Differential impact of shorter and longer periods of environmental enrichment on adult zebrafish exploratory activity (Danio rerio) in the novel tank paradigm.

Several studies have used zebrafish to investigate the effects of environmental enrichment on behavior and physiology. However, to date there are no studies evaluating the behavioral responses, such as habituation and exploration, of enriched-housed zebrafish when they are submitted to novelty paradigms. The present work was, therefore, designed to evaluate the habituation and exploratory responses of zebrafish exposed to enriched- (EE) and non-enriched (NE) environments when they face novelty. Adult wild-type zebrafish were used. Three different enriched contexts were designed. In Context 1, zebrafish was exposed to enrichment during 7 days, which reduced their total distance traveled in novel tank and social preference tests in comparison to the non-enriched animals. In Context 2, animals were exposed to same enrichment during 14 days. EE exposure did not alter the behavioral responses of zebrafish compared to NE. In Context 3, fish were exposed to enrichment during 14 days, with changing the enriching elements at day 8. Similarly to Context 1, total distance traveled was reduced by EE exposure when compared to NE. Our results suggest a modulatory effect of EE on adult zebrafish locomotion that may be dependent on the time of exposure and on the physical structure of the enriched environment.