Meeting Abstract

15.5  Sunday, Jan. 4  Kinematics and hydrodynamics among ranid and pipid frogs RICHARDS, Christopher T.*; BIEWENER, Andrew A.; Harvard University richards@fas.harvard.edu

Recent work has addressed hindlimb kinematics of swimming frogs in the context of muscle function and hydrodynamics. However, there are no detailed studies linking time-varying joint kinematics with the propulsive function of anuran feet. This study explores how individual frogs vary the thrust produced by their feet by modulating joint kinematics to achieve a range of swimming speeds. Rana pipiens and Xenopus laevis frogs were filmed at high speed. A blade element model was used to estimate hydrodynamic forces on the feet. Swimming velocities ranged from 4.4 to 25.1 body lengths/s (BL/s) in R. pipiens, similar to 2.5 to 24.0 BL/s in X. laevis. However, the relative contributions of translational and rotational velocity to total foot velocity differed between species; peak translational velocity was 65.9 7.0% of peak total foot velocity in R. pipiens, versus 32 8.0% in X. laevis (mean S.D for N=26 and 23 strokes). Likewise, translational foot motion contributed 69.3 9.0% of total thrust impulse in R. pipiens versus 1.1 21.0% in X. laevis, revealing a fundamental difference in locomotor strategy between the two species, despite their similar range of swimming velocities. The joint kinematics that govern the patterns of translational and rotational foot velocity will be explored to understand how hindlimb coordination varies within and among anuran species to control swimming performance.