Early sex differentiation in Mugil ( Liza ) auratus Risso , 1810 ( Teleost Mugilidae ) . An ultrastructural study

Grey-mullet are heterosexual fish and gonochorism is the general rule. Cytological cnalysis of sex-differentiation was studied by light microscopy (Stenger, 1959 ; Leray, 1968 ; Thong, 1969 ; Cassifour, 1975), but germ-cell characteristics were not sufficiently defined at this level and no distinction could be made between primordial germ-cells, oogonia and spermatogonia. Electron microscopy has been used to accurately describe most fish, but fine structure during early sex-differentiation was chiefly investigated on freshwater species such as Oryzias (Satoh, 1974), Poecilia (Grier, 1975) and Carassius (Yamamoto and Onozato, 1965). There are few data in the literature on the germ-cells of marine species and no information concerning grey-mullet. We used electron microscopy for cytological identification of early germ-cells