostei) and in hybrid types]. Z Tierpsychol 24, 684-754.

Helms, L. M., Grau, E. G., Shimoda, S. K., Nishioka, R. S., and Bern, H. A. (1987). Studies on the regulation of growth hormone release from the proximal pars distalis of male tilapia, Oreochromis mossambicus, in vitro. Gen Comp Endocrinol 65, 48-55.
The in vitro effects of several factors, including cortisol, somatostatin (SRIF), and medium osmotic pressure, on growth hormone (GH) release from the tilapia pituitary were examined in relation to fish size. Spontaneous GH release from the proximal pars distalis (PPD) of approximately 60-g fish was significantly less than that from tissue of fish weighing either approximately 120 or approximately 280 g when incubated in 340 m phi smolal medium. While GH content of the PPD cultures (tissue + medium measured by densitometry) increased consistently with fish size, GH concentration (per microgram of tissue protein) was variable, being highest in 120-g fish and lowest in 280-g fish. Moreover, GH concentration was not related to GH release. Fish size also appeared to be important in the responsiveness of GH cells to stimulation by cortisol (Nishioka et al., 1985) and by increased osmotic pressure. In cultures of PPD from approximately 60-g fish, in which spontaneous release was relatively low, cortisol and increased medium osmotic pressure significantly enhanced release. Cortisol and hyperosmotic medium were without significant effect, however, on GH release from PPD of approximately 120-g fish, which showed high spontaneous release. In contrast, SRIF, a potent inhibitor of GH secretion, was effective in lowering GH release regardless of fish size. Nevertheless, SRIF was apparently more effective in inhibiting GH release from tissue of 60-g fish than from tissue of 120-g fish. Our data suggest that GH secretion may be augmented when smaller tilapia (approximately 60 g) are transferred to seawater, a situation in which blood cortisol and osmotic pressure would presumably be elevated.

Helms, L. M., Grau, E. G., and Borski, R. J. (1991). Effects of osmotic pressure and somatostatin on the cAMP messenger system of the osmosensitive prolactin cell of a teleost fish, the tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 83, 111-7.
Altered osmotic pressure and somatostatin (SRIF) rapidly alter prolactin (PRL) release from the pituitary gland of the euryhaline teleost, the tilapia. The present studies were undertaken to determine whether altered osmotic pressure and SRIF influence cAMP metabolism in a manner that is correlated with the pattern of PRL release observed previously. Although PRL release is stimulated within 10-20 min when medium osmotic pressure is reduced, cAMP metabolism was not altered. However, following 1 hr of incubation in the presence of IBMX, cAMP accumulation was higher in PRL tissue exposed to medium of reduced osmotic pressure. This suggests that cAMP does not initiate an increase in PRL release in response to reduced osmotic pressure. By contrast, SRIF reduced the forskolin-stimulated increase in cAMP levels in a manner consistent with its rapid effects on PRL release. Moreover, the ability of SRIF to suppress the forskolin-stimulated increase in cAMP levels suggests that SRIF may act to render adenylate cyclase less responsive to direct stimulation by forskolin.

Hemsworth, B. N., and Wardhaugh, A. A. (1978). The induction of dominant lethal mutations in Tilapia mossambica by alkane sulphonic esters. Mutat Res 58, 263-8.
A serial mating system has been used to enable study of the effect of chemical mutagens in Tilapia mossambica. Embryopathies incompatible with survival are attributed to dominant lethal mutations induced in developing male germ cells by methyl methanesulphonate and the isomeric forms of dimethyl-myleran.

Hernandez, O., Guillen, I., Estrada, M. P., Cabrera, E., Pimentel, R., Pina, J. C., Abad, Z., Sanchez, V., Hidalgo, Y., Martinez, R., Lleonart, R., and de la Fuente, J. (1997). Characterization of transgenic tilapia lines with different ectopic expression of tilapia growth hormone. Mol Mar Biol Biotechnol 6, 364-75.
The transfer of growth hormone (GH) genes has opened new possibilities for the manipulation of growth in economically important fish species. However, the ectopic GH levels to optimize growth acceleration in fish, and specially in tilapia, are not known and must be determined experimentally. The tilapia GH (tiGH) cDNA was used to construct chimeric genes expressing different levels of tiGH in vitro and in vivo. These constructs were used to generate four lines of transgenic tilapia by microinjection into one-cell embryos. Different patterns and levels of ectopic expression of tiGH and IGF were detected in organs of transgenic tilapia by RNA or protein analysis. The two lines with lower ectopic tiGH mRNA levels were the only ones showing growth acceleration, suggesting that the expression of ectopic tiGH promoted growth only at low expression levels. The effect of higher ectopic tiGH levels resembled the physiologic situation of low condition factor and permitted us to postulate a model for growth acceleration in transgenic tilapia expressing ectopic tiGH.

Herndon, T. M., McCormick, S. D., and Bern, H. A. (1991). Effects of prolactin on chloride cells in opercular membrane of seawater-adapted tilapia. Gen Comp Endocrinol 83, 283-9.
Effects of prolactin on morphology and numbers of chloride cells in the opercular membrane of seawater-adapted tilapia (Oreochromis mossambicus) have been examined. Following five daily injections of ovine prolactin at a dose of 10 micrograms.g body wt-1, blood samples were taken and opercular membranes were removed and stained with a fluorescent mitochondrial dye (dimethylaminostyrylethylpyridiniumiodine), a fluorescent derivative of ouabain (anthroylouabain), and a histological stain specific for the extensive tubular system of chloride cells (zinc-osmium-iodine). Mean plasma osmolarity and sodium increased 23-24% following prolactin injection. An increase in the relative frequency of chloride cells between 20 and 180 microns2 in cross-sectional area and a decrease in the relative frequency of chloride cells greater than 180 microns2 were observed following prolactin injections. Average cell size decreased 46- 70% and cell height decreased 26-38% following prolactin injections. There was no significant change in cell density. Anthroylouabain staining was observed in both prolactin- and saline-injected fish, and no significant effect on Na+,K(+)-adenosinetriphosphatase activity was seen in either opercular membrane or gill tissue. The results demonstrate an effect of prolactin on chloride cell size and provide a morphological correlate for decreased secretory activity of chloride cells following prolactin injections.

Hildebrand, C., Wiberg, J., and Holje, L. (1988). Trigeminal alveolar nerve of the lower jaw in the cichlid Tilapia mariae: evidence for continual axon generation and presence of exceptionally small myelinated axons. J Comp Neurol 272, 309-16.
Cross sections from the trigeminal alveolar nerve of the lower jaw in the cichlid Tilapia mariae were examined by electron microscopy. The nerve fibers are arranged in groups with a core of unmyelinated and small myelinated axons, surrounded by myelinated axons of varying sizes. The core contains large bundles of unmyelinated axons collectively ensheathed by circumferentially located Schwann cells, as well as smaller bundles of unmyelinated axons partly separated from each other by Schwann cell processes. Among the unmyelinated axons, occasional scattered profiles resembling growth cones are seen. The total number of axons in this tooth-related nerve increases from approximately 1,500 to 5,000, as the animals grow in length from 4.5 to 21.5 cm. Some 24-49% of the axons are unmyelinated. The myelinated axons have maximum diameters of 1.0-3.0 micron, depending on body size. Most myelinated axons have diameters less than 1.0 micron and the smallest ones reach down to 0.3 micron. These results show that there is a continual addition of axons to the alveolar nerve of the lower jaw in Tilapia mariae and that the critical diameter for myelination in this peripheral nerve is similar to that typically found in the mammalian CNS.

Hilmy, A. M., el Domiaty, N. A., Daabees, A. Y., and Abdel Latife, H. A. (1987). Some physiological and biochemical indices of zinc toxicity in two freshwater fishes, Clarias lazera and Tilapia zilli. Comp Biochem Physiol C 87, 297-301.
1. The effects of lethal zinc concentrations on some physiological and biochemical parameters in Clarias lazera and Tilapia zilli were investigated. 2. The analyses of lactate, pyruvate and glycogen in both liver and muscle tissues and the relation among them have been studied in detail. 3. Significant increases were observed in liver and serum proteins, serum alkaline phosphatase (ALP), erythrocyte count (RBCs), haematocrit or packed cell volume (PCV) and haemoglobin (HB) concentrations. 4. Zinc exposure reduced liver and serum acid phosphatase (ACP) as well as liver alkaline phosphatase (ALP).

Hilmy, A. M., el-Domiaty, N. A., Daabees, A. Y., and Abdel Latife, H. A. (1987). Toxicity in Tilapia zilli and Clarias lazera (Pisces) induced by zinc, seasonally. Comp Biochem Physiol C 86, 263-5.
Subadult teleosts, Tilapia zilli and Clarias lazera, were exposed in laboratory bioassays to lethal and sublethal concentrations of zinc, seasonally (at range of temperature between 9.3 +/- 1.5 and 25 +/- 1 degree C). It appears that Tilapia is more susceptible to Zn than Clarias and both species are more resistant to Zn toxicity at lower temperature (during winter). To determine the uptake and tissue distribution of Zn in the two species, gill, liver and muscles were analysed at moderate temperature (during spring). After a 96 hr exposure period, Zn was decreased in the following order: gill greater than liver greater than muscle.

Hines, G. A., Boots, L. R., Wibbels, T., and Watts, S. A. (1999). Steroid levels and steroid metabolism in relation to early gonadal development in the tilapia Oreochromis niloticus (Teleostei: cyprinoidei). Gen Comp Endocrinol 114, 235-48.
Sex steroid levels and steroid metabolism were investigated in relation to early gonadal development in a mixed sex population of the tilapia Oreochromis niloticus. Androstenedione (AD), testosterone (T), 11- ketotestosterone (KT), and estradiol (E2) were quantified by radioimmunoassay (RIA) of whole body extracts. Androstenedione metabolism was assessed by incubations in vitro with 3H-AD and metabolites were identified by thin-layer chromatography coupled with radioisotope image analysis. Histology revealed the presence of gonadal structures at 15 days postfertilization (dpf) and ovaries at 36 dpf, with other individuals exhibiting undifferentiated gonads containing germinal cells, presumably eventual testes. Androgen levels were initially high in eggs then decreased severalfold prior to the emergence of gonads. A transient increase in the levels of T and KT occurred at 22 dpf. Levels of E2 were either low or undetectable except for a transient increase (43 dpf) after ovaries were present. Levels of T approached bimodality from 57 to 64 dpf. Steroid metabolism generally increased throughout development. Metabolites were generally similar, consisting of T predominantly as well as 5beta-reduced androgen derivatives and 11-oyxgenated derivatives. Estriol was tentatively identified. Conjugated steroids were not formed. Two types of steroid metabolic profiles occurred at 50 dpf. These results demonstrate that changes in the steroidogenic profile occur during early transitions of gonadal development. Notably, (1) steroid biosynthetic capacity preceeds gonadal differentiation, (2) evidence for estrogens occurs after ovarian development has begun, and (3) bimodality of levels of T and differential steroid metabolism later in development may reflect the onset of sexual divergence. Copyright 1999 Academic Press.

Hines, G. A., Boots, L. R., Wibbels, T., and Watts, S. A. (1999). Steroid levels and steroid metabolism in relation to early gonadal development in the tilapia Oreochromis niloticus (Teleostei : Cyprinoidei). General and Comparative Endocrinology 114, 235-248.
Sex steroid levels and steroid metabolism were investigated in relation to early gonadal development in a mixed sex population of the tilapia Oreochromis niloticus. Androstenedione (AD), testosterone (T), 11-ketotestosterone (KT), and estradiol (E-2) were quantified by radioimmunoassay (RIA) of whole body extracts. Androstenedione metabolism was assessed by incubations in vitro with H-3-AD and metabolites were identified by thin-layer chromatography coupled with radioisotope image analysis. Histology revealed the presence of gonadal structures at 15 days postfertilization (dpf) and ovaries at 36 dpf, with other individuals exhibiting undifferentiated gonads containing germinal cells, presumably eventual testes. Androgen levels were initially high in eggs then decreased severalfold prior to the emergence of gonads. A transient increase in the levels of T and KT occurred at 22 dpf. Levels of E2 were either low or undetectable except for a transient increase (43 dpf) after ovaries were present. Levels of T approached bimodality from 57 to 64 dpf. Steroid metabolism generally increased throughout development. Metabolites were generally similar, consisting of T predominantly as well as 5 beta-reduced androgen derivatives and 11-oyxgenated derivatives. Estriol was tentatively identified. Conjugated steroids were not formed. Two types of steroid metabolic profiles occurred at 50 dpf These results demonstrate that changes in the steroidogenic profile occur during early transitions of gonadal development. Notably, (1) steroid biosynthetic capacity preceeds gonadal differentiation, (2) evidence for estrogens occurs after ovarian development has begun, and (3) bimodality of levels of T and differential steroid metabolism later in development may reflect the onset of sexual divergence. (C) 1999 Academic Press.

Hiroi, J., Kaneko, T., and Tanaka, M. (1999). In vivo sequential changes in chloride cell morphology in the yolk-sac membrane of Mozambique tilapia (Oreochromis mossambicus) embryos and larvae during seawater adaptation. J Exp Biol 202, 3485-3495.
Changes in chloride cell morphology were examined in the yolk-sac membrane of Mozambique tilapia (Oreochromis mossambicus) embryos and larvae transferred from fresh water to sea water. By labelling chloride cells with DASPEI, a fluorescent probe specific for mitochondria, we observed in vivo sequential changes in individual chloride cells by confocal laser scanning microscopy. In embryos transferred from fresh water to sea water 3 days after fertilization, 75 % of chloride cells survived for 96 h, and cells showed a remarkable increase in size. In contrast, the cell size did not change in embryos and larvae kept in fresh water. The same rate of chloride cell turnover was observed in both fresh water and sea water. Using differential interference contrast (DIC) optics and whole-mount immunocytochemistry with anti- Na(+)/K(+)-ATPase, we classified chloride cells into three developmental stages: a single chloride cell without an apical pit, a single chloride cell with an apical pit, and a multicellular complex of chloride and accessory cells with an apical pit. DIC and immunofluorescence microscopy revealed that single chloride cells enlarged and were frequently indented by newly differentiated accessory cells to form multicellular complexes during seawater adaptation. These results indicate that freshwater-type single chloride cells are transformed into seawater-type multicellular complexes during seawater adaptation, suggesting plasticity in the ion-transporting functions of chloride cells in the yolk-sac membrane of tilapia embryos and larvae.

Holje, L., Hildebrand, C., and Fried, K. (1986). On nerves and teeth in the lower jaw of the cichlid Tilapia mariae. Anat Rec 214, 304-11.
The anatomy of the teeth and tooth-related nerves in the lower jaw was examined in the cichlid Tilapia mariae. This was done in order to establish a basis for studies on dental neuroplasticity in a polyphyodont vertebrate. The region of interest was explored in specimens fixed by glutaraldehyde perfusion, and by using X-ray photography, maceration, scanning electron microscopy, gross dissection, and light microscopic examination of serial sections. The results show that the lower jaw carries some 60-65 functional teeth. In addition, numerous replacement teeth and tooth germs in various stages of development are located in a cavity in the dentary bone. Numerous nerve bundles are present in immediate relation to the dental follicles of tooth germs. Unerupted teeth do not contain light-microscopically discernible pulpal axons, but the pulps of functional teeth contain myelinated axons. Both perifollicular and pulpal nerve bundles derive from a nerve plexus, which is formed by branches from r. mandibularis trigemini. This nerve is easily accessible to experimental manipulation, where it courses through the adductor mandibulae muscular complex. Thus, the lower jaw of T. mariae seems to represent a suitable system for the study of tooth-nerve interactions in a polyphyodont species.

Holladay, S. D., Smith, S. A., Besteman, E. G., Deyab, A. S., Gogal, R. M., Hrubec, T., Robertson, J. L., and Ahmed, S. A. (1998). Benzo[a]pyrene-induced hypocellularity of the pronephros in tilapia (Oreochromis niloticus) is accompanied by alterations in stromal and parenchymal cells and by enhanced immune cell apoptosis. Vet Immunol Immunopathol 64, 69-82.
Numerous reports indicate that carcinogenic polycyclic aromatic hydrocarbons (PAH) are mammalian immunotoxicants. These environmental contaminants are widely distributed in both freshwater and costal marine ecosystems where they have been found to bioaccumulate in aquatic species, yet limited information exists regarding potential adverse effects of specific PAH on fish immune function. In the present report, Oreochromis niloticus fish (tilapia) were exposed by intraperitoneal injection to 5, 25, or 50 mg/kg of the PAH, benzo[a]pyrene (B[a]P). Histopathologic evaluation of the primary hematopoietic compartment of fish, the pronephros, demonstrated increased vacuolation of both stromal and parenchymal cells, reduction of lymphoid elements, and immune cell apoptosis. Total pronephros cell counts were diminished in a dose-dependent manner by the chemical exposure. The oxidative metabolic burst in phorbol myristate acetate (PMA)-simulated macrophages isolated from the pronephros was significantly inhibited by B[a]P, but only at the highest dose level employed. The phagocytic capacity of pronephros macrophages was not altered by the chemical treatment.

Houdebine, L. M., Farmer, S. W., and Prunet, P. (1981). Induction of rabbit casein synthesis in organ culture by tilapia prolactin and growth hormone. Gen Comp Endocrinol 45, 61-5.

House, C. R. (1991). Conductance rise induced by the calcium ionophore A23187 in unfertilized eggs of tilapia. Exp Physiol 76, 619-22.
Current-clamp measurements on unfertilized tilapia eggs gave linear current-voltage relations in the range 0 to -120 mV. Eggs had low resting potentials (-22 mV) and high specific membrane resistances (500 k omega cm2) and specific membrane capacitances (0.9 microF cm-2) indicating no marked folding of their plasma membrane. Application of A23187 induced a small depolarization and a conductance rise, the response having a reversal potential of about -16 mV. The results suggest that tilapia eggs have a calcium-gated conductance probably activated at fertilization.

Hsiao, Y. M., Ho, H. C., Wang, W. Y., Tam, M. F., and Liao, T. H. (1997). Purification and characterization of tilapia (Oreochromis mossambicus) deoxyribonuclease I--primary structure and cDNA sequence. Eur J Biochem 249, 786-91.
DNase I of tilapia (Oreochromis mossambicus) was purified to homogeneity. Tilapia DNase I is most active at pH 8.5 with Mg2+ as activator. The Ca2+/Mg2+ pair has a synergistic effect on activation. The enzyme is readily inactivated by heating above 55 degrees C, but is not inactivated by trypsin or 2-mercaptoethanol under alkaline conditions, with or without CaCl2. Its isoelectric point is 6.0. The 258-amino-acid sequence of tilapia DNase I was derived from overlapping sequences of tryptic, chymotryptic and CNBr peptides. The purified enzyme has two variants differing by a single Lys-->Arg mutation at position 125. The polypeptide chain has one disulfide bridge and one carbohydrate side chain. By mass spectrometry, the purified enzyme shows many molecular mass forms differing by Lys/Arg substitution and sugar-chain length. The major form has a molecular mass of 30,914 Da. A 1061-bp nucleotide sequence for the cDNA of tilapia DNase I, obtained by gene cloning and DNA sequencing, contains an ORF coding for a putative 26-residue transmembrane peptide and the mature DNase I polypeptide.

Huang, C. J., Lin, J. Y., and Tsai, H. J. (1999). Two distinct c-ski cDNAs of fish, tilapia (Oreochromis aurea). Mol Reprod Dev 54, 223-31.
Two classes of tilapia c-ski cDNA (accession nos. AJ012011, AJ012012), designated as tski1 and tski2, respectively encoded a 687 and a 714 AA protein and shared a 57% AA identity. Comparison with the Ski proteins of chickens, humans and Xenopus, tilapia TSki polypeptides shared a 60, 57, and 57% (TSki1) and 67, 63, and 61% (TSki2) AA identity, respectively. The most and the least abundant c-ski mRNAs are located in the brain and the skeletal muscle, respectively. Both tski1 and tski2 were widely expressed in the adult tissues examined, but tski2 transcripts were at higher levels except in the ovary and oocytes: tski1 transcripts were predominant in the ovary, whereas tski2 transcripts were predominant in the testes. In the oocytes, the tski1 mRNA was a maternally-inherited stockpile that subsequently was degraded, so that the expression ratio of tski1 to tski2 transcripts declined gradually as the fish developed from oocyte to 4-cm fry. Mol. Reprod. Dev. 54:223- 231. Copyright 1999 Wiley-Liss, Inc.

Huang, S. L., Chen, W. C., Shei, M. C., Liao, I. C., and Chen, S. N. (1999). Studies on epizootiology and pathogenicity of Staphylococcus epidermidis in Tilapia (Oreochromis spp.) cultured in Taiwan. Zoological Studies 38, 178-188.
Studies on epizootiology and pathogenicity of Staphylococcus epidermidis in Tilapia (Oreochromis spp.) cultured in Taiwan. Zoological Studies 38(2). 178-188. This paper describes the epizootiology of a disease of tilapia with clinical signs that include white nodules and microscopic granulomatous formations. Diseased fish showed splenomegaly with diffusion of numerous white nodules. The most severe lesions were presented in the spleen and anterior kidney. Morphological, biological, and biochemical characteristics of microorganisms isolated from the diseased tilapia were examined and classified by Baird-Parker's biochemical subgrouping scheme. Strain LK0728 identified as Staphylococcus epidermidis, was used in a challenge test. Histopathological changes were similar to those seen in naturally infected fish. This is the ist report on the isolation of staphylococci pathogenic to tilapia and on the confirms the etiological agent causing mass mortality in tilapia from 1992 to 1996 in taiwan.

Hwang, P. P., and Sun, C. M. (1989). Putative role of adenohypophysis in the osmoregulation of tilapia larvae (Oreochromis mossambicus; Teleostei): an ultrastructure study. Gen Comp Endocrinol 73, 335-41.
Ultrastructure of the secretory cells in the adenohypophysis of tilapia (Oreochromis mossambicus) larvae hatched in fresh water or sea water was compared. Adenohypophysis of newly hatched larvae of tilapia is a short columnar body attached to the ventral floor of the diencephalon. The adenohypophysis is at its early differentiation stage, i.e., various types of secretory cells are still undistinguishable. Only part of the cells in the putative rostral pars distalis look like typical endocrine cells, containing well-developed rough endoplasmic reticulum, Golgi apparatus, and numerous secretory granules. The average size of secretory granules in freshwater-hatched larvae is significantly larger than those in seawater-hatched larvae (12,936 +/- 2854 nm2, N = 11 vs 3375 +/- 810 nm2, N = 10), suggesting some role of adenohypophysis in the osmoregulation of the early developmental stage of teleosts.

Hwang, P. P., and Wu, S. M. (1993). Role of cortisol in hypoosmoregulation in larvae of the tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 92, 318-24.
The total cortisol content in tilapia was 55 pg immediately following fertilization, then decreased abruptly and maintained a lower level of 10-20 pg until hatching; after hatching the cortisol content increased to 50 pg by the 7th day. Fertilized eggs were incubated in either 32% saltwater or fresh water and sampled at various developmental stages. Both groups showed dramatic changes in cortisol content following development. However, no significant difference in the cortisol level was found between the two groups. Tilapia larvae, hatched in fresh water, were reared with feed containing 0 (control) or 150 mg/kg wt/day cortisol, corticosterone, 17 alpha-hydroxyprogesterone (17 alpha-OHP) or 11 alpha-deoxycortisol (11 alpha-DC) for 8 days and then transferred directly to 27.5% saltwater. Those reared with corticosterone, 17 alpha- OHP, or 11 alpha-DC, similar to the control, all died within 4-8 hr after the transfer. However, the larvae treated with cortisol showed a much higher survival rate of 40-60%. The tissue osmolality in the control larvae, 394.3 +/- 3.7 (mmol/kg), increased abruptly after transfer to 26% saltwater and reach a peak, 681.5 +/- 47.5, before the larvae all died (12th hr after the transfer). In contrast, tissue osmolality in cortisol-treated (150 mg/kg wt/day for 12 days) larvae was 570.7 +/- 62.6 at the 12th hr and then began to decrease to 448.5 +/- 9.4 at the 24th hr and 386.0 at the 48th hr. These findings suggest that cortisol could play a critical role in the hypoosmoregulation in tilapia larvae.

Hyder, M. (1969). Gonadal development and reproductive activity of the cichlid fish Tilapia leucosticta (Trewavas) in an equatorial lake. Nature 224, 1112.

Hyder, M., and Kirschner, M. A. (1969). Detection and estimation of testosterone in the testes of Tilapia leucosticta (Pisces: Cichlidae). J Endocrinol 44, 281-2.

Hyder, M. (1969). Histological studies on the testis of Tilapia leucosticta and other species of the genus Tilapia (Pisces: Teleostei). Trans Am Microsc Soc 88, 211-31.

Hyder, M., Shah, A. V., and Kirschner, M. A. (1970). Effect of chorionic gonadotrophon on testicular histology and testosterone production in Tilapia Leucosticta (Teleostei: Cichlidae). Endocrinology 87, 819-22.

Hyder, M. (1970). Histological studies on the testes of pond specimens of Tilapia nigra (Gunther) (Pisces: Cichlidae) and their implications of the pituitary- testis relationship. Gen Comp Endocrinol 14, 198-211.

Hyder, M., Shah, A. V., Campbell, C. M., and Dadzie, S. (1974). Methallibure studies on Tilapia. II. Effect of Tilapia pituitary homogenate (TPH), human chorionic gonadotropin (HCG) and testosterone propionate (TP) on the testes of methallibure-treated Tilapia nigra. Gen Comp Endocrinol 23, 245-55.

Hyder, M., Shah, A. V., and Hartree, A. S. (1979). Methallibure studies on Tilapia. III. Effects of Tilapian partially purified pituitary gonadotrophic fractions on the testes of methallibure-treated Sarotherodon spirulus (= Tilapia nigra). Gen Comp Endocrinol 39, 475-80.

Ibrahim, A. A., and el-Zanfaly, H. T. (1980). Boulti (Tilapia nilotica Linn.) fish paste. 1. Preparation and chemical composition. Z Ernahrungswiss 19, 159-62.
Boulti fish (Tilapia nilotica Linn.) from Naser's lake in Aswan was converted to a ready marketable product (paste) in aluminium tubes. The quality of the product was ascertained by chemical indices. The product has a good flavour and can be kept for 5 weeks without undesirable changes. It is concluded that the production of fish paste in aluminium tubes is one of the possibilities of converting fish to precooked product.

Inaba, K., Buerano, C. C., Natividad, F. F., and Morisawa, M. (1997). Degradation of vitellogenins by 170 kDa trypsin-like protease in the plasma of the tilapia, Oreochromis niloticus. Comp Biochem Physiol B Biochem Mol Biol 118, 85-90.
Proteolytic degradation of plasma vitellogenins during purification procedure has been noted in several teleost fishes. We have characterized here a trypsin-like serine protease in the plasma of the tilapia, Oreochromis niloticus, which degrades vitellogenins. The molecular mass of the protease was estimated as 230 kDa by gel filtration and as 170 kDa both by nondenaturing and by SDS- polyacrylamide gel electrophoresis. The protease efficiently hydrolyzed the synthetic peptide substrates for trypsin-like proteases but not the substrates for chymotrypsin-like proteases nor aminopeptidases. Hydrolysis of the peptide substrates was strongly inhibited by leupeptin, aprotinin and N-tosyl-L-lysine chloromethyl ketone and to certain extent by chymostatin, 3,4-dichloroisocoumarin, phenylmethanesulfonyl fluoride, and soybean trypsin inhibitor. Leupeptin and aprotinin also inhibited the degradation of a vitellogenin in the plasma. Although the physiological functions of the 170 kDa protease in vivo have not been elucidated, the results on exzymatic properties of this protease will be useful for the isolation and characterization of vitellogenin not only in tilapia but also in other organisms.

Isik, O., Sarihan, E., Kusvuran, E., Gul, O., and Erbatur, O. (1999). Comparison of the fatty acid composition of the freshwater fish larvae Tilapia zillii, the rotifer Brachionus calyciflorus, and the microalgae Scenedesmus abundans, Monoraphidium minitum and Chlorella vulgaris in the algae-rotifer-fish larvae food chains. Aquaculture 174, 299-311.
The proximate and the fatty acid analysis of the warm freshwater fish, Tilapia zillii larvae, the freshwater rotifer Brachionus calyciflorus and the microalgae Scenedesmus abundans, Monoraphidium minitum and Chlorella vulgaris each constituting a different food chain with B. calyciflorus and T. zillii larvae have been carried out. C. vulgaris had significantly higher lipid content than the other two microalgae and this was also reflected in the lipid content of B. calyciflorus fed each of the microalgae separately. Five fatty acids dominated in all the microalgae, namely 18:3n - 3, 18:2n - 6, 18:0, 18:1 and 16:0 though there were significant differences both in quantitative distribution of these acids and the total fatty acid content. The content of 18:3n - 3, 18:2n - 6 and 16:0 and the total fatty acid content of C. vulgaris were considerably higher than the corresponding values in the other two microalgae. But interestingly, these strong differences were not reflected in B. calyciflorus samples fed these microalgae separately though the one fed C. vulgaris had slightly higher total fatty acid content than the other two rotifer samples. One can consider that the freshwater rotifer B. calyciflorus is capable of creating its own characteristic fatty acid content up to a sufficient level even when cultured with a fatty acid deficient algae probably by consuming excessive amounts of this algae compared to other algae of relatively high fatty acid content. The proximate and fatty acid analysis results of the three T. zillii larvae fed the three B. calyciflorus samples obtained by culturing with three different microalgae were very similar. This was an expected result because the three B. calyciflorus samples did not differ much from each other. The low 18:2n - 6 (1.66-3.53 mg g(-1) DM) and 18:3n - 3 (1.14-1.22 mg g(-1) DM) content and the relatively high 22:6n - 3 (10.72-14.38 mg g(-1) DM) content of the T. zillii larvae samples indicated that they were capable of elongating and desaturating both linoleic and linolenic acids of the B. calyciflorus samples. (C) 1999 Elsevier Science B.V. All rights reserved.

Jaso-Friedmann, L., and Evans, D. L. (1999). Mechanisms of cellular cytotoxic innate resistance in tilapia (Oreochromis nilotica). Dev Comp Immunol 23, 27-35.
Mechanisms of innate cytotoxic immunity in tilapia (O. nilotica) were measured by characterization of the activity, distribution and functions of nonspecific cytotoxic cells (NCC). Active cytotoxic cells were obtained from anterior kidney. spleen and peripheral blood whereas nonlytic but anti-NCC monoclonal antibody 5C6 positive cells were obtained from tilapia liver. Thymocytes were not cytotoxic and were mab 5C6+. Unfractionated anterior kidney cells were 6% mab 5C6+ and had very low cytotoxicity of HL-60 target cells. Percoll (45.5%) purified NCC were 44% mab 5C6+ and had 35% HL-60 cytotoxicity (160:1 E:T ratio). Transformed mouse and human target cells were tested for sensitivity to NCC lysis. HL-60, U937, K562, IM-9 and NC-37 human targets were lysed by NCC. YAC-1 targets were insensitive to lysis. The killing of HL-60 targets by tilapia NCC was inhibited by mab 5C6. Experiments to determine optimal conditions for the cytotoxicity assay revealed that tilapia required 15-20h for optimum lysis of targets. Incubation at 37 C produced the highest cytotoxicity. The proliferative competence of Percoll purified anterior kidney cells was determined. A significant increase in in vitro uptake of tritiated thymidine by anterior kidney cells occurred following stimulation by mab 5C6, Con-A, PMA and calcium ionophore A23187. Purified spleen cells also produced significant increased uptake of tritiated thymidine following in vitro activation with PMA and mab 5C6, but not Con-A. These studies indicated that NCC may provide innate cytotoxic immunity similar to that provided by the NCC of catfish.

Jayaraman, S., Mohan, R., and Muthukkaruppan, V. R. (1979). Relationship between migration inhibition and plaque-forming cell responses to sheep erythrocytes in the teleost, Tilapia mossambica. Dev Comp Immunol 3, 67-75.

Jirge, S. K. (1971). Histochemical investigations on the mucoid substances of developing kidney to Tilapia mossambica. Acta Histochem 40, 8-15.

Joshi, U. M., and Desai, A. K. (1988). Biochemical changes in the liver of fish, Tilapia mossambica (Peters), during continuous exposure to monocrotophos. Ecotoxicol Environ Saf 15, 272-6.
The purpose of the present investigation was to determine the effect of continuous exposure to the organophosphate monocrotophos at 2.5 ppm for over a period of 2 through 45 days on protein, RNA, and DNA contents and on 5'-nucleotidase activity in the liver of Tilapia mossambica. Protein content was decreased by 45% after 5 days, returned to control levels at 10-30 days, and again decreased by 45 days. DNA content was decreased by 2 days, returned to control values by 5 days, and remained constant throughout the exposure. In contrast, RNA content was significantly lower starting from 2 through 45 days of exposure. 5'- Nucleotidase activity showed a transient increase at 5 and 30 days of monocrotophos exposure. These results indicate that monocrotophos altered the protein, DNA, and RNA contents and the 5'-nucleotidase activity levels as early as 2 and 5 days. However, these changes were reversed by 10 days and after a short period of recovery, the alterations reappeared. This supports our earlier histological observations of hepatic pathology during monocrotophos exposure.

Joy, K. P., and Sathyanesan, A. G. (1980). Pituitary cytology of the teleost fish Tilapia mossambica (Peters). Z Mikrosk Anat Forsch 94, 337-44.
In the pituitary of Tilapia mossambica, eight cell types were identified on the basis of their staining reactions. the RPD consists of erythrosinophils and PbH positive cells. PbH cells border the NH and give amphipilic reaction to tri- and tetrachrome dyes and Halmi's stain. Erythrosinophils are also stained with acid fuchsin and orange G. The PPD is made up of acidophils and cyanophils. The acidophils are stained with orange G, acid fuchsin and erythrosin. These cells form a palisade zone between the neurohypophysis and the cyanophils. The cyanophils are AB, AF, ATh, PAS and aniline blue positive. They include both thyrotrophs and gonadotrophs and cannot be differentiated. The gonadotrophs may be those which are degranulated and vacuolated in the breeding season. The PI is formed of PAS- and PbH positive cells which lack any definite pattern of arrangement. Apart from the chromophils, scattered chromophobes were seen throughout the adenohypophysis. Occasionally, cells resembling the cyanophils of PPD were noticed in the RPD and PI also.

Kabunda, M. Y., and Sommerville, C. (1984). Parasitic worms causing the rejection of tilapia (Oreochromis species) in Zaire. Br Vet J 140, 263-8.

Kargin, F. (1996). Elimination of cadmium from Cd-contaminated Tilapia zilli in media containing EDTA and freshwater: changes in protein levels. Bull Environ Contam Toxicol 57, 211-6.

Kargin, F., and Cogun, H. Y. (1999). Metal interactions during accumulation and elimination of zinc and cadmium in tissues of the freshwater fish Tilapia nilotica. Bull Environ Contam Toxicol 63, 511-9.

Katsuyama, M., Komori, T., and Matsuno, T. (1987). Metabolism of three stereoisomers of astaxanthin in the fish, rainbow trout and tilapia. Comp Biochem Physiol [B] 86, 1-5.
In rainbow trout (Salmo gairdneri), the dietary astaxanthin diesters were mostly absorbed and accumulated in their integuments keeping their configurations, and partially metabolized to (3R, 3'R)-zeaxanthin (major) and/or (3R, 3'S)-zeaxanthin (medium) and/or (3S,3'S)-zeaxanthin (minor). In tilapia (Tilapia nilotica), the three stereoisomers of astaxanthin diesters were promptly metabolized to only (3S,3'S)- astaxanthin, and subsequently to (3R,3'R)-zeaxanthin and/or (3R,3'S)- zeaxanthin and/or (3S,3'S)-zeaxanthin at an invariable ratio, 4:1:0.3. The above facts indicate that the conversion from 3S- to 3R- configuration was carried out in vivo, and vice versa, and that astaxanthins were reductively metabolized to zeaxanthins in both the fish.

Katz, Y., Eckstein, B., Ikan, R., and Gottlieb, R. (1971). Estrone and estradiol-17 in the ovaries of Tilapia aurea (Teleostei, Cichlidae). Comp Biochem Physiol [B] 40, 1005-9.

Katz, Y., and Eckstein, B. (1974). Changes in steroid concentration in blood of female Tilapia aurea (teleostei, cichlidae) during initiation of spawning. Endocrinology 95, 963-7.

Katz, Y., Abraham, M., and Eckstein, B. (1976). Effects of adrenosterone on gonadal and body growth in Tilapia nilotica (Teleostei, Cichlidae). Gen Comp Endocrinol 29, 414-8.

Kayanja, F. I., Maloiy, G. M., and Reite, O. B. (1975). The fine structure of the intestinal epithelium of Tilapia grahami. Anat Anz 138, 451-62.
The ultrastructure of the intestinal epithelium is described in Tilapia grahami. The intestine is divisible into cranial, middle and caudal portions. The cranial intestine is involved in water anp ion transport as well as in lipid absorption. The caudal intestine is important in protein digestion and adsorption. There is likely to be some functional overlap in the intermediate middle intestine.

Kelley, K. M., Nishioka, R. S., and Bern, H. A. (1988). Novel effect of vasoactive intestinal polypeptide and peptide histidine isoleucine: inhibition of in vitro secretion of prolactin in the tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 72, 97-106.
The effects of vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) on the in vitro secretion of two prolactins (PRL) from the rostral pars distalis (RPD) and of growth hormone (GH) from the proximal pars distalis (PPD) of the pituitary of the tilapia (Oreochromis mossambicus) were studied. RPDs were incubated for 20 hr in hypoosmotic (280-300 mOsm) or hyperosmotic (340-350 mOsm) Krebs- Ringer bicarbonate medium with added peptide concentrations of 0 (control), 0.3, 3.0, 30, and 300 nM; similarly, PPDs were incubated with the same peptide concentrations in isoosmotic (325 mOsm) medium supplemented with cortisol. PRL and GH in the tissue and secreted into the medium were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by soft laser densitometry of the protein band(s). Neither VIP nor PHI has a detectable effect on the secretion of GH. Secretion of the two PRLs is significantly inhibited by VIP and PHI in both hyperosmotic and hypoosmotic medium. In hyperosmotic medium, 300 nM VIP inhibits secretion of both PRLs by 47%, whereas in hypoosmotic medium, 300 nM VIP inhibits their secretion by 27%. PHI inhibits their secretion by ca. 65% in hyperosmotic medium and by 40% in hypoosmotic medium. There is preliminary immunocytochemical evidence for some VIP-like immunoreactivity (IR), but no conclusive indication of PHI-like IR, in the hypothalamo-hypophysial area. The inhibitory actions of VIP and PHI on PRL secretion in tilapia are in contrast to the known stimulatory actions of VIP and PHI on PRL secretion in tetrapods.

Kemp, N. E., and Park, J. H. (1970). Regeneration of lepidotrichia and actinotrichia in the tailfin of the teleost Tilapia mossambica. Dev Biol 22, 321-42.

Khalaf-Allah, S. S. (1999). Effect of pesticide water pollution on some haematological, biochemical and immunological parameters in Tilapia nilotica fish. DTW Dtsch Tierarztl Wochenschr 106, 67-71.
Nine groups of Tilapia nilotica fish each consisting of 50 fish were used to assess the effect of pesticides on the haematological, biochemical and immunological parameters in fish. Four groups were injected with 0.05 ml of Staphylococcus aureus antigen plus complete Freund's adjuvant, the first group (G1) was exposed to lindane treatment, the second (G2) was exposed to dialdrin, the third (G3) was exposed to diazinon and the forth group (G4) was exposed to malathion. Four other groups were not immunized, but injected with the adjuvant and exposed to the pesticides, the fifth group (G5) was exposed to lindane, the sixth (G6) was exposed to dialdrin, the seventh (G7) was exposed to diazinon and the eighth group (G8) was exposed to malathion. The ninth group (G9) was exposed to water without any pesticide treatment and served as controls. Both vaccinated and non-vaccinated groups were exposed to 1/10 LC50 of the tested pesticides for 30 days. The results revealed that the mean total RBCs, WBCs counts, PCV, Hb, MCV, MCH, MCHC values were lower in vaccinated groups than in the groups exposed to the tested pesticides. The total protein, globulin and serum enzymes ALAT; ASAT values as well as macrophage phagocytic index and antibody titer were lower in vaccinated as compared to the non-vaccinated groups.

Khalil, A. H., and Mansour, E. H. (1997). Toxicity of crude extracellular products of Aeromonas hydrophila in tilapia, Tilapia nilotica. Lett Appl Microbiol 25, 269-73.
Extracellular products (ECP) secreted from Aeromonas hydrophila with haemolytic and proteolytic activity were studied with respect to temperature and time of incubation as well as the lethal toxicity on tilapia, Tilapia nilotica. The highest production of the haemolysin product was achieved when Aer. hydrophila was grown at 35 degrees C for 30 h. Tilapia erythrocyte was found to be more susceptible than sheep erythrocyte for determining the haemolytic activity. The haemolytic activity against tilapia erythrocyte was completely inactivated after heating the ECP at 60 degrees C for 10 min or 55 degrees C for 15 min. The proteolytic activity was maximized when the bacterium was grown at 30 degrees C for 36 h. Complete inactivation of the protease enzyme was performed after heating the ECP at 80 degrees C for 10 min or 70 degrees C for 15 min. Aeromonas hydrophila was found to produce haemolytic and proteolytic exotoxin lethal to tilapia (LD50 2.1 x 10(4) cell/fish), as well as heat stable unknown virulent factors that were responsible for 20% mortality. The lethality of ECP was decreased by heating and completely inactivated by boiling at 100 degrees C for 10 min.

Khidr, A. A. (1990). Population dynamics of Enterogyrus cichlidarum (Monogenea: Ancyrocephalinae) from the stomach of Tilapia spp. in Egypt. Int J Parasitol 20, 741-5.
In a 1-year seasonal study of the numbers of the stomach-inhabiting monogenean Enterogyrus cichlidarum in Tilapia nilotica in the River Nile, Egypt, prevalence and intensity reached a height in spring and infection levels were surprisingly high in winter. T. zillii harboured fewer parasites but seasonal changes were similar. No parasites were found in T. galilaea. The prevalence and intensity of the infection with E. cichlidarum rose significantly with increasing size of the host. Some of the possible reasons for these fluctuations are discussed. Immature enterogyrids were more abundant in the posterior sector of the stomach and adult enterogyrids showed a preference for the anterior sector. No significant difference was found in the numbers of enterogyrids in male and female hosts.

