EDWARDS, T.M.*; MOORE, B.C.; GUILLETTE, L.J.; Environmental Health Sciences/Univ. of FL; University of Florida; University of Florida: Metamorphic Sex Change: Evolutionary Insight for Endocrine Disruption Studies

Metamorphosis is marked by developmental bipotentiality. Classical metamorphosis allows an individual to express more than one phenotype in its lifetime, without a change in genotype. Consider Lythrypnus dalli, the bluebanded goby. Under permissive social conditions, this tiny, protogynous fish undergoes rapid and complete sex change. Females become males in an impressive display of adult sexual bipotentiality. In this example, sex change is easily argued to be a form of metamorphosis, defined as a developmental transition marked by anatomical and physiological remodeling. Theoretically, metamorphosis provides a dramatic model of how environment profoundly affects phenotype through changes in gene regulation. In the field of endocrine disruption, numerous studies describe the masculinization of females or the feminization of males by environmental contaminants. These changes are not metamorphic in the classical sense. However, our understanding of their underlying mechanisms is informed by our appreciation for the role of gene regulation in metamorphic sex change. In humans, for example, during the first six weeks of development, the reproductive system is anatomically indistinguishable between males and females. The cells, tissues, and primordial organs needed for either sex are present in both sexes. Therefore, despite the apparently decisive nature of genetically determined sex, there remain the vestiges of developmental sexual plasticity that result from a shared ontogeny between the sexes. We suggest that it is this shared ontogeny that makes abnormal masculinization or feminization possible.