THE LOCALIZATION OF ALUMINUM IN THE DIGESTIVE GLAND OF THE TERRESTRIAL SNAIL HELIX-ASPERSA

The terrestrial snail Helix aspersa was exposed to food containing ele vated levels of aluminium for up to 33 days and the digestive gland ex amined by light and electron microscopy and X-ray microanalysis. Four types of cell are found in the digestive gland, (digestive, excretory, calcium and thin) although aluminium was only found in the excretory cells. The aluminium was localised in the 'yellow' or excretory granul es that are a characteristic feature of the excretory cells. Aluminium was only found in the granules of snails fed aluminium but there was no difference in the appearance of granules from control or aluminium- fed snails. The granules were large (up to 20 mu m in diameter), irreg ularly shaped and electron-dense. Sulphur, phosphorus and calcium were detected in granules from all snails. The presence of sulphur may ind icate protein residues. The amount of aluminium and phosphorus in the granules increased over the experimental period but the number of gran ules did not change. Levels of aluminium in the granules decreased whe n the snails were given control food. The role of the excretory granul es in the localisation, detoxification and excretion of aluminium is d iscussed.