Linear threshold effects of Daphnia magna γ-irradiation at low doses

With y-irradiation of Daphnia magna Straus, dose-independent effects were observed in the range 0.01-0.1 Gy with a threshold transition to a new lethality level at 1.0 Gy. This 25% lethality level was retained for doses up to 100 Gy and was followed by the second transition to the 100 % lethality level at doses 250-600 Gy. Similar dose-independent threshold effects were found for Daphnia magna fertility, number of litters and cardiac rate. The mechanism of nonlinear effects of irradiation at low doses has been connecting with the epigenetic processes in the cells and the elimination of genetic damages. The obtained results provide a crucial argument in support of environmental safety of nuclear facilities at normal operation and of medical radiology techniques.