Dose-dependent growth inhibition and bioaccumulation of hexavalent chromium in land snail Helix aspersa aspersa

The toxicity of Cr6+ was determined in a laboratory environment in the snai l Helix aspersa aspersa. The effects on growth were evaluated on animals re ared in controlled conditions at the age of one month that had been exposed for 28 d to increasing doses of Cr6+ mixed in with their food. Two experim ental groups were set up with concentrations of chromium in the feed of 250 to 1,250 mu g/g (test 1) and 100 to 800 mu g/g (test 2). Growth inhibition was dose dependent, and the mean EC50 calculated at four weeks for tests 1 and 2 were, respectively, 354.7 and 298.8 mu g/g and for the EC10 195.3 an d 160.9 mu g/g. The levels of Cr6+ bioaccumulated in the foot and the visce ra of the snails were dose dependent in both types of tissues. The highest concentrations occurred in the viscera, the levels being 0.79 mu g/g in the controls and reaching 3,067 mu g/g in the animals exposed to the maximum c ontamination (1,250 mu g/g). These high levels of bioaccumulation in additi on to the lower concentrations of Cr6+ excreted in the feces than those pre sent in the food suggest that chromium is not physiologically regulated by Helix aspersa. The results provide added support for the use of snails as a model to determine the toxicity of substances in laboratory biotests by me asuring the effects on growth and by assessing bioaccumulation.