Phase Transition in The Collective State of the Nematode T. Aceti

We experimentally investigate the dependence of the collective states of the nematode T. Aceti on the density of nematodes. In the past it has been shown that this nematode can synchronize their oscillations to produce a moving metachronal wave. Such synchronization occurs at the border of a liquid droplet when its contact angle decreases below 68°. In this work we show that the transition to the collective state can occur at a much higher angle when the density of nematodes is big enough. We show that this phase transition at higher density is due to a different collective state and provide a full density-contact angle diagram.