Transmission of DNA damage and increasing reprotoxic effects over two generations of Daphnia magna exposed to uranium.

This study aimed to examine the mechanisms involved in the transgenerational increase in Daphnia magna sensitivity to waterborne depleted uranium (DU) under controlled laboratory conditions. Daphnids were exposed to concentrations ranging from 2 to 50 μg L(-1) over two successive generations. Genotoxic effects were assessed using random amplified polymorphic DNA and real time PCR (RAPD-PCR). Effects on life history (survival, fecundity and somatic growth) were monitored from hatching to release of brood 5. Different exposure regimes were tested to investigate the specific sensitivity of various life stages to DU. When daphnids were exposed continuously or from hatching to deposition of brood 5, results demonstrated that DNA damage accumulated in females and were transmitted to offspring in parallel with an increase in severity of effects on life history across generations. When daphnids were exposed during the embryo stage only, DU exposure induced transient DNA damage which was repaired after neonates were returned to a clean medium. Effects on life history remained visible after hatching and did not significantly increase in severity across generations. The present results suggest that DNA damage might be an early indicator of future effects on life history.