Two to tango: the importance of reproductive and hormonal variables in intrasexual aggression in Cichlasoma dimerus

MARÍA FLORENCIA SCAIA; RINCON CAMACHO LAURA; TRUDEAU, VANCE L.; POZZI ANDREA; GUSTAVO SOMOZA

Heraklion

Congreso; 12th International Symposium on Reproductive Physiology of Fish; 2023

INTRODUCTIONIndividuals living in social hierarchies engage in agonistic encounters throughout aggressive behavior, which induces experience-dependent shifts in social status. Aggression has been historically linked to males and androgen levels while female aggression is still widely understudied, even if females from different species also display aggressive behavior. While cichlid fish constitute ideal models to assess the physiological basis of aggression, most studies refer to African species. The aim of the present work is to disentangle how sex differences in social plasticity can be explained by sex steroid hormone levels, gonadal state and/or morphometric characteristics by using a Neotropical cichlid species.METHODSIntrasexual dyadic encounters were performed between male or female Cichlasoma dimerus of a wild stock from North Argentina. Aggressive and submissive displays from the winner and loser fish were quantified during all phases of one-hour contest: pre-conflict, conflict and post resolution. Morphometric variables, gonadal histology and hormonal levels were determined in both winners and losers.RESULTS & DISCUSSIONThis integral multivariate analysis suggests that the reproductive and hormonal variables analyzed explain the behavioral variation among winner and loser males and females, and that there are significant differences between sexes and contest outcome when individual morphometric variables are excluded from the analysis. Regarding gonadal histology in females, since both opponents were prespawning fish they show majority of mature follicles and vitellogenic oocytes, with a very low incidence of previtellogenic oocytes. Interestingly, there are no sex differences in aggressive and submissive behaviors, and clustering into winners and losers is mainly explained by specific behavioral displays, such as bites, chases, approaches, passive copings, and escapes. Correlation heatmaps show a positive correlation between estradiol with aggression and a negative correlation with submission, suggesting estrogens may have a dual role regulating agonistic behavior. Finally, these results suggest that size difference can help to understand aggression in females but not in males, and that assessment of the opponent´s body size is important to understand aggression also before the initiation of the contest in both sexes. Overall, this study constitutes an integral approach adding insights into the importance of reproductive and hormonal variables to understand social plasticity in males and females.