Timing and plasticity of shoaling behaviour in the zebrafish, Danio rerio

The zebrafish has become a major model system for biomedical research and is an emerging model for the study of behaviour. Although adult zebrafish express a visually mediated shoaling preference, the onset of shoaling behaviour and of this preference is unknown. To assess the onset of these behaviours, we first manipulated the early social environment of larval zebrafish subjects, giving them three model shoaling partners of the same pigment phenotype. We then assayed the subjects' preferences using binary preference tests in which we presented subjects with two shoals, one shoal of fish showing the same pigment pattern phenotype as their models and another shoal with a radically different pigment pattern. To determine whether the visually mediated preference could be altered once it was established, we further manipulated the social environment of a number of subjects, rearing them with one model shoal and testing them, then changing their social consorts and retesting them. Our results show that larval zebrafish shoal early in their development, but do not show a shoaling preference until they are juveniles. Moreover, we found that the shoaling preference was stable, as changing the social environment of fish after they had acquired a preference did not change their preference. These findings will facilitate investigations into the mechanisms underlying social behaviour in this vertebrate model system.