WILGA, C.D.; SANFORD, C.P.; University of Rhode Island, Kingston; Hofstra University, Hempstead, NY: Suction Generation In Bamboo Sharks

Prey capture by suction is the result of rapid expansion of head, hyoid and branchial elements that draws water, and any prey contained therein, into the mouth. Although recent studies have increased our understanding of suction generation during feeding in teleosts, similar studies on elasmobranch fishes are lacking. In this study, the kinematics of selected internal head and hypobranchial structures in whitespotted bamboo sharks, Chiloscyllium plagiosum, were measured using sonomicrometry to quantify those elements that are directly responsible for internal expansion of the orobranchial cavity, and therefore the generation of suction inflow. Simultaneous pressure readings were also recorded either internally inside the orobranchial cavity or externally at the prey item to assess pressure flow at strategically important locations in a feeding event. Preliminary results indicate that pressure in the hyoid region decreases rapidly as the mouth opens and peak subambient pressures are usually reached well before peak lower jaw and hyoid depression are achieved. Branchial expansion appears to drive subambient pressure flow from the buccal cavity towards the branchial regions. Similarly, hyoid depression appears to be responsible for drawing the prey into the mouth from the surrounding fluid. Pressure is rapidly attenuated outside of the mouth, pressure readings at the prey site, immediately before the mouth; reach only a fraction of the pressure inside the orobranchial chamber. Sonomicrometry reveals that the hyoid-ceratohyal joint is drawn anteriorly during feeding. A compressive preparatory phase may also occur prior to the expansive phase. A major advantage of sonomicrometry is continuous quantification of moving structures that are not visible externally or have moved out of camera view.