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Show 66 Sarah Campbell college of science Unlike most vertebrates, many fishes exhibit environmental sex determination. In some species of coral reef fish, the social environment governs transformations of the gender and sexual behavior of adult indi-viduals. While much progress has been made in understanding the neuroendocrine bases of these trans-formations, the mechanisms that underlie this plasticity are incompletely understood. In particular, the social interactions that govern the expression of male versus female behavior have not been completely identified. In the protogynous, sequentially hermaphroditic bluehead wrasse (Thalassoma bifasciatum), a model for investigating environmental sex determination, removal of the Terminal Phase (TP) male fish will initiate the transformation of one or more Initial Phase (IP) fish, be it male or female, into the Terminal Phase. For an IP female this transformation is manifest as a change in sex, coloration, and behavior. What mechanisms might underlie this plasticity? One possibility is that the TP removal initiates an irrevers-ible physiological process. Alternatively the presence of the TP may ‘gate' the expression of male courtship behavior in a transformation-competent, or ‘primed', IP fish. To test this ‘gating' hypothesis we recorded the behavior of a putatively ‘primed' IP female fish during a 12-Day period, spanning removal and reintroduc-tion of the TP. According to this hypothesis we predicted that the IP fish should show behavioral transfor-mation within days after removal of the TP and revert to female-like behavior upon reintroduction. In support of this hypothesis we found that the IP fish expressed TP-like courtship behavior within 1 day post TP removal, i.e. gate opened. Expression of the TP-like courtship behavior terminated within seconds following TP reintroduction, and was not seen during the remaining 3 days of the experiment. These findings call into question the notion that a rapid and irreversible physiological process underlies socially regulated plasticity in reproductive behavior. REVERSIBLE TRANSFORMATION OF SEXUAL BEHAVIOR IN BLUEHEAD WRASSES: EVIDENCE FOR THE BEHAVIORAL GATING HYPOTHESIS Sarah Campbell (Gary Rose) Department of Biology University of Utah UNDERGRADUATE RESEARCH ABSTRACTS Gary Rose |