Early asymmetries in the behaviour of zebrafish larvae

Zebrafish (Brachydanio rerio) larvae (8 days) were tested singly in a swimway made up of six compartments. The larva emerged into each compartment in turn, and its response to visual features (e.g. turning away) was affected by memory of previous layouts, as well as by home tank experience. The use of stimuli placed far to the right or left proved to engage preferentially the eye system directly fed by right or left eye system (RES, LES). At least three behavioural mechanisms appeared to show similar laterality in larva and adult. Both turned right in startle-induced locomotion. In both, LES was preferentially involved in assessment of novelty. Thus, in larvae, use of LES caused more investigation of a familiar stimulus in a strange context. Finally, in larvae there was some evidence that (as is the case in adults) RES was responsible for the visual control of response. Here the evidence for the adult was the preferential use of the right eye to view the object of response, whereas for the larva, it was the enhanced ability to sustain a motor strategy when RES was in use.