COUPLED VERSUS UNCOUPLED FUNCTIONAL-SYSTEMS - MOTOR PLASTICITY IN THEQUEEN TRIGGERFISH BALISTES-VETULA

Teleost fishes typically capture prey with the oral jaws and perform m ost types of prey-processing behavior with the pharyngeal jaw apparatu s. In these fishes, the motor patterns associated with the different s tages of feeding are quite distinct, and fish can modify muscle activi ty patterns when feeding on different prey. We examined motor pattern variation in the queen triggerfish, Balistes vetula, a versatile preda tor that both captures and processes prey with its oral jaws. During f eeding on three prey that differed in hardness and elusiveness, three distinct patterns of behavior could be identified on the basis of patt erns of muscle activity: prey capture, buccal manipulation and blowing . During prey capture by suction feeding, the retractor arcus palatini muscle (RAP) commenced activity before the levator operculi muscle (L OP). In both buccal manipulation and blowing, the RAP began activity w ell after the onset of activity in the LOP. Both prey capture and bucc al manipulation motor patterns varied when fish fed on different prey. When capturing hard-shelled and non-elusive prey, B. vetula did not e mploy suction feeding but, instead, the fish directly bit parts of its prey. The motor pattern exhibited during direct biting to capture pre y was different from that during suction feeding, but was indistinguis hable from the pattern seen during the repeated cycles of buccal manip ulation. Harder prey elicited significantly longer bursts of activity in the jaw adductor muscles than did soft prey. In spite of the involv ement of the oral jaws in virtually all stages of feeding, B. vetula s hows levels of variation between patterns of behavior and types of pre y characteristic of previously studied teleost fishes. Thus, the coupl ing of capture and processing behavior patterns in the repertoire of t he oral jaws does not appear to constrain the behavioral versatility o f this species.