Meeting Abstract

50.2  Tuesday, Jan. 5  The head-down posture of seahorses: an adaptation for pivot feeding? VAN WASSENBERGH, S.*; ROOS, G.; AERTS, P.; Univ. Antwerpen, Antwerpen; Univ. Antwerpen, Antwerpen; Univ. Antwerpen, Antwerpen sam.vanwassenbergh@ua.ac.be

Syngnathid fishes capture prey by rotating their head quickly towards prey, and subsequently sucking it into their snout. Previous studies showed that head pivoting is driven by elastic recoil of the epaxial muscle tendons. However, not only the head moves during pivot feeding in syngnathids: the head pushes off against the anterior part of the trunk, which is displaced in the opposite direction. Since the position of the trunk relative to the head is unique (for a fish) in some species of Syngnathidae (e.g. seahorses, seadragons), this could have consequences (or even be an adaptation) for pivot feeding. To study the effects of several mechanical characteristics of the head and trunk during pivot feeding, a forward dynamic model of a pipefish (closely resembling the ancestral condition) and a seahorse (phylogenetically most derived condition) was developed using Matlab-Simulink. In all simulations, an equal amount of elastic energy is released to actuate the joint between head and trunk. Increasing the pipefish’s head-to-trunk orientation from parallel to perpendicular changes the path traveled by the mouth to become more distant from the initial location of the eyes, which increases the volume of water around the eye in which the synganthid fish can strike at prey. In addition, the head-to-body angle of our seahorse model appeared to be optimized for this variable (eye to prey distance), which could imply that the head-to-body posture of seahorses may have evolved for this purpose.