Nonreciprocal phase transition in swarming C.elegans

Nonreciprocity is a very generic phenomenon in biological systems. However, it is still not clear how these types of interactions drive the collective behaviors of active biological systems including swarming animals. In this study, we investigated the emerging response of active C.elegans aggregates and passive bacterial mixture. We experimentally observed the nonreciprocal phase transition controlling the social feeding behavior of these animals. We further found that during this transition, Parity-Time symmetry-breaking process promotes the collective chemotaxis behavior of swarming animals. Finally, we speculate that this process has an evolutionary significance that promotes the survival of social animals in nature.