Responses of Zebrafish to Chronic Environmental Stressors: Anxiety-Like

Xiaohong Li Cheng Fu Xueting Tan Shijian Fu ^*

• College of Life Science, Chongqing Normal University, Chongqing, China

Fish are often subjected to various long-term environmental stressors in natural ecosystems, with anxiety representing a crucial stress response to perceived threats. It is anticipated that fish may exhibit distinct anxiety-like behavioral changes in response to different environmental stressors. These behaviors can help them survive in harsh conditions and may also impact population dynamics and the health of ecosystems. In this study, we investigated the effects of three stressors -predators, social isolation, and caffeine -on anxiety-like behavior in zebrafish (Danio rerio) over 14 days. Furthermore, we evaluated the persistence of these effects for 28 days following the removal of the stressors. During this period, we also measured the levels of cortisol, a known stress hormone. Our results revealed that after 14 days of exposure, zebrafish exhibited varying anxiety-like behavior and cortisol level changes in response to chronic environmental stressors, with differing persistence. Chronic predator stress significantly increased anxiety-like behavior and cortisol level, lasting at least seven days post-stressor removal. Social isolation led to mild reductions in anxiety-like behavior and cortisol level, persisting for at least one day after resocialization. Caffeine exposure caused a temporary anxiolytic effect, with anxietylike behavior reversing one day post-withdrawal and persisting for seven days, though cortisol level remained elevated. These findings reveal how anxiety-like behavior and cortisol level in zebrafish vary and persist under different chronic environmental stressors. These results also offer new insights into predicting the behavioral and physiological responses of fish to long-term environmental stressors.