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 snail Helix aspersa aspersa. The effects on growth were evaluated on animals reared 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 experimental groups were set up with concentrations of chromium in the feed of 250 to 1,250 μg/g (test 1) and 100 to 800 μg/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 μg/g and for the EC10 195.3 and 160.9 μg/g. The levels of Cr6+ bioaccumulated in the foot and the viscera of the snails were dose dependent in both types of tissues. The highest concentrations occurred in the viscera, the levels being 0.79 μg/g in the controls and reaching 3,067 μg/g in the animals exposed to the maximum contamination (1,250 μg/g). These high levels of bioaccumulation in addition to the lower concentrations of Cr6+ excreted in the feces than those present 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 measuring the effects on growth and by assessing bioaccumulation.