Meeting Abstract
Suction feeding across the vast diversity of acanthomorph fishes is thought to involve a highly stereotyped sequence of movements. Yet, previous research suggests that seahorses and pipefish may be an exception. They use their long snout in a unique form of ram prey capture whereby rapid dorsal head rotation brings the mouth close to prey. In addition, it has been shown that they power amplify their strikes, making them some of the fastest fish feeders in the ocean. But how different are the strikes of seahorses and pipefish compared to their close relatives and other acanthomorph suction feeders? To address this, high-speed videos of strikes on live prey were collected from lineages across the syngnathiform tree (pipefish, trumpetfish, snipefish, and razorfish) and compared to typical suction feeding outgroups. The contributions of head rotation, body ram, jaw protrusion and suction to prey capture were quantified using vector analysis, and timing of key events in suction feeding were compared. We find that syngnathiform strikes rely on dorsal head rotation to bring the mouth close to prey; this is the largest component of movement toward prey in all syngnathiforms, while it is near zero in typical suction feeders. In syngnathiforms, onset of hyoid rotation occurs simultaneously with (or even just before) onset of head rotation, a pattern that has never been reported in any other teleost. Rearrangement of kinematics across syngnathiforms points to a novel roll of the hyoid in the suction feeding mechanism that is not unique to seahorses and pipefish but most likely evolved at the base of the syngnathiform tree. In addition, we propose that simultaneous onset of hyoid rotation with head elevation supports the role of the hyoid as a potential trigger for fast head rotation in syngnathiforms.
