SCALING THE FEEDING MECHANISM OF LARGEMOUTH BASS (MICROPTERUS-SALMOIDES) - KINEMATICS OF PREY CAPTURE

We present the first analysis of scaling effects on prey capture kinem atics of a feeding vertebrate. The scaling of feeding kinematics of la rgemouth bass (Micropterus salmoides) was investigated using high-spee d 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. Maxi mal linear and angular displacements of the strike scaled isometricall y. The time course of the strike was longer in larger fish. Maximal ve locities of displacement were more rapid in larger fish, but their sca ling 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 thefeeding m echanism were made to relate possible biomechanical changes in the fee ding mechanism to the observed kinematic relationships. The lever arms of the lower jaw and the muscles scaled isometrically; hence, the rel ative slowing of movements with increasing body size cannot be attribu ted to changes in mechanical advantage with change in body size. The s caling of feeding kinematics in the largemouth bass is in accord with the scaling of rates of muscle contraction found in other lower verteb rates. These findings demonstrate that body size can have major effect s on feeding kinematics and that future comparative studies of feeding kinematics should use empirical data on size effects in kinematic com parisons between taxa.