メダカの卵巣における生殖原細胞の異常増殖と, その一部による精子形成

概要

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Hyperplasia of the gonial germ cells sometimes occurred in female medaka (Oryzias latipes) reared in an isotonic solution at 25℃ with a short photoperiod (8 hrs light, 16 hrs dark). Mitotic division of the gonia and oocytes in the process of oogenesis were observed in the ovigerous fold. Besides these normal phenomena, germ cells in spermatogenesis were found which invaded ovarian connective tissues or were forming large clusters. After a sham ovariectomy, a great hyperplasia of the gonial germ cells also appeared in the ovary of a spawning female fish kept under long photoperiod (14 hrs light, 10 hrs dark) at 25℃ for 20 days following 70 days of natural winter photoperiod. In this individual, germ cells protruded from the ovary and made big clusters located outside of the ovarian wall. Furthermore, germ cells were dislocated on the liver, also forming large clusters. In the extraovarian germ cells, mitotic division and spermatogenesis was observed. In the clusters of germ cells which were in the process of spermatogenesis, no testicular elements other than the germ cells were encountered. Sometimes, liver-like cells appeared among germ cells on the liver. Possible causes of the hyperplasia of the gonial germ cells and their sexual differentiation are discussed.
社団法人日本動物学会の論文
1973-06-25