The Body Size of Stimulus Conspecifics Affects Social Preference in a Binary Choice Task in Wild-Type, But Not in Mutant, Zebrafish.

The zebrafish has become an appropriate animal model in the analysis of numerous human brain disorders. A variety of neuropsychiatric conditions and neurodevelopmental disorders are comorbid with abnormal social behavior. Given the translational relevance of zebrafish, multidisciplinary studies employing behavioral, neurobiological, and molecular methods with this species may provide insights into human central nervous system (CNS) disorders. Many of these studies impinge upon our ability to properly induce and quantify the behavior of zebrafish, a relatively understudied aspect of this species. In this study, we investigate how the body size of conspecifics relative to that of the test subject influences social (shoaling) responses in zebrafish. We found a robust preference by wild-type (WT) test zebrafish toward big conspecifics, but not toward smaller conspecifics. Additionally, we tested an autism-relevant zebrafish knockout (KO) model. The KO zebrafish showed impaired social preference compared with WT in the social behavior test. Our results confirm the effect of relative body size on social preference and that the social preference task developed for zebrafish may uncover the function of genes and biological mechanisms potentially associated with human CNS disorders.