There is no clear evolutionary conservation between phyla of the mechanisms underlying sex determination. In contrast, many studies indicate that various downstream products of sex-determination genes are functionally similar in different species. In the teleost fish medaka, Oryzias latipes, the sex-determining gene, dmy/dmrt1bY, has already been identified (1-3). Morphogenesis during gonadal differentiation is also conserved, as is evident from the differentiation and development of the parenchyma/germinal epithelium cells (testis cord) and follicles. Therefore, it is crucial to understand the molecular mechanisms of gonadal sex differentiation from the perspective of the relationship between conserved gene expression cascades and morphogenesis during gonadal sex differentiation (2, 4). We have clarified the mechanisms of a gonadal sex differentiation and development pathway (4-6).
It is also well known that environmental factors such as temperature and environmental endocrine disrupting chemicals affect the phenotypic sexes and reproductive phenotypes. We have also examined the molecular mechanisms of how environmental factors affect gonadal differentiation and development and reproduction. These studies are relevant to environmental preservation and may help improve aquaculture and fisheries.