Dramatic differences between the sexes are normally established early in development and remain fixed for life. However, in many fishes, reproductive function shows life-long plasticity, with sexual transitions occurring in response to varying social and life history conditions. By manipulating social group composition in bluebanded gobies (Lythrypnus dalli), one can predictably induce the establishment of dominance and subsequent sex change in a targeted female. This female exhibits a stereotyped sequence of behavioral, physiological and anatomical changes as she transforms into a male. One can use early behavioral indicators of dominance to examine the mechanisms that drive both increased social status and the initiation of sex change. Sex steroids have been implicated in the regulation of both of these processes, but gonadal production of sex steroids does not change in the early stages of sex change. However the vertebrate brain synthesizes sex steroids and these enzymatic processes can be down-regulated in minutes. The current project critically examines the relationship between changing social status, rapid regulation of neurosteroid pathways, and the initiation of sex change. Through the determination of brain steroid levels, the rates of enzymatic conversion of one steroid to another and observations of how the animals are behaving, one can determine the dynamic interactions between social and endocrine signals in regulating adult sex change. The evolution and development of sex differences is an area of fundamental importance for biologists and the results of this work will enhance our understanding of how social processes regulate reproductive behavior, anatomy and physiology. The resources of the Education directorate at the Center for Behavioral Neuroscience will be used to recruit women and minorities into the undergraduate and graduate training opportunities available through this grant and the PI has an outstanding record of mentoring women and minorities in scientific research.
