Intersexual aggression in Cichlasoma dimerus: the importance of female reproductive status

Historically aggression has been studied in intrasexual encounters specially focusing on males, while aggression between opposite sexes remains understudied. In cichlid fish, reduced intersexual aggression is associated with pair formation, and escalated aggression can impact courtship and the reproductive success. Cichlasoma dimerus is a Neotropical cichlid showing monogamous and biparental behaviour. In our laboratory we study intersexual aggression assessing its relationship with reproductive status and neuronal activation across telencephalic and hypothalamic areas from the Social Decision-Making Network. The main goal of this study is to determine whether intersexual aggression in C. dimerus is related to the gonadal state of females. We performed dyadic encounters between dominant males and females for one hour. Animals were then euthanized and gonads were fixed in Bouin’s solution. For ovarian histology different protocols were compared, either using xylene or butyl during dehydration before paraffin inclusion. After topographical coloration, our results suggest that the protocol using butyl better preserves the ovarian follicles and allows an appropriate quantification of different stages of oogenesis and vitellogenesis. These first results of this undergraduate thesis lay the foundations to characterize ovarian histology of females participating in intersexual encounters and to determine how overall levels of aggression can be related to their gonadal status.