Adult crowding induces sexual dimorphism in chronic stress-response inDrosophila melanogaster

ABSTRACT Stress-induced mood disorders such as depression and anxiety are sexually dimorphic in human beings. Studying behavioural stress-responses in non-human animal models can help better understand the behavioural manifestations of these disorders and the dimorphism in their prevalence. Here we explore how sexes show differential behavioural responses to different chronic stressors, both abiotic and biotic, by using outbred populations of Drosophila melanogaster . The behaviours studied – namely, anhedonia, motivation to explore a novel habitat, locomotor activity and sleep levels – have been well-investigated in human and rodent-based models of stress disorders. These behaviours were studied in the context of two different stressors – mechanical perturbation and adult crowding. Responses to stress were found to be sexually dimorphic, and stressed females showed more behavioural changes, such as a reduced motivation to explore a novel habitat. Furthermore, adult crowding caused a greater number of sexually dimorphic behavioural changes than mechanical perturbation. For instance, while mechanical perturbation caused anhedonia across sexes, only females were anhedonic after crowding. We thus make a case for Drosophila melanogaster as a model system for studying sexual dimorphism in stress-induced mood disorders in humans. SUMMARY STATEMENT Female fruit flies, like their human counterparts, are more prone to chronic stress-induced mood disorders like anhedonia or reduced activity. This sexual dimorphism was more evident in a biotic stress.