An analysis of shoaling behavior in the zebrafish, Danio rerio

Social behavior has long fascinated researchers in anthropology, psychology, and biology. We used the zebrafish, Danio rerio, a biomedical model system, in our investigations of shoaling, a social behavior engaged in by the majority of fishes over the course of their development. Shoaling is an adaptive behavior that impacts an individual's access to mates, ability to forage, and its vulnerability to predators. In the following work we used binary preference tests to establish the existence of a visually mediated shoaling preference. We then used classical cross-rearing methods coupled with a recently isolated pigment pattern mutation to examine the interplay of genes and environment in determining this visual preference. Finding that early life experience played a key role in determining shoaling preference, we then developed basic staging criteria for the post-embryonic zebrafish. We tested individuals at a variety of stages to determine the onset of both shoaling behavior and the first appearance of the visually mediated preference. In our later work we used the combination of binary preference tests and multidimensional scaling to examine the interior visual world of zebrafish with regards to shoaling interactions. We quantified the visual signals presented by a broad panel of zebrafish pigment pattern mutants, and closely related species, using reflectance spectrophotometry and a recently developed image analysis protocol. We tested a group of subject fish, controlling for their early life experience, giving them all possible pairs of the stimulus fishes. The results of these tests coupled with multidimensional scaling allowed us to build a model of the interior visual world of zebrafish. We then used the physical measures of the pigment pattern signal in an attempt to explain the variation exhibited in the model. While these measures explained little of the variance in the model, we found dramatic differences between the processing of visual signals by male and female subjects.