AZIZI, E.*; LANDBERG, T.; WASSERSUG , R.J.; Brown Univ., Providence, RI; Univ. of Connecticut, Storrs, CT; Dalhousie Univ., Halifax, Canada and Univ. of Hamburg, Germany: Trunk mechanics during tadpole locomotion

Anuran larvae show large lateral oscillations at both the tip of the tail and the snout while swimming in a straight line. Although the lateral deflections at the snout have long been considered an inefficient aspect of tadpole locomotion, a recent hydrodynamic model suggests that they may in fact help generate thrust. It is not clear though where this bending takes place. The vertebral column is extremely short and seemingly inflexible in anurans, and any axial flexion that might occur there is hidden within the globose body of the tadpole. Here we test the hypothesis that axial bending occurs along the vertebral column of tadpoles and drives the lateral oscillation of the snout during swimming. We used sonomicrometry to measure the instantaneous curvature of the presacral vertebral column of four bullfrog tadpoles (Rana catesbeiana ) during swimming. In each individual, three sonomicrometry crystals were surgically implanted along the dorsal midline in locations corresponding to the cranial, middle, and caudal region of the presacral vertebral column. Swimming trials were conducted in a flume where synchronized video was collected in dorsal view. Our results confirm the presence of lateral flexion during swimming and indicate that vertebral curvature is temporally in phase with lateral oscillation of the snout. The maximum vertebral curvature increases significantly with increasing lateral oscillation of the snout. Similarly, the maximum vertebral curvature also increases significantly with increasing tail beat amplitude. Our results indicate that the vertebral column and associated trunk musculature within the torso of tadpoles, contribute significantly to the undulatory swimming of anuran larvae.