Enzymatic Mechanisms of Cyanobacterial Toxin Tolerance Transfer to Offspring in the Cladoceran Daphnia Magna

The effects of cyanobacterial toxins on zooplankton are very important for understanding the freshwater ecosystem. In this work we analyzed the effects of one of the most important toxins (microcystin-LR) on the freshwater zooplankter Daphnia magna. The age dependent effects were determined, showing that neonates and adults show different responses to acute exposure to microcystin-LR. In addition, transgenerational effects were analyzed by exposing acutely and chronically the progeny of exposed and non-exposed mothers. We found that given enough time and concentration of exposure of the mothers, the progeny are born with an increased response of the biotransformation enzyme (glutathione S transferase). Moreover, we show that these groups of Daphnids have reduced mortality when exposed to the toxin compared with the progeny from non-exposed mothers. These results explain the biochemistry behind the transgenerationally acquired tolerance to microcystin and helps understanding the energy transfer on freshwater food webs under toxic stress.