Comparative undulatory locomotion in complex environments

Despite the difference in size, slithering animals from mm scale nematodes to m scale snakes are resistive-force dominated systems. These animals press lateral body bends against heterogeneities in their surroundings to overcome drag on the elongate, limbless body. To search for general principles of control in undulatory locomotion we studied the desert-specialist C. occipitalis and the nematode C. elegans traversing sparse lattices of rigid cylindrical posts, a model heterogeneous terrain. We challenged C. occipitalis to move through square arrays of 0.64 cm diameter posts embedded in a low-friction substrate and C. elegans with fluid filled PDMS lattices of comparable size. Both animals used a waveform which was largely preserved throughout a trial resulting in bouts of locomotion-when the body contacted an opportune obstacle-interspersed with large-slip-when the substrate alone provided propulsion. C. elegans’ performance was comparable to C. occipitalis; when the animals did not contact posts they moved at ~0.2 body lengths per cycle (BL/cyc) while when they were in contact with the posts they moved at ~0.35 BL/cyc by bouts of motion. This suggests the strategies employed by both animals were similar despite the difference in size.