Morphological basis of kinematic diversity in feeding sunfishes

Abstract

The effects of differences among species in the scaling of lower jaw levers on the scaling of prey-capture kinematics are explored in three species of centrarchid fishes. We consider the jaw opening and closing lever systems and calculate the consequences of differences in the scaling of the in-levers for the scaling of the time taken to open the mouth (T(o)) and the time taken to close the mouth (T(c)) during prey capture. Predictions of T(o) and T(c), based on differences in the scaling of jaw in-levers, are compared with the observed scaling of T(o) and T(c) in three centrarchid fishes. Video recordings (200 and 400 images s(-)(1)) were made of prey capture in largemouth bass Micropterus salmoides (33-206 mm standard length, SL), spotted sunfish Lepomis punctatus (24-145 mm SL) and bluegill sunfish Lepomis macrochirus (24-220 mm SL), and the fastest values of T(o) and T(c) were taken from the fastest recorded feeding event for each fish. The scaling exponents of T(o) and T(c) regressed on fish SL for largemouth bass were 0.592 and 0.572, respectively. Exponents observed for sunfishes were not significantly different from predicted values, based on scaling exponents in largemouth bass and interspecific differences in jaw lever proportions. Two conclusions are emphasized. First, between 25 and 220 mm SL, the time taken to open and close the mouth during the strike increases with body size in all three species, suggesting a general pattern for this family. Second, evolutionary changes in jaw lever mechanics are a major determinant of the diversity of prey-capture kinematics in this sample of centrarchid fishes.