Meeting Abstract

LBS1.3  Thursday, Jan. 3  Asynchrony in paired muscle motor activity GERRY, S.P.**; RAMSAY, J.B.; WILGA, C.D.; University of Rhode Island; University of Rhode Island; University of Rhode Island sgerry@mail.uri.edu

Many studies of feeding behavior have implanted electrodes unilaterally to determine the basic motor patterns of jaw muscles. However, bilateral implantation has the potential to achieve a more comprehensive understanding of modification or alteration of the motor activity that may be occurring between the left and right sides of the head. Complex prey processing, based primarily on studies of derived vertebrates, is often characterized by unilateral activation of the jaw musculature. An investigation of the evolution of asynchronous activation in species from four major groups of elasmobranchs (Squaliformes, Orectolobiformes, Carchariniformes, Rajoidea) demonstrates several methods of prey processing and associated muscle activation patterns. Electrodes were implanted in three of the jaw adductors, two divisions of the quadratomandibularis and the preorbitalis, as well as in a cranial elevator in sharks, epaxialis. Species from all four groups use synchronous activation (no difference in onset of activity) of bilateral muscle pairs during prey capture. The two functional specialists, Chiloscyllium plagiosum and Mustelus canis, use synchronous activation during prey processing whereas the two generalists, Squalus acanthias and Leucoraja erinacea, modulate activity by prey type. Furthermore, S. acanthias uses alternating asynchrony during head-shaking and L. erinacea uses complete unilateral activation. These differences in jaw muscle activity would not have been detected with unilateral implantation. Therefore, we advocate the incorporation of more bilateral studies of muscle function with skeletal kinematics that have the potential to increase our understanding of the function and evolution of musculoskeletal systems. Additionally, there appears to be a behavioral or ecological basis to these patterns.