The Role of Vision and Lateral Line Sensing for Schooling in Giant Danios (Devario Aequipinnatus)

Abstract

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.

Sensing in the dark: Constructive evolution of the lateral line system in blind populations of Astyanax mexicanus

“…However, previous work using surface fish‐Tinaja cavefish F2 hybrids showed no correlation between neuromast expansions and increased time spent schooling (Kowalko et al., 2013 ). This implies that cavefish reductions in schooling might have evolved independently from expansions of the lateral line (Kowalko et al., 2013 ), in line with findings in other non‐cavefish species, like Devario aequipinnatus (giant danios) (Mekdara et al., 2018 ; Tidswell et al., 2023 ) Hemigrammus bleheri (rummy‐nosed tetras) (Faucher et al., 2010 ; McKee et al., 2020 ) and Aldrichetta forsteri (yellow‐eyed mullets) (Middlemiss et al., 2017 ). It does not rule out, however, the possibility that schooling and lateral line expansions could be related to other cavefish populations.…”

“…Previous work in the juvenile Atlantic salmon, Salmo salar , showed an increase in aggression in the dark, providing evidence that light and visual cues are not necessary for the display of aggressive behavior (Valdimarsson & Metcalfe, 2001 ). This is in stark contrast with schooling, where studies across species show that while the lateral line is not needed for schooling, vision remains indispensable, with fish unable to school efficiently in the dark (Kowalko et al., 2013 ; Tidswell et al., 2023 ). The opposite is happening in aggression, where vision seems to be entirely dispensable for aggressive interactions to ensue among aggressive surface fish or semi‐aggressive Molino cavefish (Rodriguez‐Morales et al., 2022 ).…”