JANOVETZ, J.: Feeding in Serrasalmine Fishes: A Comparison of Suction and Biting Prey Capture

Most fishes capture prey by suction feeding, rapidly expanding the oral cavity to create an inward flow of water that transports prey into the mouth. This type of prey capture is primitive for osteichthyes and has been the subject of considerable research. Other forms of prey capture can provide a valuable contrast to this behavior but have received less attention. Biting is the dominant form of feeding in a wide variety of fishes including parrotfishes, triggerfishes, and characins of the subfamily serrasalminae (pacus, silver dollars, and piranhas). This study examines the trophic anatomy and kinematics of prey capture in a variety of serrasalmine species to correlate morphology and feeding behavior with natural diet. Measurements of jaw lever mechanics were used to compare the biological design of the feeding system. Jaw lever ratios ranged from approximately .3- .5 within the subfamily. Species that primarily bite seeds or pieces from animal prey tend to have lever mechanics emphasizing force production while species that feed on scales or whole fish have lever mechanics emphasizing velocity of jaw closing. To compare feeding behaviors, pacus (Piaractus), piranhas (Pygocentrus), and silver dollars (Metynnis) were filmed with high-speed video while capturing prey by either suction or biting. Relative to suction feeding, biting was characterized by lower values for gape, gape cycle time, and hyoid depression. These data suggest that biting is a distinct method of feeding and that serrasalmine fishes can modify prey capture according to prey type. NSF DEB 9815614; ONR N000149910184.