Meeting Abstract

94.5  Saturday, Jan. 7  Three-dimensional model of force transmission in the suction feeding system of seahorses VAN WASSENBERGH, S.; Univ. Antwerpen, Antwerpen

Seahorses and other sygnathid fishes rely on a quick increase in the volume of the snout to suck prey into the mouth. This volume increase is observed as snout widening due to abduction of the suspensoria, the bones outlining the lateral sides of the snout. However, in contrast to other fishes, the start of suction is postponed until completion of the dorsal rotation of the neurocranium, a movement that brings the mouth close to the prey. In addition, the hyoid, which is generally considered the most important transmitter of force to the suspensoria in fish, rotates over more than 90 degrees in the sagittal plane during feeding in seahorses. This is considerably higher than what’s observed in all other suction feeders studied so far. To explain how seahorses abduct the suspensoria, we performed mathematical simulations with a model of force transmission via the hyoid and lower jaw. This analysis was based on three-dimensional reconstructions of the anatomy of the feeding system of the long-snout seahorse Hippocampus reidi, together with high-speed video data on hyoid and lower jaw rotation during prey capture in this species. Our results show an important role for the inclined orientation of the hinge joint between the left and right ceratohyals, and suggest that force transmission also occurs via the lower jaw to produce suction in seahorses. The function of the peculiar arrangement of the three separate connections between the hyoid and the lower jaw in this process will be discussed as well.