Is the Cadmium Uptake from Soil Important in Bioaccumulation and Toxic Effects for Snails?

To evaluate the contribution of digestive and epithelial transfer of Cd from soil to snail, Helix aspersa was exposed to an artificial substrate contaminated with 0,100,500, and 1000 microg Cd.g(-1) for 4 weeks under laboratory conditions. Two modes of exposure were used: (1) the snails were in direct contact with the substrate (DC) or (2) were separated from substrate with a perforated plate (no contact (NC)) which allowed ingestion of substrate but avoided epithelial contact. Cd concentrations in DC snails were twice as high as in NC snails. The bioaccumulation factors were 0.51+/-0.13 in DC snails and 0.26+/-0.04 in NC snails. Dose-dependent growth inhibition was noted in DC snails (500<EC(50)<1000 microg.g(-1) and EC(10) around 100 microg.g(-1)) while only slight effects were noted in NC snails. Internal Cd concentrations in DC and NC snails were linearly correlated with growth effect whatever the contamination route.