ツチガエルRana rugosaの生殖腺の性分化過程

概要

論文の詳細を見る
Larvae of a single spawn of Rana rugosa were raised in outdoor conditions from the time of hatching to metamorphosis, and their gonads were examined histologically. Gonadal sex differentiation started and proceeded during 34 to 41 days after hatching. Ovaries were differentiated directly from the indifferent gonad, whereas testes were differentiated indirectly from the indifferent gonad through an intersexual phase but not through an ovarian phase. The intersexual phase was characterized by a progressive oogenesis in the thickened cortex and simultaneous migration of cortical germ cells into the medulla. In animals of 56-70 days after hatching, distinctly defined testes were observed, though premeiotic oocyte nests and auxocytes were frequently encountered in the testes. Thus nearly 1:1 ratio of sex distribution was established in larvae before the 100th day of larval age, when the majority of the larvae completed their metamorphosis. However, the testes of some animals naturally suspending their metamorphic changes were still provided with the surviving cortical atructures even about a year after hatching. These findings may imply that the observed hermaphroditic tendency in gonadal development of the frog may possibly account for relatively frequent occurrence of testis-ova in the testis of the adult frog.
1971-01-15