トノサマガエルの性分化過程における生殖細胞数の性差と左右差

概要

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The germ cells in the developing gonads of Rana nigraomaculata larvae were counted in order to examine sexual differences in their numbers. A testicular structure developed directly from the sexually indifferent gonads at Gosner's stage 28, and an ovarian structure also developed directly at stage 29. The germ-cell numbers in the sexually indifferent gonads were 18 on the average at stage 24, and 450 at stage 28. In the tests, the germ cells were ca. 1000 in number at stage 28. Thereafter the change in the numbers was not significant until stage 30. About 2700 germ cells were counted at stage 35, and no increasing tendency was noticed until stage 45. In the ovaries, on the other hand, the number of germ cells was ca. 2300 at stage 29, ca. 5000 at stage 33, and ca. 10000 at stage 40. During metamorphosis, the increase of germ cells was hardly notable. Thus, the number of germ cells was always greater in females than in males at the same developmental stage, and this sexual difference occured in the course of gonadal sex differentiation. Concerning the bilateral difference in germ-cell distribution, more germ cells were found in the left testis than in the right one from the beginning of the gonadal sex differentiation. Such a tendency, however, was not observed in the female gonads.
社団法人日本動物学会の論文
1975-06-25