Meeting Abstract

75.2  Sunday, Jan. 6  Dynamics of head rotation in feeding pipefish and seahorses VAN WASSENBERGH, S*; AERTS, P; Universiteit Antwerpen; Universiteit Antwerpen

A recent study showed that the extremely high speed at which pipefish (Fam. Syngnathidae) are able to rotate their snout towards prey and capture it by suction is probably caused by a catapult-like mechanism in which energy previously stored in the tendons of the post-cranial muscles is suddenly released. The evidence for this result was partly based on a relatively simple inverse-dynamical model, which divides the head of the syngnathid fish into a series of elliptical cylinders. By solving an equation of motion that takes into account steady-state drag forces, added mass and inertia of the segmented head, the instantaneous power required from the muscle-tendon complexes can be calculated. However, because of the extremely unsteady nature of the cranial movement during prey capture in these fishes (accelerations exceeding 105 rad s-2), the accuracy of this relatively simple model may be limited. To evaluate this, computational fluid dynamics (CFD) simulations of pipefish and seahorse heads rotating at velocity profiles measured from high speed videos were performed. Since the instantaneous force outputs from both models (elliptical cylinder model and CFD) matched satisfactory, these data confirm the previous result that a catapult-like mechanism is involved during prey capture in syngnathid fish.