Meeting Abstract

P3.63  Jan. 6  Comparative kinematics of convergent forelimb flapping behaviors: Swimming in Carettochelys insculpta and Caretta caretta RIVERA, A.R.V.*; WYNEKEN, J.; HAGEN, C.; BLOB, R.W.; Clemson University; Florida Atlantic University; Savannah River Ecology Lab; Clemson University arivera@clemson.edu

Though most freshwater turtles possess relatively small, paddle-like forelimbs, the forelimb morphology of Carettochelys insculpta (pig-nosed turtle) is more similar to that of distantly related sea turtles, in which the forelimbs are hypertrophied into long, flattened flippers. The swimming motions of C. insculpta also have been described as broadly resembling those of sea turtles which swim using synchronous flapping movements of the forelimbs rather than the asynchronous rowing strokes of the fore and hind limbs used by most freshwater species. Although superficially similar to the movements of sea turtles, limb kinematics have not been quantified in C. insculpta, making the extent of convergence between these independently evolved flapping behaviors uncertain. To evaluate the similarity of forelimb flapping movements in these taxa, we measured forelimb kinematics from high-speed video of C. insculpta and loggerhead sea turtles (Caretta caretta) swimming in still water. Both C. insculpta and C. caretta show limited anteroposterior movements of the forelimbs, in contrast to the primarily anteroposterior movements seen in most freshwater turtles. However, at least at slow speeds, thrust-generating movements of the forelimb in Carettochelys are accomplished primarily through extension and flexion of the elbow, rather than by abduction and adduction of the humerus as in C. caretta. Thus, despite being qualitatively similar, these independently evolved behaviors are achieved through quantitatively different patterns of joint movement.