Alteraciones fisiológicas como consecuencia de la exposición a plaguicidas en sucesivas generaciones de Daphnia Magna.

In the present study, a multigenerational chronic toxicity study is proposed in the cladoceran D. magna. The effect of sublethal concentrations of the insecticida diazinon and the herbicide molinate were evaluated in the daphnids. Parental generation (F0) and neonates from the first and third brood (F1-1st and F1-3rd, respectively) were exposed during 21 days to both pesticides, and offspring was also transfered to toxicant free medium (21 days assays) to evaluate its ability to recover from diazinon and molinate effects. On the other hand, the effect of these pesticides were evaluated during 5 days on the acetylcholinesterase (AChE) activity and protein content of all daphnid generations used in this study. Paralelly, weight changes were also evaluated in the parental daphnids (F0). The chronic multigenerational study showed that daphnids from the F1-1st and F1-3rd broods seem not to be adapted to the pesticides and they exhibited more mortality and less reproduction than F0. However, after the recovery period, offspring of D. magna pre-exposed to both pesticides was able to recover the values of the studied parameters and the third brood was the most recovered group. Diazinon effects were higher than those of the herbicide molinate in this 21 day study. Daphnids protein content decreased after exposure to both pesticides, and the effect of molinate was higher. Because molinate is an herbicide the nutritive quality of the algal food of D. magna will be affected. The decreased found in parentals weight after exposure to both pesticides was related to the effect on their reproductive ability. Finally, AChE activity was more inhibited on offspring daphnids exposed to both pesticides compared to the parentals. However, diazinon exposure showed a higher effect in this parameter than molinate because it produces a non reversible inhibition on this enzimatic activity. It was observed an interference of the protein content on the AChE activity expression, so we suggest the calculation of the AChE activity by organism nor by protein content. This suggestion could be important in those studies with small invertebrates where the AChE activity is determinated in the whole organism.