Kiliaan, A., Holmgren, S., Jonsson, A. C., Dekker, K., and Groot, J. (1992). Neurotensin, substance P, gastrin/cholecystokinin, and bombesin in the intestine of the tilapia (Oreochromis mossambicus) and the goldfish (Carassius auratus): immunochemical detection and effects on electrophysiological characteristics. Gen Comp Endocrinol 88, 351-63.
The distribution of neurotensin-, substance P-, gastrin/cholecystokinin/carerulein- and bombesin-like immunoreactivities has been studied in the gut of the tilapia (Oreochromis mossambicus) and the goldfish (Carassius auratus) using immunohistochemistry and radioimmunoassay; the electrophysiological effects of these peptides on the intestinal epithelium were also examined with the Ussing-type chamber technique. Neurotensin- and gastrin/cholecystokinin/caerulein-like immunoreactivities were present in endocrine cells in both species. Substance P- and bombesin-like immunoreactive endocrine cells were present in the intestine of the tilapia. Neurotensin-like immunoreactivity was observed in varicose fibers and nerve cell bodies in the muscle layers and myenteric plexus of both species, whereas nerve fibers showing substance P-like immunoreactivity were found in the goldfish only. Using radioimmunoassays, neurotensin- and gastrin/cholecystokinin/caerulein- like immunoreactive materials were detected in intestinal extracts of both species. The amounts of substance P- and bombesin-like material were below detection level. The ion selectivity of the intestinal epithelium of both species was modulated by exogenously applied neurotensin. This effect was blocked by tetrodotoxin in the tilapia but not in the goldfish. In the tilapia, neurotensin may act via stimulation of a cAMP-dependent increase of the Cl- conductance of the tight junctions, whereas in the goldfish, neurotensin induced, via an unknown messenger, a transient decrease of the cation selectivity without a decrease in the resistance. Substance P, cholecystokinin, and bombesin were without effect on the electrophysiological characteristics of the epithelium.

Kiliaan, A. J., Scholten, G., and Groot, J. A. (1997). Exocytotic release of vasoative intestinal polypeptide and serotonin from mucosal nerve fibres and endocrine cells of the intestine of the goldfish (Carassius auratus) and the tilapia (Oreochromis mossambicus): an ultrastructural study. Histochem J 29, 45-51.
In earlier studies were determined the effect, presence and ultrastructure of vasoactive intestinal polypeptide (VIP) and 5- hydroxytryptamine (5-HT)-containing nerve fibres in the tilapia and goldfish intestinal mucosa. 5-HT-labelled varicosities were found close to the epithelial cells; however, synaptic membrane specializations have never been observed. VIP-like immunoreactive nerve fibres appear to be located less frequently close to the goldfish epithelium, as in the tilapia intestine, in which the distance between the VIP- or 5-HT- labelled varicosities and the epithelial cells was also rather large (more than 2 micros). To establish a possible role of VIP and 5-HT as neurotransmitters involved in the regulation of fish intestinal epithelium both electron microscopical and immunoelectron microscopical methods were used to visualize the release of 5-HT and VIP from nerve fibres. We found exocytoses from VIP-ergic and serotonergic varicosities in the muscle layers of both fish. Directly underneath the intestinal epithelium of the goldfish, it was demonstrated that 5-HT could be released from scarce varicosities. The release of 5-HT in the tilapia intestinal mucosa could only be observed from endocrine cells.

Kime, D. E., and Hyder, M. (1983). The effect of temperature and gonadotropin on testicular steroidogenesis in Sarotherodon (Tilapia) mossambicus in vitro. Gen Comp Endocrinol 50, 105-15.
Testes of sexually mature Sarotherodon mossambicus were incubated at 15, 22, 30, and 40 degrees with (a) tritiated testosterone and (b) salmon pituitary extract. Formation of 11-keto- and 11 beta- hydroxytestosterone from the tritiated precursor showed little change in yield between 15 and 30 degrees but yields of glucuronides rose dramatically between 22 and 30 degrees and a significant rise was observed for formation of 5 beta-androstane-3 alpha, 17 beta-diol between 15 and 40 degrees. Yields of 3 alpha, 17 beta-dihydroxy-5 beta- androstan-11-one followed a pattern similar to that of 11- ketotestosterone. With endogenous precursors under the stimulation of salmon pituitary extract, yields of testosterone, 11-ketotestosterone, and 11 beta-hydroxytestosterone were maximal at 22 degrees after which they declined to very low levels at 40 degrees. Yields of testosterone and 11-ketotestosterone glucuronides while showing a peak at 22 degrees declined much more slowly at higher temperatures than did those of the free steroids. In the absence of pituitary stimulation, levels of all steroids were below the limits of detection. Plasma levels of testosterone (15.3 +/- 1.5 ng/ml), 11-ketotestosterone (5.3 +/- 2.7 ng/ml), 11 beta-hydroxytestosterone (5.5 +/- 2.6 ng/ml), and their glucuromides (1.5 +/- 0.5, 0.14 +/- 0.1, and 1.5 +/- 0.5 ng/ml, respectively) were measured in fish held at 25 degrees. A rapid conchromatographic method for the assay of the three free steroids is described and the results are shown to be comparable to those obtained after chromatography.

Kisia, S. M., and Hughes, G. M. (1993). Routine oxygen consumption in different sizes of a tilapia, Oreochromis niloticus (Trewavas) using the closed chamber respiratory method. Acta Biol Hung 44, 367-74.
Routine oxygen consumption (VO2) measurements on 54 specimens (0.055- 190.4 g) of a tilapia, Oreochromis niloticus (Trewavas) were carried out using two different types of closed respirometers: a modified cuvette for fish weighing 0.055-0.91 g and ordinary closed chamber respirometer for fish weighing more than 1 g. VO2 values over the weight range studied had a scaling value of 0.743 which relates closely to the values for the gill respiratory surface area and morphometric oxygen diffusing capacity of O. niloticus in a previous study /13/. This shows that a close relationship exists between changes in structural parameters involved in oxygen uptake and the routine metabolism of O. niloticus with development. The values for routine VO2 of 1.38 and 7.65 ml/h for 10 g and 100 g fish, respectively (calculated from the regression equation) show that O. niloticus is a moderately active fish.

Kista, S. M. (1993). Volume densities and absolute volumes of mitochondria in body trunk red muscle of a tilapia, Oreochromis niloticus (Trewavas). Acta Biol Hung 44, 243-8.
The volume densities /Vv(mt,f)/ and absolute volumes of mitochondria /v(mt)/ were determined in body trunk red muscle of 15 specimens of Oreochromis niloticus weighing 0.65-812.3 g. Vv(mt,f) had a volume of 0.284 +/- 0.012 (S.E.) and V(mt) a value of 0.551 +/- 0.202 (cm3) (S.E.). Both parameters had scaling values of -0.028 and 1.13, respectively, when related to body weight. These results show that there might not be much change in the oxidative metabolism of red muscle with development. The greater than unity value for the scaling value of V(mt) in relation to body weight is due to the high scaling value of body trunk red muscle (1.157) in relation to fish body weight /11/.

Kitta, K., Makino, M., Oshima, N., and Bern, H. A. (1993). Effects of prolactins on the chromatophores of the tilapia, Oreochromis niloticus. Gen Comp Endocrinol 92, 355-65.
Using isolated scales and split-fin preparations of the tilapia Oreochromis niloticus, the effects of a pair of prolactins of the tilapia Oreochromis mossambicus (tPRL177 and tPRL188) and of ovine prolactin (oPRL) on chromatophores were studied in vitro. These peptides caused melanosome aggregation and dispersion of xanthosomes, especially in the split preparations. Their relative effectiveness was as follows: tPRL177 > oPRL > tPRL188. Moreover, tPRL177 at 100 nM induced a high level of pigment dispersion in cultured xanthophores and erythrophores, but tPRL188 at the same concentration did not have this effect. We also examined the responses of chromatophores to oPRL in primary cell culture and found that xanthophores and erythrophores respond to the peptide by pigment dispersion in a dose-dependent manner, whereas cultured melanophores showed little aggregation of pigment. In denervated melanophores in the split-fin preparations, tPRL177 failed to induce aggregation of pigment. From these results, it was concluded that prolactin affects brightly pigmented cells of the tilapia directly, but affects melanophores indirectly. Norepinephrine which might leak from varicosities of chromatic nerve fibers by virtue of the action of prolactin molecules may be responsible for melanosome aggregation.

Klesius, P. H., Shoemaker, C. A., and Evans, J. J. (1999). Efficacy of a killed Streptococcus iniae vaccine in tilapia (Oreochromis niloticus). Bulletin of the European Association of Fish Pathologists 19, 39-41.
Tilapia (Oreochromis niloticus) were vaccinated intraperitoneally (IP) at mean weights of 25 and 100 g with killed Streptococcus iniae vaccine composed of whole cells and concentrated, extracellular products (greater than 2 kDa). At 30 days post vaccination, the groups of vaccinates and non vaccinates were IP challenged and monitored daily for clinical signs and mortality for 60 days. Vaccination reduced mortality 91.3 percent and prevented erratic swimming, hemorrhagic exophthalmia and ocular opacity, immunized 25g tilapia had relative percent survival (RPS) of 95.3 and 100 g tilapia had RPS's ranging from 84.2 to 94.7.

Kling, D. (1981). Total atresia of the ovaries of Tilapia leucosticta (Cichlidae) after intoxication with the insecticide Lebaycid. Experientia 37, 73-4.
Intoxication with sublethal Lebaycid concentrations led to total atresia of the ovaries in 90% of the treated specimens of Tilapia leucosticta. The gonads were filled with atretic follicles and mature eggs were never found. In regeneration trials, intoxicated fish proved to be unable to spawn for at least 9 weeks.

Kocher, T. D., Lee, W. J., Sobolewska, H., Penman, D., and McAndrew, B. (1998). A genetic linkage map of a cichlid fish, the tilapia (Oreochromis niloticus). Genetics 148, 1225-32.
We have constructed a genetic map for a tilapia, Oreochromis niloticus, using DNA markers. The segregation of 62 microsatellite and 112 anonymous fragment length polymorphisms (AFLPs) was studied in 41 haploid embryos derived from a single female. We have identified linkages among 162 (93.1%) of these markers. 95% of the microsatellites and 92% of the AFLPs were linked in the final map. The map spans 704 Kosambi cM in 30 linkage groups covering the 22 chromosomes of this species. Twenty-four of these linkage groups contain at least one microsatellite polymorphism. From the number of markers 15 or fewer cM apart, we estimate a total map length of approximately 1000-1200 cM. High levels of interference are observed, consistent with measurements in other fish species. This map is a starting point for the mapping of single loci and quantitative traits in cichlid fishes.

Kodavanti, P. R., and Ramana Rao, K. V. (1989). Studies on some kinetic parameters of aldolases in selected tissues of the freshwater fish (Tilapia mossambica) under the toxic impact of methyl parathion. J Appl Toxicol 9, 419-26.
Kinetic parameters of aldolases in muscle, gill, liver and brain tissues of the teleost Tilapia mossambica were studied at sublethal concentrations with methyl parathion (MP). The pH activity profiles were optimal at pH 7.0 and 9.0 in gill, liver and brain tissues, whereas only a single peak at pH 7.0 was observed in muscle tissue of both control and MP-exposed fish. The pH 7.0-specific peak was confirmed as aldolase A and the pH 9.0-specific peak represents the tissue-specific aldolases: aldolase B in liver, aldolase C in brain and aldolase B-C in gill. It is further confirmed with the inhibitor sensitivity of aldolases at two peaks with 6 x 10(-3) M ATP or AMP. The pH-based substrate-dependent kinetics of aldolases showed a variable trend. The tissue-specific activity of pH 7.0-specific aldolases showed low Km values for gill followed by muscle, liver and brain tissues, suggestive of its high enzyme-substrate affinity. During MP exposure, the Vmax values of pH 7.0-specific aldolases in muscle, gill and brain were unchanged compared to controls, but Km values were decreased. The pH 9.0-specific aldolases of gill and liver from MP-exposed fish showed decreased Km values with a slight increase in Vmax values. Effectors such as lysine, arginine and Ca2+ inhibited, while histidine, cysteine, aspartic acid and alpha-ketoglutaric acid elevated the activity levels of aldolases.(ABSTRACT TRUNCATED AT 250 WORDS).

Kone, T., and Teugels, G. G. (1999). Reproduction of an estuarine tilapia (Sarotherodon melanotheron Ruppell, 1852) landlocked in a West-African man-made Lake. Aquatic Living Resources 12, 289-293.
Reproduction parameters of a landlocked population of black- chinned tilapia Sarotherodon melanotheron have been studied for 2 years and compared to literature data obtained from their natural environment. Sex-ratio (year 1: 1:2.69; year 2: 1:1.96) is in favour of females and shows seasonal variations. Males mature earlier (year 1: 129 mm SL; year 2: 126 mm SL) than females (year 1: 135 mm; year 2. 136 mm SL). Gonad maturation cycle is continuous. All these results are generally similar to those obtained in the natural environment. However, a lower fecundity is noted in Lake Ayame. Accordingly, an increase in oocyte diameter is observed. The average condition factor in the lake ranges between values observed in lagoon populations and therefore indicates a good adaptation of this species to fresh water conditions. (C) 1999 Ifremer/Cnrs/lnra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS.

Koundinya, P. R., and Ramamurthi, R. (1979). Effect of organophosphate pesticide Sumithion (Fenitrothion) on some aspects of carbohydrate metabolism in a freshwater fish, Sarotherodon (Tilapia) mossambicus (Peters). Experientia 35, 1632-3.
A lethal (Lc50/48 h - 6 mg/l) concentration of the organophosphate (OP) pesticide Sumithion increased blood glucose levels and phosphorylase activity, but hepatic glycogen registered a fall which indicated that the observed hyperglycemia was due to breakdown of hepatic glycogen.

Krishnamoorthy, T. M., Gogate, S. S., and Soman, S. D. (1977). Uptake of tritium from HTO exposure in the fresh water fish Tilapia mossambica. Indian J Exp Biol 15, 570-1.

Kumazawa, T., and Fujii, R. (1984). Concurrent releases of norepinephrine and purines by potassium from adrenergic melanosome-aggregating nerve in Tilapia. Comp Biochem Physiol C 78, 263-6.
Elevation of [K+]0 elicited pigment aggregation within melanophores, and, at the same time, release of both norepinephrine (NE) and purines from split fin preparations of the tilapia, Sarotherodon niloticus, doubly labeled with [14C]NE and [3H]adenosine. This concomitant release increased with the increase in [K+]0 up to 50 mM, although a further increase in [K+]0 caused a progressive decrease in the outputs. The release of either NE or purines was significantly reduced by bretylium. It was concluded that, upon stimulation of the nerve, both the true transmitter, NE, and the co-transmitter, adenine nucleotides, are liberated for an exquisite control of chromatophore movements.

Kumazawa, T., Oshima, N., Fujii, R., and Miyashita, Y. (1984). Release of ATP from adrenergic nerves controlling pigment aggregation in tilapia melanophores. Comp Biochem Physiol C 78, 1-4.
Using split fin preparations of a tilapia, Sarotherodon niloticus, release of ATP from the adrenergic melanosome-aggregating nerve was studied. Associated with the melanosome aggregation, an apparent release of ATP was detected following electrical nervous stimulation. ATP-release increased with increases in stimulus intensity. Spontaneous release of a small amount of ATP was also detected. It was concluded that ATP may be liberated as a co-transmitter along with the true one, norepinephrine, and it may function to help melanophores recover from the effect of the latter, thus enabling fish to change their hue very rapidly.

Kuz'mina, V. V., Chuiko, G. M., and Pavlov, D. F. (1999). Effects of DDVP, naphthalene, and cadmium on intestinal proteolytic activity in Mozambique tilapia (Oreochromis mossambicus Peters). Bull Environ Contam Toxicol 62, 193-8.

Lajolo, F. M., Zucas, S. M., and Domingues, J. B. (1975). [Bromatologic study of protein concentrates obtained from Sardinella aurita and Tilapia melanopleura. I. Analysis of proteins]. Arch Latinoam Nutr 25, 67-78.

Lajolo, F. M., Zucas, S. M., and Domingues, J. B. (1976). [Bromatological study of protein concentrates from Sardinella aurita and Tilapia melanopleura. II. Analysis of minerals]. Arch Latinoam Nutr 26, 295-309.
The calcium and phosphorus of fish protein concentrates (FPC) prepared from whole sardines or tilapias have high biological availability, but the mineral fraction as a whole did not support the normal growth of young rats. Fluoride absorption and utilization is low; the amount retained in the carcass of rats depends on the amount given in the diet according to the equation: Y=0,0672X + 0,202 Y=mg of fluorine retained X=ppm of fluorine in the diet In case of sub-optimal levels of mineral ingestion, fluoride fixation increased proportionally to the deficiency. Our results demonstrate that does not seem necessary to reduce the amount of fluoride in FPC intended for human consumption, at least for people without mineral deficiency in the diet. Results concerning the Ca, P and F balance in rats are presented.

Lamers, A. E., Flik, G., and Bonga, S. E. (1994). A specific role for TRH in release of diacetyl alpha-MSH in tilapia stressed by acid water. Am J Physiol 267, R1302-8.
After exposure of tilapia for 7 days to low-pH water, plasma thyrotropin-releasing hormone (TRH) levels were elevated, and the melanocyte-stimulating hormone (MSH) cells in the pituitary pars intermedia had increased in size and showed enhanced synthetic and secretory activity. The MSH cells became more sensitive to TRH but not to corticotropin-releasing hormone (CRH). Stimulation by TRH (but not by CRH) of the MSH cells of tilapia exposed to low pH specifically enhanced the release of diacetyl alpha-MSH, the most potent corticotropic form of alpha-MSH. Acute stress imposed by handling and confinement for 1 h elevated the plasma cortisol level but did not affect blood plasma alpha-MSH levels. We conclude that stimulation by TRH is pivotal for an enhanced release of diacetyl alpha-MSH during low- pH adaptation. These results are further evidence of a role for TRH and alpha-MSH in the activation of the hypothalamopituitary-interrenal axis during adaptation to low pH.

Lamers, A. E., Groneveld, D., de Kleijn, D. P., Geeraedts, F. C., Leunissen, J. A., Flik, G., Wendelaar Bonga, S. E., and Martens, G. J. (1996). Cloning and sequence analysis of a hypothalamic cDNA encoding a D1c dopamine receptor in tilapia. Biochim Biophys Acta 1308, 17-22.
Physiological and pharmacological studies have indicated that during acid stress a D1-like dopamine receptor becomes functional on intermediate pituitary melanocyte-stimulating hormone cells of tilapia (Oreochromis mossambicus). As a first step towards physiological expression studies we isolated a D1-like dopamine receptor from a tilapia hypothalamus cDNA library. Construction of a phylogenetic tree of most of the D1-like receptors known in human, rat, Xenopus, goldfish and Drosophila revealed that the here presented clone is most likely the tilapia equivalent of the Xenopus D1c dopamine receptor.

Langescheid, C. (1968). [Comparative investigation on the inborn large-size-discrimination of Tilapia nilotica and Hemihaplochromis multicolor (Pisces; Cichlidae)]. Experientia 24, 963-4.

Lanzing, W. J., and Wright, R. G. (1974). The ultrastructure of the skin of Tilapia mossambica (Peters). Cell Tissue Res 154, 251-64.

Lanzing, W. J. (1976). The fine structure of fins and finrays of Tilapia mossambica (Peters). Cell Tissue Res 173, 349-56.
Light and electron-microscopic studies were carried out on the fins of the fish Tilapia mossambica (Peters). A detailed description is presented of the different skeletal components comprising the finrays. The mode of development of the hemisegments appears in several ways similar to that of fish scales. Each hemisegment is contained by an envelope of scleroblasts which secrete collagen fibres in a unipolar fashion. Calcification takes place as a result of deposition of hydroxyapatite-like crystals between the collagen fibres. However, the orientation of these fibres is not as regular as that of the fibres occurring in scales.

Lanzing, W. J., and Wright, R. G. (1976). The ultrastructure and calcification of the scales of Tilapia mossambica (Peters). Cell Tissue Res 167, 37-47.
The scales of Tilapia are surrounded by an envelope of scleroblasts responsible for the production of layers of collagen that constitute the bulk of the scale. The scleroblasts adjoining the lateral face of the oldest scale region gradually atrophy. New Collagen layers are deposited against the inner face of the scale, the adjoining scleroblasts showing evidence of high metabolic activity. Calcification occurs by inotropic deposition of crystals alongside the fibres. There is no sharp demarcation between calcified and non-calcified scale regions, a calcification front gradually moving towards newly formed collagen layers. It is felt that fish scales should be considered as calcified derivatives of dermal collagen layers.

Latey, A. N., and Rangneker, P. V. (1982). Role of the pituitary gland in adaption of the fish Tilapia mossambica (Peters) to contrasting backgrounds. Endokrinologie 79, 406-14.
The fish Tilapia mossambica were exposed for 30 days to continuously illuminated black or white backgrounds. When compared with the controls the black-adapted fish showed multiplication of the melanophores with a maximal dispersion of the melanosomes. The white background induced blanching of the fish because of depletion of the melanophores and aggregation of the melanosomes. The treatment evoked major changes in the pars intermedia cells. Of these, the amphiphils were stimulated in the black-adapted and regressed in the white-adapted fish indicating that these cells secrete melanophore stimulating hormone. The cyanophils showed depressed activity in the black-adapted fish, but in the white-adapted animals they were stimulated. These alterations suggest the elaboration of a melanophore concentrating hormone by the cyanophils. Regressive effects were also recorded in the gonadotrops and gonads of the experimental T. mossambica.

LaVorgna, M. W., Hafez, Y. S., Hughes, S. G., and Whittiker, M. B. (1999). Utilization of phytate phosphorus by tilapia. Faseb Journal 13, A884-A884.

Lazier, C. B., Langley, S., Ramsey, N. B., and Wright, J. M. (1996). Androgen inhibition of vitellogenin gene expression in tilapia (Oreochromis niloticus). Gen Comp Endocrinol 104, 321-9.
Treatment of mature female tilapia (Oreochromis niloticus) with high levels of androgen (17 alpha-methyltestosterone, 17 alpha MT) results in a pronounced decline in plasma vitellogenin levels as determined by gel electrophoresis. Total RNA extracted from livers of treated fish and vehicle-injected controls was analyzed by Northern and slot blot hybridization using an oligonucleotide complementary to a sequence in the 3' end of tilapia vitellogenin mRNA. The probe revealed an mRNA of 6.5 kb in liver from the control mature female fish which was decreased by 85% by androgen treatment. As expected, estradiol (E2) treatment induced the 6.5-kb mRNA in mature male tilapia. The antiestrogen, tamoxifen, strongly decreased vitellogenin mRNA levels in mature females. Radioimmunoassay of serum from control and 17 alpha MT-treated female tilapia showed a marked reduction in serum E2 levels, from 11.4 +/- 2.6 ng/ml in controls to 2.2 +/- 0.13 ng/ml in treated fish. Tamoxifen, however, resulted in increased serum E2 levels, probably by blocking E2 negative feedback. The serum E2-lowering effect of 17 alpha MT suggests an inhibitory site of action on gonadotropin production at the hypothalamic-pituitary axis, possibly through an androgen receptor or through an estrogen receptor after local aromatization of 17 alpha MT.

Leatherland, J. F., Hyder, M., and Ensor, D. M. (1974). Regulation of plasma Na+ and K+ concentrations in five African species of Tilapia fishes. Comp Biochem Physiol A 48, 699-710.

Leatherland, J. F., Ball, J. N., and Hyder, M. (1974). Structure and fine structure of the hypophyseal pars distalis in endigenous African species of the genus Tilapia. Cell Tissue Res 149, 245-66.

Leatherland, J. F., and Hyder, M. (1975). Effect of thyroxine on the ultrastructure of the hypophyseal proximal pars distalis in Tilapia zillii. Can J Zool 53, 686-90.

Lee, W. J., and Kocher, T. D. (1998). Microsatellite mapping of the prolactin locus in the tilapia genome. Anim Genet 29, 68-9.

Leung, T. C., Ng, T. B., and Woo, N. Y. (1991). Metabolic effects of bovine growth hormone in the tilapia Oreochromis mossambicus. Comp Biochem Physiol A 99, 633-6.
1. Bovine growth hormone (bGH) was injected into tilapia intramuscularly at a dose of 50 micrograms/100 g/day for a total of five injections. Control fish received saline instead. 2. The serum concentrations of amino acid and glucose were significantly higher and hepatic glycogen concentration and glycogen synthetase activity significantly lower in the bGH-treated fish than those in the control fish. 3. The serum concentrations of protein, lipid and cholesterol, and the hepatic concentrations of protein and lipid, remained unaltered after bGH treatment. 4. The results suggest that bGH exerts anti- insulin effects in tilapia.

Levavi-Sivan, B., and Yaron, Z. (1989). Gonadotropin secretion from perifused tilapia pituitary in relation to gonadotropin-releasing hormone, extracellular calcium, and activation of protein kinase C. Gen Comp Endocrinol 75, 187-94.
Gonadotropin (taGTH) secretion from perifused fragments of tilapia pituitaries was stimulated in a dose-dependent manner by an analog of gonadotropin-releasing hormone ([D-Ala6] des Gly10 ethylamide LHRH; GnRHa) in a dose range of 1.28 to 128 pM. The baseline secretion rate and taGTH secretion in response to GnRHa were both reduced when the perifusion medium lacked Ca2+. Calcium ionophore (A23187; 0.1 mM) mimicked the effect of GnRHa but only in the presence of Ca2+. The addition of cobalt chloride to the medium at 0.6 mM initially caused an increase in taGTH secretion which was followed by its decrease. At a CoCl2 concentration of 1.3 mM, the baseline secretion rate remained low and the effect of GnRHa on taGTH secretion was attenuated. Withdrawal of CoCl2 from the medium was followed by an elevated basal secretion rate. Five-minute pulses of the protein kinase C activator, 1 oleyl-2- acetyl-rac-glycerol (OAG; 0.25 to 10.4 mM) stimulated taGTH secretion in the presence of Ca2+. With the reservation that the experiments were performed on fragments containing more than one pituitary cell type, the results indicate that the stimulation of GTH secretion in this fish is dependent, as in mammals, on extracellular Ca2+ and probably involves the activation of protein kinase C. However, the fact that taGTH may be stimulated to some extent in the absence of extracellular calcium or in the presence of 1.3 mM CO2+ may point to the possibility that Ca2+ is mobilized from intracellular stores as a result of GnRH stimulation or to the involvement of an additional mechanism of GnRH action in fish independent of calcium.

Levavi-Sivan, B., and Yaron, Z. (1992). Involvement of cyclic adenosine monophosphate in the stimulation of gonadotropin secretion from the pituitary of the teleost fish, tilapia. Mol Cell Endocrinol 85, 175-82.
The present study examines the involvement of cAMP in the transduction of the short-term effect of gonadotropin-releasing hormone (GnRH) on gonadotropin release in the teleost fish, tilapia. A 5 min pulse of dibutyryl cyclic AMP (dbcAMP; 0.03-3 mM) or forskolin (0.1-10 microM) resulted in dose-dependent surges in tilapia gonadotropin (taGTH) secretion from the perifused pituitary. The initial increase in taGTH in response to dbcAMP (3 mM) occurred within 6 min. The concentration of cAMP in the effluent medium increased about 20-fold after a pulse of [D-Ala6,Pro9-NEt]-luteinizing hormone-releasing hormone (LHRH) (GnRHa; 100 nM). To rule out the possibility that the observed effects were due to stimulation by endogenous GnRH release from intact nerve terminals present in the fragments, further experiments were performed in primary cultures of dispersed pituitary cells. Exposure (30 min) of the cells to forskolin (0.01-1.0 microM) resulted in a dose-dependent increase in taGTH release similar to that achieved by GnRHa (1 pM to 10 nM). Also 8- bromo cAMP (0.01-1.0 mM) evoked a dose-related increase in taGTH release. A 3-fold increase in the release occurred in the presence of isobutylmethylxanthine (IBMX) (0.2 mM), similar to that obtained by GnRHa (1.0 nM) in the absence of IBMX. However, when combined, the increase in taGTH release was 16-fold. Moreover, exposure of the cultured cells to GnRHa (0.1 or 10 nM, 60 min) resulted in a dose- related elevation of intracellular cAMP levels and taGTH release.(ABSTRACT TRUNCATED AT 250 WORDS).

Levavi-Sivan, B., Ofir, M., and Yaron, Z. (1995). Possible sites of dopaminergic inhibition of gonadotropin release from the pituitary of a teleost fish, tilapia. Mol Cell Endocrinol 109, 87-95.
The present study is an attempt to find sites of dopaminergic inhibition along the transduction cascades culminating in gonadotropin (GtH) release in a teleost fish, tilapia. Experiments were carried out on perifused pituitary fragments and in primary culture of trypsinized pituitary cells. Salmon GnRH, chicken GnRH I and II stimulated GtH release in culture with estimated ED50 values of 15.56 pM, 2.55 nM and 8.65 pM, respectively. Apomorphine (APO; 1 microM) totally abolished this stimulation. Dopamine (DA; 1 microM) reduced both basal and GnRHa- stimulated GtH release from perifused pituitary fragments but did not alter the formation of cAMP. In a similar perifusion experiment DA abolished GtH release in response to forskolin (10 microM) with no reduction in cAMP formation. This indicates that one site of the dopaminergic inhibition is distal to cAMP formation, an indication not compatible with the classic characteristic of DA D2 type mode of action. The inhibition of GtH release in culture, caused by 1 microM APO, the specific DA D2 agonists LY 171555 (LY) or bromocryptine (BRCR) could not be reversed by activating protein kinase C (PKC) by DiC8 or the phorbol ester TPA. This would indicate a site for DA action distal to PKC. However, the stimulatory effect of arachidonic acid (AA; 50 microM) in perifusion was not reduced by DA (1 microM) or by APO, LY or BRCR in culture, which suggests a site for DA action proximal to AA formation. APO, LY and BRCR reduced GtH release in response to the Ca2+ ionophore A23187, however, their inhibitory effect was reversed by 10 microM ionomycin.(ABSTRACT TRUNCATED AT 250 WORDS).

Li, J., Eygensteyn, J., Lock, R., Verbost, P., Heijden, A., Bonga, S., and Flik, G. (1995). Branchial chloride cells in larvae and juveniles of freshwater tilapia Oreochromis mossambicus. J Exp Biol 198, 2177-84.
Branchial chloride cells in the developing larvae and juveniles of freshwater tilapia, Oreochromis mossambicus, were identified and the membrane Na+/K+-ATPase was localized in situ through binding of the fluorescent dye anthroylouabain. After co-labelling of the cells with the fluorescent probes DASPMI and Con-A-FITC, the mitochondria and apical crypt in the same chloride cells were visualized using confocal laser scanning microscopy. The high density of apical crypts indicated that many chloride cells were functional. The density of branchial chloride cells in larvae 10 days after hatching was approximately 6000 mm-2. An extremely high Na+/K+-ATPase specific activity of approximately 1500 &micro;mol Pi h-1 mg-1 was measured in the gills 10 days after hatching. With the development of secondary lamellae and hence an increase in the amount of branchial epithelial protein, a concomitant decrease in the specific activity of the enzyme in the gill tissues was observed. Total Na+/K+-ATPase activity increased markedly in the early life stages. Our data indicate that in larval stages of fish the gills form a functional ionoregulatory organ before they start functioning as a gas-exchange organ.

Li, S. F., Li, C. H., Dey, M., and Dunham, R. (1999). Seinability of four strains of Nile tilapia, Oreochromis niloticus, in Chinese ponds. Aquaculture 174, 223-227.
Seinability of four strains of Nile tilapia, Oreochromis niloticus, was studied in earthen ponds in Huzhou, Zhejiang province in China during 1995 and 1996. The accumulated seinability of the GIFT, Egypt 88, Sudan 78 and Egypt 92 strains was compared based on three trawls. Seinability of the GIFT strain was higher (P < 0.01) than that of other strains. In 1995, the seinability of the GIFT line (67% of the population captured) was higher than that of Egypt 88 (38%), Sudan 78 (23%) and Egypt 92 (22%). In 1996, the seinability of the GIFT line (81.5%) was higher than that of the Egypt 88 strain (62%). The utilization of the GIFT line will improve harvestable production in China. (C) 1999 Elsevier Science B.V. All rights reserved.

Lin, T. C., Lee, F. Y., and Lin, C. I. (1995). Comparative effects of strophanthidin in tilapia and human heart tissues [published erratum appears in Chin J Physiol 1995;38(4):265]. Chin J Physiol 38, 177-84.
It is well documented that the cardiotonic steroid strophanthidin increases myocardial contractile force through an inhibition of the sarcolemmal Na(+)-K+ pump in mammalian heart cells. The aim of the present study was to determine the effect of this digitalis substance on action potential and contraction in cardiac tissues obtained from a cultured freshwater fish tilapia (Oreochromis sp.) and compare with those observed in human heart tissues obtained at cardiac surgery. In tilapia atria superfused at 25 degrees C 1-2 microM strophanthidin shortened the spontaneous cycle length while increased progressively the twitch force. In tilapia ventricular tissues, strophanthidin also increased the force but shortened the APD50. When temperature of the superfusate was elevated from 25 to 37 degrees C, strophanthidin induced a smaller positive or even negative inotropic effect but increased significantly the diastolic tension through an inhibition of the relaxation process. High temperature also facilitated the occurrence of delayed afterdepolarizations, repetitive slow response action potentials and episodes of contracture. The same concentration of stroph induced rather sustained positive inotropic effects without deteriorating actions in human ventricular trabeculae driven at 37 degrees C. In human atrial trabeculae, however, 2 microM strophanthidin readily induced abnormal automatic and triggered rhythms along with the positive inotropy. The present findings provide the functional evidence for the presence of sarcolemmal Na+, K(+)-pump in fish myocardial fibers. The major differences in the electro-mechanical actions of strophanthidin in tilapia versus human heart tissues are the smaller positive inotropy and the proneness to contracture in tilapia heart at 37 degrees C.

Lin, H. C., and Hwang, P. P. (1998). Acute and chronic effects of antimony chloride (SbCl3) on tilapia (Oreochromis mossambicus) larvae. Bull Environ Contam Toxicol 61, 129-34.

Lin, H. C., and Hwang, P. P. (1998). Acute and chronic effects of indium chloride (InCl3) on tilapia (Oreochromis mossambicus) larvae. Bull Environ Contam Toxicol 61, 123-8.

Lin, H. C., and Hwang, P. P. (1998). Acute and chronic effects of gallium chloride (GaCl3) on tilapia (Oreochromis mossambicus) larvae. Bull Environ Contam Toxicol 60, 931-5.

Lin, G. R., Weng, C. F., Wang, J. I., and Hwang, P. P. (1999). Effects of cortisol on ion regulation in developing tilapia (Oreochromis mossambicus) larvae on seawater adaptation. Physiol Biochem Zool 72, 397-404.
The yolk diameter of cortisol-treated tilapia (Oreochromis mossambicus) larvae, immersed in freshwater (FW) containing 10 mg L-1 cortisol from 48 h postfertilization to 12 d posthatching, was significantly larger than that of control larvae after 8 d of treatment, suggesting that inhibition on larval growth occurred only after a long-term treatment with cortisol. Tilapia embryos or larvae treated with 1-10 mg L-1 cortisol for 1-2 d and then transferred to 20-30 g L-1 seawater (SW) showed reduced cumulative larval mortality in SW compared with controls. Moreover, 4-5 d of cortisol treatments significantly diminished the degree of increase in larval body Na content after the transfer to SW. Significant effect of cortisol on body Na content of larvae occurred as early as 4-8 h after the transfer to SW, while no significant difference was found in the ouabain binding of yolk-sac epithelia between control and cortisol-treated larvae even 12 h after the transfer. Cortisol may be involved in the early phase of SW adaptation in developing larvae, and this mechanism may be achieved by other means than increasing the Na-K-ATPase of yolk-sac epithelia.

Lindley, T. E., Scheiderer, C. L., Walsh, P. J., Wood, C. M., Bergman, H. L., Bergman, A. L., Laurent, P., Wilson, P., and Anderson, P. M. (1999). Muscle as the primary site of urea cycle enzyme activity in an alkaline lake-adapted tilapia, Oreochromis alcalicus grahami. J Biol Chem 274, 29858-61.
The tilapia fish Oreochromis alcalicus grahami from Kenya has adapted to living in waters at pH 10.5 by excreting the end product of nitrogen metabolism as urea rather than as ammonia directly across the gills as occurs in most fish. The level of activity in liver of the first enzyme in the urea cycle pathway, carbamoyl-phosphate synthetase III (CPSase III), is too low to account for the observed high rates of urea excretion. We report here the surprising finding that CPSase III and all other urea cycle enzyme activities are present in muscle of this species at levels more than sufficient to account for the rate of urea excretion; in addition, the basic kinetic properties of the CPSase III appear to be different from those of other known type III CPSases. The sequence of the CPSase III cDNA is reported as well as the finding that glutamine synthetase activity is present in liver but not in muscle. This unusual form of adaptation may have occurred because of the apparent impossibility of packaging the needed amount of urea cycle enzymes in liver.

Lio-Po, G., and Wakabayashi, H. (1986). Immuno-response in tilapia Sarotherodon niloticus vaccinated with Edwardsiella tarda by hyperosmotic infiltration method. Vet Immunol Immunopathol 12, 351-7.
Sarotherodon niloticus with average weight of 28.42 +/- 1.87 g were immunized with formalin-killed Edwardsiella tarda using the hyperosmotic infiltration method. Test fish maintained in 30 l aquaria were grouped into four treatments. Group 1 and 2 were exposed to a single hyperosmotic treatment on day 0. Group 1 was bled on day 14 and group 2 was bled on day 28. Group 3 was given hyperosmotic treatments twice: on day 0 and day 14 and bled on day 28. Group 4 was an untreated control bled on day 28. All sera were analyzed for agglutinating antibody titer against E. tarda flagellar and somatic antigens. Results showed that flagellar and somatic agglutinin titers in all treatments were not statistically significant. Likewise, infection experiments where test fish were challenged with intraperitoneal injection of the test bacterium showed that the vaccination experiment did not effectively protect the test fish from infection by Edwardsiella tarda.

Liu, W. K., Wong, M. H., and Cheung, Y. H. (1989). Morphological changes in the gills of tilapia fed sterilized and nonsterilized sludge. Biomed Environ Sci 2, 81-91.
The effects of digested sludge on the ultrastructure of gills of Sarotherodon mossambicus were investigated. Samples of digested sludge were collected from the Shatin Sewage Treatment Plant in Hong Kong and they were (1) sun-dried (NS) or (2) sterilized in an autoclave (SS). They were then used as supplementary fish feed to cultivate the freshwater tilapia, S. mossambicus, for 50 days under laboratory conditions. The SS at low dosage (25%) had the lowest toxicity among different treatments. A swelling of lamellar epithelium, the enlargement of the the subepithelial space, the collapse of capillaries, and the infiltration of polymorphonuclear cells in the lamellae of fish gills were common to fish fed 50 to 100% NS and SS. The thickening of the basal lamina in the gill lamellae is a common feature found in the sludge-treated fish.

Livni, N. (1971). Ovarian histochemistry of the fishes Cyprinus carpio, Mugil capito and Tilapia aurea (teleostei). Histochem J 3, 405-14.

Longalong, F. M., Eknath, A. E., and Bentsen, H. B. (1999). Response to bi-directional selection for frequency of early maturing females in Nile tilapia (Oreochromis niloticus). Aquaculture 178, 13-25.
Twenty tagged individuals were randomly sampled from each of 42 full-sib families within 21 randomly chosen half-sib families of Nile tilapia (Oreochromis niloticus) among the families representing the third generation of selection for improved growth performance in the GIFT project, and communally stocked in an earthen pond. The occurrence of sexual maturation in the females was recorded four weeks after the first swim-up fry were observed in the pond. Broodstock was selected from full- sib families with a high (> 75%) or a low (< 20%) frequency of mature females. After about 4 weeks of single pair stocking in breeding hapas, 16 pairs of breeders from families with a mean frequency of 83% early maturing females and nine pairs of breeders, all from families with 0% early maturing females, had produced fry. The fry from each pair were reared separately until a size of 3-5 g, when totally 3179 fingerlings equally representing the 25 progeny families were tagged and communally stocked in three replicated ponds for testing. Recording of sex, body weight and occurrence of sexual maturation in the females was carried out 2, 3 or 4 weeks, respectively, after observing the first swim-up fry in the three ponds. The fish were restocked and reared until recording at harvest. The age corrected least square means across ponds and across families within selection groups for frequency of sexually mature females at intermediate recording was 57.0% and 33.6% in progeny of breeders from full-sib families with a high or a low frequency of early maturing females, respectively. The response to selection, measured as the difference between the two progeny groups, was highly significant (P = 0.0002). The timings of the recording was appropriate in all three ponds. A significant correlated response in body weight of males at harvest (P = 0.027) and a nearly significant correlated response in body weight of females at intermediate recording (P = 0.052) was also observed. The age corrected least square means of body weight were higher in the progeny of breeders from full-sib families with a high frequency of early maturity in the females, suggesting an unfortunate genetic association between the two traits in Nile tilapia used in aquaculture. It is proposed to carry out combined selection for body weight and frequency of early maturing females in applied breeding programs for farmed Nile tilapia, (C) 1999 Elsevier Science B.V. All rights reserved.

Lopez, F. J. M., Diaz, I. M., Lopez, M. D., and Lopez, F. J. A. (1999). Inhibition of digestive proteases by vegetable meals in three fish species; seabream (Sparus aurata), tilapia (Oreochromis niloticus) and African sole (Solea senegalensis). Comparative Biochemistry and Physiology B-Biochemistry & Molecular Biology 122, 327-332.
The inhibitory effect of three different vegetable foodstuffs (defatted soybean meal, corn gluten meal and wheat bran) on alkaline protease activity of seabream, tilapia and sole was evaluated. Protease inhibition on crude digestive extracts was assessed using different relative concentrations of plant meals and represented by constructing inhibition curves. SDS-PAGE zymograms were utilised to obtain further details in the characterisation of sensitivity of some fish enzymes to protease inhibitors. Tilapia showed the greatest sensitivity to protease inhibitors present in the assayed meals. A high resistance of sole digestive proteases to inhibition produced by soybean meal or corn gluten meal was detected, although they were sensitive to protease inhibitor activity in wheat bran. (C) 1999 Elsevier Science Inc. All rights reserved.

