WAINWRIGHT, P.C.: The role of motor patterns in the evolution of fish feeding performance.

How are fish feeding mechanisms modified during evolution to produce diversity in feeding ability and feeding ecology? In particular, are feeding motor patterns always altered in conjunction with biomechanical changes of muscle-skeleton linkages? Studies of the evolution of fish feeding mechanisms have consistently yielded two very different answers to the latter question. The origin of novel trophic habits can be associated with considerable modification of the motor pattern that drives feeding behavior. This occurs when the new prey type is captured or processed using a new behavior or mechanism. Examples include the origin of mollusc crushing in several groups of teleosts, and the origin of algae scraping in parrotfishes. Alternatively, a number of independent, quantitative interspecific comparisons of the motor patterns used in prey capture by fishes have found that the average value of burst duration and onset time of homologous muscles does not vary significantly across species. This is true even in some cases where the jaw mechanics, feeding performance and patterns of prey use of the species differ considerably. I suggest that this evolutionary conservation of motor patterns does not represent a constraint on the malleability of the neuromuscular system. There is abundant evidence that motor patterns can readily be altered and that they are under fine control by individual fish. Rather, conservation of a functional trait that is inherently quite flexible suggests that altering it is neither effective nor necessary for modifying feeding performance. Some trophic radiations may thus involve extensive morphological changes with consequences for linkage mechanics and prey capture kinematics, but with few concomitant changes to the motor patterns that control feeding.