Behavioral responses of zebrafish (Danio rerio) to different 2D non-moving stimuli

Zebrafish (Danio rerio) is considered an experimental model organism with numerous applications in different fields. The mechanisms underlying social and reproductive preferences are complex. Most of the literature on conspecific interactions focus on the chemical communication mediated by scattered signals in the aquatic medium. The aim of this research was to evaluate the behavioral responses induced in the tested animals by artificial social stimuli. We used 20 sexually mature individuals that underwent several non-invasive behavioral tests in a cross-maze. Artificial non-moving 2D images were created for this study, using photoshop graphics software. Ethological measurements were conducted using video-tracking software (EthoVision XT). The findings showed significant sex-related differences in zebrafish responses to fixed artificial stimuli. In particular, females shoaled more with 2D non-moving images representing conspecifics phenotypically more distant (i.e. color) from them. Integrating dimension and number of individual, one large stimulus was preferred over three small stimuli in terms of cumulative and mean duration for males, and only in terms of cumulative duration for females. We concluded that 2D images representing conspecifics, even without movements, can induce a behavioral response in this species.