Evaluation of acetylcholinesterase, glutathione S-transferase and catalase activities in the land snail Helix aspersa exposed to thiamethoxam

In the present study, adult snails Helix aspersa were used to estimate the effect of a neonicotinoid insecticide, thiamethoxam on the acetylcholinesterase (AChE), glutathione S-transferase (GST) and catalase (CAT) activities after a treatment of 6 weeks. During this period, snails were exposed by ingestion and contact to fresh lettuce leaves which were soaked with an insecticide solution. The thiamethoxam test solutions were 0, 25, 50, 100 and 200 mg/L, which are lower or equal to the concentrations that are applied in field. AChE activity was concentration-dependently inhibited by thiamethoxam. Also, GST and CAT activities were induced by neonicotinoide insecticide with a dose-dependent manner. The responses of these enzymes are probably related to an increase in the release of reactive oxygen species in the presence of thiamethoxam. These results suggest the neurotoxic effect of thiamethoxam on snails exposed to the lettuce contaminated with this insecticide. In same time, this compound has effects on the digestive system, in addition to this neurotoxic effect in Helix aspersa (non-target organism).