日本産ウナギ(Anguilla japonica)の卵形成について

抄録

Oogenesis of the Japanese eel, Anguilla japonica, was studied using cultivated eels, silver eels, and those treated with hormones. Oogonia and oocytes in the premeiotic stage showed almost the same features as those of many teleostean fishes. Vitellogenesis of the Japanese eel is characterized first by the appearance of oil drops, which come to occupy alarge part of the peri-nucleus. Subsequent to this, a few small yolk vesicles appeared in the peripheral region of the cytoplasm. Soon after the formation of the vesicles yolk globules began to appear in the peripheral part of the cytoplasm. Thereafter, the globules were formed rapidly and occupy a large part of the cytoplasm. The germinal vesicle located in the centre of oocytes then moves to one pole of the oocyte and underwent decomposition. Immediately, thereafter, preparation for the first maturation began. Mature eggs of about 1.05mm in diameter were pelagic and spherical in form. Many yolk globules of large size and a few number of large oil drops were seen in the cytoplasm in the region of the vegetable pole.