Food capture kinematics of the suction feeding horn shark, Heterodontus francisci

Abstract

The goal of this study was to examine the feeding kinematics of the horn shark, Heterodontus francisci, a member of the most basal clade of galeomorph sharks, the Heterodontiformes. The accessibility of the food was manipulated to determine if the horn shark modulated capture. Three different methods of presenting food were used to mimic the different positions of prey items found in the natural diet of the horn shark. Food was presented unattached to the substrate, securely attached, or fitted snugly in a tube. Using high-speed video kinematic analysis, capture events were examined. Heterodontus francisci uses inertial suction facilitated by rapid mandible depression and labial cartilage protrusion to capture food. The horn shark conforms to a capture kinematic profile characteristic of both basal and derived inertial suction feeding sharks. Unusual post-capture behaviors include body leveraging, use of the mouth to form a seal over food, and chisel-like palatoquadrate protrusion. When presented with food of different accessibility, Heterodontus francisci used one consistent kinematic pattern for capture that was not modulated. Only post-capture behaviors varied according to food accessibility.