Meeting Abstract

P2.72  Monday, Jan. 5  Conservation of muscle activation patterns in the forelimbs of swimming turtles: A comparison of three lineages (Trionychidae, Emydidae, Cheloniidae) RIVERA, A.R.V.*; WYNEKEN, J.; BLOB, R.W.; Clemson University; Florida Atlantic Unversity; Clemson University arivera@clemson.edu

Tetrapod limbs exhibit a diverse range of forms. Correlated with the evolution of this diversity, new locomotor styles might arise through changes in anatomy, changes in the patterns of muscle activation that produce limb motion, or some combination of both. Turtles are an excellent lineage in which to test for such changes because of their diverse locomotor styles and morphologies. Although most freshwater turtles swim using asynchronous anteroposterior rowing motions of the limbs, sea turtles swim via synchronous dorsoventral flapping of forelimbs modified as flippers. To test how such different forelimb motions are produced among groups with generally similar muscle arrangements, we compared high-speed video and electromyographic (EMG) data from swimming softshell turtles (Apalone ferox, an aquatic specialist from the basal trionychid clade) and red-eared sliders (Trachemys scripta, a generalized Emydid) to data from the derived, flipper-shaped forelimbs of loggerhead sea turtles (Caretta caretta). Despite being aquatic specialists and possessing extensively webbed forelimbs, softshell turtles show muscle activation patterns and kinematics that generally resemble those of sliders. Some differences emerge between these species and sea turtles, but all three species also show markedly similar motor patterns for some forelimb muscles despite their kinematic differences. These data indicate that some motor patterns have been conserved in the evolution of turtle limb function despite major evolutionary changes in anatomical structure.