Lotan, R. (1966). Oxygen consumption in the gills of Tilapia aurea (Steindachner) (Pisces, Cichlidae) in various saline conditions. Isr J Zool 15, 33-7.

Low, K. W., and Sin, Y. M. (1995). In vitro effect of mercuric chloride and sodium selenite on chemiluminescent response of pronephros cells isolated from tilapia, Oreochromis aureus. Bull Environ Contam Toxicol 55, 909-15.

Low, K. W., and Sin, Y. M. (1995). Effects of mercuric chloride on chemiluminescent response of phagocytes and tissue lysozyme activity in tilapia, Oreochromis aureus. Bull Environ Contam Toxicol 54, 302-8.

Maclean, N., Iyengar, A., Rahman, A., Sulaiman, Z., and Penman, D. (1992). Transgene transmission and expression in rainbow trout and tilapia. Mol Mar Biol Biotechnol 1, 355-65.
We describe the production of transgenic rainbow trout (Oncorhynchus mykiss) and tilapia (Oreochromis niloticus) by microneedle injection of fertilized eggs with cloned copies of novel gene constructs. Two aspects of the work with transgenic trout are presented; namely, patterns of inheritance of transgenes by the F1 generation following in vitro fertilization of gametes from transgenic and nontransgenic fish, and the degree of DNA methylation of transgenes in different fish and in different tissues of the same fish. Work with transgenic tilapia has been only of short duration, and evidence is presented simply to indicate their transgenic status. Transient expression studies using the bacterial gene chloramphenicol acetyltransferase when driven by fish-derived promoters are also discussed.

Mainoya, J. R., and Bern, H. A. (1982). Effects of teleost urotensins on intestinal absorption of water and Nacl in tilapia, sarotherodon mossambicus, adapted to fresh water or seawater. Gen Comp Endocrinol 47, 54-8.

Malvestuto, S. P., and Ogambo-Ongoma, A. (1978). Observations on the infection of Tilapia leucosticta (Pisces: Cichlidae) with Contracaecum (Nematoda: Heterocheilidae) in Lake Naivasha, Kenya. J Parasitol 64, 383-4.

Mansour, N. S., Youssef, M. M., Awadalla, H. N., Hammouda, N. A., and Boulos, L. M. (1987). Heterophyid metacercariae in the fish Tilapia sp. (Cichlidae) from Edku, Maryut and Manzala lakes in Egypt. J Egypt Soc Parasitol 17, 481-93.

Mansour, M., Wright, J. R., Jr., and Pohajdak, B. (1998). Cloning, sequencing and characterization of the tilapia insulin gene. Comp Biochem Physiol B Biochem Mol Biol 121, 291-7.
Using degenerate primers based on insulin sequences from other organisms, we report the cloning of the complete tilapia (Oreochromis niloticus) insulin gene. Using nested primers and a cassette ligation strategy we have also cloned 932 base pairs (bp) of 5' flanking and 1152 bp of 3' flanking sequence. The tilapia insulin gene has the similar three exon (one untranslated), two intron distribution found in all insulin genes sequenced to date. However, intron 1 is unique in having a smaller size (73 bp) than found in other organisms. 5' RNA extension revealed the presence of two potential transcriptional start sites. A perfect TATA box is located at -30 bp from the first transcriptional start site. Interestingly, the 5' upstream region contains a microsatellite close to the same position of a unique minisatellite found only in humans and primates. The upstream region also contains several potential control elements to regulate insulin expression that are found in mammalian insulin genes.

Mart#nez, R., Juncal, J., Zald#var, C., Arenal, A., Guill#n, I., Morera, V., Carrillo, O., Estrada, M., Morales, A., and Estrada, M. P. (2000). Growth Efficiency in Transgenic Tilapia (Oreochromis sp.) Carrying a Single Copy of an Homologous cDNA Growth Hormone. Biochem Biophys Res Commun 267, 466-472.
Growth hormone (GH) has been shown to have a profound impact on fish physiology and metabolism. However, detailed studies in transgenic fish have not been conducted. We have characterized the food conversion efficiency, protein profile, and biochemical correlates of growth rate in transgenic tilapia expressing the tilapia GH cDNA under the control of human cytomegalovirus regulatory sequences. Transgenic tilapia exhibited about 3.6-fold less food consumption than nontransgenic controls (P 0.001). The food conversion efficiency was significantly (P 0.05) higher (290%) in transgenic tilapia (2.3 +/- 0.4) than in the control group (0.8 +/- 0.2). Efficiency of growth, synthesis retention, anabolic stimulation, and average protein synthesis were higher in transgenic than in nontransgenic tilapia. Distinctive metabolic differences were found in transgenic juvenile tilapia. We had found differences in hepatic glucose, and in agreement with previous results we observed differences in the level of enzymatic activities in target organs. We conclude that GH-transgenic juvenile tilapia show altered physiological and metabolic conditions and are biologically more efficient. Copyright 2000 Academic Press.

Martinez, R., Estrada, M. P., Berlanga, J., Guillen, I., Hernandez, O., Cabrera, E., Pimentel, R., Morales, R., Herrera, F., Morales, A., Pina, J. C., Abad, Z., Sanchez, V., Melamed, P., Lleonart, R., and de la Fuente, J. (1996). Growth enhancement in transgenic tilapia by ectopic expression of tilapia growth hormone. Mol Mar Biol Biotechnol 5, 62-70.
The generation of transgenic fish with the transfer of growth hormone (GH) genes has opened new possibilities for the manipulation of growth in economically important fish species. The tilapia growth hormone (tiGH) cDNA was linked to the human cytomegalovirus (CMV) enhancer- promoter and used to generate transgenic tilapia by microinjection into one-cell embryos. Five transgenic tilapia were obtained from 40 injected embryos. A transgenic animal containing one copy of the transgene per cell was selected to establish a transgenic line. The transgene was stably transmitted to F1 and F2 generations in a Mendelian fashion. Ectopic, low-level expression of tiGH was detected in gonad and muscle cells of F1 transgenic tilapia by immunohystochemical analysis of tissue sections. Nine-month-old transgenic F1 progeny were 82% larger than nontransgenic fish at p = .001. These results showed that low-level ectopic expression of tiGH resulted in a growth acceleration in transgenic tilapia. Tilapia GH gene transfer is an alternative for growth acceleration in tilapia.

Matei, V. E. (1993). [Changes in the cellular ultrastructure of the gill epithelium in Tilapia under the action of cadmium on the fish]. Tsitologiia 35, 34-41.
The ultrastructure of the Tilapia gill epithelium cells was studied under condition of a prolonged (2 months) treatment of these fishes with cadmium in a concentration of 5 mg/l. A decrease in the quantity of chloride cells in the primary gill epithelium, and of respiratory cells in the secondary epithelium was found. The chloride and mucous cells are, respectively, most sensitive and most resistant to the influence of cadmium. The accumulation of lysosomal structures in chloride and respiratory cells was observed, in addition to a reduced surface relief in these and some damage in mitochondria of the former being noticed. A slow development of reparation processes in the tilapia gill epithelium cells was followed after the cancellation of cadmium effect. No restoration of the original ultrastructural pattern of the gill epithelium cells was observed after a 1.5-month inhabitance of Tilapia in clean water.

Matei, V. E., Pavlov, D. F., and Chuiko, G. M. (1993). [The effect of cadmium on the gill structure in Tilapia]. Tsitologiia 35, 13-9.
The effect of a long-term (2 months) exposure to cadmium (5 mg/l), with a subsequent recovery in clean water, upon gill structural organization of Mozambique tilapia was studied using scanning and light microscopy. Some of nonspecific components of the gill response on cadmium action were revealed: hypertrophy and fusion of respiratory lamellae, swelling and lifting of the epithelium from capillaries, vascular stasis. In addition, heavy metal-specific components of this reaction were found, which are involved in the development of epithelial necrosis and leucocyte infiltration into the tissue. The gill ultrastructure recovery was not achieved completely even after a 1.5 month exposure of fishes in clean water.

Matsuyama, T., and Iida, T. (1999). Degranulation of eosinophilic granular cells with possible involvement in neutrophil migration to site of inflammation in tilapia [In Process Citation]. Dev Comp Immunol 23, 451-7.
Observations were made on stretched preparations from the swim bladder and peritoneum obtained from tilapia (Oreochromis niloticus) after injection of formalin-killed Escherichia coli, proteose peptone, compound 48/80 or HBSS into the swim bladder. The eosinophilic granular cells (EGCs) in the swim bladder degranulated rapidly after inoculation. However, the peritoneal EGCs did not degranulate, indicating that degranulation occurs only at the injected site. There was also a correlation between the ratio of the degranulated EGCs and number of the exudate neutrophils. Killed E. coli (1 mg/fish) produced the greatest degranulation response of EGCs and migration of neutrophils into the inflammatory site. Additionally, the rate of the degranulation and number of the neutrophils were lowest when HBSS was injected. The results of this study verify that degranulation of EGCs is involved in the neutrophil migration and suggest that fish EGCs are analogous to mammalian mast cells.

Matsuyama, T., and Iida, T. (1999). Degranulation of eosinophilic granular cells with possible involvement in neutrophil migration to site of inflammation in tilapia. Developmental and Comparative Immunology 23, 451-457.
Observations were made on stretched preparations from the swim bladder and peritoneum obtained from tilapia (Oreochromis niloticus) after injection of formalin-killed Escherichia coli, proteose peptone, compound 48/80 or HBSS into the swim bladder. The eosinophilic granular cells (EGCs) in the swim bladder degranulated rapidly after inoculation. However, the peritoneal EGCs did not degranulate, indicating that degranulation occurs only at the injected site. There was also a correlation between the ratio of the degranulated EGCs and number of the exudate neutrophils. Killed E. coli (1 mg/fish) produced the greatest degranulation response of EGCs and migration of neutrophils into the inflammatory site. Additionally, the rate of the degranulation and number of the neutrophils were lowest when HBSS was injected. The results of this study verify that degranulation of EGCs is involved in the neutrophil migration and suggest that fish EGCs are analogous to mammalian mast cells. (C) 1999 Elsevier Science Ltd. All rights reserved.

Matsuyama, T., Iida, T., and Endo, M. (1999). Isolation of inflammatory macrophages from swim bladder of Tilapia. Fish Pathology 34, 83-84.

McCarthy, I. D., Gair, D. J., and Houlihan, D. F. (1999). Feeding rank and dominance in Tilapia rendalli under defensible and indefensible patterns of food distribution. Journal of Fish Biology 55, 854-867.
In four scatter-fed groups of Tilapia rendalli, the distribution of food between individuals was not significantly different from that expected if the food was shared uniformly between all the fish in the group for nine of the 12 radiographic assessments of feeding behaviour. Individual fish maintained the same feeding rank over time, indicating a stable feeding hierarchy, in only one of the four scatter feeding groups. In contrast, in four point source feeding groups, the distribution of food between individuals differed significantly from uniformity in 10 of the 12 radiographic assessments of feeding behaviour and stable feeding hierarchies were maintained over time in three of the four groups. Thus, scatter feeding promoted a more uniform distribution of food between individuals within the group and prevented the formation of feeding hierarchies. There was no significant correlation between individual feeding rank and dominance index in all four scatter feeding groups. In contrast, significant positive correlations were found between individual feeding rank and dominance index in all four point source feeding groups. The results of this study confirm that feeding rank can be used as a correlate of relative social status under defensible feeding conditions. (C) 1999 The Fisheries Society of the British Isles.

McCormick, S. D. (1990). Cortisol directly stimulates differentiation of chloride cells in tilapia opercular membrane. Am J Physiol 259, R857-63.
Opercular membranes from freshwater tilapia (Oreochromis mossambicus) were maintained in vitro for 4 days and exposed to several concentrations of cortisol (0, 0.01, 0.1, 1, and 10 micrograms/ml). Chloride cell size, number, and Na(+)-K(+)-ATPase content were examined using a fluorescent mitochondrial dye (dimethylaminostyrylethylpyridiniumiodine), a fluorescent analogue of ouabain (anthroylouabain) that binds specifically to Na(+)-K(+)-ATPase, and a cytological stain specific for plasma and tubular membranes. In the absence of cortisol, chloride cell density of the freshwater tilapia opercular membrane decreased (from initial levels of 6,114 +/- 451 to 18 +/- 9 cells/cm2) and was restored by cortisol in a dose- dependent manner. Chloride cell height (5.5 +/- 0.3 microns initially and 7.8 +/- 0.5 microns after 4 days in vitro) increased twofold (13.1 +/- 0.7 microns) after exposure to 1 microgram/ml cortisol. Initially and after 4 days in control medium, there was no detectable staining with anthroylouabain; exposure to 1 microgram/ml cortisol resulted in the appearance of numerous anthroylouabain-positive chloride cells. Without cortisol, Na(+)-K(+)-ATPase activity of the opercular membrane remained constant through 4 days of culture (0.4-0.6 mumol ADP.mg protein-1.h-1); addition of cortisol caused a dose-dependent increase to a maximum of 1.2 +/- 0.1 mumol Pi.mg protein-1.h-1. In vitro cortisol also maintained the size, density, and appearance of chloride cells from opercular membrane of seawater-adapted tilapia. The results indicate that in vitro cortisol exposure causes morphological and biochemical differentiation of the seawater form of the chloride cell.

McKenzie, D. J., Piraccini, G., Felskie, A., Romano, P., Bronzi, P., and Bolis, C. L. (1999). Effects of plasma total ammonia content and pH on urea excretion in Nile tilapia. Physiol Biochem Zool 72, 116-25.
Nile tilapia (Oreochromis niloticus) were infused with ammonium salts, acid, and base to investigate the effects of changes in arterial plasma total ammonia content (Tamm) and pH (pHa) on plasma urea-nitrogen (urea- N) levels and urea-N excretory fluxes (Jurea-N). The tilapia did not possess a functional hepatic ornithine urea-cycle (no significant carbamyl phosphate synthetase III activity). Infused substances were dissolved in a saline vehicle and injected twice (5 mL kg-1), the first infusion to "prime" the animal and promote a more marked response to the second infusion, given 2.5 h later. The results reported are those of the second infusion. Infusion of 200 mM NH4Cl increased Tamm, reduced pHa, and increased plasma urea-N and Jurea-N. Two hundred mM NH4HCO3 increased Tamm and arterial plasma total CO2+ content (TaCO2+), reduced pHa, and increased Jurea-N. Fifty mM HCl reduced pHa but had no effects on urea dynamics. Fifty mM NaOH increased pHa, plasma urea-N levels, and Jurea-N. Two hundred mM NaHCO3 increased pHa, TaCO2+, plasma urea-N levels, and Jurea-N. Infusion of the saline vehicle was without effect. The results indicate that ammonia loading and plasma alkalosis both stimulate urea excretion in uricolytic fish. The responses to hyperammonemia or alkalosis were not modified when combined with elevated plasma bicarbonate levels.

Meakins, R. H., and Kawooya, J. (1973). The effects and distribution of metacercaria on the gills of the fish Tilapia zilli (gervais) 1848. Z Parasitenkd 43, 25-31.

Melamed, P., Eliahu, N., Levavi-Sivan, B., Ofir, M., Farchi-Pisanty, O., Rentier-Delrue, F., Smal, J., Yaron, Z., and Naor, Z. (1995). Hypothalamic and thyroidal regulation of growth hormone in tilapia. Gen Comp Endocrinol 97, 13-30.
A radioimmunoassay (RIA) for recombinant tilapia growth hormone (GH) was established and validated. The ability of various hypothalamic factors to regulate GH secretion in the tilapia hybrid (Oreochromis niloticus x Oreochromis aureus) was studied. Somatostatin1-14 (SRIF1- 14; 10-100 micrograms/kg) was found to reduce circulating GH levels in a dose-dependent manner. SRIF1-14 (0.1-1000 nM) inhibited GH release from perifused pituitary fragments (ED50 0.83 nM). Human growth hormone- releasing hormone fragment 1-29 (hGHRH1-29; 100 micrograms/kg) doubled circulating GH levels and modestly stimulated GH secretion in vitro. Carp growth hormone-releasing hormone (cGHRH) stimulated GH secretion in vitro to a similar degree at the same dose (1 microM). Injection of salmon gonadotropin-releasing hormone (sGnRH) superactive analog (10- 100 micrograms/kg) increased plasma GH levels sixfold. sGnRH also stimulated GH release in vitro (ED50 142.56 nM). Dopamine (0.1-10 microM) and the D1 DA receptor agonist SKF 38393 increased GH secretion from perifused pituitary fragments dose-relatedly. Thyrotropin- releasing hormone (TRH) had no effect on GH secretion from perifused pituitary fragments, but increased plasma GH levels, as did bovine thyroid stimulating hormone (bTSH). The increased plasma GH in the bTSH- treated fish coincided with a dramatic increase in T4; however, TRH increased GH without changing T4 levels. T3 increased the synthesis of GH by isolated pituitaries (incorporation of [3H]leucine). SRIF1-14 seems to be a most potent hypothalamic regulator of GH secretion in tilapia; sGnRH and DA both increased GH secretion, although sGnRH elicited considerably greater responses at lower doses. Two forms of GHRH increased GH levels, although the unavailability of the homologous peptide prevented an accurate evaluation of its importance in regulating GH secretion. The thyroid axis (TRH, TSH, and T3) stimulates both synthesis and release of GH, although TRH did not appear to have a direct effect on the level of the pituitary.

Melamed, P., Gur, G., Elizur, A., Rosenfeld, H., Sivan, B., Rentier-Delrue, F., and Yaron, Z. (1996). Differential effects of gonadotropin-releasing hormone, dopamine and somatostatin and their second messengers on the mRNA levels of gonadotropin II beta subunit and growth hormone in the teleost fish, tilapia. Neuroendocrinology 64, 320-8.
In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or activation of protein kinase C (PKC; by 12.5 nM tetradecanoyl phorbol-13-acetate: TPA, 0.5-24 h) all increased gonadotropin (GtH) II beta steady state mRNA levels by three to four-fold. The involvement of PKA and PKC in the GnRH stimulatory effect on both GtH release and GtH II beta mRNA levels was corroborated by use of the PKA and PKC inhibitors, H89 and GF109203X, respectively (100 nM) which attenuated the GnRH effect. Incubation with actinomycin D (8 microM, 4-21 h) after preexposure for 24 h to either forskolin (10 microM) or TPA (12.5 nM), revealed that rates of transcript degradation were slower in forskolin-treated cells (T 1/2 = 14.1 h) than in control or TPA-treated cells (T 1/2 = 8.47 or 8.38 h), suggesting a stabilizing effect on the mRNA. Dopamine (DA; 10 microM, 4-36 h) had no apparent effect on steady state mRNA levels of GtH II beta, but reduced GtH release by as much as 75%. Steady state levels of growth hormone (GH) mRNA were not affected by exposure to GnRH (10 nM, 4-24 h), although GH release was more than doubled. Similarly, activation of PKC (by TPA 12.5 nM, 1.5-36 h), which was shown to be essential for the GnRH-stimulatory effect on GH release, did not alter levels of the GH transcript, but increased GH release by more than fivefold. DA (10 microM, 4-24 h) moderately increased GH transcript levels (160%) with similar kinetics but lower potency than direct elevation of cAMP (by 10 microM forskolin or 0.2 mM IBMX, 0.5-36 h) which increased transcript levels by more than fourfold. The involvement of PKA in the DA effect was confirmed when the PKA inhibitor H89 (100 nM, 15 min prior to DA exposure) attenuated the DA effect on GH mRNA levels. Exposure of cells to actinomycin D (8 microM, 2-16 h) after treatment with forskolin (10 microM, 24 h) led to a slower rate of transcript degradation than in control cells (T 1/2 = 6.5 h vs. T 1/2 = 4.36 h), suggesting that cAMP also elicits a stabilizing effect on GH mRNA. Somatostatin (100 nM, 0.5-36 h) had no clear effect on GH transcript levels, but reduced GH release by as much as 90%. These results suggest that activation of either cAMP-PKA or PKC pathways can, possibly by different mechanisms, stimulate mRNA levels of the GtH II beta gene, but that only the cAMP-PKA pathway stimulates GH mRNA levels. It would appear therefore that GnRH, although stimulating GH release, does not regulate GH transcription in this fish.

Melamed, P., and Yaron, Z. (1999). Calcium ionophores lead to apoptotic-like changes in Tilapia pituitary cells. Gen Comp Endocrinol 114, 19-27.
Influx or mobilization of Ca2+ plays an important part in the signal transduction mechanisms regulating release of gonadotropin (GtH) and growth hormone (GH) in teleost fish. In mammals it may also mediate a stimulatory effect on the transcription of the genes encoding these hormones (i.e., LHbeta, FSHbeta, and GH). In the present study, exposure of tilapia pituitary cells in primary culture to two ionophores, A23187 and ionomycin, increased GtH and GH secretion over 5- 24 h but led to a significant drop in mRNA levels of GtH IIbeta and GH. The mRNA levels of beta actin were also reduced by this treatment, suggesting a general, nonspecific effect in these cells. The morphology of the ionophore-exposed cells also differed markedly; they lacked cytoplasmic extensions, appeared smaller, and were less aggregated than control cells. Staining the nuclei of these cells with 4,6-diamidino-2- phenyl-dihydrochloride revealed that they had undergone condensation and fragmentation, typical of programmed cell death. Extraction of DNA from the ionophore-exposed cells and its separation on ethidium bromide- stained gels revealed that, unlike in control cells, the DNA had been broken into fragments in multiples of approximately 180-200 bp, providing further evidence of apoptotic-like effects of the ionophores on the cells. It is speculated that Ca2+, which mediates stimulation of GtH and GH release by the hypothalamic regulatory hormones, may, under certain conditions, have apoptotic-like effects, which specifically regulate the sizes of gonadotroph and somatotroph cell populations. In addition, the fact that pituitary cells exposed to ionophores may become apoptotic should be borne in mind when experiments on signal transduction are carried out with these substances. Copyright 1999 Academic Press.

Melamed, P., Gur, G., Rosenfeld, H., Elizur, A., and Yaron, Z. (1999). Possible interactions between gonadotrophs and somatotrophs in the pituitary of tilapia: apparent roles for insulin-like growth factor I and estradiol. Endocrinology 140, 1183-91.
The unique organization of the teleost pituitary, in which cells are grouped according to their characteristic hormone, makes this a suitable model for studying pituitary paracrine interactions. In a number of fish, including tilapia, there are variations in the circulating levels of the gonadotropins and GH, which are elevated during the reproductive season, suggesting interactions between the reproductive and growth axes. The aim of this study was to investigate paracrine interactions between the gonadotrophs and somatotrophs in the tilapia pituitary. Initially, dispersed pituitary cells were separated on a density gradient in which the gonadotrophs were found in the least dense fractions, and the somatotrophs were concentrated in the densest fraction. After 4 days in culture, cells in the least dense fractions showed characteristic cytoplasmic extensions not seen in the somatotrophs, which appeared small and failed to form aggregates; somatotrophs were found, however, attached to other non-GH cells. Staining of the nuclei with 4,6-diaminidino-2-phenyl-dihydrochloride revealed that the isolated somatotrophs had undergone nuclear condensation and fragmentation typical of apoptosis. Addition of either estradiol or human recombinant insulin-like growth factor I (IGF-I; 10 nM) to the somatotroph cultures increased the number of cell aggregates and reduced the number of condensed or fragmented nuclei. Immunocytochemical studies on pituitary sections revealed IGF-I immunoreactivity in regions of the proximal pars distalis that stain with gonadotropin IIbeta antisera and also in regions of the rostral pars distalis characteristic of corticotrophs; immunoreactive IGF-I was never seen in the region of the somatotrophs. Incubation of cells from the different fractions with testosterone (10 nM; 24 h) revealed that cells of the least dense fractions, which were rich in gonadotrophs, possessed aromatizing ability, which was absent in the somatotroph- enriched fraction. These results suggest that estradiol and IGF-I, both generated from cells other than the somatotrophs, may exert antiapoptotic effects and thus possibly control the size of this population of cells.

Melamed, P., Gur, G., Rosenfeld, H., Elizur, A., Schulz, R. W., and Yaron, Z. (2000). Reproductive development of male and female tilapia hybrids (Oreochromis niloticus x O. aureus) and changes in mRNA levels of gonadotropin (GtH) ibeta and IIbeta subunits [In Process Citation]. J Exp Zool 286, 64-75.
A study was carried out in tilapia in order to see whether the gonadotropin (GtH) beta subunits show distinct patterns of expression at different stages of their reproductive development. Male and female tilapia hybrids (Oreochromis niloticus x O. aureus) were collected at various times of the year, and a number of parameters were measured in order to establish the reproductive state of the fish. Circulating testosterone (T), estradiol (E(2)) and 11 ketotestosterone (11KT) levels were assayed, gonads were removed for calculation of gonadosomatic index (GSI) values and histological studies, and RNA was extracted from the pituitaries for measurement of GtH Ibeta and IIbeta mRNA levels. In maturing fish of both sexes, the circulating steroid levels were positively correlated with each other (r(2) = 0.66-0.91) and in males, also with the GSI values (r(2) = 0.68). A positive correlation was also seen in these fish between GSI values and the prevalence of spermatocytes and spermatids (r(2) = 0.54). In maturing females, the maximal oocyte diameter was positively correlated with circulating E(2) levels (r(2) = 0.63), while GSI values showed no correlation; this presumably relates to the cycling nature of this asynchronous spawner. In regressing fish of both sexes, no clear correlation between these reproductive parameters was seen. In all fish, the GtH Ibeta mRNA levels were highest in fish with steroids ranging 1-10 ng T or E(2)/ml for males or females, respectively, and were lower in fish with steroids at higher or lower levels. In fish with high steroid levels, the IIbeta mRNA levels were also high, and in regressed males the increases were positively correlated. Exposure of cultured pituitary cells to either steroid (T at >10 nM, or E(2) at >1 nM) was followed by a decrease in the steady-state levels of the Ibeta transcript, while those of IIbeta were left unaltered. In situ hybridization studies revealed that in pituitaries of both sexes, the cells producing each of these mRNAs are located in a distinct location. These results suggest that gonadal steroids may exert differential feedback mechanisms at the level of the pituitary to control transcription of each GtH beta subunit in distinct cell types specific for each hormone. J. Exp. Zool. 286:64-75, 2000. Copyright 2000 Wiley- Liss, Inc.

Mendoza, C., and Hernandez, P. (1999). [Incidence of Plesiomonas shigelloides in tilapia tetrahibrids (Oreochromis sp.)]. Arch Latinoam Nutr 49, 67-71.
Plesiomonas shigelloides, a member of the family Vibrionaceae, is a Gram negative rod associated with several gastroenteritis outbreaks, especially in tropical and subtropical countries. In same way, it has been related to some septicemia, meningitis and cholecystitis cases. The microorganism is normally found in water, fish and birds. The aim of this work was to study the incidence of Plesiomonas shigelloides in tetrahybrids of Oreochromis sp. (Pink Tilapia) located at the central region of Venezuela. Once the samples were homogenized, the techniques of enrichment and direct streaking were used simultaneously for the isolation of the microorganism. A high incidence of P. shigelloides was determined (73%), being higher in the intestinal tract (60%), followed by the skin (36.7%) and the gills (26.67%), without any correlation among them. In the fish pond, the microorganism isolation frequency was 41.67%. The direct streaking technique presented the highest isolation values in the different Tilapia tissues (60%) and in the water as well (41.60%). No significant differences were observed on the effectivity of the selective agars used for the isolation of P. shigelloides (Plesiomonas Agar and Inositol-Brilliant Green-Bile Salts Agar). A positive correlation was observed between the microorganism incidence and the pluviosity levels. A high incidence of E. coli was observed in the samples of Tilapia tissues and the water pond. No correlation was observed between incidence of P. shigelloides and E. coli. Due to the high prevalence of P. shigelloides found in the present study, it is important to assure a proper evisceration, washing and storage at temperatures lower than 8 degrees C, and a proper product cooking to diminish the customeris risk.

Mendoza, C., and Hernandez, P. (1999). Incidence of Plesiomonas shigelloides in Tilapia tetrahibrids (Oreochromis sp.). Archivos Latinoamericanos De Nutricion 49, 67-71.
Plesiomonas shigelloides, a member of the family Vibrionaceae, is a Gram negative rod associated with several gastroenteritis outbreaks, especially ill tropical and subtropical countries. In same way, it has been related to some septicemia, meningitis and cholecistitis cases. The microorganism is normally found in water, fish and birds. The aim of this work was to study the incidence of Plesiomonas shigelloides in tetrahibrids of Oreochromis sp. (Pink Tilapia) located at the central region of Venezuela. Once the samples were homogenized, the techniques of enrichment and direct streaking were used simultaneously for the isolation of the microorganism A high incidence of P. shigelloides was determined (73%), being higher in the intestinal tract (60%), followed by the skin (36.7%) and the gills (26.67%), without any correlation among them. In the fish pond, the microorganism isolation frequency was 41.07%. The direct streaking technique presented the highest isolation values in the different Tilapia tissues (60%) and in the water as well (41.60%). No significant differences were observed on the efectivity of the selective agars used for the isolation of P. shigelloides (Plesiomonas Agar and Inositol-Brilliant Green- Bile Salts Agar). A positive col relation was observed between the microorganism incidence and the pluviosity levels. A high incidence of E. coli was observed in the samples of Tilapia tissues and the water pond. No correlation was observed between incidence of P. shigelloides and E. coli. Due to the high prevalence of P. shigelloides found in the present study, it is important to assure a proper evisceration, washing and storage at temperatures tower than 8 degrees C, and a proper product cooking to diminish the customeris risk.

Mezhnin, F. I. (1974). [Histological and histochemical study of the adrenal glands of peleds and tilapia]. Arkh Anat Gistol Embriol 66, 57-63.

Mochida, K., Adachi, S., and Yamauchi, K. (1995). Initial phase of an inflammatory reaction in testis caused by experimental testicular autoimmunity in the Nile tilapia, Oreochromis niloticus. Zoolog Sci 12, 543-50.
In order to study the pathogenesis of the testicular autoimmunity induced by the immunization with allogeneic testis homogenate (ATH) mixed with Freund's complete adjuvant (FCA) in the Nile tilapia Oreochromis niloticus, the initiation of inflammatory reactions in the testis was ultrastructurally investigated and seminal plasma was analyzed for presence of autoantigens. In the seminal plasma, mainly 120 kD and 80 kD autoantigens were identifiable by Western blotting with tilapia antisperm autoantibody. Eight weeks after injection with FCA, globate structures, possibly originating from FCA, were large and distended the interstitium where the inflammatory reactions were more frequently recognizable. The globate structures may be one of causes to break the blood-testis barrier, and the inflammatory reaction may be due to the leakage of soluble autoantigens from the lumen. In the interstitium, several kinds of immunocompetent cells formed masses which were mainly composed of lymphocytes, macrophages, eosinophils and plasma cells. We suggest that the inflammatory reactions in fish caused by the immunization with ATH+FCA are initiated by sensitization of the immunocompetent cells with testicular autoantigens, the 120 kD and 80 kD autoantigens in the seminal plasma are two of them, leaking from the lumen because of the provable effect of FCA. These initial reactions were then amplified by cellular and humoral immunity.

Mochida, K., Kondo, T., Matsubara, T., Adachi, S., and Yamauchi, K. (1999). A high molecular weight glycoprotein in seminal plasma is a sperm immobilizing factor in the teleost Nile tilapia, Oreochromis niloticus. Dev Growth Differ 41, 619-27.
Sperm that have acquired potential for motility are kept immotile in seminal plasma in the teleost, Nile tilapia. In order to investigate the mechanism of immobilization, several experiments were performed using a previously characterized monoclonal antibody (TAT-30) against a molecular weight (Mr) = 120,000 protein that is secreted by Sertoli cells and epithelial cells of the sperm duct, and is also bound to the head of the spermatozoon. First, we assessed sperm motility in the seminal plasma protein fraction (SPP), and demonstrated that the sperm motility is inhibited by SPP in a concentration-dependent manner. Furthermore, sperm motility was recovered if SPP was pretreated with TAT-30, suggesting that the TAT-30 antigen is one of the components of the sperm immobilizing factor. Calibration by gel filtration followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting with TAT-30 demonstrated that the sperm immobilizing factor was more than Mr = 1,000,000 in seminal plasma, suggesting that it is a homopolymer of the Mr = 120,000-TAT-30 positive protein. Additionally, lectin blot analysis showed that the TAT-30 antigen was reactive with Lens culinarin agglutinin (LCA) and Conavalia ensiformis agglutinin (ConA), indicating that it is a glycoprotein. Immunohistochemical studies showed that the TAT-30 antigen was localized specifically on the heads of spermatozoa and on the apical surface, lysosomes and rough endoplasmic reticulum of Sertoli cells.

Mohamed, M. P. (1981). Metabolism of Tilapia mossambica (Peters) with emphasis on hypoxia. Indian J Exp Biol 19, 1098-100.

Mohsin, M., Bakar, J., and Selamat, J. (1999). The effects on colour, texture and sensory attributes achieved by washing black tilapia flesh with a banana leaf ash solution. International Journal of Food Science and Technology 34, 359-363.
The washing of freshwater fish with clarified solutions of banana leaf ash to remove the muddy odour and flavour is common both in Bangladesh and Indian households. However, no scientific study has been done to evaluate its effectiveness. This study was, therefore, done to show the effect of the washing treatments on the following sensory attributes: odour; flavour; colour and texture. The latter two attributes were also measured by instrumental methods. The experimental animal was black tilapia (Oreochromis mossambicus), which was filleted and each fillet washed by a clarified solution of banana ash (either originally 5 or 7% ash). Controls were fillets washed in ice-slush only. Those fillets washed in 5% ash for 5 min were the most acceptable for eating, cooked or uncooked. There were highly significant differences (p < 0.01) in the L-colour values (lightness values) when treated fillets were compared to untreated fillets. However cooking the fillets reduced the difference, making it not significant. Texture was significantly affected by washing and this was retained in cooked fillets, however this was particularly significant using a 7% solution which gave a softer fillet.

Mol, K., Kaptein, E., Darras, V. M., de Greef, W. J., Kuhn, E. R., and Visser, T. J. (1993). Different thyroid hormone-deiodinating enzymes in tilapia (Oreochromis niloticus) liver and kidney. FEBS Lett 321, 140-4.
Enzymes catalyzing the outer ring deiodination (ORD) of iodothyronines are important for the regulation of thyroid hormone bioactivity. We have studied ORD of thyroxine (T4) and 3,3',5'-triiodothyronine (rT3) in liver and kidney microsomes of fish, i.e. tilapia (Oreochromis niloticus). Tilapia kidney contains an enzyme which resembles the mammalian selenoenzyme type I iodothyronine deiodinase (ID-I) with respect to substrate preference (rT3 > T4) and high (approximately microM) Km values, but is much less sensitive to selenocysteine (Sec)- targeted inhibitors, including 6-propyl-2-thiouracil (PTU). In contrast, tilapia liver contains an enzyme very similar to mammalian type II deiodinase (ID-II) with respect to substrate preference (T4 > rT3), low (approximately nM) Km values, and lack of sensitivity to Sec inhibitors.

Mol, K. A., Van Der Geyten, S., Darras, V. M., Visser, T. J., and Kuhn, E. R. (1997). Characterization of iodothyronine outer ring and inner ring deiodinase activities in the blue tilapia, Oreochromis aureus. Endocrinology 138, 1787-93.
The presence of iodothyronine deiodinases was investigated in the different tissues of blue tilapia (Oreochromis aureus), and their biochemical properties were compared with those of mammalian deiodinases. High-Km rT3 outer ring deiodination (ORD) was observed in tilapia kidney, low-Km T4 ORD in liver, and low-Km T3 inner ring deiodination (IRD) in brain and gill. The rT3 ORD activity in tilapia kidney has a very similar substrate specificity as rat liver type I iodothyronine deiodinase but is much less sensitive to inhibition by propylthiouracil, iodoacetic acid, and aurothioglucose. Tilapia liver T4 ORD activity and tilapia brain and gill T3 IRD activities show very similar substrate specificities as well as similar inhibitor sensitivities as rat type II and type III iodothyronine deiodinase, respectively. The optimal pH of the tilapian enzymes is 6-7, and the optimal incubation temperature is approximately 37 C. All tilapia deiodinases are stimulated by dithiothreitol, but the optimal DTT concentrations are generally lower than those required by the corresponding rat enzymes. The apparent Km values of the various tilapia deiodinases for their preferred substrate are in the same range as for the corresponding rat enzymes. Based on these findings, we conclude that fish deiodinases are more similar to mammalian deiodinases than generally accepted.

Mol, K. A., Van der Geyten, S., Kuhn, E. R., and Darras, V. M. (1999). Effects of experimental hypo- and hyperthyroidism on iodothyronine deiodinases in Nile tilapia, Oreochromis niloticus. Fish Physiology and Biochemistry 20, 201-207.
In the present study, we examined the effects of experimentally-induced increases or decreases in plasma concentrations of thyroid hormones on iodothyronine deiodinases in tilapia, Oreochromis niloticus. To obtain hyperthyroid tilapia, fish were injected with porcine follicle stimulating hormone (pFSH) 36 hours before sampling or fed on demand for 11 days with tilapia pellets containing 12 ppm T-3. Tilapias were made hypothyroid by providing them food containing 0.2% methimazole for 11 days. Plasma T-4 and T-3 and the in vitro deiodinase activity in liver, kidney, brain and gill were measured at the end of the treatment period. Injection with pFSH caused an increase in plasma T-4 but had no influence on plasma T-3 levels. A small increase in plasma T-3 was observed in T-3-fed fish. Plasma levels of both T-4 and T-3 were decreased by methimazole treatment. We observed no changes in kidney type I deiodinase (D1), whereas liver type II deiodinase (D2) was increased during hypothyroidism and decreased during hyperthyroidism. Hypothyroidism resulted in a significant decrease in brain, gill and liver type III deiodinase (D3). An pFSH-induced increase in T-4 stimulated brain and gill D3 but not liver D3, whereas the opposite was true in T-3-fed fish. We conclude that the regulation of D1 and D3 in tilapia is probably different compared to mammals.

Mousa, S. A., and Mousa, M. A. (1999). Immunocytochemical and histological studies on the hypophyseal-gonadal system in the freshwater nile tilapia, oreochromis niloticus (L.), during sexual maturation and spawning in different habitats. J Exp Zool 284, 343-54.
The activities of the hypophyseal-gonadal system of O. niloticus in different habitats were investigated using immunocytochemical and histological techniques. The observed physico-chemical results indicated that Lake Nasser water characteristics are within the allowed and desired safety baseline levels. In contrast, Lake Manzalah exhibited high levels of Ca(2+), Mg(2+), SO(4)(2-) and heavy metals (Zn, Pb, and Cd). These water conditions affected the activity of the hypophyseal-gonadal axis of tilapia. The secretory and the synthetic activities of GTH and SL cells in the pituitary gland, in general, underwent obvious normal changes during gonad maturation and spawning of O. niloticus in Lake Nasser. In Lake Manzalah, the secretory activity of GTH and SL cells declined. This may be due to the effect of the high levels of heavy metals which interfere with the release of hormones and disturb the feedback mechanisms. In addition, the activity of both PRL and GH cells in Lake Nasser was higher than that of Lake Manzalah, but the synthetic activity of the ACTH and MSH cells was higher in Lake Manzalah. This may be related to the increased stress on fishes and the dark polluted water in Lake Manzalah. Both the environmental and the endocrine impacts in Lake Manzalah caused a decline in the gonadal activity as reflected by the decrease of sperm amount in the ripe testis, the appearance of oocytes in the testis and the degeneration of ripe oocytes (atresia) during the spawning season. J. Exp. Zool. 284:343-354, 1999. Copyright 1999 Wiley-Liss, Inc.

Mousa, S. A., and Mousa, M. A. (1999). Immunocytochemical and histological studies on the hypophyseal- gonadal system in the freshwater Nile tilapia, Oreochromis niloticus (L.), during sexual maturation and spawning in different habitats. Journal of Experimental Zoology 284, 343-354.
The activities of the hypophyseal-gonadal system of O. niloticus in different habitats were investigated using immunocytochemical and histological techniques. The observed physicochemical results indicated that Lake Nasser water characteristics are within the allowed and desired safety baseline levels. In contrast, Lake Manzalah exhibited high levels of Ca2+, Mg2+, SO42- and heavy metals (Zn, Pb, and Cd). These water conditions affected the activity of the hypophyseal-gonadal axis of tilapia. The secretory and the synthetic activities of GTH and SL cells in the pituitary gland, in general, underwent obvious normal changes during gonad maturation and spawning of O. niloticus in Lake Nasser. In Lake Manzalah, the secretory activity of GTH and SL cells declined. This may be due to the effect of the high levels of heavy metals which interfere with the release of hormones and disturb the feedback mechanisms. In addition, the activity of both PRL and GH cells in Lake Nasser was higher than that of Lake Manzalah, but the synthetic activity of the ACTH and MSH cells was higher in Lake Manzalah. This may be related to the increased stress on fishes and the dark polluted water in Lake Manzalah. Both the environmental and the endocrine impacts in Lake Manzalah caused a decline in the gonadal activity as reflected by the decrease of sperm amount in the ripe testis, the appearance of oocytes in the testis and the degeneration of ripe oocytes (atresia) during the spawning season. (C) 1999 Wiley-Liss, Inc.

Nagahama, Y., Nishioka, R. S., Bern, H. A., and Gunther, R. L. (1975). Control of prolactin secretion in teleosts, with special reference to Gillichthys mirabilis and Tilapia mossambica. Gen Comp Endocrinol 25, 166-88.

Nagahama, Y., Olivereau, M., Farmer, S. W., Nishioka, R. S., and Bern, H. A. (1981). Immunocytochemical identification of the prolactin- and growth hormone- secreting cells in the teleost pituitary with antisera to tilapia prolactin and growth hormone. Gen Comp Endocrinol 44, 389-95.

Narasimham, C., and Parvatheswarao, V. (1974). Adaptations to osmotic stress in a fresh-water euryhyaline teleost, Tilapia mossambica X. Role of mucopolysaccharides. Acta Histochem 51, 37-49.

