The garden snail (Helix aspersa) as a bioindicator of organophosphorus exposure: Effects of dimethoate on survival, growth, and acetylcholinesterase activity

The garden snail (Helix aspersa) is currently used as bioindicator of metal lic pollution. Our objective was to extend its use to organic chemicals by studying the effects and tissue concentrations of the organophosphorus pest icide dimethoate following dietary uptake. After exposure for four weeks to increasing doses of pesticide in the diet, the median lethal concentration (LC50) was determined to be 3,700 mug/g food. Clinical signs indicated a n o-observed-effect concentration of 100 mug/g and a lowest-observed-effect c oncentration of 250 mug/g. The growth parameters were decreased with increa sing exposure to the pesticide. The median effective concentration (EC50), which was evaluated based on both shell diameter and dry weight inhibitions , was 665 and 424 mug/g, respectively, and the EC10 was 180 and 145 mug/g, respectively. Accumulation in the viscera was related to the amount of dime thoate in the food. The bioconcentration factors were low (>6 x 10(-3)). Ac etyleholinesterase (AChE) activity was strongly decreased (80% from 250 mug /g). In conclusion, we demonstrated that the species H. aspersa could be a useful sentinel organism for organophosphorus contamination surveys. Among the effects measured, the inhibition of AChE activities and clinical signs were the most sensitive, followed by the growth parameters. These results c onfirm the suitability of the garden snail for development of sublethal tox icity tests using primary consumers and aboveground organisms.