The effect of the number and size of animated conspecific images on shoaling responses of zebrafish

• Animated conspecific images induced shoaling in zebrafish.
• This shoaling response manifests as reduced distance to the images.
• The size of the image or the size of the test fish was systematically varied.
• When the images were smaller than the test fish the response diminished.
• When the test fish was larger than the images the response diminished.

The zebrafish is increasingly utilized in biomedical and psychopharmacological research aimed at modeling human brain disorders. Abnormal social behavior represents the core symptom of several neuropsychiatric and neurodevelopmental disorders. The zebrafish is a highly social species and has been proposed for modeling such disorders. Behavioral paradigms that can induce zebrafish social behavior are of importance. Here, we utilize a paradigm in which zebrafish are presented with computer animated images of conspecifics. We systematically varied the size of these images relative to the body size of the experimental fish and also investigated the potential effect of presenting different number of images in an attempt to optimize the paradigm. We report that images similar in size to the experimental fish induced a strong shoaling response (reduction of distance to the image presentation screen) both when the body size of the experimental fish was varied with the image size being held constant and when the image size was varied with the body size of the experimental fish being held constant. We also report that within the number range studied (from 1 to 8 conspecific stimulus fish), presentation of all animated shoals, but the image of a single conspecific stimulus fish, led to significant reduction of distance to the presentation screen. We conclude that the shoal image presentation paradigm induces robust social responses that are quantifiable in an automated manner, making the paradigm useful for screening of drugs and/or mutations.