A COMPARISON BETWEEN PARTICULATE (ELEMENTAL) ZINC AND SOLUBLE ZINC (ZNCL2) UPTAKE AND EFFECTS IN THE MUSSEL, MYTILUS-EDULIS

The uptake of particulate (elemental) and soluble (ZnCl2) zinc was com pared in whole animals and individual organs in the mussel Mytilus edu lis. Analysis of seawater showed that the addition of particulate zinc resulted in a maximum concentration of 0.7 mu g/g dissolved zinc bein g present in the aquaria. Mussels exposed to either form of zinc at 10 mu g/g accumulated it readily, although considerable mortality was ex perienced after 14 days. After loading with particulate zinc, depurati on for 48 h significantly lowered (p < 0.001) the concentration of zin c in whole mussels. Mussels loaded at 2 mu g/g showed a similar patter n of accumulation to those exposed at 10 mu g/g, although with a lower mortality. Greater whole body concentrations were obtained with parti culate zinc than with soluble zinc. On an organ basis, the kidney, gil l, hepatopancreas, and mantle were the major sites of accumulation fol lowing both soluble and particulate zinc loading, although generally t he levels were lower with particulate loading, indicating the possible presence of two different uptake pathways. The flesh condition index of mussels subjected to 10 mu g/g particulate zinc declined compared t o the control animals. Degeneration of the digestive tubules and the s tomach was visible in zinc-loaded mussels while no such tissue damage was seen in control animals. Tissue damage, as indicated by the presen ce of large quantities of lipofuschin, occurred in the hepatopancreas and gonads of particulate zinc-loaded mussels. The results indicate th at soluble zinc is both absorbed and taken up by the tissues far more readily than is particulate zinc, and these results may be of signific ance with regard to zinc loading in the mussel Mytilus edulis.