The Effects of Structural Environmental Enrichment and Social Enrichment on Anxiety-Like Behaviors in Zebrafish (Danio rerio)

The purpose of this study was to investigate the effects of structural and social enrichment on anxiety in zebrafish (Danio rerio). Previous research indicates that structurally-enriched environments have anxiolytic effects in zebrafish. Subjects were randomly assigned to the following groups for 14 days: Group 1 lived in a barren tank (structurally-impoverished) with six conspecifics (group-housed); Group 2 lived in a structurally-impoverished environment alone (socially isolated) in a paper-wrapped tank (no mirror condition); Group 3 was socially isolated in a structurally-impoverished environment in a mirror-wrapped tank (mirror condition); Group 4 lived in a tank containing brown gravel, three green plastic plants, and a PVC pipe (structurally-enriched) with a group; Group 5 was structurally-enriched and isolated; and Group 6 was structurally-enriched and isolated with a mirror. After 14 days of exposure, a blind, counterbalanced procedure and two well-established tests were used to assess anxiety. We hypothesized the following: both structural-impoverishment and social isolation would increase anxiety in zebrafish, both structural and social enrichment would act as anxiolytics in zebrafish, the anxiolytic effects of structural and social enrichment would be additive, and mirrors would be enriching to zebrafish and prevent the adverse effects of social isolation. Generously Supported by Schewel and Wootton Funds