Meeting Abstract

57.6  Jan. 6  Kinematics of level terrestrial and underwater walking in the California newt, Taricha torosa ASHLEY-ROSS, M.A.*; LUNDIN, R.; JOHNSON, K.L.; Wake Forest University rossma@wfu.edu

Although fossil evidence indicates that the tetrapod limb predated the move onto land, underwater locomotion involving the limbs, and how it might differ from locomotion on land, is poorly understood. We therefore quantified the movements of the body axis and limbs of the California newt, Taricha torosa, during steady-speed walking on a treadmill, and walking on a level surface while submerged in water. Angles describing the lateral flexion of the trunk, rotation of the limb girdles, and protraction/ retraction of the humerus and femur were measured in two dimensions, while angles between the humerus and forearm, between the femur and the crus, and between the various limb segments and the treadmill surface, were measured in three dimensions. Treadmill walking in Taricha demonstrated a kinematic pattern similar in its general aspects to level walking in other sprawling tetrapods; newts used a diagonal couplets lateral sequence walk with a duty factor of 77%. When submerged, the footfall pattern was altered to a diagonal couplets diagonal sequence trot, with a duty factor of 40%, and more variable timing of footfalls. Underwater walking included periods of suspension, made possible by the buoyancy of the water. In comparison to treadmill walking, submerged walking was characterized by reduced movements of the pectoral girdle, and greater extension of the limbs during all parts of the stride. Comparison of level locomotion (both environments) with walking on an incline (up and down) in and out of water demonstrated differences in the relative contribution of the axial systems (trunk bending and limb girdle rotation) versus limb movements in generating forward progression; the limbs contribute more in level walking, while the axial systems provide more of the propulsion on an incline.