Ng, T. B., Leung, T. C., and Woo, N. Y. (1991). Studies on tilapia hepatic growth hormone receptor. Biochem Int 25, 67-79.
Tilapia liver membranes were solubilized with 1% Triton X-100. The presence of growth hormone (GH) receptors was demonstrated by specific binding of radioiodinated tilapia GH (125I-tGH). The solubilized receptor possessed a molecular weight of around 400,000. It was adsorbed on Con A-Sepharose and DEAE BioGel A indicating that it contains carbohydrates and is acidic in character. Its protein nature was revealed by destruction of GH-binding activity by proteases. The involvement of essential sulfhydryl group was suggested by inhibition of 125I-tGH binding to the solubilized receptor by p- chloromercuribenzene sulfonate which could be reversed by dithioerythritol treatment.

Ng, T. B., Leung, T. C., and Woo, N. Y. (1991). Insulin-like growth factor I-like immunoreactivity in serum and tissues of the tilapia, Oreochromis mossambicus. Biochem Int 24, 359-68.
Tilapia serum was acidified with 0.5 M HCl and then chromatographed on an octadecasily-silica column. After washing with 4% acetic acid, the column was eluted with methanol. The eluate was evaporated to dryness. The sample cross-reacted in a human insulin-like growth factor I (IGF- I) radioimmunoassay, suggesting immunochemical similarity to human IGF- I. IGF-I-like immunoreactivity was present at high levels in tilapia liver. Other tissues containing IGF-I-like immunoreactivity included the gonad, kidney, heart, spleen, brain and muscle. The serum IGF-I- like immunoreactivity was attributed to substances with a molecular weight of 9,000 and 45,000 respectively, and it was elevated after treatment with bovine growth hormone and carp pituitary extract.

Ng, T. B., Leung, T. C., Cheng, C. H., and Woo, N. Y. (1992). Growth hormone binding sites in tilapia (Oreochromis mossambicus) liver. Gen Comp Endocrinol 86, 111-8.
125I-labeled bovine and tilapia growth hormones were used to assess the presence of growth hormone receptors in membranes prepared from tissues of the tilapia Oreochromis mossambicus. The highest level of specific binding was detected in liver membranes from animals of both sexes and the binding was protein-dependent. Tilapia growth hormone, bovine growth hormone, and ovine prolactin, but not tilapia prolactin, potently inhibited the hepatic binding of 125I-labeled bovine growth hormone. Scatchard analysis of the 125I-labeled bovine growth hormone binding data revealed a Bmax (maximum binding) value of 180 fmol/mg protein and a Kd (dissociation constant) value of 13 nM. Tilapia growth hormone potently inhibited hepatic binding of 125I-labeled tilapia growth hormone. Scatchard analysis revealed a single class of binding sites with Bmax and Kd values of 390 fmol/mg protein and 2.5 nM, respectively. Bovine growth hormone and ovine prolactin were less potent while tilapia prolactin was inactive in inhibiting hepatic 125I- labeled tilapia growth hormone binding.

Nguyen, T. M., Wright, J. R., Jr., Nielsen, P. F., and Conlon, J. M. (1995). Characterization of the pancreatic hormones from the Brockmann body of the tilapia: implications for islet xenograft studies. Comp Biochem Physiol C Pharmacol Toxicol Endocrinol 111, 33- 44.
The Brockmann body of the teleost fish, the tilapia (Oreochromis nilotica) has been considered as a potential source of islet xenograft tissue for patients with insulin-dependent diabetes. This study describes the purification from an extract of tilapia Brockmann bodies of insulin and several peptides arising from different pathways of post- translational processing of two proglucagons, two prosomatostatins and proPYY. The primary structure of tilapia insulin is similar to insulins from other teleosts (particularly the anglerfish, Lophius americanus) except that the strongly conserved glutamine residue at position 5 in the A-chain, a residue that is important in the binding of insulin to its receptor, is replaced by glutamic acid. In common with other teleosts, the tilapia Brockmann body expresses two non-allelic glucagon genes. Alternative pathways of post-translational processing lead to glucagons with 29 and 36 amino acid residues derived from proglucagon I and glucagons with 29 and 32 residues derived from proglucagon II. Glucagon-like peptides with 30 and 34 residues derived from proglucagon II were also isolated. In each case, the longer peptide is a C- terminally extended form of the shorter. Tilapia peptide tyrosine- tyrosine (PYY) was isolated in a C-terminally alpha-amidated from with 36 amino acid residues that is structurally similar (89% sequence identity) to anglerfish PYY. A 30-amino acid peptide, representing the C-terminal flanking peptide of PYY, was also isolated that shows only 53% sequence identity with the corresponding anglerfish peptide. Tilapia somatostatin-14 is identical to mammalian somatostatin but the [Tyr7, Gly10] somatostatin-containing peptide derived from prosomatostatin II contains the additional substitution (Phe11-->Leu) compared with the corresponding peptide from other teleosts.

Nicoll, C. S., Wilson, S. W., Nishioka, R., and Bern, H. A. (1981). Blood and pituitary prolactin levels in tilapia (Sarotherodon mossambicus; Teleostei) from different salinities as measured by a homologous radioimmunoassay. Gen Comp Endocrinol 44, 365-73.

Nishioka, R. S. (1980). Hypophysectomy of tilapia (Sarotherodon mossambicus) through the orbit. Gen Comp Endocrinol 40, 377-8.

Nishioka, R. S., Grau, E. G., and Bern, H. A. (1985). In vitro release of growth hormone from the pituitary gland of tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 60, 90-4.
The release of growth hormone from the proximal pars distalis of the tilapia, Oreochromis mossambicus, was significantly stimulated by cortisol (1 microgram/ml) in an in vitro system. Growth hormone released into the medium and remaining in the tissue was measured by densitometry after gel electrophoresis. Neither triiodothyronine (6.7 ng/ml) nor equimolar concentrations of thyroxin altered the release of growth hormone. In combination with cortisol, triiodothyronine did not alter the effect of cortisol alone.

Nishioka, R. S., de Jesus, E. G., and Hyodo, S. (1993). Localization of mRNAs for a pair of prolactins and growth hormone in the Tilapia pituitary using in situ hybridization with oligonucleotide probes. Gen Comp Endocrinol 89, 72-81.
Oligonucleotide probes were synthesized for the mRNAs of a pair of tilapia prolactins (tPRL177 and tPRL188) and growth hormone (tGH) based on cDNAs for the hormones of Oreochromis niloticus and amino acid sequences for the hormones of O. mossambicus. The three 45mer probes were labeled with 35S for hybridization studies on pituitary sections of O. mossambicus adapted to fresh water (FW) or seawater (SW). Expression of tPRL mRNA in the rostral pars distalis was clearly evident with either PRL probe in adjacent sections in PRL cells of the rostral pars distalis; mRNAs of both PRLs were colocalized in the same cells. In addition, the tGH probe demonstrated expression of tGH mRNA specifically in GH cells in the proximal pars distalis. The hybridization signals for both PRLs were significantly greater in the rostral pars distalis of FW fish than in that of SW fish, as judged by computer-aided analysis. In addition, grain concentration for both PRLs was significantly greater over centrally located PRL cells of FW fish. In addition, although overall grain concentrations were lower in SW fish, there were significantly more grains over the centrally located PRL cells with the tPRL177 probe, whereas there was no difference with the tPRL188 probe. There was no detectable difference in the occurrence of tGH mRNA between FW and SW fish.

Noga, E. J., and Flowers, J. R. (1995). Invasion of Tilapia mossambica (cichlidae) viscera by the monogenean Enterogyrus cichlidarum. J Parasitol 81, 815-7.
The monopisthocotylean monogenean Enterogyrus cichlidarum, which normally inhabits the stomach and anterior intestinal lumina of tilapine cichlids, invaded the internal organs of juvenile Mozambique tilapia (Tilapia mossambica). Adult worms infected the intestinal mucosa, peritoneal cavity, liver, heart, blood vessels, swimbladder, and braincase. Most of the parasites were adults and contained eggs. Both adults and eggs incited a mononuclear inflammatory response. Infections were associated with chronic morbidity and mortality. Although affected fishes were overcrowded, the precise stress responsible for such an unusually invasive event is unknown.

Nolan, D. T., Veld, R., Balm, P. H. M., and Bonga, S. E. W. (1999). Ambient salinity modulates the response of the tilapia, Oreochromis mossambicus (Peters), to net confinement. Aquaculture 177, 297-309.
The stress response of the euryhaline tilapia Oreochromis mossambicus adapted to either fresh water (EW) or salt water (Instant Ocean(TM), 950 mosm; (SW)) was investigated to establish the influences of ambient salinity in this species. The fish were considered to be adapted to the salinities as pre-confinement plasma cortisol and glucose levels were typical for unstressed fish. Two hour net confinement increased plasma cortisol and glucose to a similar extent in both FW and SW. Individual plasma sodium and chloride levels were unaffected by confinement, although plasma Na:Cl ratio increased in FW. Confinement increased intestinal Na+/K+-ATPase activity in EW, but not in SW. In contrast, kidney Na+/K+-ATPase activity increased in SW only. Branchial Na+/K+-ATPase activity decreased with confinement in SW, but not in FW. In SW, confinement reduced the numbers of opercular chloride cells. Increased aging of the branchial chloride cell (CC) population of SW-confined fish was indicated by large numbers of apoptotic CCs in the interlamellar areas. This effect on the CC population was absent in FW-confined fish. Overall, confinement in SW-adapted fish had a more profound impact than confinement in FW-adapted fish. This is likely to have associated energetic consequences in terms of branchial oxygen and ATP consumption. Therefore, results suggest the possibility of different effects of confinement on subsequent growth in FW and SW. (C) 1999 Elsevier Science B.V. All rights reserved.

Norberg, J. (1999). Periphyton fouling as a marginal energy source in tropical tilapia cage farming. Aquaculture Research 30, 427-430.
In aquaculture, the benefit of autotrophic production within land-based ponds for fish production has long been recognized. In cage culture, organisms growing on the cage net have so far only been considered as a problem. This study investigated the potential production of periphyton on cage nets used in a tropical mixed tilapia culture of Oreochromis mortimeri (Trewavas), Tilapia rendalli (Boulenger) and Oreochromis niloticus (Linnaeus) in Lake Kariba, Zimbabwe. The production of periphyton was assessed experimentally and compared with the energy demand of the caged fish. The tilapias were found to graze intensively on the net, and the primary production of periphyton on the cage net was approximate to 1% relative to the energy demands of the fish.

Nudelman, A., Edelson, G., Linden, A., and Raz, R. (1997). [Infection by Vibrio vulnificus after a prick from from the spine of a Tilapia]. Harefuah 133, 444-5, 502.
Vibrio vulnificus is a Gram-negative bacterium living in warm salty water that produces a spectrum of human disease which may progress to devastating, sometimes fatal infections in susceptible individuals. Such infections have rarely been reported in Israel. However, over the past few months we have been seeing a sharp increase in V. vulnificus infections with a common history of injury to extremities by the sharp spines of Tilapia zillii, ("amnon" or St. Peter's fish). Clinical suspicion and prompt intervention prevent the untoward consequences of misdiagnosis or delay.

Nxomani, C., Ribbink, A. J., and Kirby, R. (1999). DNA profiling of Tilapia guinasana, a species endemic to a single sinkhole, to determine the genetic divergence between color forms. Electrophoresis 20, 1781-5.
Northwestern South Africa and Namibia contain a number of sinkholes in the dolomitic rock formations found in this area. These contain isolated populations of Tilapia. Most contain Tilapia sparmanii, but the one in Namibia, Guinas, is of particular interest as it contains the endemic species, Tilapia guinasana, which exhibits none sex-limited polychromatisms, which is unique for Tilapia. This sinkhole is under environmental threat, particularly as a result of being a recreational diving site. This study, using randomly amplified polymorphic DNA sequences (RAPDs), when analyzed using analysis of variance (ANOVA), shows that the colour forms of Tilapia guinasana are genetically distinct. This confirms previous evidence that assortative mating between color forms takes place. The various possible hypotheses for the occurrence and genetic stability of the color polymorphism are discussed. Further, a new hypothesis is put forward based on a need to maximize outbreeding in fully isolated population with no possibility of increase in size above the maximum and limited carrying capacity of the sinkhole.

Oliveira, C., and Wright, J. M. (1998). Molecular cytogenetic analysis of heterochromatin in the chromosomes of tilapia, Oreochromis niloticus (Teleostei: Cichlidae). Chromosome Res 6, 205-11.
The structure of the heterochromatic bands in mitotic chromosomes of the important tropical aquaculture species of tilapia, Oreochromis niloticus, was investigated by the combination of the C-banding technique, chromosomal digestion with two restriction endonucleases and fluorescence in situ hybridization (FISH) of two satellite DNAs (SATA and SATB). The tilapia chromosomes presented heterochromatic bands in the centromeres and in the short arms of almost all chromosomes that were differentially digested by the restriction endonucleases HaeIII and EcoRI. FISH of SATA showed that this satellite sequence is distributed in the centromeric region of all chromosomes of tilapia. FISH also revealed an intense hybridization signal for SATB in only one chromosome pair, but less intense signals were also present in several other pairs. The digestion of tilapia chromosomes by HaeIII and EcoRI was positively correlated with the position of SATA and SATB in chromosomes as revealed by FISH. The results obtained may be useful in future molecular and genetic studies of tilapias.

Olufemi, B. E., Agius, C., and Roberts, R. J. (1983). Aspergillomycosis in intensively cultured tilapia from Kenya. Vet Rec 112, 203-4.

Osaki, A., Okida, N., Ishikawa, K., Tokumoto, M., Nagahama, Y., Lippert, T. H., Voelter, W., and Tokumoto, T. (1999). Identification of ubiquitin in seminal plasma from Tilapia, Oreochromis niloticus. Biomedical Research-Tokyo 20, 249-252.
The polypeptide ubiquitin, up to now almost exclusively discovered in intracellular spaces, was immunologically detected in Tilapia seminal plasma. Ubiquitin was purified from seminal plasma by column chromatography. N-terminal amino acid sequence analysis revealed 31 N-terminal amino acids to be identical between this ubiquitin and those of several species. Thus, we concluded that the protein detected in seminal plasma is a ubiquitin.

Oshima, N., and Yokozeki, A. (1999). Direct control of pigment aggregation and dispersion in tilapia erythrophores by light. Zoological Science 16, 51-54.
Innervated and denervated erythrophores of the tilapia, Oreochromis niloticus, responded directly to light of defined wavelength by pigment aggregation or dispersion, although similar effects did not occur in melanophores. In spectral regions between 400-440 nm and 550-600 nm, pigment aggregation took place, while the dispersion response was accelerated at wavelengths between 470-530 nm. The progress of the aggregation or dispersion response depended on the light intensity. These results may imply the coexistence of three kinds of visual pigments in tilapia erythrophores.

Overmier, J. B., and Gross, D. (1972). Quantitative study of nest building activity of the east African mouthbreeding fish, Tilapia mossambica. Z Tierpsychol 31, 326-9.

Overmier, J. B., and Gross, D. (1974). Effects of telencephalic ablation upon nest-building and avoidance behaviors in East African mouthbreeding fish, Tilapia mossambica. Behav Biol 12, 211-22.

Paflitschek, R. (1976). Investigations of the toxic effects of Bayer 73 (Bayluscid WP) on eggs and yolk-sac larvae of Tilapia leucosticta (Cichlidae). Experientia 32, 1537-8.

Panigrahi, A. K., Rath, S., and Misra, B. N. (1979). Change in DNA, protein & free amino acids of the brain of a freshwater fish Tilapia mossamblica Peters, during aging. Indian J Exp Biol 17, 699-701.

Panigrahi, A. K., and Misra, B. N. (1980). Toxicological effects of a sub-lethal concentration of inorganic mercury on the fresh water fish, Tilapia mossambica, Peters. Arch Toxicol 44, 269-78.

Papoutsoglou, S. E., and Abel, P. D. (1988). Sublethal toxicity and accumulation of cadmium in Tilapia aurea. Bull Environ Contam Toxicol 41, 404-11.

Parhar, I. S., and Sim, M. K. (1994). Central dopaminergic neurons in tilapia: effects of gonadectomy and hypothalamic lesion. Neurosci Res 18, 255-66.
The effects of gonadectomy, testosterone and estrogen on the dopamine (DA) neurons were examined by measuring the concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the brain and pituitary of male tilapia. The tuberal area and the pituitary had significantly high levels of DA and low levels of DOPAC, indicating the existence of a rich dopaminergic innervation in these areas. Gonadectomy and sex steroid replacement had no effect on DA and DOPAC levels. Preoptic lesions (14 days survival period) significantly increased DA levels of the pituitary, indicating a possible existence of a preoptico- hypophysial neural system that inhibits pituitary DA synthesis in tilapia. The lack of effect by preoptic (4 days survival period) and posterior hypothalamic lesions on the DA content of the pituitary indicates the absence of dopaminergic innervation of the pituitary by the preoptic and the posterior hypothalamus. Instead, the overall results do suggest the anterior periventricular area as a possible source of pituitary dopaminergic innervation.

Parhar, I. S., Soga, T., and Sakuma, Y. (1996). In situ hybridization for two differentially expressed GnRH genes following estrogen and triiodothyronine treatment in the brains of juvenile tilapia (cichlid). Neurosci Lett 218, 135-8.
Using in situ hybridization, messenger RNAs for gonadotropin-releasing hormone (GnRH) were seen distributed differently in the brains of 40- day-old juvenile tilapia Oreochromis mossambicus. While salmon-GnRH mRNA was localized in the nucleus olfactoretinalis (terminal nerve ganglia), chicken II-GnRH mRNA mRNA was observed in the midbrain nucleus. Various concentrations (0.1-10 mg) of estradiol benzoate and triiodothyronine, given over a 24 h period, had no effects on mRNA levels of salmon- and chicken II-GnRH. Analysis of variance indicated significantly higher levels of salmon- but not chicken II-GnRH mRNA in larger (> 1.5 mm) versus smaller (1.3 mm) brains, among juveniles of the same age and same genetic brood. Thus, salmon-GnRH neurons in the nucleus olfactoretinalis display greater variance depending on the body mass. Since reproductively active tilapia differ with respect to body size at sexual maturation, therefore, besides the age and treatment effects, body size should be taken into consideration.

Parhar, I. S., Soga, T., and Sakuma, Y. (1998). Quantitative in situ hybridization of three gonadotropin-releasing hormone-encoding mRNAs in castrated and progesterone-treated male tilapia. Gen Comp Endocrinol 112, 406-14.
We investigated the effects of castration and progesterone administration on the three gonadotropin-releasing hormone (GnRH)- encoding mRNAs in sexually mature male tilapia Oreochromis niloticus. In situ hybridization histochemistry was performed using 35S-labeled antisense oligonucleotide probes complementary to salmon-, seabream-, and chicken II-GnRH cDNAs to quantify cellular GnRH mRNA expression in the terminal nerve ganglia (nucleus olfactoretinalis), preoptic area, and midbrain tegmentum of animals castrated for 2 weeks and injected intraperitoneally with sesame oil or progesterone. Castration significantly elevated salmon-GnRH mRNA but not seabream- or chicken II- GnRH mRNA levels. Progesterone treatment had no effect on salmon-, seabream-, or chicken II-GnRH mRNA levels. Comparisons between intact, castrated, and progesterone-treated animals showed no change in the total volume of nucleus olfactoretinalis, cell sizes, and total numbers of cells expressing GnRH mRNA within the midbrain and preoptic area. These results demonstrate that salmon-GnRH but not seabream- or chicken II-GnRH-synthesizing neurons are under a gonadal steroid negative feedback control and that progesterone might not be the main hormone regulating the three GnRH-encoding mRNAs in the male tilapia. Copyright 1998 Academic Press.

Pelissier, C., Tack, D. L., and Gras, G. (1982). [Effect of temephos on the acetylcholinesterase activity of the brain of Tilapia guineensis. 2: Experimental study of 24-hour exposure to the toxic compound]. Toxicol Eur Res 4, 309-14.
The exposition of the Tilapia guineensis to concentrations used in the field to destroy the simulium larvae in their aquatic biotopes is 0,05 mg/l/10 minutes. The authors have previously remarked a significant lowering of acetylcholinesterasic brain activity in this fish. In the case of a much prolonged contact (24h corresponding 144 times the theoretic time of contact), it is noticed that, if this immediate effect is not more pronounced, on the other hand it is noticeable for a much longer acetylcholinesterasic activity extends beyond forty days. In the same conditions, three successive weekly treatments lead the acetylcholinesterasic activity to the level of vital activity.

Pellissier, C., Leung Tack, D., and Gras, G. (1983). [Effect of temephos on acetylcholinesterase activity in the brain of Tilapia guineensis. 3: Comparative effect of temephos and 3 substitute insecticides]. Toxicol Eur Res 5, 63-9.
The Onchocerciasis Control Programme (OCP) is realized in the major part of the treated area by weekly applications of temephos in biotopes of simulles larvae. This insecticide is very effective and its impact on the aquatic fauna is evaluated by means of periodic samplings of the fauna. Therefore, the most sensitive way of tracking down fish poisoning is by studying the brain acetylcholinesterase depression. Evaluated on Tilapia guineensis this lowering is moderate when operational doses are used by OCP. The discovery of resistence to temephos incited researchers of OCP to try remplacement insecticides. Among these, chlorphoxim, chlorpyrifos-methyl and pirimiphos-methyl proved to be the most effect of these three organophosphorus compounds to that of temephos on the acetylcholinesterasic activity of the brain of Tilapia but using a much higher dosage (0,05 mg/l during 24 hrs that is 144 times more than for temephos). The results demonstrate that the three remplacement insecticides have on inhibitive effect plainly more important than that of temephos and that the retour to normal activity requires a much longer time.

Perez, J. E., Gomez, A., and Nirchio, M. (1999). FAO and tilapia. Interciencia 24, 321-323.
As a consequence of problems with the production of high quality seed and the attainment of all-males red tilapia, officials from FAO decided to start a study in order to genetically improve these fishes. To accomplish this goal a Technical Cooperation Project was approved to Venezuela. Among other purposes the Project includes an analysis of the environmental impact, a campaign to raise awareness on the preservation of biodiversity, the selection of breeders from stocks available in the country. It must be asked: A campaign to preserve biodiversity, after red tilapia has proliferated in many rivers, lakes and estuarine habitats in the country? One wonders why FAO has spent large sums of money investigating something that everybody knows: After generations of inbreeding and reversion to the,wild type, hew could Ive select breeders from stocks available in the country? We believe that FAO's financial plan is not only an unnecessary waste of resources and efforts in an already well known matter, it also cuts short the possibilities of orienting research toward the development of native species culture technologies with large potential for aquaculture.

Piavaux, A., and Dandrifosse, G. (1972). [Intestinal laminarinases of a cichlid fish Tilapia macrochir Boulenger]. Arch Int Physiol Biochim 80, 51-7.

Piront, A., Hamoir, G., and Crokaert, R. (1968). Proteinic composition of the low ionic strength extracts of Tilapia macrochir Boulenger white muscles. Arch Int Physiol Biochim 76, 1-25.

Pisam, M., Auperin, B., Prunet, P., Rentier-Delrue, F., Martial, J., and Rambourg, A. (1993). Effects of prolactin on alpha and beta chloride cells in the gill epithelium of the saltwater adapted tilapia "Oreochromis niloticus". Anat Rec 235, 275-84.
Tilapia (Oreochromis niloticus), 21 g average body weight, were divided into two groups. A group was maintained in fresh water, whereas another group was adapted for 2 weeks to 20% salt water. Among the latter, fishes were injected every 2 days for a week with tilapia prolactin (ti- PRL I). Gills were prepared for electron microscopy in order to determine the types and surface areas of chloride cells in each experimental condition. Two types of chloride cells, the alpha and beta cells were easily distinguished on the basis of their location and ultrastructural features in the gills of freshwater fishes, while only one type of cell, the saltwater alpha cells presumably derived from the transformation of the freshwater alpha cells, were encountered in saltwater adapted animals. After PRL injection of saltwater adapted fishes, small chloride cells, which displayed ultrastructural features similar to those of beta cells in freshwater tilapia, reappeared in interlamellar regions of the gills. In the same experimental conditions, the voluminous saltwater alpha cells showed a tendency to resume ultrastructural features more characteristic of the freshwater alpha cells from which they were derived. These observations tend to indicate that prolactin behaves as a "freshwater adapting hormone" and that beta cells are specifically involved in fish adaptation to freshwater living conditions.

Planas, J., Bern, H. A., and Millar, R. P. (1990). Effects of GnRH-associated peptide and its component peptides on prolactin secretion from the tilapia pituitary in vitro. Gen Comp Endocrinol 77, 386-96.
The rostral pars distalis (RPD), containing mainly prolactin (PRL)- secreting cells, of the pituitary from immature and mature tilapia was incubated for 16 hr at 27 degrees in hypoosmotic medium (300 mOsm/kg) in the presence (10(-8) and 10(-11) M) or absence of the human GnRH- associated peptide (GAP) molecule, a potent PRL-inhibiting factor in mammals (Nikolics et al., Nature (London) 316, 511, 1985), and of a series of its component peptides. The release of the two forms of PRL in tilapia into the medium was measured by sodium dodecyl sulfate- polyacrylamide gel electrophoresis followed by densitometry. The variability inherent in this method was normalized by calculating PRL release as the percentage of the total hormone present in both tissue and medium. Newly synthesized PRL was detected by incorporation of [35S]methionine, introduced into the culture medium, by the PRL molecules. In immature tilapia, GAP inhibited the release of total PRL while stimulating the release of newly synthesized large PRL. Among the GAP fragments tested, 28-36 was the fragment that most significantly affected PRL secretion. Both concentrations of fragment 28-36 stimulated the release of newly synthesized PRL from immature rostral pars distalis (RPDs). This stimulation appears to be dependent on the osmotic pressure of the medium since this fragment did not affect PRL secretion in hyperosmotic medium (340 mOsm/kg). Fragment 38-49 inhibited total PRL release from mature RPDs. Fragment 51-66 stimulated the release of total PRL from mature RPDs. Examination of tissue and medium values in densitometric units after incubation with fragments 28- 36 and 51-66 indicated that while the tissue content of PRL was decreased, the medium content of PRL was not affected. This suggests that fragments 28-36 and 51-66, in opposition to the situation found when the data are expressed as percentage release of PRL, may not stimulate PRL release but may instead decrease the tissue content of PRL. These results suggest that the entire human GAP molecule, as well as some of its fragments, may have direct effects on the PRL cells in the tilapia pituitary.

Poncelet, A. C., Levavi-Sivan, B., Muller, M., Yaron, Z., Martial, J. A., and Belayew, A. (1996). The tilapia prolactin I gene: evolutionary conservation of the regulatory elements directing pituitary-specific expression. DNA Cell Biol 15, 679-92.
To study the elements involved in the pituitary specific transcriptional regulation of the tilapia prolactin I gene (tiPRL I), we have cloned and entirely sequenced a 3.4-kb genomic fragment immediately upstream from the first exon. In footprinting experiments, three tilapia sequences are protected from DNase I digestion by rat pituitary extracts (base pair coordinates -643 to -593, -160 to -111, and -73 to -46). Computer analysis of the nucleotide sequence reveals significant homology to mammalian binding sites for Pit-1, a transcription factor that is known to mediate pituitary-specific expression of the PRL genes in mammals. The tiPRL I 5'-flanking sequences can direct transient expression of a linked luciferase reporter gene in transfected rat pituitary cell lines and tilapia pituitary primary cell cultures. Transient expression experiments with 5'-deletion mutants reveal three regulatory regions. Two have a stimulatory effect on transcription and one an inhibitory effect. Electrophoretic mobility-shift assays (EMSA) demonstrate that the rat Pit-1 factor specifically binds to tilapia DNA sequences. Several such tilapia Pit-1 binding sites mediate activation of a linked heterologous promoter in transfected rat and tilapia pituitary cells. As evidenced by EMSA, a Pit-1-like protein is present in tilapia pituitary extracts. All these data point to a high conservation of the molecular mechanisms involved in pituitary-specific expression of the PRL genes in vertebrates.

Potts, W. T., Foster, M. A., Rudy, P. P., and Howells, G. P. (1967). Sodium and water balance in the cichlid teleost, Tilapia mossambica. J Exp Biol 47, 461-70.

Pouyaud, L., Desmarais, E., Chenuil, A., Agnese, T. F., and Bonhomme, F. (1999). Kin cohesiveness and possible inbreeding in the mouthbrooding tilapia Sarotherodon melanotheron (Pisces Cichlidae). Molecular Ecology 8, 803-812.
Four microsatellite markers were used to study genetic variation among individuals of the mouthbrooding tilapia Sarotherodon melanotheron (Ruppel 1852) caught in separate but adjacent shoals. A comparison was also made with fish from six other localities. Populations originating from riverine environments appear to be panmictic, while samples from open waters such as lagoons showed highly significant heterozygote deficiencies. For instance, at the 33-allele locus SMEL4, 32 homozygous individuals were observed among the 82 individuals from the same lagoon location instead of only five homozygotes expected if random mating occurred. A further assessment of the genetic similarity of individuals within each shoal, validated by robust permutation techniques requiring no precise knowledge of gene frequencies, showed that related individuals tend to aggregate, and suggested that mating occurs preferentially within small groups of kin. Cichlids are often presented as a group of fish where microallopatric speciation takes place. The possible link between kin aggregation, inbreeding and shoaling behaviour we propose here may have important consequences for our understanding of the mechanisms involved in this fast speciation process.

Prasad, T. A., Srinivas, T., Rafi, G. M., and Reddy, D. C. (1991). Effect in vivo of atrazine on haematology and O2 consumption in fish, Tilapia mossambica. Biochem Int 23, 157-61.
Studies were conducted on haematological constituents such as Red blood cells (RBC), White blood cells (WBC), Haemoglobin (Hb), Packed cell volume (PCV), Mean cell volume (MCV), Mean corpuscular haemoglobin (MCH), Mean corpuscular haemoglobin concentration (MCHC), Blood volume (BV), Blood water content (BWC) and Whole animal oxygen consumption (WAOC) in the fish exposed to sublethal concentration of atrazine. Significant changes were seen in the constituents of the blood and O2 consumption of fish suggesting the existence of respiratory distress in the fish as a consequence of atrazine toxicity.

Prasad, T. A., Srinivas, T., and Reddy, D. C. (1991). Modulations in nitrogen metabolism in the hepatic and neuronal tissues of fish, Tilapia mossambica exposed to atrazine. Biochem Int 23, 271-9.
The present study deals with the effect of atrazine on nitrogen metabolism in the liver and brain of fish. Significant changes were seen in the levels of proteins, free amino acids, ammonia, urea, glutamine and the activity levels of proteases, glucogenic aminotransferases, branched-chain aminotransferases, glutamate dehydrogenase, glutaminase, arginase, AMP deaminase and adenosine deaminase in both the tissues of fish exposed to sublethal concentration of atrazine. The study reflects a shift in nitrogen concentration of atrazine. The study reflects a shift in nitrogen metabolism in the tissues of fish for efficient mobilization of end products of protein catabolism as a consequence of atrazine.

Prasad, T. A., and Reddy, D. C. (1994). Atrazine toxicity on hydromineral balance of fish, Tilapia mossambicus. Ecotoxicol Environ Saf 28, 313-6.
The chronic effects of atrazine on total body weight, hydration level, and serum inorganic electrolytes in the tissues of freshwater fish, Tilapia mossambicus, were studied. Significant changes were observed in the tissues indicating the disturbances in the hydromineral balance of the fish as a consequence of atrazine.

Prasada Rao, K. S., and Ramana Rao, K. V. (1984). Tissue specific alteration of aminotransferases and total ATPases in the fish (Tilapia mossambica) under methyl parathion impact. Toxicol Lett 20, 53-7.
The activity levels of aspartate aminotransferase (AAT), alanine aminotransferase (AlAT) and total adenosine triphosphatase (ATPase) were studied in muscle, gill, liver and brain tissues of control and methyl parathion exposed (MPE) fish. Both aminotransferases were elevated in all the tissues inferring the diversion of alpha-amino acids into the TCA cycle as keto acids to augment energy production during methyl parathion (MP) stress. In gill, liver and brain tissues, there seemed to be a shift in the aminotransferase reactions under MP impact. The total ATPase activity was decreased in all tissues, suggesting inhibition of active transport and oxidative phosphorylation.

Prasada Roa, K. S., Ahammad Sahib, I. K., and Ramana Rao, K. V. (1985). Methyl parathion (O-O-dimethyl O-4-nitrophenyl thiophosphate) effects on whole-body and tissue respiration in the teleost, Tilapia mossambica (Peters). Ecotoxicol Environ Saf 9, 339-45.
The respiratory parameters of a freshwater teleost, Tilapia mossambica Peters, were studied under sublethal intoxication of methyl parathion. The rate of oxygen consumption by whole fish and selected tissues decreased during a 48-hr time-course study. The activities of the respiratory enzymes succinate dehydrogenase, malate dehydrogenase, and cytochrome-c oxidase also decreased considerably under methyl parathion exposure in muscle, gill, liver, and brain tissues. These results suggest that methyl parathion has a profound effect on the oxidative metabolism of the fish which results in low ATP turnover, possibly due to its influence on the respiratory center of the brain.

Press, N., Bryce, E., and Stiver, G. (1998). Strain characteristics of Streptococcus iniae isolated from tilapia species in Vancouver, British Columbia. Can Commun Dis Rep 24, 181-2.

Privat, F. (1970). [Changes in nutrition behavior of Tilapia rendalli after ablation of the dorsal telencephalic region, in different conditions of temperature and lighting]. Rev Suisse Zool 77, 651-62.

Quabius, E. S., Balm, P. H. M., and Wendelaar Bonga, S. E. (1997). Interrenal stress responsiveness of tilapia (Oreochromis mossambicus) is impaired by dietary exposure to PCB 126. Gen Comp Endocrinol 108, 472-82.
Activation of the hypothalamus-pituitary-interrenal (HPI) axis is characteristic of stress responses, which may result from a variety of environmental challenges. To investigate whether the stress response, and in particular the HPI axis, in tilapia (Oreochromis mossambicus) is compromised by short-term exposure to PCB 126, fish of both sexes were fed diets containing PCB 126 (50 microg/kg fish . day) for 5 days. In the first approach, which was performed twice, fish were acutely stressed for periods varying between 1 and 30 min at the end of the exposure period; in the second approach fish were sampled at the end of the exposure period either at rest or after 2 h of stress (confinement). After 5 days, the body weights in all experiments were significantly lower in PCB-fed fish than in control fish. There were no changes in basal plasma glucose levels, plasma ion concentrations, or branchial, renal, and intestinal Na,K-ATPase activity following PCB exposure. In the first experimental approach, in which fish experienced acute sampling stress, plasma cortisol levels reached lower levels in PCB-fed fish than in controls. This suggests an impaired ability to acutely activate interrenal steroidogenesis in PCB-treated tilapia. Adrenocorticotropic hormone (ACTH)- and cAMP-stimulated in vitro cortisol release from superfused head kidneys was lower in tissues from tilapia exposed to PCB 126 than in tissues from control animals. This effect persisted after 24 h in vitro, which, together with the high PCB 126 concentrations measured in the head kidneys of PCB-fed fish, may indicate direct toxic effects on the interrenal cells. The second experimental approach demonstrated that basal plasma cortisol and ACTH levels were not influenced by PCB treatment, but that the basal ACTH content of the rostral pars distalis (RPD) of the pituitary gland of PCB-fed fish was lower than that of control fish. After 2 h confinement, plasma cortisol levels and ACTH content of the RPD rose to similar values in both groups, whereas plasma ACTH levels were higher in confined PCB-fed fish than in confined controls. PCB-fed fish showed a lower hyperglycemic response to confinement than control fish. Confinement resulted in similarly elevated renal and intestinal Na,K- ATPase activities in both PCB-fed and control fish; branchial enzyme activities were not affected. Since PCB did not affect Na,K-ATPase activities and plasma ion concentrations, it is concluded that the effects of PCB 126 on the HPI axis in tilapia are not secondary to ionoregulatory dysfunction. Copyright 1997 Academic Press.

Radhaiah, V., Joseph, K. V., and Rao, K. J. (1989). Toxic effect of fenvalerate on fructose-1,6-diphosphate aldolase activity of liver, gill, kidney, and brain of the fresh water teleost, Tilapia mossambica. Bull Environ Contam Toxicol 42, 150-3.

Radhaiah, V., and Rao, K. J. (1990). Toxicity of the pyrethroid insecticide fenvalerate to a fresh water fish, Tilapia mossambica (Peters): changes in glycogen metabolism of muscle. Ecotoxicol Environ Saf 19, 116-21.
Toxic effects of a pyrethroid insecticide, fenvalerate, on fish muscle glycogen metabolism were investigated. Estimations were made after 10 and 20 days of exposure, and altered muscle glycogen metabolism was observed. The changes included a significant (P less than 0.001) decrease in the levels of glycogen, pyruvate, maleate dehydrogenase (MDH), succinate dehydrogenase (SDH), and phosphorylase a, b, and ab activities, while elevated levels of lactic acid, aldolase, and lactate dehydrogenase (LDH) activity were observed under fenvalerate intoxication. There was a decrease in opercular movement and oxygen consumption with an increase in concentration of fenvalerate.

Rahamim, E., Sandri, C., Akert, K., and Abraham, M. (1980). Bacilliform inclusions in cells of the proximal pars distalis in the pituitary of four species of Tilapia (Teleostei). Cell Tissue Res 205, 245-51.
Thin sections and replicas of freeze-etched pituitaries from six species of the teleostean family of Cichlidae were studied by electron microscopy. Four species belonging to the genus Tilapia exhibit rod- like structures, i.e., "bacilliform inclusions" (BI), about 1-2 micrometer in length in cells of the proximal pars distalis. The BI are found either isolated or fused in small groups. They are enclosed in an envelope similar to that of secretory granules. Both the BI and the secretory granules give a positive PAS-reaction.

Rahman, M. A., Mak, R., Ayad, H., Smith, A., and Maclean, N. (1998). Expression of a novel piscine growth hormone gene results in growth enhancement in transgenic tilapia (Oreochromis niloticus). Transgenic Res 7, 357-69.
Several lines of transgenic G1 and G2 tilapia fish (Oreochromis niloticus) have been produced following egg injection with gene constructs carrying growth hormone coding sequences of fish origin. Using a construct in which an ocean pout antifreeze promoter drives a chinook salmon growth hormone gene, dramatic growth enhancement has been demonstrated, in which the mean weight of the 7 month old G2 transgenic fish is more than three fold that of their non transgenic siblings. Somewhat surprisingly G1 fish transgenic for a construct consisting of a sockeye salmon metallothionein promoter spliced to a sockeye salmon growth hormone gene exhibited no growth enhancement, although salmon transgenic for this construct do show greatly enhanced growth. The growth enhanced transgenic lines were also strongly positive in a radio-immuno assay for the specific hormone in their serum, whereas the non growth enhanced lines were negative. Attempts to induce expression from the metallothionein promoter by exposing fish to increased levels of zinc were also unsuccessful. Homozygous transgenic fish have been produced from the ocean pout antifreeze/chinook salmon GH construct and preliminary trials suggest that their growth performance is similar to that of the hemizygous transgenics. No abnormalities were apparent in the growth enhanced fish, although minor changes to skull shape and reduced fertility were noted in some fish. There is also preliminary evidence for improved food conversion ratios when growth enhanced transgenic tilapia are compared to their non- transgenic siblings. The long term objective of this study is to produce lines of tilapia which are both growth enhanced and sterile, so offering improved strains of this important food fish for aquaculture.

Rakover, S. S. (1979). Fish (Tilapia aurea), as rats, learn shuttle better than lever-bumping (press) avoidance tasks: a suggestion for functionally similar universal reactions to a conditioned fear-arousing stimulus. Am J Psychol 92, 489-95.
Fish learned a shuttle avoidance task faster than a lever-bumping task. The latter task was hardly mastered at all. These and other results tend to support the suggestion for functionally similar universal reactions to a conditioned fear-arousing stimulus.

Ranganatha Koudinya, P., and Ramamurthi, R. (1978). Effect of sumithion (Fenitrothion) on some selected enzyme systems in the fish Tilapia mossambica (Peters). Indian J Exp Biol 16, 809-11.

Rao, D. S., and Raghuramulu, N. Vitamin D3 in Tilapia mossambica: relevance of photochemical synthesis. .
The capability of fish to synthesize vitamin D on exposure to ultraviolet (UV) light was examined. Purposeful exposure of the freshwater fish Tilapia mossambica (Tilapia) to artificial UV light (300 nm) resulted in a significant increase of vitamin D3 with a concomitant decrease in provitamin D3 [7-dehydrocholesterol (7-DHC)], indicating that provitamin D3 was converted to vitamin D3. However, only 0.13% of the intraperitoneally injected 4-14C cholesterol was recovered in the vitamin D3 and 25-hydroxyvitamin D3 (25-OH-D3) fractions after 15 h.

Rao, K. S., and Rao, K. V. (1983). Regulation of phosphorylases and aldolases in tissues of the teleost (Tilapia mossambica) under methyl parathion impact. Bull Environ Contam Toxicol 31, 474-8.

Rao, D. S., and Raghuramulu, N. (1998). Vitamin D metabolism in tilapia (Oreochromis mossambicus). Comp Biochem Physiol C Pharmacol Toxicol Endocrinol 120, 145- 9.
The present investigation was carried out to study the conversion of [3H]vitamin D3 and 25-OH-D3 in vivo and in vitro in freshwater tilapia (Oreochromis mossambicus). A metabolite co-migrating with 1,25-(OH)2D3 formed from [3H]vitamin D3 in vivo was about 3-fold more concentrated than that of 25-OH-D3. The conversion of 25-OH-[3H]D3 to a product co- eluting with 1,25-(OH)2D3 was several-fold higher in liver than in kidney. Our data suggests that the tilapia 'liver' may be a major site for vitamin D metabolism.

