Abstract
In adults of the small fresh water teleost, Oryzias latipes, it was shown that the curve showing the relationship between the survival time after X-irradiation and the dose applied is similar in shape to those reported for laboratary rodents : Small doses of X-rays did not exert acute lethal effect on the fish, while very large doses killed the irradiated fish instantaneously. Between these extremes, some dose ranges were distinguishable from others by the difference in effects on the post-irradiation survival time. The survival times of adult fish irradiated with various doses within the range from 4 kR to 32 kR were approximately the same. When the fish were irradiated during early embryonic stages, such “dose-independent range” as demonstrated in adult, was not demonstrated and dose-survival time relationship curves for the embryos were simpler in shape than those for adults of the same species. A possible explanation for the change in the relationship during embryonic development is discussed.
