The Role of Spermatogonia in the Recovery Process from Temporary Sterility Induced by Gamma-Ray Irradiation in the Teleost Oryzias latipes

Adult males of the fish Oryzias latipes were irradiated with 0.5 or 1 kR of 137Cs-gamma-rays (100 R/min). From the viewpoint of the cell-population shift and cell differentiation, the radiation effects on the spermatogenesis in the testis were analyzed. Among the three types of spermatogonia, the first type, the spermatogonia As, were very resistant to radiation, judging from the survival of the cells, but the other types, the spermatogonia Ad and the spermatogonia B, were sensitive to radiation. The spermatogonia As began to proliferate after the degeneration and disappearance of the spermatogonia Ad following the irradiation. During the proliferation phase of the cells, some of the spermatogonia As were morphologically transformed into the spermatogonia Ad, which contributed to the repopulation of the spermatogenetic cells in the testis following the cell loss induced by radiation damage.