Rao, D. S., and Raghuramulu, N. (1999). Vitamin D3 and its metabolites have no role in calcium and phosphorus metabolism in Tilapia mossambica. J Nutr Sci Vitaminol (Tokyo) 45, 9-19.
The physiological function of vitamin D in fishes still remains uncertain. Earlier we observed no relationship between vitamin D3 content of several freshwater fishes and their calcemic/phosphatemic status and bone mineral content. In the present study the effects of vitamin D3 and its metabolites, 25-hydroxy vitamin D3 (25-OH-D3) and 1,25-dihydroxy vitamin D3 [1,25-(OH)2D3], administration on serum calcium-phosphorus levels, intestinal calcium absorption, whole-body calcium-phosphorus uptake, and gill calcium binding protein (CaBP) activity in the freshwater fish, Tilapia mossambica (Tilapia) was examined. It was observed that vitamin D3 and its metabolites could alter neither serum calcium-phosphorus levels nor intestinal calcium absorption and gill CaBP activity in fish at various doses. Further, the whole-body uptake of labelled calcium and phosphorus was also unaffected by vitamin D3/1,25-(OH)2D3 at different levels and/or at various lengths of time. Thus these studies indicate that unlike in terrestrial vertebrates, vitamin D3 or its metabolites are not needed for calcium-phosphorus homeostasis in fish.

Rath, S., and Misra, B. N. (1979). Relative toxicity of Dichlorvos (DDVP) to Tilapia mossambica, Peters of 3 different age groups. Exp Gerontol 14, 307-9.

Rath, S., and Misra, B. N. (1979). Sub-lethal effects of dichlorvos (DDVP) on respiratory metabolism of Tilapia mossambica, Peters of 3 age groups. Exp Gerontol 14, 37-41.

Rath, S., and Misra, B. N. (1981). Toxicological effects of dichlorvos (DDVP) on brain and liver acetylcholinesterase (AChE) activity of Tilapia mossambica, Peters. Toxicology 19, 239-45.
Acetylcholinesterase (AChE) activity of T. mossambica in relation to the interacting effects of aging and sub-lethal concentrations of Dichlorvos was studied. The enzyme activity of brain and liver decreased with increasing size (and age) and DDVP-exposed fish showed considerable inhibition of brain and liver AChE. The degree of enzyme inhibition followed a positive correlation with the insecticide concentration and the time of exposure. Brain exhibited a higher degree of enzyme inhibition in all age groups of fish as compared to liver. Small fish were more susceptible to the insecticide with respect to AChE activity. When transferred to clean water most of the exposed fish recovered their AChE activity and the recovery was greater in liver than in brain. Small fish exhibited comparatively a high level of recovery in the AChE activity. The degree of recovery followed an inverse relationship with the time of exposure.

Rawdon, B. B., and Cornish, E. M. (1973). Intestinal water absorption in Tilapia mossambica. I. Water movement in everted sacs of intestine bathed on both surfaces by identifcal ringer solution. Comp Biochem Physiol A 45, 549-53.

Reddy, P. K., and Lam, T. J. (1991). Effect of thyroid hormones on hatching in the tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 81, 484-91.
Incubation of fertilized eggs of Oreochromis mossambicus in media containing varying doses of T3, T4, and phenylthiocarbamide (PTC) indicated that the thyroid hormones delayed hatching, while the antithyroid drug accelerated it. Denuded eggs were also incubated in the above media and the media were assayed at various time intervals for hatching enzyme. The thyroid hormones delayed hatching enzyme release, while PTC enhanced it. The possible role of thyroid hormones in the control of the hatching process in fish eggs is discussed.

Reddy, A. T., Ayyanna, K., and Yellamma, K. (1991). Cypermethrin induced modulations in lipid metabolism of freshwater teleost, Tilapia mossambica. Biochem Int 23, 963-7.
Significant changes in lipid metabolic profiles were observed in brain, liver and gill tissues of T. mossambica under chronic exposure to sublethal concentrations of cypermethrin. Increase in total lipid, lipase and free fatty acids with decrease in glycerol content suggests simultaneous operation of lipogenesis and lipolysis during cypermethrin stress. Phospholipid levels dropped, while cholesterol content increased in all the tissues as a consequence of cypermethrin toxicity.

Reddy, A. T., Ayyanna, K., and Yellamma, K. (1991). Sensitivity of brain cholinesterase to cypermethrin toxicity in freshwater teleost Tilapia mossambica. Biochem Int 23, 959-62.
Cypermethrin at sublethal concentrations induced significant changes in acetylcholinesterase (AChE) activity and acetylcholine (ACh) content in the brain tissue of both juvenile and adult-fish. Maximum inhibition of AChE activity is noticed at 6h and 12h after exposure to cypermethrin in juvenile and adult fish respectively. In contrast, the ACh levels registered an elevation in both the cases. During subsequent periods the rate of recovery in AChE activity and ACh content is variable in both the groups.

Reddy, A. T., and Yellamma, K. (1991). Cypermethrin induced changes in nitrogen metabolism of fish, Tilapia mossambica. Biochem Int 23, 649-54.
At sublethal concentrations, cypermethrin caused a decrease in total proteins and an increase in free amino acids, protease, alanine aminotransferase and aspartate aminotransferase in liver, brain and gill tissues of Tilapia mossambica. Nitrogen metabolic profiles like ammonia, urea and glutamine were also elevated in all the tissues as a consequence of cypermethrin toxicity. Glutamate dehydrogenase, AMP deaminase and adenosine deaminase activity was also increased in the present study.

Reddy, A. T., and Yellamma, K. (1991). Perturbations in carbohydrate metabolism during cypermethrin toxicity in fish, Tilapia mossambica. Biochem Int 23, 633-8.
Sublethal concentrations (0.04 ppm) of cypermethrin induced significant metabolic changes in brain, liver and gill tissues of fish, T. mossambica. While cypermethrin caused depletion in glycogen and pyruvate levels lactate content was elevated in all the tissues. While phosphorylase 'a' and aldolase activity increased, phosphorylase 'b' activity registered a decrease in the present study. A decrease in lactate dehydrogenase activity with increase in lactate levels suggests reduced mobilization of pyruvate into citric acid cycle. Glucose-6- phosphate dehydrogenase activity was also elevated indicating enhanced oxidation through HMP pathway during cypermethrin toxicity. Inhibition of succinate, malate and isocitrate dehydrogenases and cytochrome c oxidase activity indicates impaired oxidation of carbohydrates through citric acid cycle.

Reinecke, M., Schmid, A., Ermatinger, R., and Loffing-Cueni, D. (1997). Insulin-like growth factor I in the teleost Oreochromis mossambicus, the tilapia: gene sequence, tissue expression, and cellular localization. Endocrinology 138, 3613-9.
Using reverse transcription-PCR and molecular cloning, the complementary DNA sequence encoding preproinsulin-like growth factor I (IGF-I) of a teleost, the tilapia (Oreochromis mossambicus) was established from liver. At the amino acid level, tilapia IGF-I shows all residues necessary for the maintenance of tertiary structure and shares about 80% identity with IGF-I from other teleosts. The B and A domains of tilapia IGF-I show more than 90% homology to those of other teleosts and 86-93% to those of human. However, in contrast to salmonids, the C domain of tilapia is truncated. Reverse transcription- PCR analysis followed by Southern blotting with an internal probe specific for tilapia IGF-I indicated a transcript in liver, pancreas, gut, kidney, head kidney, gill, ovary, testis, eye, and brain. In correlation, parenchymal cells were identified as likely local production sites by the use of immunohistochemistry. IGF-I immunoreactivity was confined to D cells in pancreatic islets, gastroentero-endocrine cells, cells of renal proximal tubules, interrenal cells of the head kidney, gill chondrocytes, chloride cells of the gill epithelium, granulosa cells in the ovary, spermatocytes and Sertoli cells in testis, and neurons in retina and brain. The local production of IGF-I in multiple organs of the tilapia indicates paracrine/autocrine actions of IGF-I involved in organ-specific functions. The results further demonstrate that the primary structure of IGF-I, especially in the B and A domains, is highly conserved during phylogeny.

Rentier-Delrue, F., Swennen, D., Philippart, J. C., L'Hoir, C., Lion, M., Benrubi, O., and Martial, J. A. (1989). Tilapia growth hormone: molecular cloning of cDNA and expression in Escherichia coli. Dna 8, 271-8.
A cDNA library was prepared from poly(A)+RNA extracted from tilapia Oreochromis niloticus anterior pituitaries. The recombinant clones carrying the cDNA sequence of tilapia growth hormone (tiGH) were selected using a fragment of the trout growth hormone (tGH) cDNA as hybridization probe. The nucleotide sequence of the full-length tiGH cDNA was determined. This cDNA encodes a protein of 204 amino acids, including the putative signal peptide of 17 amino acids. Mature tiGH cDNA was inserted in an Escherichia coli expression vector which led to the production of tiGH protein with a yield estimated to be 20% of the total bacterial proteins.

Rentier-Delrue, F., Swennen, D., Prunet, P., Lion, M., and Martial, J. A. (1989). Tilapia prolactin: molecular cloning of two cDNAs and expression in Escherichia coli. Dna 8, 261-70.
We have isolated cDNA clones encoding tilapia prolactin (tiPRL) from a cDNA library prepared from tilapia (Oreochromis niloticus) anterior pituitary glands. A trout PRL cDNA fragment was used as hybridization probe to select the recombinant plasmids carrying the tiPRL coding sequence. Two types of PRL cDNA were isolated and their complete nucleotide sequence determined. The larger cDNA (tiPRL-I) codes for a polypeptide of 212 amino acids, including a putative signal sequence of 24 amino acids, and contains a 3' untranslated region of 787 bp. The second prolactin cDNA (tiPRL-II) encodes a polypeptide of 200 amino acids, including a presumptive signal peptide of 23 amino acids, and contains a noncoding region of 512 bp. tiPRL-I and tiPRL-II cDNA sequences are 81% similar, whereas the encoded proteins share 69% amino acid identity at optimal alignment. Mature tiPRL-I was efficiently expressed in Escherichia coli carrying a plasmid in which the tiPRL-I cDNA was under the control of the phi 10 promoter of T7 bacteriophage. The new recombinant protein representing about 45% of the total cellular proteins was found in inclusion bodies and cross-reacted with salmon PRL antiserum.

Reshkin, S. J., Grover, M. L., Howerton, R. D., Grau, E. G., and Ahearn, G. A. (1989). Dietary hormonal modification of growth, intestinal ATPase, and glucose transport in tilapia. Am J Physiol 256, E610-8.
The effect of growth stimulatory and inhibitory dietary applications of hormones [3,5,3'-triiodo-L-thyronine (T3) and 17 alpha- methyltestosterone (MT)] on Na+-K+-adenosinetriphosphatase (ATPase) activity and glucose transport by upper and lower intestinal brush- border membrane vesicles of tilapia (Oreochromis mossambicus) were characterized. Both enzyme activity and glucose transport were greater in growth-stimulatory treatments and lower in growth-inhibitory treatments than in the control. Growth on stimulatory hormone treatments increased apparent glucose influx kinetics (one-half maximum glucose influx, maximum glucose influx, and apparent diffusion coefficient) in both intestinal segments, whereas inhibitory treatments reduced these parameters in upper intestine but had no effect on these parameters in lower intestine. All hormone treatments increased the stoichiometry of Na-glucose cotransport from 1:1 in the control to 2:1 under test conditions. It is suggested that observed patterns of altered growth are due, in part, to hormonally modified intestinal nutrient transport and Na+-K+-ATPase activities.

Richman, N. H. d., Helms, L. M., Ford, C. A., Benishin, C., Pang, P. K., Cooke, I. M., and Grau, E. G. (1990). Effects of depolarizing concentrations of K+ and reduced osmotic pressure on 45Ca2+ accumulation by the rostral pars distalis of the tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 77, 292-7.
The accumulation of 45Ca2+ into tilapia prolactin (PRL) tissue was examined under conditions which alter prolactin release. In initial experiments, PRL tissue was incubated in medium containing 12 microCi/ml 45Ca2+ in hyperosmotic medium (355 mOsmolal). Under these conditions, 45Ca2+ accumulated steadily, reaching a plateau within 15- 20 min. Subsequent exposure to La3+, which displaces Ca2+ from superficial pools in a wide variety of tissues, rapidly (within 5 min) removed nearly 70% of the 45Ca2+ associated with the tissue. Following this initial removal of 45Ca2+, the level of 45Ca2+ in the PRL tissue remained constant, and is referred to as the La3(+)-resistant pool of Ca2+. This pool of Ca2+ is thought to reflect the entry rate of Ca2+ from extracellular sources. Prolactin tissue exposed to hyposmotic medium or to depolarizing [K+], which stimulates PRL release, significantly increased 45Ca2+ accumulation in this La3(+)-resistant pool. These results indicate that reduced osmotic pressure and depolarization may alter release from tilapia PRL cells, in part, through their ability to increase the entry of extracellular Ca2+.

Richman, N. H. d., Ford, C. A., Helms, L. M., Cooke, I. M., Pang, P. K., and Grau, E. G. (1991). The loss of 45Ca2+ associated with prolactin release from the tilapia (Oreochromis mossambicus) rostral pars distalis. Gen Comp Endocrinol 83, 56-67.
The relationship between tritium 3H-labeled prolactin (PRL) release and the loss of tissue-associated 45Ca2+ was examined in the tilapia rostral pars distalis (RPD) using perifusion incubation under conditions which inhibit or stimulate PRL release. Depolarizing [K+] (56 mM) and hyposmotic medium (280 mOsmolal) increased both the release of [3H]PRL and the loss of 45Ca2+. The responses to high [K+] were faster and shorter in duration than those produced by reduced osmotic pressure. The depletion of Ca2+ from the incubation medium with 2 mM EGTA suppressed the [3H]PRL response evoked by high [K+] or reduced osmotic pressure. Exposing the tissues to Ca(2+)-depleted medium in the absence of high [K+] or reduced osmotic pressure produced a sharp, but brief, increase in 45Ca2+ loss. Cobalt (10(-3) M), a competitive inhibitor of calcium-mediated processes, inhibited the [3H]PRL response to hyposmotic medium and to high [K+]. Cobalt also diminished the increased loss of 45Ca2+ evoked by exposure to reduced osmotic pressure, but was ineffective in altering responses to high [K+]. Methoxyverapamil (D600; 10(-5) M), a blocker of certain voltage- sensitive Ca2+ channels, did not alter either the [3H]PRL or the 45Ca2+ responses to high [K+] and reduced osmotic pressure. Taken together with our earlier studies, the present findings suggest that exposure to high [K+] or hyposmotic medium produces rapid changes in the Ca2+ metabolism of the tilapia RPD that are linked to the stimulation of PRL secretion. Nevertheless, the increased 45Ca2+ loss, but not [3H]PRL release, upon exposure to Ca(2+)-depleted media suggests that Ca2+ loss may not always reflect intracellular events that lead to PRL release.

Richter, H., Focken, U., Becker, K., Santiago, C. B., and Afuang, W. B. (1999). Analysing the diel feeding patterns and daily ration of Nile Tilapia, Oreochromis niloticus (L.), in Laguna de Bay, Philippines. Journal of Applied Ichthyology-Zeitschrift Fur Angewandte Ichthyologie 15, 165-170.
Cage cultured Nile tilapia, Oveochromis niloticus, were sampled at a commercial set-up on two occasions in 1995 in Laguna de Bay, Philippines, each time over a 24 h cycle. The stomach content weights were averaged for each subsample and analysed with the computer model MAXIMS. The model predicted that, in May, larger fish (mean total weight: 31.5 g) feeding on natural food alone fed continuously from dawn to dusk, ingesting 5.1 % body mass equivalent (% BME, wet weight basis) whereas smaller fish (mean total weight: 9.8 g) had two feeding periods per day, from sunrise to mid-morning and again from mid-afternoon until after sunset, ingesting 13.7 % BME. In August, fish were given supplemental feed once daily at 07:00 h. These fish (mean total weight: 81.7 g) fed intensely until supplemental feed ran out before mid-day, after which some ingestion of natural food took place later in the day. The fish ingested 5.8 % BME supplemental feed and 5.1% BME natural food per 24 h. In May, most of the stomach contents consisted of the blue-green alga Anabaena spiroides, whereas in August, the natural food was made up principally of detritus.

Ridha, M. T., and Cruz, E. M. (1999). Effect of different broodstock densities on the reproductive performance of Nile tilapia, Oreochromis niloticus (L.), in a recycling system. Aquaculture Research 30, 203-210.
The present study was conducted to evaluate the effect of different stocking densities on the seed production of Nile tilapia, Oreochromis niloticus (L.), under intensive recycling hatchery system conditions. Males and females with mean body weights of 163.2 and 105.0 g, respectively, were stocked at three broodstock densities (4, 8 and 12 fish m(-2)) at a male:female ratio of 1:3 in 1 x 1 x 0.43m (W x L x H) fibreglass tanks. The tanks were illuminated at 2500 lux for 18 h day(-1) and the water temperature was maintained at 29 +/- 1 degrees C. Effluent from spawning tanks was recycled through a biological filter with 10-15% replacement of new water per day. The experiment lasted for 126 days. The results showed that breeders stocked at 4 fish m(-2) had significantly higher (P < 0.05) mean values for total seed production, seed kg(-1) female day(-1), seed female(-1) day(-1), seed m(-2) day(-1) and spawning synchrony than at 8 and 12 fish m(-2) broodstock densities. The mean percentage of seeds in the yolk-sac and swim-up fry stages was highest at 4 fish m(-2) broodstock density. However, the recovery rate was not affected by broodstock density. It is recommended that further research should be conducted to determine whether weight m(-2), number m(-2) or age of broodstock should be the basis for stocking broodstock.

Rivas, R. J., Nishioka, R. S., and Bern, H. A. (1986). In vitro effects of somatostatin and urotensin II on prolactin and growth hormone secretion in tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 63, 245-51.
The control of release of two recently characterized forms of prolactin (PRL) of molecular mass 24 and 20 kDa was investigated. The rostral pars distalis of male tilapia was incubated singly in a hypotonic modified Krebs-Ringer bicarbonate medium in order to stimulate PRL release; for comparison, the proximal pars distalis containing growth hormone (GH) cells was incubated in isotonic medium with or without 1 microgram/ml cortisol to stimulate GH release. The release of both PRLs and GH into the medium was measured by sodium dodecyl sulfate (SDS)-- polyacrylamide gel electrophoresis followed by densitometry. Both somatostatin and synthetic (Gillichthys) urotensin II, a partial somatostatin homolog and analog from the teleost caudal neurosecretory system, significantly inhibited the release of both PRLs. Somatostatin significantly inhibited GH release, but urotensin II had no significant effect.

Rocha, M. J., and Reis-Henriques, M. A. (1996). Plasma and urine levels of C18, C19 and C21 steroids in an asynchronous fish, the tilapia Oreochromis mossambicus (Teleostei, Cichlidae). Comp Biochem Physiol C Pharmacol Toxicol Endocrinol 115, 257- 64.
Female and male tilapia, Oreochromis mossambicus, were treated with luteinizing hormone-releasing hormone analogue (LH-RHa) and pimozide (PIM) or with human chorionic gonadotropin (hCG) to stimulate gonadal development and sexual maturation. Plasma (both sexes) and urine (males) samples were collected periodically for steroid analysis by radioimmunoassay. Plasma levels of estradiol-17 beta (3-6 ng/ml) and testosterone, higher in female (up to 25 ng/ml) than in male (6-13 ng/ml; P 0.05), were in the range of those established in other tilapia species. Plasma levels of the established teleost oocyte maturation-inducing steroids (MIS), that is 17 alpha,20 beta-dihydroxy- 4-pregnen-3-one (17,20 beta-P) and 17 alpha,20 beta, 21-trihydroxy-4- pregnen-3-one (17,20 beta,21-P) were low (1-9 ng/ml) and were not different between treated and control fishes at 8, 12, 16, 24, 48, 72 and 96 hr after injection. Furthermore, in male O. mossambicus, 17,20 beta,21-P was undetectable. Plasma levels of 3 alpha,17 alpha,21- trihydroxy-5 beta-pregnan-20-one (3,17,21-P-5 beta) were very high in both sexes (up to 700 ng/ ml), mostly in hormone-treated groups, whose levels were higher than controls (P 0.05). Urine levels of conjugated 17,20 beta,21-P (glucuronides and sulphates) were not detectable, but those of 17, 20 beta-P (up to 25 ng/ ml) and 3,17,21-P-5 beta (up to 1 microgram/ml) were higher than free 17,20 beta-P and 3,17,21-P-5 beta measured in the plasma of the same animals (P 0.05). Both LH-RHa + PIM and hCG induced sexual maturation of O. mossambicus (histological data); nevertheless, during that period all measured steroids, either in plasma or urine, almost did not fluctuate. Thus, this study does not make any comment about the MIS of tilapia. Nevertheless, the high levels of conjugated 3,17,21-P-5 beta and 17,20 beta-P in urine suggest a probable pheromone role for these steroids in this species.

Rodgers, B. D., Helms, L. M., and Grau, E. G. (1992). Effects of fasting, medium glucose, and amino acid concentrations on prolactin and growth hormone release, in vitro, from the pituitary of the tilapia Oreochromis mossambicus. Gen Comp Endocrinol 86, 344-51.
Previous investigations have shown that the release of PRL and GH from the tilapia pituitary is directly sensitive to osmotic pressure and a variety of endocrine and neuroendocrine factors. The present studies were aimed at determining whether the spontaneous release of PRL and GH, in vitro, is: (1) sensitive to the nutritional status of the fish, and (2) responsive to variations in the D-glucose and total amino acid content of the incubation medium. In the first series of experiments, male fish (50 to 60 g) were divided into two groups. One group was fed twice daily for 2 weeks while the second received no food. A nearly homogeneous mass of PRL-secreting cells was dissected from the rostral pars distalis (RPD) and incubated for 18 to 20 hr in either hyposmotic (300 mOsmolal) or hyperosmotic (355 mOsmolal) medium. Similarly, a mass of GH-secreting cells was dissected from the proximal pars distalis (PPD) and incubated for 18 to 20 hr in isosmotic (320 mOsmolal) medium. Fasting was found to alter the total amount of PRL and GH in the culture well (tissue + medium) at the end of the incubations, decreasing PRL and increasing GH. Fasting was also found to both reduce spontaneous PRL release in vitro and suppress its stimulation by reduced osmotic pressure (P less than 0.01). By contrast, fasting resulted in a substantial increase in spontaneous GH release from the PPD in vitro (P less than 0.01). In the second series of experiments, GH release was found to increase as the D-glucose concentration of the medium decreased (P less than 0.01), while prolactin release was unresponsive.(ABSTRACT TRUNCATED AT 250 WORDS).

Rognon, X., and Guyomard, R. (1997). Mitochondrial DNA differentiation among East and West African Nile tilapia populations. Journal of Fish Biology 51, 204-7.
Variation of the ND5/6 mtDNA fragment was studied in six Nile tilapia populations using PCR and RFLP analysis. The observed variation allows a strict discrimination between eastern and western African populations.

Romana-Eguia, M. R. R., and Eguia, R. V. (1999). Growth of five Asian red tilapia strains in saline environments. Aquaculture 173, 161-170.
Growth of five Asian red tilapia strains (BFS, NIFI, FAG, PF and HL) were evaluated in brackish and seawater. Eight-week-old juveniles from the five test strains were size-matched with similarly aged Oreochromis mossambicus which served as internal reference. Fish were stocked at a ratio of 15 test:15 reference in 100-1 tanks supported by a recirculating system. Commercial feed was given twice daily at 10-20% of the fish biomass. Growth, measured from length and weight increment at 10 weeks, was recorded. Statistical analyses on mean specific growth rates showed significant differences among the strains reared in seawater. The Philippine strain PF grew best in seawater while the Thai strain NIFI performed well in brackishwater. In the Philippines, red tilapias are farmed in intensive freshwater culture systems by few aquaculturists. Results of this study indicate that some Asian strains can be developed for use in more sustainable brackish and seawater culture systems. (C) 1999 Elsevier Science B.V. All rights reserved.

Ruangpan, L., Kitao, T., and Yoshida, T. (1986). Protective efficacy of Aeromonas hydrophila vaccines in nile tilapia. Vet Immunol Immunopathol 12, 345-50.
Protection and serum antibody production against Aeromonas hydrophila was examined in nile tilapia, Tilapia nilotica (L.). Intraperitoneally injected formal in-killed and Freunds complete adjuvant vaccines were compared using different doses (2.9 X 10(7) and 2.9 X 10(9) cfu/ml). Upon challenge, the protective ability and antibody titers resulting were significantly different between vaccinated and unvaccinated groups. A relative level of protection of 100% was obtained within two- weeks, and a maximum level of 53-61% protection was found one-week post- vaccination.

Rubin, D. A., and Specker, J. L. (1992). In vitro effects of homologous prolactins on testosterone production by testes of tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 87, 189-96.
The tilapia, Oreochromis mossambicus, produces two prolactins designated tPRL177 and tPRL188 to indicate the number of amino acid residues in each. The direct in vitro actions of tPRL177 and tPRL188 on basal and ovine luteinizing hormone (LH)-induced testosterone production in minced testes of courting and noncourting (bachelor) tilapia were examined. Courting males were housed with females and were used as soon as they built a spawning pit; noncourting males were housed with other males and were used when they appeared female-like in coloration. The in vitro culture system consisted of two phases. In phase 1 (0-10 hr), testicular tissue was incubated without (control) or with the tPRLs--both alone and together and in doses ranging from 0.5 to 32 microM. In phase 2 (10-16 hr), the culture medium was replaced with medium containing 6.25 microM (0.25 micrograms/ml) ovine LH. Testosterone production during both phases was determined by radioimmunoassay of the medium. The tPRLs stimulated testosterone production during phase 1 in courting males (by 25%) but not in noncourting males. Exposure to either or both tPRLs in phase 1 enhanced the response of testicular tissue from courting males to ovine LH (by 10%) and inhibited the response of minced testes taken from noncourting males (by 12%). This is the first evidence to demonstrate direct gonadal activity of homologous PRL in a teleost.

Ruparelia, S. G., Verma, Y., Saiyed, S. R., and Rawal, U. M. (1990). Effect of cadmium on blood of tilapia, Oreochromis mossambicus (Peters), during prolonged exposure. Bull Environ Contam Toxicol 45, 305-12.

Russock, H. I. (1999). Filial social bond formation in fry of the maternal mouthbrooding tilapia (Pisces : Cichlidae): A comparative study. Behaviour 136, 567-594.
The mother - fry relationship in the maternal mouthbrooding species of tilapia has become a model of social bond formation in fish because of the relatively extensive care given to the young. This relationship has been extensively studied in Oreochromis,nossambicus. In order to determine if the response pattern observed in O.,mossambicus fry has broader applications, the critical experiments of these studies were replicated in two closely related species of maternal mouthbrooding tilapia, O. niloticus and O. esculentus. All fry used in the study were removed from their mother's mouth as eggs and hatched artificially in groups. The fry were also exposed to maternal models in groups, but all fry in the study were tested for their responsiveness or preferential behaviour to maternal models individually. Experiment I determined the responsiveness of fry naive to maternal models in order to establish a baseline for future comparisons. O. niloticus fry exhibited a significant decline in responsiveness to models between days 11 and 12 post-hatching while O. esculentus fry exhibited a significant decline between days 16 and 18, suggesting the possible existence of a sensitive period in these two species. In order to obtain evidence for the existence of a sensitive period, naive fry of both species in Experiment II were exposed to maternal models at their peak of responsiveness and then tested at a later age at which responsiveness in naive fry had fallen significantly. In 15 of the 18 comparisons involving the two species, exposure to a maternal model at the peak of responsiveness for naive fry prevented the later decline in responsiveness. Experiment III examined whether experience with maternal models effected how exclusively fry responded to such models in the future. It was predicted that, like O, mossambicus fry,experienced fry of both species would exhibit a decline in responsiveness to models that formed at least a partial mismatch with the fry's initial schema for maternal stimuli. This prediction was not supported. Experiment IV examined preferential behaviour. It was predicted that fry exposed to a maternal model would later behave preferentially toward whichever model of a pair formed a closer match with their schema, and not necessarily toward the model to which they had been previously exposed. Maternally naive fry were not expected to behave preferentially. These predictions were en generally supported, although the effect was less vigorous or consistent than in O. mossambicus. Filial social bond formation in these species of maternal mouthbrooding tilapia appears to be characterized by strong predispositions for maternally relevant visual stimuli which require appropriate experience for their maintenance and for the induction of preferences. Since a similar developmental pattern in seen in (e.g.) song learning in passerine birds, imprinting in precocial birds and filial following in substrate spawning cichlid fish, the phenomenon appears to be of broad significance.

Sahib, I. K., and Ramana Rao, K. V. (1980). Toxicity of malathion to the freshwater fish Tilapia mossombica. Bull Environ Contam Toxicol 24, 870-4.

Sahib, I. K., and Rao, K. V. (1980). Correlation between subacute toxicity of malathion and acetylcholinesterase inhibition in the tissues of the teleost Tilapia mossambica. Bull Environ Contam Toxicol 24, 711-8.

Sahib, I. K., Rao, K. R., and Rao, K. V. (1984). Effect of malathion on protein synthetic potentiality of the tissues of the teleost, Tilapia mossambica (Peters), as measured through incorporation of [14C]amino acids. Toxicol Lett 20, 63-7.
The protein turnover was studied in muscle, gill and liver tissues of the fish, Tilapia mossambica, under malathion impact through the incorporation of labelled amino acids using [14C]glutamic acid, [14C]leucine and [14C]arginine as representatives of acidic, neutral and basic types of proteins, respectively. The labelled amino acid incorporation indicated the synthetic potentiality of proteins to be elevated in all the tissues of malathion-exposed (ME) fish. The results are discussed in relation to the degradative and synthetic capability of tissue proteins under malathion exposure.

Sahib, I. K., Prasada Rao, K. S., Sambasiva Rao, K. R., and Ramana Rao, K. V. (1984). Sublethal toxicity of malathion on the proteases and free amino acid composition in the liver of the teleost, Tilapia mossambica (Peters). Toxicol Lett 20, 59-62.
Exposure of fish to a sublethal concentration of malathion showed a significant inhibition of acetylcholinesterase (AChE) activity. The levels of protease were markedly elevated with a consequent increase in most of the free amino acids. However, the levels of glutamic acid and valine, phenylalanine and methionine complex remained unchanged, while aspartic acid showed a marked drop. These changes are discussed in relation to the sublethal stress induced by malathion.

Said, R., Volpin, G., Grimberg, B., Friedenstrom, S. R., Lefler, E., and Stahl, S. (1998). Hand infections due to non-cholera Vibrio after injuries from St Peter's fish (Tilapia zillii). J Hand Surg [Br] 23, 808-10.
We report 49 patients with a wide variety of hand infections, which developed after injuries from St Peter's fish (Tilapia zillii). Twenty- eight of 36 patients who had been operated on had non-cholera Vibrio infections, all identified as Vibrio vulnificus. The course in these patients was characterized by rapid spread of the infection with progressive necrosis of the tendon sheath, subcutaneous tissues and the skin. Two of them required amputations but the others had satisfactory functional results. Thirteen other patients were managed nonoperatively with intravenous antibiotics and all of them recovered completely.

Sailatha, D., Sahib, I. K., Rao, K. R., Rao, K. S., and Rao, K. V. (1983). Effects of technical and commercial grade malathion on nitrogen metabolism of the teleost, Tilapia mossambica (Peters) [letter]. Indian J Physiol Pharmacol 27, 355-7.

Sailendri, K., and Muthukkaruppan, V. (1975). Morphology of lymphoid organs in a cichlid teleost, Tilapia mossambica (Peters). J Morphol 147, 109-21.
In Tilapia mossambica organized lymphoid tissues are present in the thymus, head-kidney and spleen, whereas they are lacking in pericardial tissue, liver, mesonephros, intestine and rectum. No lymphoid tissue was observed in the chondrocranium and cartilaginous viscerocranium of young adults. The thymus in Tilapia is encapsulated by thin strands of collagen fibers and consists of outer, middle and inner zones. While middle and inner zones are comparable to the thymic cortex and medulla of higher vertebrates, the homology of the outer zone is not clear. At the anterior end of the thymus, a loose aggregation of lymphocytes without a definite boundary has been observed. The head-kidney is characterized by the presence of lymphoid follicles, a subcapsular sinus, a hilus-like area and lymphatic vessels. The spleen is grossly divisible into white pulp and red pulp; the white pulp contains only a reticular area without definite lymphoid centers and the latter contains predominantly erythrocytes. Morphological changes in the lymphoid organs associated with immune response have been discussed.

Sailendri, K., and Muthukkaruppan, V. R. (1975). The immune response of the teleost, Tilapia mossambica to soluble and cellular antigens. J Exp Zool 191, 371-82.
The immune response of Tilapia mossambica to bovine serum albumin (BSA) and sheep red blood cells (SRBC) was characterized in detail in terms of the appearance of hemolysin plaque-forming cells and circulating antibodies at 30 degrees C. Plaque-forming cells (PFC) were detected in the spleen, head-kidney and thymus of immunized fish and the maximum number was observed in these organs on the fifth day after immunization with SRBC. Peak circulating antibody response occurred on day 8 for SRBC and on day 11 for BSA. Following the second injection of the same antigen, a specific anamnestic response was observed with increased production of PFC and serum antibody. No cross reactivity was found when anti-SRBC antibody was tested with rat erythrocytes. Tests with 2- mercaptoethanol showed that all of the agglutinating antibody produced after both the first and second injection was mercaptoethanol sensitive. Analysis of histological and smear preparations revealed that there were consistent cellular changes occurring in the spleen as well as the head-kidney due to immunization.

Sakr, S. A., Gabr, S. A., and el-Saadany, M. M. (1991). Effect of diazinon on freeze-fracture images of microvilli of intestinal epithelial cells of Tilapia nilotica. Z Ernahrungswiss 30, 268-75.
The effect of the organophosphate insecticide, diazinon on the intramembranous particles (IMPs) of the microvilli of the intestinal epithelial cells of Tilapia nilotica fish was studied using freeze- fracture technique. Exposing fish to different repeated concentrations of diazinon (1/2LC50) caused a significant decrease in population density of IMPs in P- and E-faces. IMPs of microvilli found in intestinal epithelial cells are thought to represent many kinds of proteins including enzymes. In the present work, it is suggested that diazinon induced a reduction in enzymatic content of the membrane which was accompanied by a decrease in IMPs density of the microvilli.

Sakr, S. A., and Gabr, S. A. (1992). Ultrastructural changes induced by diazinon and neopybuthrin in skeletal muscles of Tilapia nilotica. Bull Environ Contam Toxicol 48, 467-73.

Sakr, S. A., and Gabr, S. A. (1992). A freeze-fracture study on the effect of neopybuthrin on the intestinal epithelial cells of Tilapia nilotica. Funct Dev Morphol 2, 259-63.
Freeze-fracture replicas of the plasma membrane and tight junctions (Tj) of intestinal epithelial cells were studied in Tilapia nilotica fish exposed to the pyrethroid insecticide, neopybuthrin. Exposing fishes to different repeated concentrations of 1/2 LC50 of neopybuthrin caused a significant decrease in the population density of IMPs in P- and E-faces. Tight junctions were also affected by neopybuthrin treatment. They appeared fragmented and discontinued, and their strands were fewer in number as compared with controls. Since the structure and number of Tj are major determinants of epithelial permeability, it is postulated that neopybuthrin treatment may affect the intestinal permeability of T. nilotica.

Sanderson, S., Stebar, M., Ackermann, K., Jones, S., Batjakas, I., and Kaufman, L. (1996). Mucus entrapment of particles by a suspension-feeding tilapia (Pisces: Cichlidae). J Exp Biol 199, 1743-56.
A miniature fiberoptic endoscope was used to observe the processes of particle encounter and retention inside the buccopharyngeal cavity of suspension-feeding tilapia. Small particles (38 &micro;m to 1.0 mm in diameter) were trapped in strands and aggregates of mucus, which usually slid posteriorly on the ceratobranchials of arches I&shy;IV towards the esophagus while the fish pumped water through the buccopharyngeal cavity. During stage 1 of periodic reversals of water flow inside the buccopharynx, mucus-bound particles usually lifted off the arch surfaces and travelled a short distance in an anterior or anterodorsal direction. During stage 2 of a reversal, the mucus usually resumed travel in a posterior or posteroventral direction and exited the field of view. Mucus was present less often during feeding on large particles (3&shy;10 mm in diameter) than on small particles, and large particles were rarely observed to be attached to mucus. We discuss the advantages to suspension-feeding fishes of using aerosol filtration by mucus entrapment rather than sieving, and predict that many cichlid and cyprinid suspension feeders that consume bacteria and phytoplankton use mucus for aerosol filtration.

Santiago, C. B., and Lovell, R. T. (1988). Amino acid requirements for growth of Nile tilapia. J Nutr 118, 1540-6.
A series of feeding experiments was conducted in aquaria to determine the quantitative requirements of the 10 essential amino acids for growth of young Nile tilapia (Oreochromis niloticus). The test diets contained casein and gelatin supplemented by crystalline L-amino acids to provide an amino acid profile similar to 28% whole egg protein except for the test amino acid. Each set of test diets consisted of seven isonitrogenous diets containing varying levels of the amino acid to be tested. Weight gains analyzed by the broken line regression method indicated the following requirements as a percentage of the dietary protein: lysine, 5.12; arginine, 4.20; histidine, 1.72; valine, 2.80; leucine, 3.39; isoleucine, 3.11; threonine, 3.75; tryptophan, 1.00; methionine with cystine (0.54% of the protein), 3.21; and phenylalanine with tyrosine (1.79% of the protein), 5.54.

Sarder, M. R., Penman, D. J., Myers, J. M., and McAndrew, B. J. (1999). Production and propagation of fully inbred clonal lines in the Nile tilapia (Oreochromis niloticus L.). J Exp Zool 284, 675-85.
Fully inbred clonal lines of fish are likely to be of great value in research on immunology, sex determination, quantitative genetics, and toxicology. In this study on the Nile tilapia (Oreochromis niloticus), gynogenesis or androgenesis were used to produce a first generation of completely inbred fish, from which clonal lines were established using gynogenesis, androgenesis, hormonal sex reversal and intraline crosses. The clonal nature of these lines was verified by using multilocus DNA fingerprinting and the isozyme locus ADA*. Although these lines might be expected to be monosex in nature (all-female XX or all-male YY depending on the clone), one line did contain both sexes of fish. The presence of males in this gynogenetic clonal line and data from progeny testing of these males suggested that this line was homozygous for an allele or combination of alleles at an autosomal locus or loci which caused female to male sex reversal but with limited penetrance. Outbred clonal lines were also produced by crossing between different inbred clones. J. Exp. Zool. 284:675-685, 1999. Copyright 1999 Wiley-Liss, Inc.

Sarder, M. R. I., Penman, D. J., Myers, J. M., and McAndrew, B. J. (1999). Production and propagation of fully inbred clonal lines in the Nile tilapia (Oreochromis niloticus L.). Journal of Experimental Zoology 284, 675-685.
Fully inbred clonal lines of fish are likely to be of great value in research on immunology, sex determination, quantitative genetics, and toxicology. In this study on the Nile tilapia (Oreochromis niloticus), gynogenesis or androgenesis were used to produce a first generation of completely inbred fish, from which clonal lines were established using gynogenesis, androgenesis, hormonal sex reversal and intraline crosses. The clonal nature of these lines was verified by using multilocus DNA fingerprinting and the isozyme locus ADA*. Although these lines might be expected to be monosex in nature (all-female XX or all-male YY depending on the clone), one line did contain both sexes of fish. The presence of males in this gynogenetic clonal line and data from progeny testing of these males suggested that this line was homozygous for an allele or combination of alleles at an autosomal locus or loci which caused female to male sex reversal but with limited penetrance. Outbred clonal lines were also produced by crossing between different inbred clones. J. Exp. Zool. 284:675-685, 1999. (C) 1999 Wiley-Liss, Inc.

Sasagawa, I. (1995). Fine structure of tooth germs during the formation of enameloid matrix in Tilapia nilotica, a teleost fish. Arch Oral Biol 40, 801-14.
Tooth germs were examined by light and transmission electron microscopy. Collagen fibrils were relatively dispersed and thin at the early and middle stages of formation of the enameloid matrix, when the enameloid layer was thin. At the late stage, the fibrils became thicker, reaching nearly 30 nm dia, and formed the interwoven thick bundles that are characteristic of teleost cap enameloid. Abundant flocculent and/or fine, network-like material, probably representing glycosaminoglycans or proteoglycans, was located between the collagen fibrils. Tall, columnar, inner dental epithelial cells contained abundant rough endoplasmic reticulum and many mitochondria, and a well- developed Golgi apparatus was seen around the nuclei at the late stage. Elongated vesicles enclosing fine, filamentous material that resembled procollagen granules, and large granules containing fibril-like structures that were 150 nm in thickness and had periodic cross-banding at 32-nm intervals, were usually observed near the Golgi apparatus. The contents of the large granules were well stained with phosphotungstic acid, which suggests that inner dental epithelial cells synthesize collagen fibrils. At this time, odontoblasts also contained abundant rough endoplasmic reticulum and mitochondria, a well-developed Golgi, several kinds of granule including those that probably contained procollagen, and many microtubules. It is proposed that odontoblasts are involved in the formation of a considerable portion of the enameloid matrix, including collagen fibrils.

Sasagawa, I. (1997). Fine structure of the cap enameloid and of the dental epithelial cells during enameloid mineralisation and early maturation stages in the tilapia, a teleost. J Anat 190, 589-600.
Morphological features of the cap enameloid and dental epithelial cells were investigated by light and transmission electron microscopy during the various stages of enameloid mineralisation and early maturation in the tilapia. The pattern of mineralisation along collagen fibrils in the enameloid differed from that in the dentine. Many matrix vesicles were found in the predentine and in the enameloid, suggesting that they may be involved in the initial mineralisation in both regions. Most of the organic matrix disappeared from the cap enameloid during mineralisation and maturation. The disappearance of the organic matrix could be divided into 2 stages. Initially a fine network-like matrix, which probably consisted of glycosaminoglycans and extended between collagen fibrils, began to disappear. At the same time, fine crystallites and electron-dense, fine granular material covered the collagen fibrils as mineralisation of the enameloid began. In the second stage, the maturation of the enameloid, the collagen fibrils degenerated completely and disappeared from the cap enameloid, being replaced by large numbers of large crystals. At the mineralisation stage, the numbers of lysosomal bodies tended to increase in the inner dental epithelial (IDE) cells, which contained a well developed Golgi apparatus and rough endoplasmic reticulum (rER). At the early stage of maturation, a ruffled border was noted at the distal ends of the IDE cells, which contained many mitochondria and lysosomal bodies, but less rER. These features suggest that the cells actively absorb the organic matrix, which includes collagen fibrils, in the cap enameloid. The outer dental epithelial (ODE) cells were translucent cells that contained well developed labyrinthine canalicular spaces from the onset of the mineralisation stage to the middle stage of maturation. The IDE and ODE cells were clearly involved in the mineralisation of the cap enameloid at the mineralisation and maturation stages.

