Meeting Abstract
Undulatory locomotion is ubiquitous across scales. A well-studied system is the nematode C. elegans, which moves through propagation of dorsoventral waves of body curvature. Surprisingly few studies have focused on the worm’s control of these waves to generate effective interactions in its natural environment (e.g. rotting fruit). In contrast, progress has been made in discovery of control principles in undulatory macroscopic systems (e.g. snakes, snake-like robots) that move in complex terrain. We posit that environmental interactions from frictional/yielding surfaces and rigid heterogeneities are similar in dissipative macroscopic and microscopic systems. To discover if similar control principles for undulatory locomotion in heterogeneous landscapes exist across scales, we studied a habitat generalist snake, P. guttatus, a desert specialist snake, C. occipitalis, and the mm-long C. elegans traversing sparse lattices of rigid cylindrical posts, a model of heterogeneous terrain. Snakes were tested in hexagonal arrays of 0.64 cm diameter posts on a low-friction board. Unlike P. guttatus which modulates body shape to generate appropriate reaction forces using the posts, C. occipitalis adheres to a simple wave which we hypothesize generates propulsion via a random but opportunistic post use. Experiments on C. elegans, conducted in fluid-filled PDMS lattices of comparable scaled dimensions, revealed that the worm used a strategy similar to C. occipitalis, leading to bouts of effective locomotion interspersed with periods of large slip. Without post-contact C. elegans and C. occipitalis moved at ~0.2 body lengths per undulation cycle (BL/cyc); when contacting the posts both snakes and worms moved at ~0.35 BL/cyc, indicating similarities in task-level control.
