Radiation in low doses reduces life span of Daphnia magna

The effects of low-dose gamma-irradiation on the crustacean Daphnia magna have been analyzed. Given that the LD50 for this species is approximately 100 Gy, one-day-old daphnids were exposed to 10, 100 and 1000mGy of acute gamma-rays. The survival of irradiated animals was evaluated over the maximum lifespan of 90 days. Increased mortality among irradiated at doses of 100 and 1000 mGy daphnids was found. Our data also showed that the observed decrease in survival of irradiated animals was attributed to their early aging, thus providing an important evidence for the effects of low-dose irradiation on early senescence. Overall, the results of our studies have shown that low-dose irradiation can result in a significant reduction in life span of exposed daphnids. As the majority of irradiated Daphnia showed reduced viability regardless the dose, our data therefore imply the presence of a threshold of dose of low-LET exposure capable of impairing the viability of this species. We have also found that parental irradiation significantly affected the survival of first-generation offspring, the magnitude of which cannot be attributed to the segregation of radiation-induced deleterious mutations. Potential implications of the results of our studies for the risk assessment of low-dose exposure have been discussed.