SGER: Biomechanics of Suction Feeding in Teleost Fishes

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SGER: Biomechanics of suction feeding in teleost fishesPeter C. Wainwright, Angela Cheer, and Harry A. DwyerUniversity of California, DavisThis research will investigate the mechanics of aquatic suction feeding, the most widespread method of aquatic prey capture used by vertebrate animals. Suction feeding is found in at least some members of every major group of tetrapods, and is the principal prey capture mechanism used by teleost fishes. The behavior involves the explosive expansion of the mouth and oral cavity to accelerate water and prey into the mouth. The aim of this research is to use a new method to visualize and measure the water flows generated by fishes during suction feeding. The lack of existing data on suction feeding flows is due to the considerable difficulty of visualizing and measuring water flow in biological systems. These flows are the focus of this research proposal because they exert forces on prey, transporting them to the predator and determine the success of suction feeders. Understanding the spatial and temporal pattern of water flow generated by suction feeders and how they exert forces on prey is the key to understanding the mechanics of suction feeding and its broader biology. Digital Particle Image Velocimetry (DPIV), a technology that permits the visualization and quantification of water motion, will be developed as a tool for studying suction feeding in experiments with a focal species, the bluegill sunfish, Lepomis macrochirus. DPIV will be used in conjunction with measurements of suction pressure and ultrasound of skull movements to address three issues. First, what are the magnitudes of the forces exerted on prey during suction feeding and what is the relative importance of drag and the acceleration reaction in generating these forces? Preliminary calculations with a computational fluid dynamics model indicate that acceleration reaction, a previously ignored force that is generated by flows of changing velocity, may outpace the more familiar drag forces. Demonstrating an important role for acceleration reaction would greatly alter the picture of forces that are experienced by prey, and may help to explain the explosive nature of suction feeding, one of the fastest feeding behaviors seen among vertebrate animals. Second, the quantitative relationship between suction pressure and the flow velocities that are generated during prey capture will be determined. This relationship will be used to test the widely held assumption that peak suction flows are proportional to peak suction pressure. Third, the temporal and spatial patterns of flow velocity during suction feeding will be measured. This will establish the critical area and time-course of predator-prey interactions and provide a benchmark for future comparative studies.This research represents a novel application of DPIV technology in studies with live aquatic organisms that has not previously been applied to feeding behavior. Developing this method presents significant challenges associated with animal training and visualization of flow close to moving jaw structures. The risk of attempting to establish this new method for research on suction feeding is justified because of the fundamental nature of flow data to understanding suction feeding mechanics. Measuring the spatial and temporal pattern of flow velocity is a key to inferring forces and hence suction feeding performance. This research project will establish a new technology for studying suction feeding and will contribute to a deeper understanding of a major step in vertebrate evolution. A greater knowledge of suction feeding will broaden our insights into the relationship between skull design and biomechanics in teleost fishes. Broader impacts of this project include the application of unsteady flows in surgical suction devices. This research will also provide training for a postdoctoral researcher who is bridging engineering and biology disciplines.