Sex differences in aggression and its neural substrate in a cichlid fish

Abstract

AbstractBackgroundAggression is ubiquitous among social species and functions to maintains social dominance hierarchies. The African cichlid fishAstatotilapia burtoniis an ideal study species for studying aggression due to their unique and flexible dominance hierarchy. However, female aggression in this species and the neural mechanisms of aggression in both sexes is not well understood.MethodsTo further understand the potential sex differences in aggression in this species, we characterized aggression in male and femaleA. burtoniin a mirror assay. We then quantified neural activation patterns in regions of the social behavior network (SBN) to investigate if differences in behavior are reflected in the brain with immunohistochemistry by detecting the phosphorylated ribosome marker phospho-S6 ribosomal protein (pS6), a marker for neural activation.ResultsWe found thatA. burtoniperform both identical and sex-specific aggressive behaviors in response to a mirror assay. We observed sex differences in pS6 immunoreactivity in the Vv, a homolog of the lateral septum in mammals. Males but not females had higher ps6 immunoreactivity in the ATn after the aggression assay. The ATn is a homolog of the ventromedial hypothalamus in mammals, which is strongly implicated in the regulation of aggression in males. Several regions also have higher pS6 immunoreactivity in negative controls than fish exposed to a mirror, implicating inhibitory neurons in suppressing aggression until a relevant stimulus is present.ConclusionsMale and femaleA. burtonidisplay both similar and sexually dimorphic behavioral patterns in aggression in response to a mirror assay. There are also sex differences in the corresponding neural activation patterns in the SBN. These findings suggest that distinct neural circuitry underlie aggressive behavior in male and femaleA. burtoni, serving as a foundation for future work investigating the molecular and neural underpinnings of sexually dimorphic behaviors in this species to reveal fundamental insights into understanding aggression.