ABS 2023
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Navigating social waters: sex differences in zebrafish cortisol expression across social situations
Genevieve Fontana1, Amanio Deemer1, Ryan D. Wynne2, Jennifer L. Snekser1. 1Canisius University, Buffalo, NY, United States; 2University at Buffalo, Buffalo, NY, United States

Sex differences in behavior are often explained evolutionarily by differential reproductive investment: females invest more than males in reproductive outcomes. Yet, it could be predicted that some behaviors, like social preferences, should be similarly expressed by both sexes. Male and female zebrafish (Danio rerio) often make different choices in contrived forced-choice shoaling tests: females tend to be more discriminative than males regarding shoal size, shoalmate body color, and sex of shoalmates. We examined if stress and the associated excreted cortisol levels could be underlying proximate mechanisms contributing to different social choices. Individual zebrafish were presented with a shoal of four males, a shoal of four females, and left in isolation, and water was collected during each behavioral test to extract water-borne cortisol. This design allowed a single individual to be tested in multiple social scenarios while measuring endocrine response. Behavioral observations revealed a preference to be near a shoal, regardless of sex. Hormone analysis indicated a significant sex difference in cortisol expression and an effect of social setting.