Sasagawa, I. (1998). Activity of alkaline and acid phosphatases in dental epithelial cells and enameloid during odontogenesis in two teleost fish, Oreochromis niloticus and Tilapia buttikoferi. Eur J Oral Sci 106 Suppl 1, 513-8.
The dental epithelial cells and enameloid at the stages of enameloid matrix formation, mineralization and maturation in the teleosts Oreochromis niloticus and Tilapia buttikoferi were investigated by means of enzyme histochemistry in order to identify their functions associated with the structural modification. No marked enzyme activities were found in the inner dental epithelial cells in the stage of enameloid matrix formation, although the outer dental epithelial cells often exhibited moderate alkaline phosphatase (ALPase) activity. In the stages of enameloid mineralization and maturation, the inner dental epithelial cells, which possessed a ruffled border at the distal ends, showed intense ALPase activity at their lateral and proximal cell membranes. At the same time, many acid phosphatase (ACPase)-positive vesicles and granules were localized at the distal cytoplasm of the inner dental epithelial cells. The outer dental epithelial cells, which contained well-developed labyrinthine canalicular spaces, showed neither marked ALPase nor ACPase activity. It is postulated that the dental epithelial cells in these two teleosts are mainly involved in the removal of the organic matrix from the enameloid, and in material transport to the enameloid during the later half of odontogenesis.

Schmid, A. C., Naf, E., Kloas, W., and Reinecke, M. (1999). Insulin-like growth factor-I and -II in the ovary of a bony fish, Oreochromis mossambicus, the tilapia: in situ hybridisation, immunohistochemical localisation, Northern blot and cDNA sequences. Mol Cell Endocrinol 156, 141-9.
There is accumulating evidence that insulin-like growth factor (IGF)-I and IGF-II are present in the mammalian ovary but comparable studies on bony fish remain scarce. Thus, the present study aims to analyse several parameters of the IGFs in the ovary of a bony fish, the tilapia, (Oreochromis mossambicus). Molecular biological and morphological techniques were applied. The IGF-I and IGF-II cDNA sequences established from the ovary indicate that the same molecules are present in ovary and liver. Northern blot analysis revealed four IGF-I mRNA transcripts (6.0, 3.9, 1.9, 0.5 kb) and three IGF-II mRNA transcripts (5.0, 4.0, 2.0 kb) in ovary and liver. The amounts of IGF-I and IGF-II mRNA in the ovary were considerably high when compared to those in liver (IGF-I: 80.7%; IGF-II: 63.7%). The expression of IGF-I mRNA and IGF-II mRNA in the ovary were studied by in situ hybridisation and the peptides located by immunohistochemistry. The expression of IGF- I varied between the different developmental stages. Both IGF-I mRNA and IGF-I immunoreactivity were present in small oocytes. Moderate IGF- I expression and immunoreactivity occurred in granulosa cells of follicles at the lipid stage. A high IGF-I expression was observed in the granulosa and theca cells surrounding oocytes at the yolk globule stages and mature oocytes but neither IGF-I mRNA nor IGF-I immunoreactivity occurred in oocytes of the later stages. Thus, the IGF- I production seems to change from the young oocyte to the surrounding follicle cells at the later stages. In contrast, IGF-II mRNA and IGF-II- immunoreactivity occurred only in granulosa cells of the late follicle stages. The results suggest that both IGF-I and IGF-II are involved in the maturation of bony fish oocytes and in follicle development in a paracrine/autocrine manner. IGF-I and IGF-II may exert their effects at different stages of development. Furthermore, the intraovarian IGF-I and IGF-II systems seem to have a long phylogenetic history indicating the importance of the IGFs in reproductive biology.

Sekkali, B., Belayew, A., Bortolussi, M., Martial, J. A., and Muller, M. (1999). Pit-1 mediates cell-specific and cAMP-induced transcription of the tilapia GH gene. Mol Cell Endocrinol 152, 111-23.
Expression of the tilapia growth hormone (tiGH) gene is pituitary- specific and controlled by intracellular cAMP levels. DNaseI protection experiments allowed us to identify four Pit-1 binding sites in the tiGH - 465/ + 19 region. Deletion and mutagenesis analysis revealed that the - 131/+ 19 region, containing two Pit-1 sites, or four copies of the most proximal site tiGHF1 fused to the heterologous Tk promoter, confer high level expression in rat pituitary cells and direct transcription in non-pituitary cells only after expression of rat Pit-1. We show that a tilapia pituitary factor specifically binds to site tiGHF1 and obtained a partial cDNA sequence coding for tilapia Pit-1. The cAMP stimulation is mediated by the proximal (- 131/- 31) promoter region. It is Pit-1-dependent and requires the tiGHF1 site. In addition, four copies of this site confer cAMP inducibility to the Tk promoter in GC cells.

Sekkali, B., Brim, H., Muller, M., Argenton, F., Bortolussi, M., Colombo, L., Belayew, A., and Martial, J. A. (1999). Structure and functional analysis of a tilapia (Oreochromis mossambicus) growth hormone gene: activation and repression by pituitary transcription factor Pit-1. DNA Cell Biol 18, 489-502.
A gene encoding the Tilapia mossambica (Oreochromis mossambicus) growth hormone (tiGH) was isolated and sequenced. The gene spans 5.6 kb, including 3.7 kb of 5' and 0.2 kb of 3' flanking sequences and a 1.7-kb transcription unit comprised of six exons and five introns. The gene and the 5' flanking region contain several potential binding sites for Pit-1, a key transcription activator of mammalian GH genes. One of these (-57/-42) is highly conserved in fish GH genes. It activates transcription in pituitary cells and binds Pit-1. Transfection of luciferase reporter plasmids containing either the -3602/+19 tiGH sequence or one of its 5' deletion mutants (-2863/, -1292/, and - 463/+19) resulted in strong activity in Pit-1-producing rat pituitary GC cells. A dose-dependent activation of the tiGH promoter was achieved in nonpituitary fish EPC and monkey COS cells cotransfected with a rat Pit-1 expression vector, demonstrating the crucial role played by Pit-1 as an activator of the tiGH gene. Fusion of the tiGH promoter with the beta-galactosidase gene led to transient expression specifically in the nervous system of microinjected zebrafish embryos. The activity of the tiGH promoter in GC and EPC cells was strongly repressed by extending its 3' end from +19 to +40, a sequence in which a Pit-1-binding site was identified using gel retardation assays. Point mutations of the site that suppressed Pit-1 binding in vitro restored full tiGH promoter activity. Thus, a Pit-1-binding site located in the 5' untranslated region mediates Pit-1-dependent repression of the tiGH gene.

Shapiro, C. M., and Hepburn, H. R. (1976). Sleep in a schooling fish, Tilapia mossambica. Physiol Behav 16, 613-5.

Shepherd, B. S., Sakamoto, T., Nishioka, R. S., Richman, N. H., 3rd, Mori, I., Madsen, S. S., Chen, T. T., Hirano, T., Bern, H. A., and Grau, E. G. (1997). Somatotropic actions of the homologous growth hormone and prolactins in the euryhaline teleost, the tilapia, Oreochromis mossambicus. Proc Natl Acad Sci U S A 94, 2068-72.
It is increasingly clear that growth hormone (GH) has growth-promoting effects in fishes, which are mediated in part by the insulin-like growth factor (IGF)-I. Growth-promoting actions of prolactin (PRL) have been reported in higher vertebrates, but are less well established in teleosts. We examined the effects of injecting homologous GH or the two homologous tilapia PRLs (tPRL177 and tPRL188) on the in vitro incorporation of [35S] sulfate (extracellular matrix synthesis) and [3H]thymidine (DNA synthesis) by ceratobranchial cartilage explants and on IGF-I mRNA levels in tilapia liver. Tilapia GH (tGH) and tPRL177 stimulated sulfate uptake at the highest doses examined. Thymidine incorporation was stimulated by tPRL177. tPRL188 was without these effects. Consistent with its somatotropic actions, tGH elevated IGF-I mRNA levels in the liver. tPRL177 also elevated liver IGF-I levels. Consistent with the previously described osmoregulatory actions of GH and PRL in teleosts, we observed that tGH elevated and tPRL177 and tPRL188 lowered levels of gill Na+,K+-ATPase activity. High-affinity, low-capacity binding sites for tGH in the tilapia liver were identified. tPRL177 binds with lower affinity than tGH to these sites but can displace 125I-labeled tGH from its receptor. The ability of tPRL177 to displace tGH was similar to that of ovine GH. tPRL188 did not displace 125I-labeled tGH binding. Collectively, this work suggests that tPRL177 may possess somatotropic actions similar to tGH, but only in freshwater tilapia where tPRL177 levels are sufficiently high for it to act as a competitive ligand for GH receptors.

Shepherd, B. S., Sakamoto, T., Hyodo, S., Nishioka, R. S., Ball, C., Bern, H. A., and Grau, E. G. (1999). Is the primitive regulation of pituitary prolactin (tPRL177 and tPRL188) secretion and gene expression in the euryhaline tilapia (Oreochromis mossambicus) hypothalamic or environmental? J Endocrinol 161, 121-9.
We examined the effects of environmental salinity on circulating levels of the two prolactins (tPRL177 and tPRL188) and levels of pituitary tPRL177 and tPRL188 mRNA in the euryhaline tilapia, Oreochromis mossambicus. Fish were sham-operated or hypophysectomized and the rostral pars distalis (RPD) autotransplanted onto the optic nerve. Following post-operative recovery in (1/4) seawater, tilapia were transferred to fresh water (FW), (1/4) seawater (SW) or SW. Serum tPRL177 and tPRL188 levels in sham-operated and RPD-autotransplanted fish were highest in FW and decreased as salinity was increased. tPRL177 and tPRL188 mRNA levels in RPD implants as well as in pituitaries from the sham-operated fish were also highest in FW and decreased with increasing salinity. Serum osmolality increased with salinity, with the highest levels occurring in the seawater groups. We conclude that some plasma factor (probably plasma osmolality), in the absence of hypothalamic innervation, exerts a direct regulatory action on prolactin release and gene expression in the pituitary of O. mossambicus. This regulation is in accord with the actions of the two prolactins in the freshwater osmoregulation of the tilapia.

Shepherd, B. S., Sakamoto, T., Hyodo, S., Nishioka, R. S., Ball, C., Bern, H. A., and Grau, E. G. (1999). Is the primitive regulation of pituitary prolactin (tPRL(177) and tPRL(188)) secretion and gene expression in the euryhaline tilapia (Oreochromis mossambicus) hypothalamic or environmental? Journal of Endocrinology 161, 121-129.
We examined the effects of environmental salinity on circulating levels of the two prolactins (tPRL(177) and tPRL(188)) and levels of pituitary tPRL(177) and tPRL(188) mRNA in the euryhaline tilapia, Oreochromis mossambicus. Fish were sham-operated or hypophysectomized and the rostral pars distalis (RPD) autotransplanted onto the optic nerve. Following post-operative recovery in 1/4 seawater, tilapia were transferred to fresh water (FW), 1/4 seawater (SW) or SW. Serum tPRL(177) and tPRL(188) levels in sham-operated and RPD- autotransplanted fish were highest in FW and decreased as salinity was increased. tPRL(177) and tPRL(188) mRNA levels in RPD implants as well as in pituitaries from the sham-operated fish were also highest in FW and decreased with increasing salinity. Serum osmolality increased with salinity, with the highest levels occurring in die seawater groups. We conclude that some plasma factor (probably plasma osmolality), in the absence of hypothalamic innervation, exerts a direct regulatory action on prolactin release and gene expression in the pituitary of O. mossambicus. This regulation is in accord with the actions of the two prolactins in the freshwater osmoregulation of the tilapia.

Sherekar, S. V., Gore, M. S., and Ninjoor, V. (1990). Aminopeptidase from the skeletal muscle of fresh water fish Tilapia mossambica. Indian J Biochem Biophys 27, 316-23.
An aminopeptidase from the skeletal muscle of fish, Tilapia mossambica, was partially purified to 96-fold using salt precipitation, ion- exchange chromatography and molecular sieve chromatography. The enzyme showed optimum activity between pH 6.5-7.5 at 43 degrees C and Vmax and Km of 14.36 units/mg and 0.059 mM respectively with alanine beta- naphthylamide as the substrate. The aminopeptidase having a molecular weight of 305 kDa was activated by sulphydryl compounds and CO2+ and inhibited by bestatin, puromycin and metal chelators. Inhibition caused by metal chelators could be reversed by the addition of CO2+. Inclusion of L-amino acids, particularly isoleucine and leucine, in the assay medium caused inhibition of the enzyme activity. Substrate specificity together with inhibition and activation pattern indicated that the enzyme is alanine aminopeptidase.

Shiau, S. Y., and Suen, G. S. Estimation of the niacin requirements for tilapia fed diets containing glucose or dextrin. .
Two 12-wk experiments were conducted to determine the adequate dietary niacin levels for juvenile hybrid tilapia, Oreochromis niloticus x O. aureus, when diets containing either 38% D(+)-glucose or 38% dextrin (type III, from corn) as the carbohydrate source were fed. In Experiment 1, we used 0, 40, 80, 120, 160 and 200 mg/kg of supplemental niacin in both the glucose- and dextrin-containing diets. In Experiment 2, 0, 10, 25, 40 and 55 mg/kg or 0, 10, 25, 40, 80, 120 and 160 mg/kg of supplemental niacin was incorporated in diets containing glucose or dextrin, respectively. In both experiments, fish fed niacin-deficient diets grew poorly. They developed skin, fin and mouth lesions and hemorrhages; the snout was deformed and there was gill edema. These pathologies began 6 wk after the experiments started. Plasma glucose concentrations wer.

Shiau, S. Y., and Chen, M. J. (1993). Carbohydrate utilization by tilapia (Oreochromis niloticus x O. aureus) as influenced by different chromium sources. J Nutr 123, 1747-53.
An experiment was conducted to study the influence of three different forms of chromium (CrCl3.6H2O, Na2CrO4.4H2O and Cr2O3) on the utilization of two carbohydrates (glucose and cornstarch) by juvenile hybrid tilapia (Oreochromis niloticus x O. aureus). Average initial body weight of the fish was 1.13 +/- 0.02 g. Fish were fed 5% body wt/d. Significantly (P 0.05) greater body weight gain, food intake, protein retention, energy retention and body lipid concentration were observed in fish fed the starch diet than in those fed the glucose diet. Fish fed the glucose diet supplemented with any type of chromium had significantly greater weight gain than those fed the glucose diet without chromium supplementation. Fish fed the glucose diet supplemented with Cr2O3 had greater weight gain, food intake, protein retention, energy retention and body lipid concentration than those fed the unsupplemented glucose diet or the glucose diet supplemented with CrCl3.6H2O or Na2CrO4.4H2O. Delayed plasma glucose peak time was observed in tilapia fed the glucose diet supplemented with any type of chromium. Chromium supplementation generally lowered the glucose-6- phosphatase activity in tilapia. Phosphofructokinase activity was significantly higher in fish fed the glucose diet supplemented with Cr2O3 than in the other glucose-fed groups. These data suggest that chromium supplementation improved glucose utilization by tilapia and that Cr2O3 supplementation was markedly more effective than other chromium forms.

Shiau, S. Y., and Liang, H. S. (1995). Carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus, are affected by chromic oxide inclusion in the diet. J Nutr 125, 976-82.
A 12-wk feeding trial was conducted to study the influence of chromic oxide (Cr2O3) on carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus. Two levels of chromic oxide (0.5 and 2%) were each incorporated into diets containing glucose or starch. Chromic oxide was added at 0 or 8 wk. The diets were fed to triplicate groups of fish weighing 1.11 +/- 0.05 g. Fish fed the starch diet had greater (P 0.05) weight gain, feed efficiency ratio, protein efficiency ratio, protein deposition and digestibility of protein, lipid, carbohydrate and dry matter than fish fed the glucose diet irrespective of the time and level of chromic oxide supplementation. Fish fed the glucose diet with 0.5% chromic oxide had higher weight gain, feed efficiency ratio, protein efficiency ratio and protein deposition than fish fed the glucose diet with 2% chromic oxide. The ingredient digestibility estimated using 0.5% chromic oxide as the marker was greater than that estimated with 2% chromic oxide. Higher phosphofructokinase and lower glucose-6-phosphatase activity was found in fish fed the starch diet than in fish fed the glucose diet regardless of the time and level of chromic oxide inclusion. Fish fed the glucose diet with 0.5% chromic oxide had higher phosphofructokinase activity and lower tissue chromium concentration than fish fed the glucose diet with 2% chromic oxide irrespective of chromic oxide inclusion time. These data suggest that the level of chromic oxide in the diet alters glucose utilization by tilapia and affects nutrient digestibility by tilapia. The time of chromic oxide inclusion had no effect on carbohydrate utilization and digestibility.

Shiau, S. Y., and Lei, M. S. (1999). Feeding strategy does affect carbohydrate utilization by hybrid Tilapia Oreochromis niloticus x O. aureus. Fisheries Science 65, 553-557.
An eight-week growth trial was conducted to evaluate the effect of feeding strategy (continuous fed vs two meals per day) on the utilization of carbohydrate by juvenile hybrid tilapia, Oreochromis niloticus x O. aureus. The carbohydrates were starch and glucose, and included at 44% of the diet. Average initial body weight of the fish was 0.47+/-0.01 g, and fish were fed at a rate of 5% body weight per day. The results indicated that weight gain was significantly higher (p<0.05) for fish fed continuously than for those fed two meals a day for both carbohydrate diets. Higher hepatic phosphofructokinase (PFK) and malic enzyme (ME) activities were observed in the continuous-fed fish than in meal-fed fish. Hepatic asparate transaminase (AST) and alanine transaminase (ALT) activities of the continuous-fed fish with glucose diet were lower than those of the meal-fed fish. Plasma AST and ALT activities were higher in the meal-fed fish than in the continuous-fed fish. These data suggest that carbohydrate utilization by tilapia is affected by feeding strategy and that continuous fed improves carbohydrate utilization.

Shiau, S. Y., and Yu, Y. P. (1999). Dietary supplementation of chitin and chitosan depresses growth in tilapia, Oreochromis niloticus x O-aureus. Aquaculture 179, 439-446.
The effect of chitin, poly-beta-(1 --> 4)-N-acetyl-glucosamine, and chitosan, a polymer of glucosamine obtained by the deacetylation of chitin, on growth and nutrient digestibility was studied in tilapia, Oreochromis niloticus X O. aureus, fed diets containing fiber at 0, 2, 5 or 10% of a basal diet for 8 weeks. Each diet was fed to triplicate groups of fish with a mean initial body weight of 0.99 +/- 0.01 g. Significantly (P < 0.05) lower body weight gains were observed in fish fed chitin and chitosan containing diets than fish fed the control diet regardless of the supplementation level. The weight gain of fish decreased as dietary chitin and chitosan supplementation level increased (chitin, r = 0.97, P < 0.05; chitosan, r = 0.73, P < 0.05). Higher (P < 0.05) weight gains were observed in fish fed 5 and 10% chitin diets than fish fed the chitosan diets. Feed conversion ratio (FCR) followed the same pattern of the weight gain. Lipid and dry matter digestibilities were lower in fish fed the 10% chitin diet than in fish fed the control diet. Lower lipid and dry matter digestibilities and lower body lipid content were observed in fish fed chitosan containing diets irrespective of supplementation level. Fish fed 2 and 5% chitin diet had higher lipid digestibility than fish fed chitosan diet. Body lipid content of the fish reflect the general pattern of the lipid digestibility. These data suggest that both chitin and chitosan supplementation depresses tilapia growth regardless of the supplementation level. (C) 1999 Elsevier Science B.V. All rights reserved.

Shiau, S. Y., and Cheng, D. J. (1999). Ammonia excretion and oxygen consumption of Tilapia are affected by different carbohydrate ingestion. Fisheries Science 65, 321-322.

Shiau, S. Y., and Hsu, T. S. (1999). Quantification of vitamin C requirement for juvenile hybrid tilapia, Oreochromis niloticus X Oreochromis aureus, with L- ascorbyl-2-monophosphate-Na and L-ascorbyl-2-monophosphate-Mg. Aquaculture 175, 317-326.
A growth experiment was conducted to quantify the level of L- ascorbyl-7-monophosphate-Na (C2MP-Na) to satisfy the dietary vitamin C requirement for juvenile hybrid tilapia. L-Ascorbyl- 2-monophosphate-Mg (C2MP-Mg) was also included in the study for comparison. Purified diets with six levels of ascorbic acid (0, 30, 50, 70, 90 and 120 mg/kg diet) from either supplemental C2MP-Na or C2MP-Mg were each fed to triplicate groups of fish (mean initial weight: 1.22 +/- 0.07 g) for 8 weeks. Fish fed greater than or equal to 38.97 mg C2MP-Na/kg diet and greater than or equal to 22.92 mg C2MP-Mg/kg diet gained significantly (P < 0.05) more body weight than fish fed the unsupplemented diet. Hepatic ascorbate concentrations in fish generally increased as the dietary ascorbate level increased. Results of the broken Line analysis indicated that the adequate dietary ascorbic acid From each source for growing fish is 63.4 mg of C2MP-Na/kg (equivalent to 15.98 mg of ascorbic acid/kg) diet and 40.5 mg of C2MP-Mg/kg (equivalent to 18.82 mg ascorbic acid/kg) diet, and it also indicated that C2MP-Mg was about 85% as effective as C2MP-Na in meeting the vitamin C requirement for tilapia. (C) 1999 Elsevier Science B.V. All rights reserved.

Shiau, S. Y., and Lo, P. S. (2000). Dietary choline requirements of juvenile hybrid tilapia, oreochromis niloticus x O. aureus [In Process Citation]. J Nutr 130, 100-3.
An 8-wk feeding trial was conducted to determine the dietary choline requirement for juvenile hybrid tilapia, Oreochromis niloticus x O. aureus. Purified basal diets were formulated using vitamin-free casein (contained 370 mg choline/kg) as the protein source. Graded levels (0, 100, 200, 400, 600, 800, 1,000 and 2,000 mg choline/kg diet) of choline chloride were added to the basal diet, resulting in eight dietary treatments in the experiment. Each diet was fed to three replicate groups of tilapia initially averaging 0.62 +/- 0.01 g/fish in a closed, recirculating rearing system. Feed efficiency, survival and blood triglyceride, cholesterol and phospholipid concentrations were generally high in fish fed choline-supplemented diets compared to fish fed the control diet. Analysis by broken-line regression of weight gain and body choline concentration and by polynomial regression of liver lipid concentration of the fish indicated that the dietary choline concentration for tilapia is about 900 mg/kg. Taking into account the choline concentration of the unsupplemented basal diet, the optimal dietary choline requirement for growing tilapia is about 1,000 mg/kg.

Shiraishi, K., Kaneko, T., Hasegawa, S., and Hirano, T. (1997). Development of multicellular complexes of chloride cells in the yolk- sac membrane of tilapia (Oreochromis mossambicus) embryos and larvae in seawater. Cell Tissue Res 288, 583-90.
Morphological changes in the chloride cells (CCs) in the yolk-sac membrane of euryhaline tilapia (Oreochromis mossambicus) embryos and larvae were examined in relation to environmental salinity. Half of a brood of embryos spawned in fresh water (FW) were transferred directly to seawater (SW) 1 day before hatching; the other half was maintained in FW. The embryos and larvae in both FW and SW contained a rich population of CCs in the yolk-sac membrane; the CCs were visualized by whole-mount immunocytochemistry with an antiserum specific for Na+,K+- ATPase. The sectional areas of CCs increased markedly following SW transfer, whereas they remained small in the embryos and larvae maintained in FW. Scanning electron microscopy showed that the apical opening of CCs was enlarged in the fish transferred to SW. Transmission electron microscopy revealed enhanced cellular activity in SW, as evidenced by well-developed mitochondria and tubular systems. The CCs in SW frequently formed a multicellular complex, consisting of a main CC and one or two accessory cells. Accessory cells interdigitated with the main cells and extended their cytoplasmic processes to the apex of the main cell. The three-dimensional arrangement of the cells participating in the complex was identified by confocal laser scanning microscopy. Such complexes were rarely observed in FW fish. The activated CCs in the yolk-sac membrane in the SW fish probably function as ion-extruding sites during embryonic and larval stages until gill CCs become functional.

Shiraishi, K., Matsuda, M., Mori, T., and Hirano, T. (1999). Changes in expression of prolactin- and cortisol-receptor genes during early-life stages of euryhaline tilapia (Oreochromis mossambicus) in fresh water and seawater. Zoological Science 16, 139-146.
Expression of prolactin receptor (PRLR) and cortisol receptor (CR) mRNAs was examined during early-life stages of euryhaline Mozambique tilapia (Oreochromis mossambicus) by competitive reverse transcription-polymerase chain reaction (cRT-PCR). Concentration of prolactin receptor mRNA was higher in the gills of mature fish reared in fresh water (FW) than in those reared in seawater (SW), whereas no difference was seen in CR mRNA. Whole eggs just after fertilization contained the receptor mRNAs for both prolactin and cortisol. The concentration of PRLR mRNA increased gradually as the embryo grows both in FW and in SW. On the other hand, the concentration of CR mRNA was highest in the egg just after fertilization, decreased rapidly toward hatching, and increased slightly thereafter. When embryos 3 days before hatching were transferred to SW, the levels of PRLR mRNA were significantly lower at the time of hatching and also 3 days after hatching than in the embryo and larvae maintained in FW. Environmental salinity did not affect CR mRNA content at any stage examined. Both PRLR and CR mRNAs were identified in the yolk-sac membrane and in the embryonic body. Significantly more PRLR gene was expressed in the embryonic body developing in FW than in SW, whereas no difference was seen in the yolk-sac membrane. The greater expression of PRLR gene in embryos and larvae developing in FW than in those in SW clearly indicates the presence of regulatory mechanisms of gene expression in early- life stages of tilapia.

Shumkov, M. A., and Nagornyi, S. A. (1993). [The prospects for using Tilapia fry in a biological method of mosquito control]. Med Parazitol (Mosk) , 43-5.

Signoret, M. (1974). [Microorganisms present in the digestive content of Tilapia species (Pisces, Cichlidae)]. Rev Latinoam Microbiol 16, 153-4.

Sinha, R. K., Singh, S. P., and Singh, S. B. (1981). Olfactory organs in the exotic fish Tilapia mossambica (Peters). Folia Morphol 29, 258-62.

Siva Prasada Rao, K., and Ramana Rao, K. V. (1984). Impact of methyl parathion toxicity and eserine inhibition on acetylcholinesterase activity in tissues of the teleost (Tilapia mossambica)--a correlative study. Toxicol Lett 22, 351-6.
Acetylcholinesterase (AChE) activity and acetylcholine (ACh) content of muscle, gill, liver and brain tissues of control and methyl parathion- exposed (MPE) fish were determined. In addition, in vitro concentrations of eserine necessary to produce inhibition of AChE equivalent to in vivo inhibition by sublethal amounts of methyl parathion (MP) were also investigated. AChE activity decreased in all tissues, while ACh content showed a corresponding increase. These observations indicate disruption of nerve impulse conduction. The in vitro effect of eserine on AChE activity differed with the type of MP action. These results are discussed in relation to the sensitivity and extent of innervation of various tissues.

Sivadas, P. (1965). Absorption of fat in the alimentary canal of Tilapia mossambica (Peters) (Teleostei). J Cell Physiol 65, 249-51.

Skliris, G. P., and Richards, R. H. (1999). Nodavirus isolated from experimentally infected tilapia, Oreochromis mossambicus (Peters). Journal of Fish Diseases 22, 315-318.

Smith, C. J., and Haley, S. R. (1988). Steroid profiles of the female tilapia, Oreochromis mossambicus, and correlation with oocyte growth and mouthbrooding behavior. Gen Comp Endocrinol 69, 88-98.
Plasma levels of progesterone, 17 alpha-OH-progesterone, testosterone, and estradiol-17 beta were measured by radioimmunoassay during the ovarian cycles of two groups of female tilapia, Oreochromis mossambicus. One group included females that successfully mouthbrooded fry, while the other group consisted of females in which the zygotes were either removed or swallowed within 1 day after spawning. The mouthbrooders had a longer ovarian cycle (about 40 days) and were sampled 1, 3, 5, 7, 10, 15, 20, 25, 30, 35, and 40 days after spawning. The non-mouthbrooders had an ovarian cycle of about 25 days. They were sampled 3, 5, 7, 10, 15, 20, and 25 days after spawning. Initial peaks in levels of testosterone, estradiol-17 beta, and progesterone occurred later in the cycle of mouthbrooders. The first peak of testosterone and estradiol-17 beta occurred at 15 days after spawning. While estradiol- 17 beta levels remained high, testosterone levels fell at 25 days after spawning, and increased again just prior to spawning. In the latter phase of mouthbrooding (15-25 days after spawning), the oocytes in the ovary did not increase in size, and testosterone and estradiol levels were high. During this time, estradiol may have a function other than stimulating vitellogenesis, such as an involvement (with testosterone?) in parental behavior, or protecting the oocytes from atresia. In non- mouthbrooders, testosterone, estradiol-17 beta, and progesterone levels initially peaked at 10 days after spawning, then dropped at 15 days after spawning. At the end of the cycle, testosterone and estradiol-17 beta levels increased again. The drop in estradiol levels is contrary to the profile seen in mouthbrooders. Also in mouthbrooders, progesterone levels did not rise until 25 days after spawning, then decreased and peaked again towards the end of the cycle. 17 alpha-OH- progesterone concentrations were low, with a single peak at 7 days after spawning in non-mouthbrooders, and at 40 days after spawning in mouthbrooders. There appears to be a relationship between the delayed initial peaks of the steroid hormones measured, oocyte growth arrestment, and longer-lived postovulatory follicles in mouthbrooding female tilapia.

Smith, D. A., Schurig, G. G., Smith, S. A., and Holladay, S. D. (1999). Tilapia (Oreochromis niloticus) and rodents exhibit similar patterns of inhibited antibody production following exposure to immunotoxic chemicals [In Process Citation]. Vet Hum Toxicol 41, 368-73.
The hemolytic plaque forming cell assay (PFC), a measure of ability to produce specific antibodies following challenge with antigen, is a powerful predictor of immunosuppression in chemical-exposed rodents. The efficacy of this assay for predicting humoral immunosuppression in non-rodent species remains unknown. In the present report, tilapia (Oreochromis niloticus) were exposed to 9 chemical agents known to inhibit antibody production in mice (benzo[a]pyrene, 7,12- dimethylbenzanthracene, 2,3,7,8-tetrachlorodibenzo-p-dioxin, dimethyl nitrosamine, cadmium chloride, azathioprine, hexachlorocyclohexane, T2 mycotoxin and toluene) and 5 chemical agents which do not inhibit this response (oxymethalone, acetonitrile, diethylstilbesterol, t- butylhydroquinone and formaldehyde). Eight of 9 agents which inhibit antibody production in rodents caused decreased PFC responses in fish. All 5 compounds with negative humoral effects in rodents were also negative in fish. Thus, 13/14 chemical agents tested gave similar results in tilapia as reported in rodents, suggesting a comparable pattern of humoral immunosuppression in chemical-exposed tilapia to that seen in laboratory rodent models.

Smith, D. A., Schurig, G. G., Smith, S. A., and Holladay, S. D. (1999). Tilapia (Oreochromis niloticus) and rodents exhibit similar patterns of inhibited antibody production following exposure to immunotoxic chemicals. Veterinary and Human Toxicology 41, 368-373.
The hemolytic plaque forming cell assay (PFC), a measure of ability to produce specific antibodies following challenge with antigen, is a powerful predictor of immunosuppression in chemical-exposed rodents. The efficacy of this assay for predicting humoral Immunosuppression in non-rodent species remains unknown. In the present report, tilapia (Oreochromis niloticus) were exposed to 9 chemical agents known to inhibit antibody production in mice (beozo[a]pyrene, 7,12- dimethylbenzanthracene, 2,3,7,8-tetrachlorodibenzo-p-dioxin, dimethyl nitrosamine, cadmium chloride, azathioprine, hexachlorocyclohexane, T-2 mycotoxin and toluene) and 5 chemical agents which do no: inhibit this response (oxymethalone, acetonitrile, diethylstilbesterol, t- butylhydroquinone and formaldehyde). Eight of 9 agents which inhibit antibody production in rodents caused decreased PFC responses in fish. All 5 compounds with negative humoral effects in rodents were also negative in fish. Thus, 13/14 chemical agents tested gave similar results in tilapia as reported in rodents, suggesting a comparable pattern of humoral immunosuppression in chemical;exposed tilapia to that seen in laboratory rodent models.

Smith, D. A., Schurig, G. G., Smith, S. A., and Holladay, S. D. (1999). The hemolytic plaque-forming cell assay in tilapia (Oreochromis niloticus) exposed to benzo[a]pyrene: Enhanced or depressed plaque formation depends on dosing schedule. Toxicology Methods 9, 57-70.
The prospect of utilizing the cichlid teleost tilapia (Oreochromis niloticus) as an alternative experimental model to mammals for preliminary chemical immunotoxicity risk assessment is being evaluated by examining the National Toxicology Program's standard battery of rodent immunotoxicity assays in chemical-treated tilapia. The present report examines the hemolytic plaque forming cell assay (PFC) a quantitative indicator of antibody production in tilapia exposed to the polycyclic aromatic hydrocarbon (PAH) benzo[alpha]pyrene (B[alpha]P). Reduced antibody production against sheep red blood cell (SRBC) antigen in response to B[alpha]P was observed using the PFC assay, via reduction in plaque number. Under specific immunization circumstances, increased plaque formation was observed in chemical-exposed fish, art effect also reported in rodents. Although the normal teleost immune responsiveness was weaker than seen with mice under comparable conditions (presumably due to differences in antibody structure of teleosts), tilapia were found to exhibit well-defined primary and secondary humoral responses to SRBC, and an immunotoxic response to B[alpha]P comparable to the rodent model.

Smith, D. A., Schurig, G. G., Smith, S. A., and Holladay, S. D. (1999). Inhibited cytotoxic leukocyte activity in tilapia (Oreochromis niloticus) following exposure to immunotoxic chemicals. International Journal of Toxicology 18, 167-172.
The measure of the ability of cytotoxic immune cells to target and lyse foreign cells has been widely used as a predictor of immunosuppression in chemical-exposed rodents. However, the efficacy of this function for predicting immunosuppressive chemical exposure in nonrodent species remains unknown. In the present report, tilapia (Oreochromis niloticus) were exposed to 9 chemical agents known to inhibit rodent cytotoxic T lymphocyte (CTL) activity in mice, benzo[a]pyrene (B[a]P), 7,12-dimethylbenzanthracene (DMBA), 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), dimethylnitrosamine (DMN), cadmium chloride (CdCl2), azathioprine (AZA), T-2 mycotoxin (T2 toxin), hexachlorocyclohexane (lindane), and diethylstilbesterol (DES); and five chemical agents which do not inhibit this response, oxymethalone, acetonitrile, tert-butylhydroquinone (TBHQ), toluene, and formaldehyde, Eight of the nine agents which inhibit rodent CTL responses also caused decreased cytolytic responses in fish. All five of the compounds with negative CTL effects in rodents were also negative in fish. Thus, 13 of the 14 chemical agents tested gave similar results in fish as reported in rodents, indicating a comparable pattern of inhibited immune cell cytolytic responses in chemical-exposed tilapia to that seen in the laboratory rodent models.

Soga, T., Sakuma, Y., and Parhar, I. S. (1998). Testosterone differentially regulates expression of GnRH messenger RNAs in the terminal nerve, preoptic and midbrain of male tilapia. Brain Res Mol Brain Res 60, 13-20.
The purpose of the present study was to examine the regulation of three molecular variants of gonadotropin-releasing hormone (GnRH)-encoding mRNAs by testosterone in the male tilapia Oreochromis niloticus. Tilapias castrated for two weeks were injected intraperitoneally with sesame oil or 5 microgram/g testosterone for 7 days. In situ hybridization histochemistry was performed using 35S-labelled 30-mer antisense oligonucleotide probes complementary to exon two (bases 1-30) of salmon-, seabream-, and chicken II-GnRH. Computerized image analysis was performed to quantify GnRH mRNA expression in the terminal nerve ganglia (nucleus olfactoretinalis) and in individual cells of the preoptic area and the midbrain tegmentum. Testosterone treatment significantly elevated terminal nerve salmon-GnRH mRNA, reduced preoptic seabream-GnRH mRNA but had no effect on midbrain chicken II- GnRH mRNA levels. The total number and size of preoptic and midbrain GnRH mRNA-containing neurons or the total volume of the terminal nerve ganglia in testosterone-treated animals did not differ significantly from oil-treated animals. The midbrain chicken II-GnRH neurons are not targets of testosterone. These results demonstrate for the first time differential regulation of subpopulations of GnRH neurons with molecular diversity and different topography. Copyright 1998 Elsevier Science B.V.

Sohm, F., Pezet, A., Sandra, O., Prunet, P., de Luze, A., and Edery, M. (1998). Activation of gene transcription by tilapia prolactin variants tiPRL188 and tiPRL177. FEBS Lett 438, 119-23.
In the tilapia species Oreochromis niloticus, the pituitary releases two forms of prolactins (tiPRL188 and tiPRL177). The binding parameters and the activation of tiPRL-induced JAK2/Stat5 signalling pathway were analysed using a mammalian cell line transiently transfected with the tiPRL receptor (tiPRLR). Our data indicate that the tiPRLR is able to mediate transcriptional activation of the PRL responsive element. At nanomolar concentrations, tiPRL188 activates gene transcription whereas at micromolar concentrations it inhibits luciferase transcription from the lactogenic responsive element. This is consistent with a model of receptor dimerisation. In contrast, the activation by tiPRL177 was only reached at high (microM) concentrations. The transcriptional activities induced by tiPRL177 and tiPRL188 are discussed in the context of the physiology of these hormones.

Solomon, K., and Allanson, B. R. (1968). The effects of exposure to low temperatures on the serum protein of Tilapia mossambica Peters. Comp Biochem Physiol 25, 485-92.

Specker, J. L., Kishida, M., Huang, L., King, D. S., Nagahama, Y., Ueda, H., and Anderson, T. R. (1993). Immunocytochemical and immunogold localization of two prolactin isoforms in the same pituitary cells and in the same granules in the tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 89, 28-38.
The tilapia pituitary secretes two forms of prolactin (tPRL) and a single growth hormone (tGH). The tPRLs share only 69% sequence identity and are designated tPRL177 and tPRL188 to indicate the number of amino acid residues in each isoform. Our aim was to develop specific antisera for detection of these three related polypeptides. Ten peptides corresponding to unique epitopes on the tPRLs and two peptides of tGH were synthesized using solid-phase methods, conjugated to carrier proteins, and used as immunogens for antibody production in rabbits. Select antisera for the tPRLs were highly specific, exhibiting only 1% cross-reactivity to the alternate tPRL under noncompetitive ELISA conditions at dilutions used in immunocytochemical analysis. The anti- tGH specifically bound to cells in the proximal pars distalis. Production of both tPRLs by a single cell type was indicated by the binding of both anti-tPRL177 and anti-tPRL188 to the same cells in the rostral pars distalis. Ultrastructural analysis of PRL-producing cells stained sequentially using the two different anti-tPRL antibodies labeled with immunogold of two size classes indicated that both tPRLs appear in the same granules. These findings suggest that the biological significance of two forms of PRL in the adult tilapia is not a function of differential regulation of two different classes of PRL cells or differential release of unique secretory granules.

Srivastav, A. K., Flik, G., and Wendelaar Bonga, S. E. (1998). Plasma calcium and stanniocalcin levels of male tilapia, Oreochromis mossambicus, fed calcium-deficient food and treated with 1,25 dihydroxyvitamin D3. Gen Comp Endocrinol 110, 290-4.
The vitamin D metabolite 1,25 dihydroxyvitamin D3 (1,25(OH)2D3; calcitriol) was injected ip (5 microg/kg-1 body mass daily) into male tilapia, Oreochromis mossambicus, fed calcium-deficient food. Plasma calcium (total and free) and stanniocalcin levels, as well as calcium contents of vertebral and opercular bone and scales, were determined on days 1, 3, and 5. In the treated fish, total plasma calcium levels increased on days 3 and 5. Plasma-free calcium levels remained unaffected. Plasma stanniocalcin levels increased, indicating a response of the Stannius corpuscles to redress 1, 25(OH)2D3-induced hypercalcemia. The calcium contents of bone, operculum, and scales were unchanged. It is concluded that in fish, which lack parathyroid hormone, 1,25(OH)2D3 is hypercalcemic and its action is independent of dietary calcium. Copyright 1998 Academic Press.

Stevens, E. D., and Fry, F. E. (1970). The rate of thermal exchange in a teleost, Tilapia mossambica. Can J Zool 48, 221-6.

Sukumar, P., Munro, A. D., Mok, E. Y., Subburaju, S., and Lam, T. J. (1997). Hypothalamic regulation of the pituitary-thyroid axis in the tilapia Oreochromis mossambicus. Gen Comp Endocrinol 106, 73-84.
Electrolytic lesioning of the preoptic area resulted in an increase in plasma thyroxine (T4) and reverse triiodothyronine (rT3) 10 days later; plasma triiodothyronine (T3) levels were not affected, so that there was also a significant decrease in the T3:T4, but not rT3:T4, ratios. No significant changes in T4, T3, or rT3 levels were observed in fish with lesions in either the anterior or posterior portions of the lateral tuberal nucleus. The pituitary contents of growth hormone and the two prolactins were not affected by any lesion. This indicates that the preoptic area may play a role in the inhibitory regulation of the pituitary-thyroid axis in Oreochromis mossambicus, presumably by way of effects on thyrotropin secretion.

