Tissue steroid levels are associated with female social status, but not rates of behavior, nor ovarian function (#293)
A variety of factors affect circulating and/or tissue hormone levels in females during the breeding season. Cyclical changes in ovarian hormones influence context-specific interactions and can confound simple hormone-behavior relationships. Here, we examined the roles of morphology, behavior, and female social status in establishing brain and ovarian levels of steroid hormones in females of a bi-directionally hermaphroditic fish, the bluebanded goby, Lythrypnus dalli. The alpha female maintains the highest social status among females in a harem and is subordinate to the male. Male reproductive success is associated with agonistic and courtship behavior of alpha females. For 4 weeks, we observed social groups (n=34), consisting of one male and two size- and status-mismatched females. There were significant morphological differences between alpha and beta females, however, there were no relationships between steroid levels and morphology nor rates of agonistic interactions. Short-term, transient changes in social context also did not affect steroid levels. Interestingly, beta females had 2x higher brain levels of testosterone, 11-ketotestosterone, and cortisol than alpha females; however, alpha females had higher ovarian 17ß-estradiol levels. Lower brain androgens and glucocorticoids in alpha females might minimize physiological costs and permit transient elevation during sustained changes in social context. Brain 17ß-estradiol levels were dramatically lower compared to the ovary and the ratio of steroids were different for brains and ovaries, likely due to local synthesis and regulation of steroids. Despite changes in short-term context and the high variation in ovarian morphology, dominant and subordinate females maintain robust tissue-specific differences in steroid hormones. Tissues of females can be used as an informative proxy to evaluate steroid levels and endocrine mechanisms that regulate reproductive phenotypes.