Effect of carbaryl (carbamate insecticide) on acetylcholinesterase activity of two strains of Daphnia magna (Crustacea, Cladocera).

The present study was designed to investigate the effect of carbaryl (carbamate insecticide) on the acetylcholinesterase activity in two strains (same clone A) of the crustacean cladoceran Daphnia magna. Four carbaryl concentrations (0.4, 0.9, 1.8 and 3.7 µg L(-1)) were compared against control AChE activity. Our results showed that after 48 h of carbaryl exposure, all treatments induced a significant decrease of AChE activities whatever the two considered strains. However, different responses were registered in terms of lowest observed effect concentrations (LOEC: 0.4 µg L(-1) for strain 1 and 0.9 µg L(-1) for strains 2) revealing differences in sensitivity among the two tested strains of D. magna. These results suggest that after carbaryl exposure, the AChE activity responses can be also used as a biomarker of susceptibility. Moreover, our results show that strain1 is less sensitive than strain 2 in terms of IC50-48 h of AChE activity. Comparing the EC50-48 h of standard ecotoxicity test and IC50-48 h of AChE inhibition, there is the same order of sensitivity with both strains.