GENETIC CONSEQUENCES OF GAMMA-IRRADIATION OF CHIRONOMUS-THUMMI VIABILITY AND REPRODUCTION

Viability and reproduction of Chironomus thummi exposed to gamma-irrad iation at doses of 0.09, 0.9, 9, and 90 Gy and their nonirradiated pro geny were studied in subsequent generations. The radiosensitivity of C . thummi was shown to change during ontogeny. The highest radiosensiti vity is characteristic of embryonic developmental stages. After irradi ation of embryos, the radiation effect was expressed in the same gener ation. This allowed a comparison of radiation-induced genetic effects in irradiated chironomids and their nonirradiated progeny in subsequen t generations. The length of existence of populations derived from irr adiated C. thummi depended on radiation dose. At all doses, gamma-irra diation ultimately led to death of irradiated populations. Generation length, beginning moment, and duration of the reproductive period chan ged in consecutive generations of C. thummi irradiated at a dose of 0. 09 Gy. gamma-irradiation increased the proportion of sterile egg batch es both in irradiated animals and in their progeny in subsequent gener ations, indicating the appearance and maintenance of radiation-induced lethal mutations in populations.