Scaling the feeding mechanism of largemouth bass (Micropterus salmoides): kinematics of prey capture

We present the first analysis of scaling effects on prey capture kinematics of a feeding vertebrate. The scaling of feeding kinematics of largemouth bass (Micropterus salmoides) was investigated using high-speed video (200 fields s-1) to determine what functional changes occur in the feeding mechanism as a consequence of body size. A size series of ten bass ranging from 32 to 210 mm standard length was used for the study and ten feeding sequences from each individual were analyzed to quantify movements of the feeding apparatus during prey capture. Maximal linear and angular displacements of the strike scaled isometrically. The time course of the strike was longer in larger fish. Maximal velocities of displacement were more rapid in larger fish, but their scaling exponents indicated that the intrinsic rate of muscle shortening decreased with fish size. Morphological measurements of the lever arms of the lower jaw and of the two major muscles that drive the feeding mechanism were made to relate possible biomechanical changes in the feeding mechanism to the observed kinematic relationships. The lever arms of the lower jaw and the muscles scaled isometrically; hence, the relative slowing of movements with increasing body size cannot be attributed to changes in mechanical advantage with change in body size. The scaling of feeding kinematics in the largemouth bass is in accord with the scaling of rates of muscle contraction found in other lower vertebrates. These findings demonstrate that body size can have major effects on feeding kinematics and that future comparative studies of feeding kinematics should use empirical data on size effects in kinematic comparisons between taxa.