Meeting Abstract

45.4  Sunday, Jan. 5 11:00  The allometry of tongue-flicking mechanics in colubrid snakes RYERSON, WG*; SCHWENK, K; University of Connecticut william.ryerson@uconn.edu

Oscillatory tongue-flicking in snakes enhances the rate of diffusion of odorant molecules onto the mucus covering the tongue, which is then delivered to the vomeronasal organ. The multiple oscillations of the tongue generate a unique airflow pattern, with two pairs of standing, counter-rotating vortices, one above the other. The vortices pull previously unsampled air in from the sides, jetting it vertically upward and downward into the path of the oscillating tongue, refreshing the supply of odorant molecules to be sampled. We have shown previously that this airflow pattern maximizes the rate of molecular transfer of volatile chemicals onto the tongue tips for vomeronasal sampling. Using high speed video and DPIV, we explored the mechanics of tongue-flicking in five species of colubrid snakes: northern black racer (Coluber constrictor); northern water snake (Nerodia sipedon); eastern garter snake (Thamnophis sirtalis); northern ringneck snake (Diadophis punctatus); and Dekay’s brown snake (Storeria dekayi). All snakes generated the same pattern of vortices, but with different kinematic profiles. The largest snakes (C. constrictor) have a smaller tongue relative to body size, fewer oscillations per flick (3-4), and a lower tongue tip velocity (1 m/s). The smallest snakes (S. dekayi) have larger tongues relative to body size, more oscillations per flick (9-11), and a higher tongue tip velocity (3 m/s). Given the nearly identical fluid dynamic outcomes in all species, despite differences in tongue kinematics suggests that tongue size, velocity, and number of oscillations interact in a way to maintain the generation of vortices and optimization of molecular sampling. Tongue size and tongue tip velocity, and oscillation number all scale negatively with body size. It may be necessary to maintain a similar Reynolds number in order to generate the observed airflow pattern.