Introduction: Social isolation is a valuable approach for studying the neural and behavioral mechanisms that govern interactions among social animals. The impact of social isolation and loneliness on health and disease has become more prevalent after the COVID-19 pandemic, affecting millions of lives, causing anxiety and depression in humans across ages and genders worldwide. Zebrafish are increasingly utilized as a model organism in behavioral neuroscience; however, the effects of long-term social isolation on their behavior, physiology, and overall life outcomes are yet to be fully investigated and require further extensive study. Materials and methods: This research study aimed to examine the impact of social isolation on affective behaviors, viz., anxiety-like and depressive-like behaviors in zebrafish. In the present study, 15 age- and size-matched adult zebrafish were used for each control and isolated group (per isolation week). The zebrafish were isolated for 1–13 weeks in individual tanks and subjected to a set of behavioral assessments, including the novel tank test, open tank test, light/dark test, and social interaction test, to evaluate anxiety- and depression-related behaviors. Results: The findings indicated that solitude did not induce depression in zebrafish; however, it did significantly alter their exploratory behavior. In the novel tank and open tank tests, zebrafish exhibited anxiety-like behavior across all weeks of isolation, with this behavior more prevalent during the 5–9-week period. Socially isolated zebrafish responded significantly more to social stimuli than the control group, indicating an increased preference or need for conspecifics after prolonged social isolation. In the light/dark test, the number of entries remained consistent across different weeks of isolation with minor changes. This indicates stable, natural exploratory behavior in the light/dark test. Conclusions: Our findings demonstrate that zebrafish subjected to social isolation exhibit significant behavioral changes that lead to anxiety-like behavior, potentially affecting their quality of life.
Sekhon et al. (Wed,) studied this question.