Abstract
The oogenesis of the Japanese sea bass, Lateolabrax japonicus, one of the common marine teleosts in Japanese coast, is fundamentally similar to those of the other bony fishes described so far.However, in this fish, oogenensis is marked by the characteristic pattern of distribution of the yolk vesicles and the rather shorter period needed for the maturation of the oocyte in the yolk vesicle stage into the ripe ovum.Though sufficient explanations for these characteristic patterns of maturation process are not available, the shorter period required for oogenesis seems to be closely related to the mode of their life.The follicular cells play an important role in the supply of nutrition for the growing oocyte and phagocytic function for the atretic oocyte.In this respect, the follicular cells seem to function like the seminiferous epithelial cells of the testis, intensely suggesting that their origins are homologous genetically.It was also ascertained that the seasonal change of the values of gonad index reflects somewhat precisely the fish maturity.Both a microscopical observation of ovary and the data of gonad index indicate that in Wakasa Bay spawning occurs from late December to middle of January, mostly in early January.The biological minimum size of the female is about 350 mm in body length which corresponds to the size of two or three year age group.
