Sound production during feeding in Hippocampus seahorses (Syngnathidae)

While there have been many anecdotal reports of sounds produced by Hippocampus seahorses, little is known
about the mechanisms of sound production. We investigated clicking sounds produced during feeding strikes
in H. zosterae and H. erectus. Descriptions of head morphology support the idea that feeding clicks may
represent stridulatory sounds produced by a bony articulation between the supraoccipital ridge of the neurocranium
and the grooved anterior margin of the coronet. Analysis of high-speed video and synchronous
sound recordings of H. erectus indicate that the feeding click begins within 1-2 msec of the onset of the rapid
feeding strike (4 msec mean duration). Surgical manipulations of the supraoccipital-coronet articulation resulted
in a decreased proportion of feeding strikes that produced clicks. This study provides several lines of
evidence in support of the hypothesis that feeding clicks in Hippocampus seahorses are stridulatory in origin
and are produced by the supraoccipital-coronet articulation. Our results are not consistent with previous
suggestions that sounds may be produced by cavitation due to rapid pressure changes within the buccal cavity
during the feeding strike.