70.3 Jan. 7 The forces exerted by suction feeders on their prey DAY, SW*; WAINWRIGHT, PC; Rochester Inst. of Tech.; Univ. of California, Davis firstname.lastname@example.org
Suction feeders feed by generating a flow of water that quickly transports prey into their mouth. All of the forces that the predator exerts on the prey item are caused by this temporally and spatially varying water flow. Because successful prey capture depends on the predator overcoming any movements and forces that the prey uses to escape, the nature and magnitude of these forces is key to a full understanding of suction feeding performance. We identify three forces associated with the generated flow field: drag, acceleration reaction and the pressure gradient force. Using a simple mathematical model parameterized with empirical data from feeding bluegill we explore the relative magnitude of these forces under three encounter scenarios: an immobile mid-water prey, a similar prey that executes an escape response, and a prey that grips a substratum. In all three scenarios the pressure gradient is the largest of the three forces. However, the relative magnitude of the forces varied in the different scenarios, indicating that inferences about the nature of forces experienced by prey must be made with reference to the conditions surrounding the interaction. The historical tendency to ignore the pressure gradient when considering forces generated by suction feeders results in severe underestimates of the forces experienced by the prey. Our simulations suggest that suction feeders can enhance the forces that they exert by increasing the pressure gradient that prey are exposed to. This can be accomplished temporally – doubling the rate of increase in fluid velocity doubles force due to the pressure gradient, or spatially – halving the size of the mouth and maintaining a constant fluid velocity at the mouth opening doubles the magnitude of the pressure gradient force experienced by a prey item at the mouth aperture. Supported by NSF IOB-0610310.