The effects of individual differences in anxiety on anti-predator responses, thermal and hypoxia tolerance in zebrafish (Danio rerio).

Anxiety, as a crucial stress response to potential threats in animals, exhibits significant individual differences, with high-anxiety individuals typically allocating greater attentional resources to threat detection. We hypothesized that such individuals would demonstrate enhanced threat sensitivity and anti-predator responses, but compromised stress tolerance due to constrained energy allocation. Using the novel tank diving test, we screened zebrafish (Danio rerio) with high- and low-anxiety phenotypes and compared their anti-predator responses (anxiety-like behaviors, metabolic rates, and predator avoidance behaviors) under predator chemical or visual cues, along with their thermal and hypoxia tolerance capacities under baseline conditions. The results demonstrate that high-anxiety zebrafish exhibit enhanced anti-predator responses in threatening environments, while showing no compromised stress tolerance at baseline. These findings demonstrate the adaptive superiority of the high-anxiety phenotype in high-predation-risk environments, providing theoretical foundations for understanding the evolutionary role of anxiety in fish.