カジカガエルRhacophorus buergeriの生殖腺の性分化

概要

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Using the larvae and froglets of Rhacophorus buergeri brought up from the eggs collected at a mountainous district of Niigata Prefecture, the development and sex differentiation of the gonads were studied histologically. In the indoor-reared froglets of 60 day-age (one week after the completion of metamorphosis), the ovaries were developing directly from the sexually indifferent gonads, on the other hand, the testes were differentiating indirectly from the sexually indifferent gonads through an intersexual structure, composed of a few premeiotic oocyte nests in the cortex and numerous spermatogonia surrounded by the rete cells in the medulla. In 77 day-aged male froglets (3.5 weeks after metamorphosis), a definite testicular structure was observed, though a few degenerative premeiotic oocytes were still seen in the cortex. Therefore, the mode of sex differentiation of the gonads belongs to an early semidifferentiated type. The development and sex differentiation of the gonads of the specimens collected at their natural habitat nearly coincided with those of the indoor-reared ones. In newly metamorphosed frogs, however, the gonadal development and sex differentiation were more accelerated in specimens which metamorphosed later in the season than in individuals which metamorphosed early. Higher temperature of water during the summer season is suggested to be at least a cause of this acceleration.
1973-03-15