Gait Modulation in C. Elegans: It's Not a Choice, It's a Reflex!

In their perspectives article, Mesce and Pierce-Shimomura (2010) make a case for the existence of two locomotion gaits in C. elegans, and for the ability of this nematode worm to choose between them. Here, we offer a counter-perspective, namely, that the variety of observed behaviors are more appropriately described as a single gait. In what follows we focus on pure forward locomotion, which is generally believed to be controlled by a dedicated circuit, distinct from the circuits that control backward locomotion and head motor behavior. With regard to our question of gaits, we are not aware of any evidence that links head swings with the generation of propulsive (forward/backward) locomotion, so these will not be considered here.