| In vertebrates living in dominance hierarchies, the neuroendocrine system is likely to regulate temporal aspects of aggressive interactions during status establishment. However, sex differences and brain region-specific regulation of multiple steroids in response to aggression is not fully understood. In teleost fishes, 17β-estradiol (E2) the primary estrogen, has a been linked to rapid regulation of aggression in both males and females. 11-ketotestosterone (KT) the primary androgen and glucocorticoid cortisol (CORT) are directly linked in the steroidogenic pathway. Bluebanded gobies, Lythrypnus dalli are bidirectionally hermaphroditic fish that live in linear hierarchies with a nesting male and many subordinate females. Disruption of hierarchy via male removal (MR) or male addition (MA) rapidly leads to social instability. We made social groups of L. dalli comprising of one male and two females and verified stable status via behavioral observations. We then disrupted hierarchy via MR or MA and within 30 min of social instability. Males exhibited high rates of physical aggression inside the nest while females exhibited chases outside the nest. While systemic (water-borne) steroids were not affected, brain E2 was higher in all fish and CORT was lower in male brains. Brain KT was higher in males who emerged as dominant compared to dominant females. Overall, a combination in differences of E2, CORT, and KT in the brain played a role in the aggressive differences key in the regulation of hierarchy re-establishment and maintenance. Rapid responses during conspecific aggressive encounters are mediated by neural steroid synthesis that precedes changes in systemic steroids. |