The effect of γ-radiation on resting eggs and life cycle of cladoceran Moina macrocopa

The Sensitivity of Resting Eggs of the Cladoceran Moina macrocopa to the Effect of Ionizing Radiation during the Reactivation of the Eggs

We investigated the sensitivity of resting eggs of the cladoceran Moina macrocopa to the effect of ionizing radiation during the reactivation of the eggs. The study showed that the resting eggs during reactivation are more vulnerable to irradiation than the resting eggs in a stage of deep dormancy. The decrease in the efficiency of egg reactivation was observed at high doses, the growth rate of juveniles, fecundity, and the number of produced clutches by females strongly decreased when resting eggs at the reactivation stage absorbed doses of 64 Gy and higher.

Gamma irradiation of resting eggs of Moina macrocopa affects individual and population performance of hatchlings

We investigated the effects of γ-radiation on the survival of resting eggs of the cladoceran Moina macrocopa, on the parameters of the life cycle of neonates hatched from the irradiated eggs and on the performance of the population initiated from irradiated eggs. The study showed that γ-radiation in a range of doses from the background level to 100 Gy had no effect on survival of irradiated eggs. The absorbed dose of 200 Gy was lethal to resting eggs of M. macrocopa. The number of clutches and net reproductive rate (R₀) of hatchlings from eggs exposed to radiation were the strongly affected parameters in experiments with individual females. The number of clutches per female was drastically reduced for females hatched from egg exposed to 80-100 Gy. The most sensitive parameter was the R₀. The estimated ED₅₀ for the R₀ (effective dose that induces 50% R₀ reduction) was 50 Gy. Population performance was also affected by the irradiation of the resting stage of animals that initiated population. Populations that was initiated from hatchlings from resting eggs exposed to 100 Gy was of smaller size and with fewer juvenile and parthenogenetic females in comparison with control populations. Thus, we determined the dose-response relationship for the effect of gamma radiation on survival of resting eggs and individual and population responses of hatchlings from irradiated resting eggs. We conclude that for highly polluted areas contamination of bottom sediments with radioactive materials could affect zooplankton communities through adverse chronic effects on resting eggs, which will be transmitted to hatchlings at individual or population levels.