The weight change in the testes and the behavior of the primary spermatogonia Ia and Ib in the testes of the fish Oryzias latipes continuously exposed to tritiated water at concentrations of 5× 10-3, 10-2, 5× 10-2, and 10-1 Ci/liter were investigated at 25°C. A marked weight loss of the testes (42 and 37% of the control in the fish exposed to 5× 10-2 and 10-1 Ci/liter, respectively) was demonstrated 30 days after the exposure to tritium. Although in the primary spermatogonia Ia the reduction in number was not significant, in the primary spermatogonia Ib the cell number decreased in the fish of all groups exposed to tritiated water during the first 5 days. Ten days after the exposure a considerable reduction in the number of the primary spermatogonia Ib was observed in the fish kept in tritiated water at 10-2 Ci/liter. Thereafter, in the fish exposed to tritiated water (concentrations of 5× 10-2 and 10-1 Ci/liter), a further marked decrease in the cell number was noted. In the fish kept in lower concentrations of tritiated water (10-2 and 5× 10-3 Ci/liter), a recovery in the number of the primary spermatogonia Ib took place during 15 to 30 days of incubation time. The β-irradiation dose at the concentration of 10-2 Ci/liter was estimated to give a whole-body dose rate of 2.03 rad/day. It was shown in the present experiment that the spermatogenetic cells are more radiosensitive than are fish embryos.

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Copyright 1977 Academic Press, Inc.
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