Quantification of cadmium transfers in crayfish: Marked differences between natural predation of field contaminated prey and force-feeding exposure.

O. Simon* and A. Boudou Actes du congrès ECORAD, 3-7 sept 2001, Aix en Provence, France Radioprotection - Colloques, volume 37, C1-841/ C1-846. * étudiant en contrat de thèse au laboratoire de l'IRSN.

The bioaccumulation of heavy metals depends on the uptake via both contaminated food and water, however the relative importance of these two routes often remains uncertain. The contributions of the direct and the trophic routes for cadmium (Cd) and zinc (Zn) contamination is unknown for most freshwater organisms. The aim of this work was to investigate Cd and Zn trophic bioaccumulation in crayfish Astacus astacus from Corbicula fluminea exposed in-situ at a contaminated site for 30 days. Zn concentrations in the crayfish after trophic exposure were found to be independent of the Cd contamination level of C. fluminea, demonstrating the homeostic regulation of this essential element. In contrast, Cd bioaccumulation at the whole body level of A. astacus reflected the level of contamination in the prey, Cd accumulated particularly in the digestive gland. The average transfer was be close to 5 % after 30 days' exposure. However, we a force feeding exposure experiment performed in order to control the mass prey consumed by the crayfish resulted in a much higher level of accumulation, after a 48 bout exposure, the trophic transfer was 58 %. The results of both experimental approaches show the importance of the trophic contamination route as q source of Cd and indicate that ingested Cd may be transferred via the hemolymph to other tissues, especially the digestive gland.