Detour tests reveal task- and stimulus-specific behavioral lateralization in mosquitofish (Gambusia holbrooki).

We studied detour responses of male mosquitofish faced with a vertical-bar barrier through which a group of females was visible. Mosquitofish showed a consistent population bias to detour the barrier preferentially leftwise when a straight barrier was used, whilst the asymmetry disappeared if a U-shaped barrier was used. The leftward bias was apparent even when using a simulated-predator as a target (which induced detour behaviour for predatory-inspection responses), but not when using an empty environment or a group of males as a target. Moreover, when faced with an opaque barrier, mosquitofish tended to turn on their right side. These lateral biases could be accounted for in terms of a right eye preference during lateral (monocular) fixation of any stimulus of interest, suggesting functional lateralization in a teleost species for the analysis of visual information.