Suzuki, E. Y., Early, R. J., and Patterson, P. H. (1994). Energy metabolism in isolated chick (Gallus domesticus) gastrocnemius and tilapia (Tilapia mossambica) epaxial muscle at various temperatures in vitro. Comp Biochem Physiol Physiol 109, 139-50.
Muscle respiration experiments on inhibitor dosage (experiment 1), muscle preparation (tendons removed vs. unstretched vs. stretched muscles; chick muscle only; experiment 2) and media temperature (26.5, 32, 37, 42 degrees C; experiment 3) were conducted on chick (Gallus domesticus) gastrocnemius and tilapia (Tilapia mossambica) epaxial muscle in vitro. Experiment 1: The dosage of cycloheximide and ouabain required for maximum inhibition of protein synthesis and Na+,K+ ATPase, respectively, in chick and tilapia muscle was approximately 6 x 10(-5) M. Experiment 2: Removing the tendons of chick muscle decreased (% inhibition, P = 0.05) cycloheximide-sensitive respiration compared to stretched and unstretched muscles (tendons intact). However, muscle preparation had little influence on ouabain-sensitive respiration. Experiment 3: Cycloheximide-sensitive respiration tended to increase (microliter O2/mg DNA.hr, P = 0.054) with media temperature in tilapia muscle. Chick muscle was less responsive in this respect. Ouabain- sensitive respiration increased at lower temperature in chick muscle (% inhibition, cubic relationship, P = 0.001) and at higher temperature in tilapia muscle (% inhibition, quadratic relationship, P = 0.0002).

Swallow, R. L., and Fleming, W. R. (1969). The effect of starvation, feeding, glucose and ACTH on the liver glycogen levels of Tilapia mossambica. Comp Biochem Physiol 28, 95-106.

Swallow, R. L., and Fleming, W. R. (1970). The effect of oxaloacetate, ACTH and cortisol on the liver glycogen levels of Tilapia mossambica. Comp Biochem Physiol 36, 93-8.

Swennen, D., Rentier-Delrue, F., Auperin, B., Prunet, P., Flik, G., Wendelaar Bonga, S. E., Lion, M., and Martial, J. A. (1991). Production and purification of biologically active recombinant tilapia (Oreochromis niloticus) prolactins. J Endocrinol 131, 219-27.
Recombinant expression vectors carrying tilapia prolactin-I or -II (tiPRL-I or tiPRL-II) cDNA were constructed and the tiPRL-I and II proteins were produced in E. coli as inclusion bodies. These inclusion bodies were dissolved in 6 mol urea/l. Refolding of the proteins was followed by SDS-PAGE under non-reducing conditions so as to visualize the oxidized state of the molecules. Proteins tiPRL-I and tiPRL-II were purified by gel filtration and ion-exchange chromatography. The N- terminal sequence and bioactivities of both purified proteins were then analysed. Recombinant tiPRL-I and tiPRL-II induced a significant rise in plasma calcium levels as well as in mucocyte density in the abdominal skin epithelium. When tested on kidney membrane, both proteins exhibited potency in competing with 125I-labelled tiPRL-I for binding sites, but tiPRL-I seemed to be more potent than tiPRL-II in competing for these sites. The results obtained for the biological activities tested suggest that both recombinant prolactins were correctly refolded and had retained the full biological activity previously observed with the natural hormone preparations extracted from the animals.

Swennen, D., Poncelet, A. C., Sekkali, B., Rentier-Delrue, F., Martial, J. A., and Belayew, A. (1992). Structure of the tilapia (Oreochromis mossambicus) prolactin I gene. DNA Cell Biol 11, 673-84.
The tilapia (Oreochromis mossambicus) prolactin-I (PRL-I) gene has been cloned and sequenced. Its transcript (3,677 bases long) begins with a guanine and is organized in five exons and four introns like the other known prolactin genes. Analysis of the 1,555-bp 5'-flanking region suggests that pituitary-specific expression of the gene could be regulated through a trans-factor related to the mammalian pituitary- specific factor Pit-1. Two potential binding sites for such a factor were found in the first intron, suggesting a possible regulatory role for this region. Moreover, two potential Z-DNA regions are located at positions -837 to -812 and -246 to -179 from the transcription start site. These two regions could play an important role in the regulation of PRL gene expression.

Tabche, L. M., Martinez, C. M., and Sanchez-Hidalgo, E. (1990). Comparative study of toxic lead effect on gill and haemoglobin of tilapia fish. J Appl Toxicol 10, 193-5.
This study was designed to determine the 72-h LC50 of lead for tilapia fish (Oreochromis hornorum), as well as the effect of exposure to sublethal lead concentrations (15, 23, 31, 39 and 47% of the LC50) on gill tissue lysosomal membranes of the fish and thaemoglobin concentration in blood. The LC50 value was found to be 202 mg Pb2+ l-1. Exposure to sublethal lead concentrations for 72 h showed significant increases in the lability of gill lysosomal membranes, measured by the release of acid phosphatase. Changes in membrane lability and in haemoglobin concentration were dependent on the amount of lead used during the exposure. We considered that the membrane lability is an adequate parameter to assay for monitoring lead contamination in water, because it is more sensitive than the haemoglobin concentration in blood.

Tagawa, M., Hagiwara, H., Takemura, A., Hirose, S., and Hirano, T. (1997). Partial cloning of the hormone-binding domain of the cortisol receptor in tilapia, Oreochromis mossambicus, and changes in the mRNA level during embryonic development. Gen Comp Endocrinol 108, 132-40.
Cortisol is one of the central hormones in osmoregulation in fish, especially in seawater adaptation. A cDNA of 453 bp was cloned from liver mRNA of freshwater-reared tilapia (Oreochromis mossambicus), by reverse transcription polymerase chain reaction (RT-PCR) with primers designed for the hormone-binding domain of glucocorticoid receptors (GRs) in mammals and rainbow trout. The sequence of PCR product has 83% homology to the trout GR at the nucleotide level and 92% at the amino acid level. The PCR product of tilapia showed highest homology (74% at the amino acid level) to GR among human steroid hormone receptors, including mineralocorticoid receptor. The length of the receptor mRNA of tilapia was about 6.5 kb as determined by Northern blot hybridization. The mRNA concentration in the gills was relatively higher among various organs, the highest concentration being observed in blood cells. Signal intensity of the receptor message in the gills was stronger in fish reared in freshwater than in those reared in seawater or in concentrated (160%) seawater. During early development of tilapia, the highest concentration of receptor mRNA in the total RNA extracted from the whole egg was found just after fertilization, and its concentration decreased steadily toward hatching. The absolute amount of receptor mRNA per egg increased gradually before the initiation of cortisol production by the embryo. When embryos were transferred from fresh water to seawater 2 days before hatching, no difference was observed in the signal intensity of the receptor mRNA among embryos after 1, 2 (the day of hatching), 4, and 7 days. Copyright 1997 Academic Press.

Takeda, Y., Kawasaki, Y., Sugita, T., Sakamoto, S., Sato, K., Yashida, R., Maitani, T., Ishiwata, H., and Yamada, T. (1995). [Inspection of carbon monoxide in imported tilapia]. Eisei Shikenjo Hokoku 113, 74-6.
Carbon monoxide in imported tilapia was determined with a gas chromatograph equipped with a molecular sieve 13x column (2.3 m), a methanizer and a FID for the inspection of imported food. The concentration of carbon monoxide in the sample, which was vacuum packed and suspected to be treated with carbon monoxide, was 16 x 10 micrograms/kg in fish meat, and 37 x 10(3) microliters/l in the bubble in the package. On the other hand, carbon monoxide in the reference, which was vacuum packed but was not treated with carbon monoxide, was 10 micrograms/kg in fish meat and 76 microliters/l in the bubble in the package. Carbon monoxide was less than 4 micrograms/kg in two vacuum packed fish meat of tilapia sold in a market in Tokyo. From these results, the suspected sample was concluded to be treated with carbon monoxide for color fixating of protoheme in fish meat.

Tan, B., and Melius, P. (1983). Effects of 3-methylcholanthrene on the hepatic microsomal enzymes in a teleost, Tilapia aurea. Bull Environ Contam Toxicol 31, 292-6.

Tavolga, W. N., and Jacobs, D. W. (1971). Scotopic thresholds for monochromatic light in the cichlid fish, Tilapia heudelotii macrocephala. Vision Res 11, 713-7.

Terkatin-Shimony, A., Ilan, Z., Yaron, Z., and Johnson, D. W. (1980). Relationship between temperature, ovarian recrudescence, and plasma cortisol level in Tilapia aurea (Cichlidae, Teleostei). Gen Comp Endocrinol 40, 143-8.

Thangnipon, W., Luangpaiboon, P., and Chinabut, S. (1995). Effects of the organophosphate insecticide, monocrotophos, on acetylcholinesterase activity in the nile tilapia fish (Oreochromis niloticus) brain. Neurochem Res 20, 587-91.
The neurotoxic effects of monocrotophos on the brain of the nile tilapia fish (Oreochromis niloticus) were examined, using a static bioassay under laboratory conditions. By probit analysis the 96 h LC50 value of monocrotophos was 4.9 mg/l. After 96 h exposure to acute levels of monocrotophos, the brain acetylcholinesterase (AChE) activity decreased progressively as the concentration of monocrotophos increased. In addition, four weeks following transfer to toxicant-free water after exposure to 1 mg monocrotophos, nile tilapia fish brain regained 95% of control AChE activity. The results indicate that inhibition of AChE activity in fish exposed to monocrotophos may serve as an indicator of hazard due to application of this chemical in the natural environment.

Titus, E., Karasov, W. H., and Ahearn, G. A. (1991). Dietary modulation of intestinal nutrient transport in the teleost fish tilapia. Am J Physiol 261, R1568-74.
Tilapia (Oreochromis mossambicus) were fed a diet with either 60% carbohydrate (70% grain-4% fish meal) or 17% carbohydrate (11% grain- 65% fish meal) for greater than or equal to 4 wk. Intestinal uptake of radiolabeled acetate, D-glucose, and L-proline was measured in brush- border membrane vesicles. As expected, fish fed high carbohydrate had significantly higher D-glucose uptake than those fed low carbohydrate [maximal uptake rate (Vmax), respectively, 84.2 +/- 18.2 vs. 37.4 +/- 10.9 pmol.mg protein-1.s-1; n = 4 batches of vesicles in each case; t test, P less than 0.025]. The change in glucose transport was specific, because in the same batches of vesicles there was no significant diet effect on carrier-mediated uptake of L-proline or acetate. Also as expected, dietary modulation of carrier-mediated transport was effected primarily by alterations in Vmax and not apparent Michaelis constant (Km); Km was not significantly altered by diet for either D-glucose (high carbohydrate vs. low carbohydrate, respectively, 0.34 +/- 0.17 vs. 0.12 +/- 0.03 mM; P greater than 0.2), L-proline (respectively, 0.10 +/- 0.03 vs. mM 0.13 +/- 0.05), or acetate (respectively, 4.8 +/- 1.4 vs. mM 6.5 +/- 2.2).

Toguyeni, A., Fauconneau, B., Boujard, T., Fostier, A., Kuhn, E. R., Mol, K. A., and Baroiller, J. F. (1997). Feeding behaviour and food utilisation in tilapia, Oreochromis niloticus: effect of sex ratio and relationship with the endocrine status. Physiol Behav 62, 273-9.
The feeding behaviour of male monosex, female monosex, and mixed groups of Oreochromis niloticus was studied under conditions of self-feeding. Feeding activity was observed almost exclusively during the light period. The food intake pattern was similar whatever the sex ratio, and voluntary food intake (VFI) appeared lower in the male monosex groups than in the others. Male monosex groups displayed higher specific growth rates (SGR) and a lower food conversion ratio than female monosex and mixed groups. The SGR of males was higher in the monosex than in the mixed groups, whereas females of mixed and monosex groups displayed no significant difference in SGR. The efficiency of food utilisation was also analysed: nutrient retention ratios were higher in male monosex than in female monosex and mixed groups. Males displayed a distinctly higher metabolic capacity. Differences in sex-related hormones (11 ketotestosterone = 11-KT, 17beta-Oestradiol = 17beta-E2) and a metabolic hormone (triiodothyronine = T3) were observed between males and females. The hypothesis of an involvement of these hormones in the higher metabolic capacity of males is discussed. The observed differences in feeding behaviour between the different groups also suggest an effect of social interactions on the efficiency of food conversion and thus on the differential growth of males and females.

Tsai, C. L., Jang, T. H., and Wang, L. H. (1995). Effects of mercury on serotonin concentration in the brain of tilapia, Oreochromis mossambicus. Neurosci Lett 184, 208-11.
In order to know the effect of mercury pollution on the serotonergic system of fish, serotonin concentrations in a discrete brain region of tilapia, Oreochromis mossambicus, were examined. Serotonin concentration was measured using a high performance liquid chromatography system with electrochemical detector. In male fish, the concentrations of serotonin were 1.468 +/- 0.350, 0.811 +/- 0.190 and 0.330 +/- 0.061 micrograms/g wet tissue in hypothalamus, telencephalon and optic lobe, respectively. The serotonin content was significantly different between each region; the hypothalamus had a higher content than that of the telencephalon and optic lobe. The serotonin concentration in female hypothalamus was 1.102 +/- 0.112 micrograms/g wet tissue which was significantly lower than that in males. However, serotonin concentration in the telencephalon and optic lobe showed no difference between male and female. After exposure to 0.015 and 0.03 ppm HgCl2 for 6 months beginning 7 days posthatching, male sample fish showed a significantly dose-dependent decrease in serotonin concentration in the hypothalamus. But a similar phenomenon was not found in other regions of the brain. These results suggest that exposure to HgCl2 results in an attenuated development of the serotonergic system in the hypothalamus of fish.

Tsai, C. L., and Wang, L. H. (1997). Effects of thermal acclimation on the neurotransmitters, serotonin and norepinephrine in the discrete brain of male and female tilapia, Oreochromis mossambicus. Neurosci Lett 233, 77-80.
Effects of thermal acclimation on the serotonin (5-HT) and norepinephrine (NE) contents in the discrete brain of male and female tilapia, Oreochromis mossambicus were investigated. Sexually mature males and females were exposed to 26 degrees C, 29 degrees C, or 32 degrees C of water temperature for 3 weeks. The hypothalamic 5-HT content in the 29 degrees C and 32 degrees C acclimated male was lower than that in the 26 degrees C group. In females, the hypothalamic 5-HT content in the 32 degrees C acclimated group was less than those in the 26 degrees C and 29 degrees C groups. Similar results were found in the hypothalamic NE contents of males and females. In the optic lobe, the elevated temperature acclimation (29 degrees C and 32 degrees C) resulted in a higher 5-HT content in both males and females; whereas, the NE content was increased by the elevated temperature acclimation in females but not altered in that of males. In the telencephalon, the elevated temperature acclimation had no influence on the 5-HT content of males and females, but resulted in a lower NE content in both males and females. These results demonstrate that the neurotransmitter activity of teleost is influenced by the thermal acclimation in a sex- and regional-dependent pattern. The alterations of 5-HT and NE in the central nervous system might be involved in the physiological and biochemical responses that occur during thermal acclimation in fish.

Tsai, C. L., and Wang, L. H. (1997). Effects of estradiol on the serotonin secretion and turnover in the hypothalamus of male tilapia, Oreochromis mossambicus, in vitro. Gen Comp Endocrinol 106, 175-80.
The effects of estradiol on the secretion and turnover of serotonin in the hypothalamic fragments of male tilapia, Oreochromis mossambicus, were studied using a static incubation system. The quantitative analysis of serotonin and its related metabolite, 5-hydroxyindoleacetic acid, were performed by high-performance liquid chromatography with electrochemical detection. The hypothalamic fragments were incubated with 17 beta-estradiol at a concentration of 2 x 10(-8), 8 x 10(-8), 2 x 10(-7), 4 x 10(-7), or 4 x 10(-6) g/ml. The low dose of estradiol, 2 x 10(-8) g/ml, had no effect on the concentration of serotonin and 5- hydroxyindoleacetic acid or serotonin turnover in the hypothalamic incubation media. The moderate doses of estradiol 8 x 10(-8) and 2 x 10(-7) g/ml, increased the concentrations of serotonin and 5- hydroxyindoleacetic acid in the hypothalamic incubation media, but had no effect on the serotonin turnover. The high doses of estradiol, 4 x 10(-7) and 4 x 10(-6) g/ml, did not alter the serotonin concentration in the hypothalamic incubation media, but increased the 5- hydroxyindoleacetic acid concentration and serotonin turnover. These results demonstrate that the moderate dose of estradiol increases the serotonin activity by increasing the serotonin concentration, whereas the high dose of estradiol increases the serotonin activity by increasing the ratio of 5-hydroxyindoleacetic acid and serotonin. However, the serotonin concentration is homeostatically maintained in the extracellular fluid of hypothalamus under the high dose of E2 treatment.

Tsai, J. C., and Hwang, P. P. (1998). Effects of wheat germ agglutinin and colchicine on microtubules of the mitochondria-rich cells and Ca2+ uptake in tilapia (Oreochromis mossambicus) larvae. J Exp Biol 201, 2263-71.
The organization of the microtubules and actin filaments in the gills of tilapia (Oreochromis mossambicus) larvae was revealed by confocal microscopy. The fluorescence intensity of the microtubules in the gills was increased by adding wheat germ agglutinin (WGA, 40 ng ml-1) to the ambient water for 30 min, but the staining pattern of the actin filaments was not changed. The fluorescence intensity of the microtubules in the gills was decreased by treatment with the microtubule-disrupting reagent colchicine at 0.2 mmol l-1 for 4 h. WGA treatment concurrently raised Ca2+ influx rates, and the increase was particularly large when the larvae were kept in water with extremely low Ca2+ levels ([Ca2+]=0.002 mmol l-1). Colchicine treatment, in contrast, reduced the Ca2+ influx rate. These results indicate that the microtubule network in tilapia gills, particularly in mitochondria-rich cells, could play a critical role in the uptake of Ca2+ in tilapia larvae.

Tsai, C. L., and Wang, L. H. (1999). Effects of gonadal steroids on the serotonin synthesis and metabolism in the early developing tilapia brain. Neurosci Lett 264, 45-8.
The effects of gonadal steroids on serotonin (5-HT) synthesis and metabolism in the early developing brain were investigated. Seven-day- old (7 days post-hatch) tilapia, Oreochromis mossambicus were continuously treated with 17beta-estradiol (E2), methyltestosterone (MT) and para-chlorophenylalanine (p-PCA) up to the age of 30 days. The brain 5-HT content, before 30 days, increased with age. The result indicates that this is a developing period of the central 5-HTergic system. During this developing period, the activity of tryptophan hydroxylase (TPH) and monoamine oxidase (MAO) was not altered by age. Both E2 and MT influence the central 5-HT content during its restricted developmental period. E2 has an initial inhibitory effect and then a facilitative effect while MT only has a facilitative effect. The initial inhibitory effect of E2 is mediated by decreasing TPH activity and increasing MAO activity to decrease the 5-HT content. The facilitative effect of both E2 and MT is suppressed by p-CPA.

Tuisku, F., and Hildebrand, C. (1995). Immunohistochemical and electron microscopic demonstration of nerve fibres in relation to gingiva, tooth germs and functional teeth in the lower jaw of the cichlid Tilapia mariae. Arch Oral Biol 40, 513-20.
Immunohistochemistry revealed the presence of numerous neurofilament (NF)-like immunoreactive axons in relation to gingiva and dental follicles surrounding mineralizing tooth germs. The gingival nerve fibres frequently approached the prospective papilla of early tooth primordia. Electron microscopic (EM) analysis revealed the presence of bundles of unmyelinated axons immediately below the epithelial-proprial junction of the gingiva. Bundles of nerve fibres were also present in the border zone between the prospective papilla of bud-stage tooth germs and surrounding mesenchyme and in close proximity to blood vessels of the follicles surrounding older tooth germs, but no axons were observed within the emerging dental papilla. In the individual functional tooth, a bundle of NF-like immunoreactive nerve fibres entered the apical part of the pulp forming a subodontoblastic plexus at mid-pulpal levels. EM analysis showed that the apical bundle consisted of many unmyelinated and a few myelinated axons invested by Schwann cell processes. The subodontoblastic plexus contained unmyelinated axons only. Thin, axon-like profiles were also seen in predentinal tubules. Nerve fibres were not observed at pulpal horn levels and in the ligamentous attachment. It is concluded that both immature and mature parts of the lower-jaw dentition of the cichlid T. mariae are innervated and that the microscopic anatomy of this innervation is partly similar to the pattern seen in developing and adult mammals.

Tuisku, F., and Hildebrand, C. (1997). Combined retrograde tracing and immunohistochemistry of trigeminal ganglion neurons projecting to gingiva or tooth pulps in the lower jaw of the cichlid Tilapia mariae. J Neurocytol 26, 33-40.
Rat trigeminal ganglion neurons projecting to the oral mucosa or to tooth pulps have different cell diameters and contain different chemical markers. In the present paper we examine whether trigeminal ganglion neurons sending axons to gingiva or tooth pulps in the lower jaw of the cichlid Tilapia mariae differ in a similar way. Retrograde tracing with fluorescent latex microspheres revealed labelled gingival and pulpal neurons in the caudal part of the trigeminal ganglion. The gingival neurons had a unimodal size distribution (peak 11 microns; range 8-14 microns) and the pulpal neurons exhibited a bimodal size distribution (peaks 12 and 25 microns; range 10-40 microns). Immunohistochemistry revealed a calcitonin gene-related peptide-like immunoreactivity in some 40% of the gingival neurons and a substance P- like immunoreactivity in 30%. Of the small pulpal neurons about 60% exhibited a calcitonin gene-related peptide-like immunoreactivity and 15% showed a substance P-like immunoreactivity. Of the large pulpal neurons some 70% exhibited a calcitonin gene-related peptide-like immunoreactivity. These neurons did not show a substance P-like immunoreactivity. In some animals a few trigeminal ganglion neurons showed a neuropeptide Y- or a vasoactive intestinal polypeptide-like immunoreactivity. Perikarya with a tyrosine hydroxylase- or a choline acetyl transferase-like immunoreactivity were not observed. We conclude that gingiva and tooth pulps in the lower jaw of T. mariae are innervated by trigeminal ganglion neurons, the cell diameters and neuropeptide contents of which differ in a pattern similar to that in the rat. Hence, this seems to represent a conserved evolutionary pattern.

Ueda, H., Kagawa, H., and Fujimoto, S. (1985). Immunoelectron microscopic localization of growth hormone in the pituitary glands of two teleosts, tilapia (Sarotherodon mossambicus) and amago salmon (Oncorhynchus rhodurus). Gen Comp Endocrinol 59, 149-54.
Growth hormone (GH) cells were investigated with the protein A-gold technique on the pituitary glands of tilapia (Sarotherodon mossambicus) and amago salmon (Oncorhynchus rhodurus). By the use of specific antiserum against tilapia GH to both species, the immunoreactive gold particles were demonstrated to be preferentially located on the secretory granules of the GH cells. Specimens fixed only with periodate- lysine-paraformaldehyde (PLP) preserved the hormonal antigenicity well. Osmium postfixation, although considerably reducing the antigenicity and thus resulting in a decrease in number of the gold particles on the GH cells, gave much more satisfactory ultrastructural preservation and immunoreactive localization of immunoreactive material. This investigation demonstrated that, after combined fixation with PLP and PLP-osmium, we could determine the function of a given cell type in various endocrine organs as well as the precise antigenic sites in such cells.

Ueng, Y. F., and Ueng, T. H. (1995). Induction and purification of cytochrome P450 1A1 from 3- methylcholanthrene-treated tilapia, Oreochromis niloticus x Oreochromis aureus. Arch Biochem Biophys 322, 347-56.
Pretreatments of freshwater fish tilapia, Oreochromis niloticus x O. aureus, with 3-methylcholanthrene (3-MC) and polychlorinated biphenyls (PCBs) increased liver microsomal cytochromes P450 (P450) and b5 contents, benzo[a]pyrene hydroxylation, and 7-ethoxyresorufin and 7- ethoxycoumarin O-dealkylations. The pretreatments also increased gill microsomal benzo[a]pyrene and 7-ethoxyresorufin oxidations. Immunoblot analysis of liver and gill microsomes revealed that 3-MC and PCBs induced a protein recognized by the mouse monoclonal antibody (MAb) 1- 12-3 against scup P450 1A1. Northern analysis of liver and gill RNA showed that 3-MC and PCBs increased the intensity of 2.9-kb- and 1.5-kb- sized mRNA bands hybridizable to a trout P450 1A1 cDNA probe. Pretreatment with phenobarbital was without effects on the monooxygenase activity or protein or mRNA levels in liver and gill. A 3- MC-inducible P450 hemoprotein (M(r) = 59,000) and a NADPH-cytochrome P450 reductase flavoprotein (M(r) = 74,000) were purified from liver microsomes. The tilapia P450 hemoprotein showed an absorption maximum at 447 nm in CO-difference spectrum and a strong immunoreactivity with MAb 1-12-3. A reconstituted tilapia monooxygenase system consisting of P450 and NADPH-cytochrome P450 reductase was effective in the catalysis of 7-ethoxyresorufin, benzo[a]pyrene, and 7-ethoxycoumarin oxidations, but not in N-nitrosodimethylamine demethylation. These results show that 3-MC and PCBs can induce P450 1A1 in tilapia liver and gill and the tilapia P450 is highly similar to other teleost P450 1A1 with respect to spectral, immunochemical, and catalytic properties.

Ueng, Y. F., Liu, T. Y., and Ueng, T. H. (1995). Induction of cytochrome P450 1A1 and monooxygenase activity in tilapia by sediment extract. Bull Environ Contam Toxicol 54, 60-7.

Ueng, Y. F., Liu, C., Lai, C. F., Meng, L. M., Hung, Y. Y., and Ueng, T. H. (1996). Effects of cadmium and environmental pollution on metallothionein and cytochrome P450 in tilapia. Bull Environ Contam Toxicol 57, 125-31.

Umesh, N. R., Shankar, K. M., and Mohan, C. V. (1999). Enhancing growth of common carp, rohu and Mozambique tilapia through plant substrate: the role of bacterial biofilm. Aquaculture International 7, 251-260.
Experiments were conducted to enhance the growth of common carp (Cyprinus carpio), rohu (Labeo rohita) and Mozambique tilapia (Oreochromis mossambicus) through use of sugarcane bagasse as substrate. Bagasse was suspended in water with or without supplementation with fertilizers. Bagasse supplemented with cattle dung and urea favoured higher zooplankton production and significantly (p < 0.05) increased fish growth by over 50% compared to bagasse or fertilizers on their own. This higher production of fish is attributed to bacterial biofilm promoted on the substrate which, apart from forming food for zooplankton and fish, contributed to improved water quality by lowering ammonia.

Usha Rani, A., and Ramamurthi, R. (1989). Histopathological alterations in the liver of freshwater teleost Tilapia mossambica in response to cadmium toxicity. Ecotoxicol Environ Saf 17, 221-6.
The effects of lethal (50 ppm) and sublethal (5 ppm) concentrations of CdCl2 on the liver of the freshwater teleost Tilapia mossambica were studied by routine histological techniques. Engorged blood vessels, congestion, vacuolar degeneration of hepatocytes, necrosis of pancreatic cells, and fatty changes in the peripancreatic hepatocytes were the pathological alterations observed in liver.

van der Heijden, A. J., van der Meij, J. C., Flik, G., and Wendelaar Bonga, S. E. (1999). Ultrastructure and distribution dynamics of chloride cells in tilapia larvae in fresh water and sea water. Cell Tissue Res 297, 119-30.
Integumental and branchial chloride cells of tilapia larvae (Oreochromis mossambicus) were studied at the light-microscopical and ultrastructural level. Total numbers and distribution of chloride cells were quantified after immunostaining of cross sections of the entire larvae with an antibody against the alpha-subunit of Na+/K+-ATPase. The majority (66%) of Na+/K+-ATPase-immunoreactive (ir) cells, i.e. chloride cells, of freshwater tilapia larvae were located extrabranchially up to 48 h after hatching. Five days after hatching, the majority (80%) of chloride cells were found in the buccal cavity. Transfer of 24-h-old larvae to 20% sea water speeded up this process; 24 h after transfer (i.e. 48 h after hatching), the majority (59%) of chloride cells were located in the buccal cavity. The branchial chloride cell population of 24-h- and 120-h-old larvae consisted of immature, mature, apoptotic and necrotic chloride cells. However, relatively more immature chloride cells were observed in freshwater larvae (42-63%) than in (previously studied) freshwater adults (21%), illustrating the developmental state of the gills. After transfer to sea water, the incidence of degenerative chloride cells did not change. Furthermore, the incidence of immature cells had decreased and a new subtype of chloride cells, the "mitochondria-poor" cells, appeared more frequently. These mitochondria-poor chloride cells were characterised by an abundant tubular system and relatively few mitochondria, which were aligned at the border or concentrated in one part of the cytoplasm. Most of these cells did not contact the water. The function of their enhanced appearance after seawater transfer is unknown.

van Ginneken, V. J., van Den Thillart, G. E., Muller, H. J., van Deursen, S., Onderwater, M., Visee, J., Hopmans, V., van Vliet, G., and Nicolay, K. (1999). Phosphorylation state of red and white muscle in tilapia during graded hypoxia: an in vivo (31)P-NMR study. Am J Physiol 277, R1501-12.
The aim of this study was to measure the energetic consequences of hypoxia in different types of skeletal muscle within a single tilapia species (n = 5). To that aim, 81.0 MHz (31)P-nuclear magnetic resonance (NMR) spectra were collected, alternately, from three surface coils placed adjacent to the tissues of interest (dorsal white muscle, ventral white muscle, and lateral red muscle) during a graded hypoxia load over 6 h followed by a 5-h recovery period. The fish were contained in a flow cell, enabling us full control of the oxygen content of the bathing medium. The intracellular pH and the concentrations of ATP, phosphocreatine (PCr), and P(i) were determined from the NMR spectra. For normoxia, biochemical differences for [gamma- ATP], [PCr], and [sugar phosphates] (SP) were observed between all three locations, especially between the red and white muscle. During hypoxia stress, loss of phosphorylated compounds (PCr+P(i)+SP) was observed at all locations but was the most severe in red muscle. When the aerobic (respirometry) and anaerobic ((31)P-NMR) ATP production via an energy balance are compared, flexible metabolic depression is demonstrated during anaerobioses. It is concluded that control of the aerobic and anaerobic component of metabolism during metabolic depression is independent of each other.

van Pittius, M. G., van Vuren, J. H., and Du Preez, H. H. (1992). Effects of chromium during pH change on blood coagulation in Tilapia sparrmanii (Cichlidae). Comp Biochem Physiol C 101, 371-4.
1. Tilapia sparrmanii was exposed to 0.098 mg/l potassium dichromate. 2. The effect of chromium on blood coagulation was measured with a thrombelastograph at a pH of 5, 7.4 and 9 over 96 hr, as well as an uncontrolled pH after 2 weeks of exposure. 3. The prolonged kinetic times and reduced maximal amplitudes at a pH of 7, 4 and 9, differed significantly from the control values. 4. Thrombelastograms reflected a decrease in the clotting ability of fish blood, with an increase in pH, which is typical of thrombocytopenia. 5. It was evident that the exposure of fish to chromium led to clotting defects that caused internal bleeding.

Verbost, P. M., Schoenmakers, T. J., Flik, G., and Wendelaar Bonga, S. E. (1994). Kinetics of ATP- and Na(+)-gradient driven Ca2+ transport in basolateral membranes from gills of freshwater- and seawater-adapted tilapia. J Exp Biol 186, 95-108.
Plasma membranes of the gills of freshwater- and seawater-adapted tilapia were analyzed for Ca(2+)-ATPase and Na+/Ca2+ exchange activity. The relative importance of ATP-driven and Na(+)-gradient-driven Ca2+ transport in Ca2+ extrusion was evaluated on the basis of kinetic analyses in vitro. The Na+/Ca2+ exchangers in branchial membranes from freshwater or seawater fish displayed similar kinetics. The ATP-driven Ca2+ pump, however, showed a somewhat lower affinity for Ca2+ in membranes isolated from seawater gills than in membranes from freshwater gills; no difference in Vmax was found. The activity of the exchanger was estimated to be 50% of that of the ATP-driven pump at prevailing cytosolic Ca2+ concentrations (10(-7) mol l-1). Opercular ionocyte densities and branchial Na+/K(+)-ATPase content were not significantly different in fish residing in fresh water or sea water. We conclude that the gills of tilapia living for prolonged periods in fresh water or sea water do not differ in the make-up of their basolateral membrane with regard to Ca(2+)-ATPase, Na+/Ca2+ exchange and Na+/K(+)-ATPase activity. Apparently, the densities of these carriers suffice for calcium and sodium homeostasis under these vastly different ambient conditions.

Vijayan, M., Morgan, J., Sakamoto, T., Grau, E., and Iwama, G. (1996). Food-deprivation affects seawater acclimation in tilapia: hormonal and metabolic changes. J Exp Biol 199, 2467-75.
We tested the hypothesis that nutritional state affects seawater acclimation by transferring either fed or food-deprived (2 weeks) male tilapia (Oreochromis mossambicus) from fresh water to full-strength sea water. Food-deprivation resulted in a significant increase in plasma concentrations of Na+, Cl-, cortisol, glucose, total amino acid, glutamate, serine and alanine, and in hepatic pyruvate kinase (PK) and lactate dehydrogenase (LDH) activities, whereas the prolactin-188 to prolactin-177 ratio (tPRL188:tPRL177) and plasma prolactin-188 (tPRL188), lactate, arginine and hepatic glycogen content and hepatic alanine aminotransferase (AlaAT) and 3-hydroxyacyl-Coenzyme A dehydrogenase (HOAD) activities were lower than in the fed group. Seawater transfer significantly increased the tPRL188:tPRL177 ratio and plasma concentrations of Na+, Cl-, K+, growth hormone (GH), glucose, aspartate, tyrosine, alanine, methionine, phenylalanine, leucine, isoleucine and valine levels as well as gill Na+/K+-ATPase activity and hepatic PK and LDH activities, whereas plasma tPRL177, tPRL188, glycine and lysine concentrations were significantly lower than in fish retained in fresh water. There was a significant interaction between nutritional state and salinity that affected the tPRL188:tPRL177 ratio and plasma concentrations of Cl-, GH, glucose, aspartate, tyrosine, serine, alanine, glycine, arginine and hepatic PK, LDH, AlaAT, aspartate aminotransferase, glutamate dehydrogenase and HOAD activities. These results, taken together, indicate that food-deprived fish did not regulate their plasma Cl- levels, despite an enhancement of plasma hormonal and metabolic responses in sea water. Our study also suggests the possibility that plasma prolactin and essential amino acids may be playing an important role in the seawater acclimation process in tilapia.

Villani, L. (1999). Development of NADPH-Diaphorase Activity in the Central Nervous System of the Cichlid Fish, Tilapia mariae. Brain Behav Evol 54, 147-158.
The distribution of nicotinamide adenine dinucleotide phosphate (NADPH)- diaphorase activity was studied in the cichlid fish Tilapia mariae during ontogenesis by the histochemical reaction of NADPH-diaphorase that indicates, in aldehyde-fixed tissue, the presence of nitric oxide synthase, which is the enzyme responsible for nitric oxide production. The first appearance of NADPH-diaphorase-positive neurons has a striking bilateral symmetry and occurs 20 h after fertilization (stage 8) in the olfactory placodes and in the neural tube where two clusters of positive neurons were seen in the diencephalon and in the rhombomere r4 of the hindbrain. Two days after fertilization (stage 10), the clusters of positive neurons showed labeled axons. The two longitudinal fiber bundles that arose from the diencephalic positive neurons ran caudally in the tract of the postoptic commissure. At stage 12 (3.5 days after fertilization), new populations of NADPH-diaphorase-positive neurons appeared in the telencephalon, in some diencephalic nuclei, and in the hypothalamus. Several trigeminal motor neurons showed strong NADPH-diaphorase activity, whereas the optic tectum and cerebellum were completely free of enzymatic activity. In the hindbrain, clusters of positive neurons were seen in the octavolateral region and in the region defined by the exit of the vagus nerve. In the cervical spinal cord, some ventral putative motor neurons were labeled. At stage 14 (5.5 days after fertilization), several periventricular neurons of the optic tectum and some neurons of the cerebellar lamina were labeled. Dorsal neurons, including a few large superficial neurons were also labeled in the cervical spinal cord. NADPH-diaphorase activity was seen in the neuropil area of the telencephalon, the target of olfactory inputs, and in the sensory dorso-lateral area of the spinal cord.

Villani, L. (1999). Developmental pattern of NADPH-diaphorase activity in the peripheral nervous sistem of the cichlid fish Tilapia mariae. European Journal of Histochemistry 43, 301-310.
The distribution of NADPH-diaphorase: activity was studied in the cichlid fish Tilapia mariae, during the first developmental stages by means of the tetrazolium salt technique. The reaction product was first found, 48 hours after fertilization (stage 10), in the cells of the olfactory placodes and in the superficial neuromasts. A faint positivity was Seen in some hair cells of the otic vesicles. The epithelial cells of the most caudal part of the intestinal tract showed a strong labeling. At stage 12 (hatch), the reaction product was in addition detected:in scattered enteric neurons surrounding the digestive tract. At stage 13 (4.5 days after spawning), the reaction product was also found in the putative sympathetic trunk, which supplies the gill arches and digestive tract. The epithelial cells of the gastrointestinal canal showed a more strong positive labeling and two large clusters of cells near the pronephritic tubules (the putative adrenomedullar tissue) were also labeled. The present results indicate an early activity of NADPH-diaphorase during the development of the peripheral nervous system of Tilapia and reveal a gradual maturation of NADPH-diaphorase positive structures.

Visoottiviseth, P., Thamamaruitkun, T., Sahaphong, S., Riengrojpitak, S., and Kruatrachue, M. (1999). Histopathological effects of triphenyltin hydroxide on liver, kidney and gill of Nile tilapia (Oreochromis nilotica). Applied Organometallic Chemistry 13, 749-763.
The histopathological effects of triphenyltin hydroxide (TPTH) on the liver kidney and gill of Nile tilapia (Oreochromis nilotica) one month old was studied by light microscopy, Two concentrations of TPTH were used: 1 mg l(-1) and 3 mg l(-1). The fish were sacrificed at the end of one, two, three and four months, The results showed that the hepatocytes underwent a variety of changes from congestion and dilatation of sinusoidal space, pallor of cytoplasm, vacuolation and accumulation of hyaline droplets, Subcapsular and scattered focal necrosis was also observed, In the kidney, hydropic degeneration and accumulation of hyaline droplets in the tubular epithelial cells were noted, In addition, a congestion of peritubular capillaries and detachment of tubular epithelial cells were observed. In more severe case there was a collapse of glomerular capillary tuft with a widening of the Bowman's capsule, There were some changes in the gill filaments and lamellae, namely hyperplasia of the covering gill epithelium, congestion of gill capillaries and vessels, and aneurysmal formation of gill lamellar capillaries. These alterations were time-and dose-dependent. Copyright (C) 1999 John Wiley & Sons, Ltd.

Vogel, W., Vogel, V., and Kremers, H. (1973). New aspects of the intrafilamental vascular system in gills of a euryhaline teleost, Tilapia mossambica. Z Zellforsch Mikrosk Anat 144, 573-83.

Vogel, W., Vogel, V., and Schlote, W. (1974). Ultrastructural study of arterio-venous anastomoses in gill filaments of Tilapia mossambica. Cell Tissue Res 155, 491-512.

Wang, H. C., Chen, J. D., Li, G. C., and Yew, F. H. (1989). Characterization of a heat-resistant strain of Tilapia ovary cells. J Cell Sci 92, 353-9.
Tilapia ovary cells (TO-2) cease to proliferate when moved from normal growth temperature of 31 degrees C to 37 degrees C, and arrest in G1 and G2 phases of the cell cycle. The ability of the arrested cells to re-enter the cell cycle when restored to 31 degrees C decreases inversely with time spent at 37 degrees C. A heat-resistant strain, TO- 37c, cloned from the surviving fraction of TO-2 after heat treatment, has been found to re-enter the cell cycle with greater facility and to have a higher rate of survival. TO-37c cells have a smaller cell volume than TO-2 and show a distinct morphology at 37 degrees C. Most of the heat-shock proteins (hsps) induced on temperature change were similar, but in TO-37c the decline in the synthesis of a 27 X 10(3) Mr hsp was faster and a 37 degrees C-specific 60 X 10(3) Mr hsp was missing. Ultraviolet (u.v.) sensitivity was slightly affected if heat treatment was given after irradiation. However, when cells were preheated and then u.v. irradiated, the u.v. sensitivity increased sharply for TO-2 cells but not for TO-37c.

Wang, W. S., and Wang, D. H. (1997). Enhancement of the resistance of tilapia and grass carp to experimental Aeromonas hydrophila and Edwardsiella tarda infections by several polysaccharides. Comp Immunol Microbiol Infect Dis 20, 261-70.
Efficacies of eleven polysaccharides including Bar (glycan extracted from Barley), curdlan, Dex (dextran sulfate), inulin, krestin, laminaran, levan, PO (glycan extracted from Pleurotus ostreatus), scleroglucan, YG (yeast glucan), and zymosan, in the protection of tilapia, Tilapia aureus P., and grass carp, Ctenopharyngodon idellus, against bacterial infections in vivo were examined. Four glycans. namely, Bar, krestin, scleroglucan, and zymosan were observed to significantly increase the survival rates of tilapia (80, 60, 70, and 60%) and grass carp (60, 70, 90, and 60%) (p 0.05) after injection with Aeromonas hydrophila. The above mentioned four glycans were also found to raise the survival rates of tilapia (70, 60, 80, and 50%) and grass carp (50, 50, 70, and 50%) (p 0.05) significantly after infection with Edwardsiella tarda. Moreover, Bar, curdlan, krestin, scleroglucan, and zymosan were also found to significantly increase the number of NBT-positive staining cells (p 0.05), which might indicate that to activate non-specific phagocytes in fish is one of the antibacterial mechanisms of polysaccharides.

Wang, L. H., and Tsai, C. L. (1999). Effects of gonadal steroids on the GABA and glutamate contents of the early developing tilapia brain. Brain Res Dev Brain Res 114, 273-6.
The effects of gonadal steroids on the gamma-aminobutyric acid (GABA) and glutamate (Glu) contents of the early developing brain were investigated. Seven-day-old (7 days post-hatch) tilapia were divided into three groups which were continuously treated with 100 mg/kg diet 17beta-estradiol (E2), 100 mg/kg diet methyltestosterone (MT), and a normal diet, respectively. Until 10, 20, and 30 days old, the GABA and Glu contents of the brains were detected by HPLC-ECD. The brain GABA and Glu contents, before 30 days old, significantly increased with age. These results demonstrate that before 30 days old is a developing period of both GABA and Glu systems in the tilapia brain. During this period, both E2 and MT have a facilitative effect on the GABAergic and Gluergic system during a restricted effective period. Copyright 1999 Elsevier Science B.V.

