Diferenças sexuais na expressão de comportamentos tipo-ansioso em zebrafish (Danio rerio)

Abstract

Anxiety is an emotional process that, in humans and at appropriate levels, constitutes a behavioral system that is adaptive and essential for survival. At higher levels, however, it becomes a major public health concern, with 1 in 8 individuals worldwide and 9.3% of the Brazilian population experiencing some form of anxiety disorder. Cognitivebehavioral models have been proposed to explain the mechanisms of anxiety in humans, often based on clinical observations. Following Charles Darwin’s evolutionary theory, it is possible to draw analogies between the behaviors of other animals (both mammalian and non-mammalian) and human behaviors. These analogies not only enhance our understanding of anxiety but may also provide new insights for therapeutic interventions. In this context, the use of animal models in the study of various psychopathologies, such as anxiety disorders and depressive disorder, has grown significantly. More recently, the zebrafish (Danio rerio) has emerged as a promising model due to physiological, economic, and ethical considerations. It is a low-cost species with high reproductive capacity and phenotypic traits that allow for parallels with human behavior. The present study aimed to investigate, through two experiments, the magnitude of anxiety-like behaviors in zebrafish as a function of sex. To this end, a modified version of the Novel Tank Test, named the Tower Novel Tank Test, was employed. The results of the first experiment revealed significant differences in the expression of anxiety-like behaviors based on sex, suggesting that female zebrafish exhibit a greater intensity of such behaviors compared to males. This experiment also enabled the initial classification of animal groups as anxiety-like or non-anxiety-like. The second experiment examined the stability of behavioral expression in the selected groups using the Tower Novel Tank Test after a 30-day retest period. The retesting results demonstrated consistent behavioral patterns in both the anxiety-like and nonanxiety-like groups. Together, the findings support previous studies that indicate significant sex-based differences in anxiety-like behaviors in the zebrafish model. Finally, the results also highlight the suitability of the Tower Novel Tank Test for the divergent selection of anxiety-like behaviors in zebrafish.