Effects of Tritiated Water on Germ Cells in Medaka: II. Diminished Reproductive Capacity Following Embryonic Exposure

To determine the effects of early radiation-induced germ cell loss on lifetime reproduction, the fecundity and fertility of fish exposed to chronic irradiation as embryos were investigated. Embryos of the medaka, Oryzias latipes, were exposed to tritiated water (0.05-2.0 mCi/ml) and137 Cs γ rays (6.1-254 rad/day) continuously from the morula stage until hatching (10 days at 26°C). Newly-hatched fry were removed from the radioactive environment. At 4-8 months after hatching, pairs consisting of irradiated males and nonirradiated females or the reverse were mated. When irradiated females were mated with unirradiated males, both the total number of ovipositions and the number of eggs per fish decreased with increasing dose. However, most eggs laid were fertilized and hatched normally in all groups. Tritium β rays were more effective than137 Cs γ rays in reducing the fecundity of the irradiated females. In pairs where the male had been irradiated, the total number of ovipositions did not decrease, but the num...