Localization and fate of aluminium in the digestive gland of the freshwater snail Lymnaea stagnalis

The digestive gland of the freshwater snail Lymnaea stagnalis, exposed to w ater containing an elevated concentration of aluminium at neutral pH for up to 30 days, followed by a 20 day recovery period, was examined by light an d electron microscopy and X-ray microanalysis. Aluminium was localized in t he yellow granules present in the digestive and excretory cells and in the green and small granules present in the digestive cells. More aluminium, si licon, phosphorus and sulphur were present in all three granule types from aluminium exposed snails. The number of yellow and green granules from the digestive gland of aluminium exposed snails showed a progressive increase o ver the experimental period compared to controls. The number and aluminium content of the granules is likely to reflect the role of the digestive glan d as a 'sink' for accumulated aluminium, We propose that intracellular mono meric silica is involved in the detoxification of aqueous aluminium which a t neutral pH is largely in the form of an insoluble polyhydroxide, The incr eased amounts of sulphur and phosphorus in the granules are likely to be pa rt of a broad response to metal loading but probably do not play a signific ant role in the storage and detoxification of aluminium. (C) 2000 Harcourt Publishers Ltd.