Centipede locomotion on rough terrain

Multi-limbed invertebrates such as centipedes negotiate diverse environments via propagation of coordinated travelling waves of body and limb flexion. While progress has been made studying how these animals locomote on flat terrain, less is known about their navigation in complex environments. Here we challenged S. polymorpha (N=4, L = 7.7±1.5 cm, 19 joints and leg pairs) to transverse a flat frictional surface and Gaussian-distributed rough terrains (12 x 24 cm² with variable height of blocks ranging from 0 to 1.5 cm). On the flat frictional surface, centipedes moved at speeds of 1.44±0.54 body lengths per second (BL/s) by generating a traveling wave along their limbs and bodies, maintaining a constant phase shift between these two waves. On the rough terrains, the centipedes moved at speeds of 1.79±0.45 BL/s and 0.77±0.51 BL/s for lower and higher roughness, respectively. Unexpectedly, wave dynamics were similar on flat ground and the lower roughness terrain. Traversal of the rough terrains was facilitated by passive limb bending when in contact with blocks of different heights. Centipedes negotiated collisions with blocks by passively gliding their limbs to resume locomotion.