P1.109 Wednesday, Jan. 4 Comparative adductor mandibula architecture and muscle fiber type composition within Cyprinidae MULLER, LJ*; STAAB, KL; HERNANDEZ, LP; George Washington University email@example.com
The adductor mandibula complex of fishes has long been of interest to functional morphologists interested in feeding. In basal teleosts this muscle serves only to close the jaws, while in more derived species (characterized by the evolution of separate divisions) the adductor mandibulae may also serve an important role in premaxillary protrusion. Indeed previous research has shown that contraction of the A1 division of cypriniform fishes is important in kinethmoid-mediated premaxillary protrusion. Thus given the importance of this division of the adductor mandibula in cypriniform feeding there may be greater variation in architecture of this division as compared with that of the other divisions. Significant research effort has been expended in examining the comparative morphology of this muscle mass within perciform fishes, however less data exist for cypriniform fishes. Moreover, very little comparative data exist for muscle fiber type distribution for many fish groups. Muscle fiber type is inherently related to muscular function, so muscle fiber type composition may be an important determinant of feeding ecology. Here we examine not only the relative architecture of the divisions of the adductor mandibulae, but also determine muscle fiber composition and distribution patterns within ten genera of cypriniform fishes. Using standard immunohistochemistry with a number of discrete myosin antibodies we have characterized fiber type composition within a number of cypriniform species with greatly differing trophic habits. We were especially interested in testing whether there was greater variation in fiber type in the A2 division (responsible for lower jaw adduction, and thus biting) versus the A1 division (responsible for premaxillary protrusion, and thus suction feeding).