The Role of Vision and Lateral Line Sensing for Schooling in Giant Danios (Devario Aequipinnatus)
To protect themselves from predators, fishes often form schools with other fish. Previous work has identified abstract "rules" of schooling - attraction to neighbours that are far away, repulsion from neighbours that are too close, and alignment with neighbours at the correct distance - but we do not understand well how these rules emerge from the sensory physiology and behaviour of individual fish. In particular, fish use both vision and their lateral lines to sense other fish, but it is unclear how they integrate information from these sensory modalities to coordinate schooling behaviour. To address this question, we studied how the schooling of giant danios (Devario aequipinnatus) changes when they are either unable to see or unable to use their lateral lines. We found that giant danios were able to school normally without their lateral lines, but did not school in darkness. Surprisingly, giant danios in darkness had the same attraction and alignment properties as fish in light, potentially indicating that they do not feel as much risk in darkness. Overall, we suggest that differences among schooling species in sensory integration between vision and lateral line may depend on their natural predators and environment.