海産無脊椎動物の生殖腺の成熟に関する研究-I : イボニシの生殖腺にみられた季節的変化

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The present paper deals with the seasonal histological changes in the gonads of the purple snail, Purpura clavigera, known as an enemy of young oysters and clams. The materials used were collected every 21st day from the beach of Niigata on the coast of the Japan Sea. The period of collection extended from April to December, 1963. Vitellogenesis begins in this mollusc in April or early in May, and the ovum reaches a ripe state in early in July. As the ovary matures, periphery of the nucleus of ovum is sur-rounded chiefly with smaller yolk granules, while the eccentric zone of the ovum is occupied by larger ones. Up to the breeding season, smaller granules around the nucleus change into larger ones. There is no detectable change of the amount of yolk granules during and after the breeding season, however a considerable number of young oocytes which may have origi-nated from the residual oogonia are recognized in the cystic wall (ovigerous fold). During April to early May, the testis is filled with spermatogonia and spermatocytes, and the formation of spermatids takes place in the latter part of May. The highest activity of the spermiogenesis is reached early in July. Cells in various stages of spermatogesis are found throughout the year, however, Accordingly, the breeding season of the present species extends from late spring to summer, although it is difficult to decide histologically a precise period of spawning. There appeared two types of regression in the gonads after the breeding season. Many of the specimens inspected carefully show that the glands become degenerated by degrees. On the contrary, in a small number of the specimens regarded as the senile ones hole glands degenerate very rapidly. It is very interest to find out many strange spherical cells in the seminiferous tubules. The cells contain granules stained deeply with hematoxylin (and anilin blue). According to histochemical examination the granules in question probably are of mucopolysaccharide (Feulgen negative but PAS positive etc.). A marked increase in the amount of the granules is encountered as the ovary matures. During breeding season these cells are pushed forwarded into the vas defference together with the sperm. It is not yet determined whether or not the cells are ejected into the vagina of the female. It seems likely that the cells are homologous to the so-called free-cell reported by Nishiwaki15) of a very related species, Purpura bronni.

海産無脊椎動物の生殖腺の成熟に関する研究-I : イボニシの生殖腺にみられた季節的変化

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