Analysis on the interactions between germ cells and somatic cells in the developing fish gonads.

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1. In order to analyze the interactions between germ cells and somatic cells during the sex differentiation of gonads, differentiation markers are indispensable. The sex differentiations of germ cells in Oryzias latipes has been identified from the kinetics of their proliferation as well as from the ultrastructure. In the present study, histological observation on testes and ovaries which were stained with 13 kinds of lectins revealed that we can discern spermatogonia and oogonia from the differences of the stainability with BPA or SBA, also Sertoli cells and granulosa cells with BPA, MPA and PNA.We also stained the developing gonads with lectins. Prespermatogonia and supporting cells in the fry just after hatching did not bind with BPA, but stained with BPA when the rudiments of testicular architecture begin to be constructed in the 7-8mm fry. SBA-positive germ cells noted in the female fry just after hatching, whereas they did not appeared in males younger than 5-6mm fry. These results indicate that lectins can be a differentiation marker from prespermatogonia to spermatogonia as well as from coelomic epithelial cells to Sertoli cells in this fish.2. It is known that the sex is determined by the presence of Ychromosome in Oryzias latipes. In the study about the hybrid sterility in fishes of Oryzias, we noticed that XY hybrids between O. latipes of east Korean population and O. curvinotus become female, an indication that the testis determining gene (s) on Y chromosome of O. curvinotus cannot be expressed in the presence of genes of O. latipes of east Korean population. The genetic analysis clarified that the genes on X chromosome dose not involved in the male determination, but that more than two autosomal genes have a relation to the sex-determining processes.