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.