RENEWAL AND PROLIFERATION OF SPERMATOGONIA DURING SPERMATOGENESIS IN THE JAPANESE-QUAIL, COTURNIX-COTURNIX-JAPONICA

Four different types of spermatogonia were identified in the seminiferous tubules of the Japanese quail: a dark type A (A(d)), 2 pale A types (A(p1) and A(p2)), and a type B. A model is proposed describing the process of spermatogonial development in the quail. The A(d) spermatogonia are considered to be the stem cells. Each divides to produce a new A(d) spermatogonium and a A(p1) spermatogonium during Stage IX of the cycle of the seminiferous epithelium. An A(p1) spermatogonium produces two A(p2) spermatogonia during Stage II of the cycle, A(p2) spermatogonia produce four type B spermatogonia during Stage VI of the cycle, and type B spermatogonia produce eight primary spermatocytes during Stage III of the cycle. Consequently, 32 spermatids can result from each division of an A(d) spermatogonium. Spermatogonial development in the quail differs from the process described in mammals in that there are fewer mitotic divisions and they are all synchronized with the cycle of the seminiferous epithelium. It is suggested that the fewer mitotic divisions explain why a smaller area of the seminiferous tubule is occupied by a cellular association in the quail than in mammals like the rat, ram and bull. The duration of spermatogenesis from the division of the A(d) spermatogonia to sperm release from the seminiferous epithelium was estimated to be 12.77 days.