92.3 Saturday, Jan. 7 A comparative examination of forelimb kinematics and muscle function during rowing and flapping-style swimming in four species of turtle RIVERA, A.R.V.; Florida Atlantic University, Boca Raton email@example.com
Evolution has resulted in a diverse array of limb-based locomotor strategies. Changes in muscle activation patterns can lead to new locomotor strategies. Aquatic turtles are an excellent group in which to test for such changes because species typically use one of two general swimming styles (rowing or flapping), both of which depend exclusively on limb-based propulsion. Whereas all sea turtles swim using synchronous flapping of foreflippers, all but one freshwater turtle swims using asynchronous rowing of the limbs. The one exception, Carettochelys insculpta, has converged on a flapping-like style of swimming using synchronous motions of foreflippers. To examine how different forelimb motions are produced across species with generally similar muscle arrangements, I compared high-speed video and electromyographic (EMG) data from four species, including C. insculpta and the sea turtle Caretta caretta, as well as specialized and generalized rowing in Apalone ferox (sister taxa to C. insculpta) and Trachemys scripta, respectively. My study provides the first opportunity to evaluate whether the two ‘flapping’ lineages have converged on similar limb kinematics and/or motor patterns, and by including A. ferox and T. scripta, provides a test of whether ‘phylogenetic relatedness’ or ‘locomotor strategy’ better predicts forelimb kinematics and motor patterns. My findings indicate that ‘flapping’ in Carettochelys is only superficially similar to flapping in Caretta, and is, in fact, more similar to rowing. My data indicate a general conservation of motor patterns across the species. However, the deltoideous serves a new function in sea turtles; interestingly, C. inscultpa, with its intermediate kinematics, exhibits deltoideous activity intermediate to rowers and flappers.