Wardhaugh, A. A. (1981). Dominant lethal mutations in Tilapia mossambica (Peters) elicited by myleran. Mutat Res 88, 191-6.
Tilapia mossambica (Peters) Teleostei, Cichlidae, is of commercial importance being farmed for human consumption. An effective means of sterilization would be of value since prolific breeding under farming conditions reduces growth rate. The possibility of using the antileukaemic drug myleran as a chemosterilant has been investigated previously, however the present study indicated that it can induce dominant lethal mutations in this species.

Warrier, S. B., Ninjoor, V., Sawant, P. L., Hirlekar, M. G., and Kumta, U. S. (1972). Differential release of latent lysosomal hydrolases in muscle of Tilapia mossambica by whole body gamma radiation. Indian J Biochem Biophys 9, 278-9.

Weber, G. M., Okimoto, D. K., Richman, N. H. d., and Grau, E. G. (1992). Patterns of thyroxine and triiodothyronine in serum and follicle-bound oocytes of the tilapia, Oreochromis mossambicus, during oogenesis. Gen Comp Endocrinol 85, 392-404.
This study describes simultaneous measurements of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), in the oocytes and serum of a female teleost fish over a complete reproductive cycle. We have identified patterns in circulating T4 and T3 levels as well as their accumulation into oocytes during the reproductive cycle of the tilapia (Oreochromis mossambicus). This is the first description of the patterns with which thyroid hormones accumulate in teleost oocytes. The sampling strategy used in the study eliminated the possible influences of covarying environmental factors that may affect thyroid hormone levels independently of reproductive events. Hormones in serum and oocytes were measured by radioimmunoassay utilizing miniature Sephadex columns. The total content of both thyroid hormones in the oocytes increased throughout most of the ovarian cycle as the oocytes increased in size from less than 2 mg to approximately 6.5 mg by ovulation. By contrast, concentrations of thyroid hormones in the oocytes rose only during the first third of post-spawning oocyte growth (up to approximately 2 mg) before attaining plateaus at approximately 6 ng/g for T4 and 13 ng/g for T3. Serum concentrations of T4 and T3 varied in cyclical patterns during oogenesis, dropping to lows of 3.4 ng/ml (T4) and 2.7 ng/ml (T3) when the oocytes were 1.5 and 2 mg, respectively, and then increasing to 6.5 ng/ml (T4) and 4.8 ng/ml (T3) when the oocytes reach approximately 6 mg. The concentrations of both hormones decreased shortly before spawning. Maximum concentrations of thyroid hormones in the oocytes were reached approximately 10 days prior to those in the serum. Although the serum levels of T4 were greater than those of T3, the reverse was found in the oocytes. Triiodothyronine appears to be accumulated selectively over T4 and the patterns with which both thyroid hormones accumulate in the oocytes of the tilapia do not appear to be tied to serum levels.

Weber, G. M., and Grau, E. G. (1999). Changes in serum concentrations and pituitary content of the two prolactins and growth hormone during the reproductive cycle in female tilapia, Oreochromis mossambicus, compared with changes during fasting. Comparative Biochemistry and Physiology C-Pharmacology Toxicology & Endocrinology 124, 323-335.
Patterns of change in serum concentrations and pituitary content of GH and two tilapia prolactins (PRL177 and PRL188) were examined during the reproductive cycle of female tilapia, Oreochromis mossambicus, adapted to fresh water and to seawater. Changes in these hormones during fasting were examined to elucidate whether changes observed during brooding could be attributed to a reduction in feeding during brooding. Serum concentrations of GH increased prior to pituitary content during the brooding phase of the reproductive cycle. In contrast, pituitary content of GH increased prior to serum concentrations during fasting. There was no consistent pattern of change in serum or pituitary PRL levels during the reproductive cycle, among experiments. Serum concentrations of PRL177 were elevated in all fasted fish, whereas PRL188 was elevated during fasting in males but not females. The increases in the serum concentration of PRLs and GH, and in the pituitary content of GH in response to fasting support the notion that these hormones are involved in the regulation of the use of metabolic substrates in tilapia. We conclude that reduced food intake during brooding may contribute to changes in serum and pituitary levels of the PRLs and GH observed during the reproductive cycle. Nevertheless, differences between changes in serum and pituitary GH during brooding and fasting suggest GH has actions in reproduction, and changes in GH during brooding are not only in response to fasting. (C) 1999 Elsevier Science Inc. All rights reserved.

Welch, T. J., Stauffer, J. R., Jr., and Morgan, R. P. d. (1989). Temperature preference as an indicator of the chronic toxicity of cupric ions to Mozambique tilapia. Bull Environ Contam Toxicol 43, 761-8.

Wepener, V., Van Vuren, J. H., and Du Preez, H. H. (1992). Effect of manganese and iron at a neutral and acidic pH on the hematology of the banded tilapia (Tilapia sparrmanii). Bull Environ Contam Toxicol 49, 613-9.

Wepener, V., van Vuren, J. H., and Du Preez, H. H. (1992). The effect of hexavalent chromium at different pH values on the haematology of Tilapia sparrmanii (Cichlidae). Comp Biochem Physiol C 101, 375-81.
1. The haematology of Tilapia sparrmanii (Smith) was investigated after exposure to 0.098 mg.l-1 hexavalent chromium at three different pH values. 2. Statistically significant changes occurred between the values of parameters of experimental and control fish. 3. At lower pH values erythrocytosis and leucocytosis were evident. 4. At an alkaline (9) pH anaemic and leucopenic conditions were observed. 5. T. sparrmanii adapted to chronic exposure to hexavalent chromium.

Wigham, T., Nishioka, R. S., and Bern, H. A. (1977). Factors affecting in vitro activity of prolactin cells in the euryhaline teleost Sarotherodon mossambicus (Tilapia mossambica). Gen Comp Endocrinol 32, 120-31.

Winfree, R. A., and Stickney, R. R. (1981). Effects of dietary protein and energy on growth, feed conversion efficiency and body composition of Tilapia aurea. J Nutr 111, 1001-12.
The optimum dietary protein to energy (P:E) ratio for rapid and efficient gain of juvenile Tilapia aurea was shown to fall with increasing size of fish. The optimum concentration of protein and energy also fell with growth. A diet providing roughly 56% protein at 4,600 kcal/kg digestible energy (gross energy adjusted for indigestible fiber) with a P:E ratio of 123 mg potential/kcal produced highest gains of fry (2.5 g). Larger fish (7.5 g) grew most rapidly when fed a 34% protein, 3,200 kcal/kg diet with a P:E ratio of 108. Apparent feed conversion (grams of feed offered/grams of fish weight gain) was superior on diets having lower P:E ratios and was best on the 34% protein, 3,200 kcal/kg diet. Linear regression analysis indicated highly significant differences in average fish weight, condition [10(5) x weight (g)/total length (mm)3], and feed conversion efficiency attributable to changes in either protein or energy concentration. Significant interaction between protein and energy was also demonstrated. Condition and level of carcass fat were high on all diets which produced good growth rates and were inversely related to P:E ratio. Moisture and ash were inversely related to carcass fat. No trend was established for carcass protein.

Wolf, J. C., and Smith, S. A. (1999). Systemic zygomycosis in farmed tilapia fish. J Comp Pathol 121, 301-6.
Decreased feed intake and persistent low-level mortality in a production tank of hybrid tilapia (Oreochromis niloticus x Oreochromis mossambicus x Oreochromis aureus) prompted the submission of three affected fish for diagnosis. Consistent macrosopical findings included multifocal dermal haemorrhage, excess abdominal fluid and an enlarged friable liver. On microscopical examination, broad non-septate fungal hyphae and chlamydospores were identified within numerous internal organs, often within and adjacent to blood vessels. The fungal hyphae were readily seen by silver staining (GMS) and the chlamydospores were stained deep magenta by the periodic acid-Schiff reaction. In addition to several species of Gram-negative bacteria, moderate growths of woolly white fungal colonies were obtained from the posterior part of the kidney in two of the three tilapia. These colonies were identified as a Rhizomucor sp. on the basis of the morphological characteristics of the sporulating fungi in culture. This represents the first reported episode of zygomycosis in fish. Copyright 1999 Harcourt Publishers Ltd.

Wood, C. M., Perry, S. F., Wright, P. A., Bergman, H. L., and Randall, D. J. (1989). Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment. Respir Physiol 77, 1-20.
The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2+ = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 degrees C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (less than 5% of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 mumol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85% ammonia-N and 15% urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33% upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 mumol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami is an evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.

Wood, C., Bergman, H., Laurent, P., Maina, J., Narahara, A., and Walsh, P. (1994). Urea Production, Acid-Base Regulation and Their Interactions in the Lake Magadi Tilapia, a Unique Teleost Adapted to a Highly Alkaline Environment. J Exp Biol 189, 13-36.
The Lake Magadi tilapia, Oreochromis alcalicus grahami, thrives in highly alkaline geothermal springs and pools surrounding Lake Magadi, Kenya (control pH=9.9, CCO2+=173 mmol l-1), has a functional hepatic ornithine&shy;urea cycle (OUC) and excretes all nitrogenous waste as urea-N at variable rates (JUrea) related to O2 consumption (M&middot;O2). The mean value of JUrea/M&middot;O2 (N/O2=0.183) was high for fish but below the theoretical maximum (approximately 0.27) for 100 % aerobic respiration of protein, so an exogenous source of substrates is not required to explain the observed JUrea. JUrea was insensitive to thiourea. Urea excretion occurred largely (80 %) through the gills, but urea-N was also present in bile and urine. Control blood pHe, pHi and [HCO3-] (approximately 8.1, 7.6 and 15 mmol l-1, respectively, at approximately 32&deg;C) were extremely high. When fish were exposed to lake water titrated with HCl and aerated to remove CO2+, N/O2 progressively declined. At a lake water pH of 7.05 and CCO2+ of 0 mmol l-1, N/O2 was reduced by 80 % and an intense metabolic acidosis occurred (pHe=7.04, [HCO3-]=1.5 mmol l-1). Restoration of control water pH 9.9 at a CCO2+ of 0 mmol l-1 resulted in intermediate levels of N/O2 and internal acid&shy;base status. Additional experiments confirmed that urea production was inhibited by low pHe, was dependent on blood [HCO3-] with a Km of 3.06 mmol l-1 and was insensitive to acetazolamide. While metabolic acidosis clearly inhibited OUC ureagenesis, the system appeared to be saturated with HCO3- under control conditions so that additional basic equivalent loading would not stimulate ureagenesis. Urea production in the Lake Magadi tilapia does not appear to remove exogenous HCO3- or to play a role in normal acid&shy;base regulation.

Wright, J. M. (1989). Nucleotide sequence, genomic organization and evolution of a major repetitive DNA family in tilapia (Oreochromis mossambicus/hornorum). Nucleic Acids Res 17, 5071-9.
A highly repetitive DNA sequence from tilapia (Oreochromis mossambicus/hornorum) has been cloned and sequenced. It is a tandemly arrayed sequence of 237 bp and constitutes 7% of the fish genome. The copy number of the repeat is approximately 3 x 10(5) per haploid genome. DNA sequence analysis of 7 cloned repeats revealed a high degree of conservation of the monomeric unit. Within the monomeric unit, a 9 bp AT rich motif is regularly spaced approximately 30 bp apart and may represent the progenitor of the amplified sequence. One cloned repeat, Ti-14, contained a 30 bp deletion at a position flanked by a 7 bp direct repeat. The Ti-14 sequence appears to have been amplified independently of the major 237 bp tandem array. A higher- order repeat unit, defined by longer-range periodicities revealed by restriction endonuclease digestion, is further imposed on the tandem array.

Wright, J. R., Jr., Polvi, S., and MacLean, H. (1992). Experimental transplantation with principal islets of teleost fish (Brockmann bodies). Long-term function of tilapia islet tissue in diabetic nude mice. Diabetes 41, 1528-32.
Certain teleost fish have macroscopically visible islets called BBs that are anatomically discrete. BBs were harvested from Oreochromis nilotica (tilapia) with microscissors, divided, and cultured overnight at 37 degrees C before transplantation into STZ-induced diabetic nude mice. Each mouse received BB fragments from 3-5 fish weighing in aggregate approximately 1.7 kg. Non-FPGs were monitored 5 days/wk. Recipients remained normoglycemic (plasma glucose 22.2 mM. Histological examination of graft-bearing kidneys showed viable, vascularized islet tissue containing numerous well-granulated beta-cells; examination of recipient native pancreases revealed small islets composed predominantely of non-beta-cells.

Wright, J. R., Jr., and Yang, H. (1997). Tilapia Brockmann Bodies: an inexpensive, simple model for discordant islet xenotransplantation. Ann Transplant 2, 72-5.
Brockmann bodies (BBs), large anatomically discrete islet organs found in some teleost fish, are much more easily harvested than pancreatic islets from mammalian donor sources. Tilapia islets, when transplanted into streptozotocin-diabetic athymic nude mice, will produce long-term normoglycemia and mammalian-like glucose tolerance profiles. Our laboratory has used tilapia BBs as an inexpensive model for studying islet xenograft rejection between discordant species. When transplanted into immunocompetent diabetic mice, tilapia BBs reject in roughly 7-8 days. Results to date suggest that tilapia islets are very immunogenic and that encapsulation is necessary to achieve long-term function in euthymic recipients. Continuous, high-dose immunosuppression using 15- DSG is also effective but causes lethal bone marrow suppression. Less aggressive immunosuppression regimens have achieved only modest prolongation of mean graft survival time. Thus far, immunomodulation techniques and transplantation into immune-privileged sites have been ineffective at prolonging graft survival. Tilapia islets currently represent an excellent, inexpensive donor source for discordant islet xenotransplantation studies. In the not distant future, encapsulated islets harvested from transgenic tilapia bearing humanized tilapia insulin genes may also play a role in establishing clinical islet xenotransplantation as a useful treatment modality for type I diabetes mellitus.

Wright, J. R., Jr., O'Hali, W., Yang, H., Han, X. X., and Bonen, A. (1998). GLUT-4 Deficiency and severe peripheral resistance to insulin in the teleost fish tilapia. Gen Comp Endocrinol 111, 20-7.
Teleost fish, in general, are glucose intolerant; this trait has been attributed to piscine islets secreting insulin primary in response to amino acid secretogogues rather than glucose. However, pancreatic islet from the teleost fish tilapia, when transplanted into diabetic nude mice, were glucose responsive even though tilapia were severely glucose intolerant. This suggested a strong peripheral resistance to the glucostatic effects of insulin. Using Western blotting with polyclonal antibodies as well as Northern analysis for mRNA, tilapia tissues were found to be devoid of GLUT-4, the insulin-sensitive glucose transporter responsible for the hypoglycemic effect of insulin in mammals. The absence of GLUT-4 in peripheral tissues may explain why tilapia, and possibly other teleost fish, are severely glucose intolerant. This suggests that tilapia islets have evolved along mammalian lines to be glucose sensitive while tilapia peripheral tissue have diverged widely. Using the same methods, tilapia were found to have a very limited tissue distribution of the insulin-independent glucose transporter, GLUT-1, which is responsible for basal glucose transport in mammalian cells. It is suggested that tilapia provide a naturally occurring GLUT- 4 knockout model.

Wright, J. R., Jr., Yang, H., and Dooley, K. C. (1998). Tilapia--a source of hypoxia-resistant islet cells for encapsulation. Cell Transplant 7, 299-307.
Encapsulation of pancreatic islets prevents graft revascularization after transplantation, resulting in graft hypoxia and attrition. Hypoxia-resistant islets would be ideal for encapsulation. Tilapia, a tropical teleost fish, have large, anatomically discrete islets that can be easily harvested without expensive, fickle islet isolation procedures and that provide mammalian-like glucose tolerance profiles when transplanted into diabetic recipients. Because tilapia can live in stagnant water, we speculated that tilapia islets might tolerate lower oxygen tensions than mammalian islets. Tilapia and rat islets (n = 30) were placed in paired 60-mm Petri dishes containing 10 mL of deoxygenated CMRL-1066 media and cultured together in sealed chambers gassed with 95% N2/5% CO2+. Islet viability was determined by fluorscein diacetate/ethidium bromide staining at intervals varying from 2.5 h to 7 days; blood gas measurements were obtained on media samples at the end of selected incubation intervals. Rat islets underwent near-total necrosis and fragmentation in 24 h; occasional viable single cells could be identified until about 72 h. On the other hand, the fish islets showed no loss of viability until about 72 h when some showed mild central necrosis. Even at 7 days, all fish islets appeared roughly 50% viable. Fish islets cultured under hypoxic conditions for 72 h (media, pO2 = 27.8 mmHg) and then transplanted into streptozotocin- diabetic athymic nude mice were viable (6/6) but showed some diminished function (3/6) over a 25-day follow-up period. Our results suggest that tilapia islets will survive and function at lower oxygen tensions than mammalian islets.

Wright, J. R., Jr., Abraham, C., Dickson, B. C., Yang, H., and Morrison, C. M. (1999). Streptozotocin dose-response curve in tilapia, a glucose-responsive teleost fish. Gen Comp Endocrinol 114, 431-40.
Streptozotocin (STZ) causes beta cell necrosis and insulin-dependent diabetes in many species. The specificity of this beta cell toxin relates to its structure as an alkylating agent with an attached glucose moiety. STZ uptake by rodent beta cells appears to be via the GLUT-2 glucose transporter. Teleost fish, in general, are severely glucose intolerant. The effects of STZ were examined in tilapia, a teleost fish with highly glucose-responsive islets. Fasted tilapia were given 0, 100, 150, 200, 250, 300, or 350 mg/kg STZ iv. Plasma glucose levels were followed for 72 h and the fish autopsied. Histological sections of islets were stained by immunoperoxidase for tilapia insulin. Severe hyperglycemia was seen in 20, 80, and 100% of fish receiving 250, 300, and 350 mg/kg doses; however, sections of islets showed only partial degranulation with no evidence of beta cell necrosis. Another group of fish receiving the highest dose were followed longer to determine whether beta cell necrosis and permanent hyperglycemia ensued. All fish died or were killed within 9 days because of severe hepatic failure characterized by hepatic necrosis, jaundice, and ascites; islet morphology was relatively normal suggesting, even in a glucose-sensitive species, that fish islets either do not take up STZ or are highly resistant to its "diabetogenic" effects. Tilapia may thus be a useful model to elucidate mechanisms of action of STZ. Furthermore, STZ may provide important insights into differences in glucose uptake and metabolism by mammalian and piscine beta cells. Copyright 1999 Academic Press.

Wu, S. M., Weng, C. F., Yu, M. J., Lin, C. C., Chen, S. T., Hwang, J. C., and Hwang, P. P. (1999). Cadmium-inducible metallothionein in tilapia (Oreochromis mossambicus). Bull Environ Contam Toxicol 62, 758-68.

Wu, Y. V., Tudor, K. W., Brown, P. B., and Rosati, R. R. (1999). Substitution of plant proteins or meat and bone meal for fish meal in diets of Nile tilapia. North American Journal of Aquaculture 61, 58-63.
Five experimental diets containing plant proteins and synthetic amino acids with and without fish meal or meat and bone meal were fed to Nile tilapia Oreochromis niloticus averaging 13 g for 84 din aquaria. Each experimental diet contained 20% corn gluten meal, 34-40% high-lysine corn, 29-36% soy grits, 0 or 6% fish meal or meat and bone meal, and supplemented with synthetic lysine, tryptophan, and threonine. There were no significant differences (P > 0.05) in weight gain, feed conversion ratio, and protein efficiency ratio for Nile tilapia fed the all plant protein diet, the fish meal diets with two levels of fat, the meat-and-bone-meal diets with two levels of fat, and the commercial diet containing fish meal and meat and bone meal. Thus, substitution of plant proteins or meat and bone meal for fish meal in Nile tilapia diets did not affect growth response.

Yada, T., Hirano, T., and Grau, E. G. (1994). Changes in plasma levels of the two prolactins and growth hormone during adaptation to different salinities in the euryhaline tilapia, Oreochromis mossambicus. Gen Comp Endocrinol 93, 214-23.
Studies were undertaken to determine whether the adaptation of the tilapia, Oreochromis mossambicus, to different salinities was accompanied by changes in plasma levels of growth hormone (GH) and its two prolactins (tPRL177 and tPRL188). Transfer from fresh water to 70% seawater (22 ppt) produced significant increases in plasma GH levels in males, but not in females. Both tPRLs decreased by the first sampling interval (6 hr) after transfer to seawater in both sexes. A second group of tilapia were adapted gradually to seawater (32 ppt) and were maintained in seawater for an additional 2 weeks. The fish were then transferred from seawater to fresh water. The transfer to fresh water induced a significant decline in plasma GH levels in both males and females. Both tPRLs increased within 6 hr after transfer to fresh water in both sexes. Then, plasma tPRL177 levels decreased gradually. By contrast, tPRL188 continued to increase and attained its highest levels 3 days after transfer to fresh water. These findings show that blood levels of the two tPRLs change rapidly during freshwater and seawater adaptation. The fact that tPRL177 and tPRL188 levels followed distinctly dissimilar patterns as freshwater acclimation proceeded suggests that the secretion and/or metabolic clearance of the two PRLs may be differentially regulated. The changes in GH which occurred when tilapia were moved between fresh water and seawater are compatible with the idea proposed by others for salmonids that GH may have an important role for seawater adaptation.

Yagi, K., and Bern, H. A. (1965). Electrophysiologic analysis of the response of the caudal neurosecretory system of Tilapia mossambica to osmotic manipulations. Gen Comp Endocrinol 5, 509-26.

Yamada, S., Tanaka, Y., and Furuichi, M. (1995). Partial purification and characterization of histidine acetyltransferase in brain of Nile tilapia (Oreochromis niloticus). Biochim Biophys Acta 1245, 239-47.
High activity of histidine acetyltransferase (HISAT) was found in the brain and the lens of Nile tilapia Oreochromis niloticus. HISAT was semi-purified 4166-fold from the brain of Nile tilapia. The affinity chromatography using a Blue Sepharose 6 FF column was very effective for purification of this enzyme. The enzyme had a broad pH optimum from pH 7.0 to pH 9.5, and did not require any divalent metal ion. The semi- purified HISAT showed a strict substrate specificity for L-histidine (and its methyl derivatives) and acetylcoenzyme A (CoASAc). The reaction velocity fits normal Michaelis-Menten kinetics with respect to both L-histidine (Km, 0.45 mM) and CoASAc (Km, 0.027 mM). Gel filtration on Superdex 200 HR indicated the molecular weight of 39,000. It was presumed that the 38.5 kDa protein, which was intensely visualized in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was a single subunit derived from HISAT.

Yamaguchi, K., Specker, J. L., King, D. S., Yokoo, Y., Nishioka, R. S., Hirano, T., and Bern, H. A. (1988). Complete amino acid sequences of a pair of fish (tilapia) prolactins, tPRL177 and tPRL188. J Biol Chem 263, 9113-21.
The complete amino acid sequences of a pair of tilapia (Oreochromis mossambicus) prolactins (PRLs) were determined. The larger PRL of molecular mass 20,836 Da consists of 188 amino acid residues. The smaller PRL of molecular mass 19,584 Da is 11 residues shorter. On alignment of the two sequences, the 19.6-kDa PRL (tPRL177) has two conspicuous deletions on the NH2-terminal side of the disulfide bond which connects the first and second cysteine residues. The degree of similarity between the two PRL sequences is unexpectedly low (130 identical residues, 69%) compared with that between the variants of other teleostean PRLs. Circular dichroism spectra and hydropathy profiles suggest structural similarity of the two PRLs. The sequence of the 20.8-kDa PRL (tPRL188) has 69% identity with that of salmon PRL. The sequence of tPRL177 is 56% identical with that of salmon PRL. Each tilapia PRL is equally similar to mammalian PRLs (about 30% identical residues). Regions highly conserved among teleostean and mammalian PRLs were identified on the COOH-terminal side of the disulfide bond connecting the first and second cysteine residues.

Yamaguchi, K., King, D. S., Specker, J. L., Nishioka, R. S., Hirano, T., and Bern, H. A. (1991). Amino acid sequence of growth hormone isolated from medium of incubated pituitary glands of tilapia (Oreochromis mossambicus). Gen Comp Endocrinol 81, 323-31.
The amino acid sequence of tilapia (Oreochromis mossambicus) growth hormone (GH) was determined directly by Edman degradation of peptide fragments generated by lysyl endopeptidase and trypsin digestion. The N- terminal residue was deduced to be pyroglutamic acid through the use of pyroglutamyl aminopeptidase; its removal allowed amino acid sequence determination of the remainder of the N-terminal trypsin peptide by Edman degradation. Tilapia GH is composed of 187 amino acid residues and shows high similarity to other perciform GHs. Sequence identities are: 89% with tuna GH, 83% with bonito GH, 85% with yellowtail GH, 89% with red sea bream GH, and 34% with bovine GH. The two asparagine residues (Asn-148 and Asn-184) were recovered by Edman degradation, suggesting the absence of N-glycosylation.

Yan, S. Y., Mao, Z. R., Yang, H. Y., Tu, M. A., Li, S. H., Huang, G. P., Li, G. S., Guo, L., Jin, G. Q., He, R. F., and et al. (1991). Further investigation on nuclear transplantation in different orders of teleost: the combination of the nucleus of Tilapia (Oreochromis nilotica) and the cytoplasm of Loach (Paramisgurnus dabryanus). Int J Dev Biol 35, 429-35.
The nucleus of a blastula cell from Tilapia (Oreochromis nilotica, family Cichlidae, order Perciformes) was transplanted into an enucleated egg of Loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes). From among 3747 nucleo-cytoplasmic hybrid (NCH) eggs two NCH larval fish (0.05%) were obtained; one died on the 6th day and the other died on the 12th day after the operation. Morphological examinations showed that both NCH larval fish had developed normally with an opened mouth except they could not take food after complete utilization of their egg yolk on the 5th day of development. The possible mechanisms for obtaining such inter-order NCH larval fish are discussed. This is the first report indicating that inter-order NCH larval fish can be obtained in spite of their evolutionary divergence.

Yang, H., Morrison, C. M., Conlon, J. M., Laybolt, K., and Wright, J. R., Jr. (1999). Immunocytochemical characterization of the pancreatic islet cells of the Nile Tilapia (Oreochromis niloticus). Gen Comp Endocrinol 114, 47-56.
The cellular composition and topography of the pancreatic islet of Oreochromis niloticus, now known to be a donor source for islet xenotransplantation studies, were characterized. Whole tilapia islets were harvested using an enzymatic method and then further digested into single-cell preparations. Cell cytospin preparations of islet cells and paraffin sections of whole islets were stained using antisera against tilapia insulin, human glucagon, salmon somatostatin-25 (SST-25), human somatostatin-14 (SST-14), and salmon peptide tyrosine-tyrosine (PYY) using the immunoperoxidase method. Cell counts, performed on cytospin preparations using a Quantimet 570 computerized image analysis system, revealed that O. niloticus islets contained 78% endocrine cells and 22% immunonegative cells (i. e., mainly nucleated erythrocytes and rare tissue eosinophils). The proportions of immunopositive endocrine cell types were: 42.3% insulin immunopositive cells, 11.5% glucagon immunopositive cells, 23.1% SST-25 immunopositive cells, 21.8% SST-14 immunopositive cells, and 1.3% PYY immunopositive cells. Islet cell topography was evaluated using histologic sections of whole endocrine pancreata including large, medium, and small islets. Round to polygonal insulin immunopositive cells with round central nuclei were distributed in clusters throughout both the principal and the smaller islets. Elongate SST-14 immunopositive cells were closely associated with the clusters of insulin immunopositive cells; both were surrounded by SST- 25 immunopositive cells, which were similar in shape to the insulin immunopositive cells. There were elongate glucagon immunopositive cells throughout the islets, whereas the PYY immunopositive cells were restricted to the periphery and to channels of fibrovascular connective tissue penetrating the islets. Copyright 1999 Academic Press.

Yaron, Z. (1966). Demonstration of 3-beta-hydroxysteroid dehydrogenase in the testis of Tilapia mossambica (Cichlidae, Teleostei). J Endocrinol 34, 127-8.

Yaron, Z. (1971). Observations on the granulosa cells of Acanthobrama terrae-sanctae and Tilapia nilotica (Teleostei). Gen Comp Endocrinol 17, 247-52.

Yaron, Z., Terkatin-Shimony, A., Shaham, Y., and Salzer, H. (1977). Occurrence and biological activity of estradiol-17 beta in the intact and ovariectomized Tilapia aurea (Cichlidae, Teleostei). Gen Comp Endocrinol 33, 45-52.

Yaron, Z., and Levavi-Sivan, B. (1990). Intracellular events associated with GnRH and dopamine effects on GTH secretion in tilapia. Prog Clin Biol Res 342, 409-14.

Yew, F. H., and Chang, L. M. (1984). DNA replication and repair in Tilapia cells. I. The effect of ultraviolet radiation. J Cell Sci 72, 213-26.
The effect of ultraviolet radiation on a cell line established from the warm water fish Tilapia has been assessed by measuring the rate of DNA synthesis, excision repair, post-replication repair and cell survival. The cells tolerate ultraviolet radiation better than mammalian cells with respect to DNA synthesis, post-replication repair and cell survival. They are also efficient in excision repair, which in other fish cell lines has been found to be at a low level or absent. Their response to the inhibitors hydroxyurea and 1-beta-D- arabinofuranosylcytosine is less sensitive than that of other cell lines, yet the cells seem to have very small pools of DNA precursor.

Yi, Y. (1999). Modeling growth of Nile tilapia (Oreochromis niloticus) in a cage-cum-pond integrated culture system. Aquacultural Engineering 21, 113-133.
A bioenergetics model was developed to simulate growth of both caged and open-pond Nile tilapia in a cage-cum-pond integrated culture system. The model incorporated six key variables affecting Nile tilapia growth in the cage-cum-pond integrated culture system: body size, water temperature, photoperiod, dissolved oxygen, unionized ammonia and food availability. Caged tilapia were given artificial feed, while growth of open- pond tilapia was dependent on uneaten artificial feed from the caged tilapia and natural foods derived from cage wastes. In the model, availability of natural foods was estimated by a relative feeding level parameter, which was a function of potential net primary productivity based on fish standing crop and the limiting nutrients in the ponds. The model was validated using growth data for both caged and open-pond tilapia in 28 ponds. The model described 96 and 85% of the variance in growth of caged and open-pond tilapia, respectively. Statistical analyses indicated significant agreements between predicted and observed values for both cage and open-pond systems. The model showed that the growth of open-pond tilapia was limited by phosphorus limiting primary production when the total number of tilapia stocked in cages was not greater than 200 fish pond(-1), beyond which the limiting nutrient was phosphorus at the beginning of experiments and then shifted to nitrogen. The percentages of the culture period during which nitrogen limitation occurred increased from 0 to 84.4% with the increase of artificial feed inputs. The model revealed nitrogen from biological nitrogen fixation accounted for 44.2-74.8% of total nitrogen available for primary production. Under the model assumptions, pelleted feed accounted only for 13.8-14.6% growth of open-pond tilapia when dissolved oxygen was above the critical limit (1.2 mg 1(- 1)) for caged tilapia during entire experimental period, however, the percentages ranged from 19.0 to 51.0% when dissolved oxygen was below this critical limit. Sensitivity analysis showed that parameters for caged tilapia affected growth of open-pond tilapia but not the reverse, and lowering water quality by decreasing dissolved oxygen or raising unionized ammonia for 10% further reduced growth of caged tilapia, but increased growth of open-pond tilapia. (C) 1999 Elsevier Science B.V. All rights reserved.

Yildiz, H. Y., and Pulatsu, S. (1999). Evaluation of the secondary stress response in healthy Nile tilapia (Oreochromis niloticus L.) after treatment with a mixture of formalin, malachite green and methylene blue. Aquaculture Research 30, 379-383.
To determine the effects of exposure to a mixture of formalin, malachite green and methylene blue (FMC) on the secondary stress indices, changes in glucose, phosphorus, calcium, magnesium, sodium, potassium and haematocrit were monitored in healthy Nile tilapia, Oreochromis niloticus L. Fish were exposed separately to varying concentrations of a mixture of formalin, malachite green and methylene blue (0.1, 0.5 and 1 p.p.m.) for 1, 10 and 60 min. In general, treatment of fish with FMC elicited marked elevations of plasma glucose. Plasma phosphorus levels dropped after FMC treatment. In fish exposed to FMC, calcium levels in general were lower than those of the controls. Magnesium levels were not influenced by FMC treatment. Plasma sodium and potassium levels showed an unclear pattern for differing FMC concentrations and exposure times. Haematocrit values were affected by FMC treatment.

Yoshimoto, M., Albert, J. S., Sawai, N., Shimizu, M., Yamamoto, N., and Ito, H. (1998). Telencephalic ascending gustatory system in a cichlid fish, Oreochromis (Tilapia) niloticus. J Comp Neurol 392, 209-26.
Central fiber connections of the gustatory system were examined in a percomorph fish Oreochromis (Tilapia) niloticus by means of the horseradish peroxidase (HRP), biocytin, and carbocyanine dye tracing methods. The primary gustatory areas in tilapia are the facial, glossopharyngeal, and vagal lobes of the medulla. The secondary gustatory nucleus (SGN) is a dumb-bell-shaped structure located in the isthmic region. In the SGN, there are two or three layers of neurons lining the ventromedial periphery of the nucleus and a molecular layer constituting of the major part of the nucleus. The SGN receives bilateral projections from the facial lobes and ipsilateral projections from the glossopharyngeal and vagal lobes. Ascending fibers originating from the SGN form the ipsilateral tertiary gustatory tract. A major part of the tract courses rostrally and terminates ipsilaterally in several diencephalic nuclei: the preglomerular tertiary gustatory nucleus (pTGN), the posterior thalamic nucleus, the nucleus diffusus lobi inferioris, the nucleus centralis of inferior lobe, and the nucleus recessus lateralis. The remaining small fiber bundle enters the medial and lateral forebrain bundles and terminates directly in two telencephalic regions; the area ventralis pars intermedia (Vi) and the area dorsalis pars posterior (Dp). Ascending fibers from the pTGN pass through the lateral forebrain bundle and terminate ipsilaterally in the dorsal region of area dorsalis pars medialis (dDm) of the telencephalon. Following biocytin injections into the dDm, small, round cells were labeled in the pTGN. After biocytin injections into the Vi and Dp of the telencephalon, retrogradely labeled cells were found in the ipsilateral SGN. The results show that the ascending fiber connections of the central gustatory system in the percomorph teleost tilapia are essentially similar to those of mammals. That is, the pathway from the primary gustatory areas (facial, glossopharyngeal, and vagal lobes) through the SGN and pTGN to the dDm in tilapia corresponds with the mammalian gustatory pathway from the solitary nucleus through the pontine taste areas (nucleus parabrachialis) and the thalamic relay nucleus (ventral posteromedial nucleus) to gustatory neocortices. In addition, the pathway from the primary gustatory areas through the SGN to the Vi and Dp in tilapia corresponds with the pathway from the solitary nucleus through the pontine taste areas to the amygdala in mammals.

Young, P. S., McCormick, S. D., Demarest, J. R., Lin, R. J., Nishioka, R. S., and Bern, H. A. (1988). Effects of salinity, hypophysectomy, and prolactin on whole-animal transepithelial potential in the tilapia Oreochromis mossambicus. Gen Comp Endocrinol 71, 389-97.
We have examined whether two recently isolated forms of tilapia (Oreochromis mossambicus) prolactin exert similar effects on osmoregulatory physiology. The effects of salinity, hypophysectomy, and replacement therapy with tilapia prolactins on whole-animal transepithelial potential (TEP), gill Na+, K+-ATPase activity, and plasma ions were determined. When intact fish adapted to 25% seawater (SW) were transferred to different salinities, TEP reached a steady state after 10 hr; TEP increased with increasing salinity from fresh water (FW) to 75% SW but was stable from 75 to 125% SW. Plasma osmolality, [Na+], and [Cl-] of these fish 24 hr after salinity change showed that fish in 100 and 125% SW had greater osmotic perturbation than those transferred to lower salinities. Following a 5-day recovery period in 25% SW, hypophysectomized fish transferred to FW for 10 hr had significantly lower TEP and plasma ion levels than either sham- operated fish or intact fish under the same conditions. Injection of hypophysectomized fish with "small" prolactin (tPRL177), "large" prolactin (tPRL188), or a combination of both (0.5 micrograms/g body weight) 22 hr and again 20 min prior to transfer from 25% SW to FW, restored TEP and plasma ion levels to those of sham-operated fish. Neither prolactin affected the TEP or plasma ions of sham-operated (intact) fish. Hypophysectomized fish had lower gill Na+,K+-ATPase activity than sham-operated fish in FW, but prolactin injections as described above did not affect gill Na+,K+-ATPase activity in either hypophysectomized or sham-operated fish. Our results indicate that the two forms of prolactin are indistinguishable with regard to several aspects of tilapia osmoregulation.

Youssef, M., Mansour, N. S., Hammouda, N. A., Awadalla, H. N., and Boulos, L. M. (1981). Effect of freezing and drilling on Pygidiopsis genata metacercariae in Tilapia. J Egypt Soc Parasitol 11, 425-8.

Zaki, M. S., Hassan, Y. M., and Rahma, E. H. (1976). Technological studies on the dehydration of the Nile bolti fish (Tilapia nilotica). Nahrung 20, 467-74.
Chemical and microbiological analysis of bolti fish: moisture, chloride, fat, total volatile bases (T.V.B.), thiobarbituric acid value (T.B.A.), total bacterial count and coliforms were estimated in fresh bolti fish, after brining, drying and during storage at room temperature for 3 months. The moisture content decreased after drying but become stable during the storage period. Chloride increased after bringing but no noticeable changes were observed after drying and during 3 months storage. The fat content was not affected by previously processes. T.V.B. and T.B.A. increased after brining, drying and throughout storage period. The rate of increase was higher for dehydrated samples than for sun-dried ones. The reduction of total bacterial count is due to the high salt content and the lack of free water in fish tissues after drying. Coliforms were not present after brining, drying and throughout the storage periods.

Zaki, M. S., El Mansy, H. A., Hassan, Y. M., and Rahma, E. H. (1976). Effect of nisin in saturated brine and storage on the quality of dried bolti fish (Tilapia nilotica). Nahrung 20, 691-7.
Bolti fish which had been eviscerated and brined in a saturated brine containing 0.5 mg nisin/g of fish for 10, 15 and 20 min, were divided into two parts, one for dehydration and the second for sun-drying. The dried products were packed in polyethylene bags and stored at room temperature for 3 months. The quality attributes were estimated during processing and monthly during storage. Total volatile bases showed a certain increase after salting, drying and throughout storage periods; thiobarbituric acid value gave the same trend, total microbial load showed a slight increase during storage, but coliform bacteria were not present after salting.

Zambrano, D., Clarke, W. C., Hawkins, E. G., Sage, M., and Bern, H. A. (1973). Influence of 6-hydroxydopamine on hypothalamic control of prolactin and ACTH secretion in the teleost fish, Tilapia mossambica. Neuroendocrinology 13, 284-98.

Zein, G. N., el-Bedawey, A. E., el-Sherbiney, A. M., and Dawoud, F. M. (1985). Studies on fish protein concentrate and fish meal from river Nile bolti fish (Tilapia nilotica). Nahrung 29, 523-32.
Fish protein concentrate (FPC) from river Nile bolti fish (Tilapia nilotica) was prepared and compared with commercial FPC and fresh bolti fish flesh. Fish meal (FM) from bolti fish offals was prepared and compared with commercial FM and also fresh bolti fish flesh. FPC from bolti fish showed a higher crude protein content but less fat, ash, calcium and sand than the commercial sample, while FM from bolti fish showed a higher content of ash and phosphorus than commercial FM but was nearly similar in crude protein, fat, calcium and sodium chloride. FPC from bolti fish had a higher content of lysine, arginine, aspartic acid, glycine and glutamic acid and a lower content of the other free amino acids. The bolti fish FM had a lower content of total amino acids and the contents of the free amino acids cysteine, glycine, aspartic acid, serine, alanine, valine, and methionine increased slightly. The yield was 12% for FPC and 19.5% for FM. Coliform bacteria were not present in both FPC and FM from bolti fish. Low moisture contents of FPC and FM were essential for preventing microbiol growth and to attain a good keeping quality. The FPC and FM from bolti fish reached moisture equilibrium and stopped increasing in weight within 144 to 192 h.

Zhou, H. Y., Cheung, R. Y., and Wong, M. H. (1999). Residues of organochlorines in sediments and tilapia collected from inland water systems of Hong Kong. Arch Environ Contam Toxicol 36, 424-31.
The levels and patterns of organochlorines including DDTs, HCHs, and PCBs were investigated in sediments and tilapia (Tilapia mossambica) collected from inland water systems [Tai Wai (S1), Fo Tan (S2), Siu Lek Yuen (S3), Tai Po (S4), and Tai Wo (S5)] in the New Territories of Hong Kong. Sediment and tilapia samples were also collected from two fish ponds for comparison. The ranges of DDTs, HCHs, and PCBs in river sediments were 2.82-8.63 ng/g (DW), 0.05-2.07 ng/g (DW), and 43-461 ng/g (DW), respectively. All these values were significantly higher (p 0.05) than the pond sediments. Low chlorinated congeners (especially mono-, tri-, and tetrachlorobiphenyls) were enriched in sediment samples accounting for 70-80% of total PCBs. The ranges of DDTs, HCHs, and PCBs in tilapia muscle collected from Fo Tan and Tai Wai were 28.2- 40.1 ng/g (DW), 2.04-3.76 ng/g (DW) and 267-310 ng/g (DW), respectively. These values were also significantly higher (p 0.05) than those collected from the fish ponds. Higher chlorinated PCBs (tetra-, penta-, hexa-, and heptachlorobiphenyls) were commonly found in tilapia accounting for almost 60% of the total PCBs. The effect of lipid contents in organochlorines accumulation was not significant (p 0.05) in general.