Increased H-Y antigen levels associated with behaviorally induced, female-to-male sex reversal in a coral-reef fish.

It has been proposed that H-Y antigen is the synthetic product of sex-determining genes, and that H-Y antigen controls ontogenetic differentiation of the heterogametic sex throughout vertebrates. The coral-reef fish Anthias squamipinnis is a protogynous hermaphrodite in which all individuals mature initially as females. Males result when adult females change sex as a consequence of alterations in behavioral interactions within social groups. Three assay methods were used to measure H-Y antigen levels in the spleens, gonads, and epidermal tissue of 16 adult females and in 16 males that had been induced to change sex from a prior female phase by the removal of a pre-existing male from each of 16 social groups. In 15 male-female pairs, the H-Y antigen levels were higher in male than in female spleen, gonad, and epidermis tissues. The precise temporal relationship between the onset of sex change and the increase in the H-Y antigen level was not examined. If, as we strongly suspect, the temporal relationship proves to be close, the inference will be that the behavioral cues inducing sex change also influence the synthetic activity of genes controlling H-Y antigen production.