Patterns of accumulation, distribution and liberation of Zn, Cu, Cd and Pb in different organs of the land snail Helix pomatia L.

The snail Helix pomatia was fed lettuce enriched with zinc, cadmium, lead and copper for 32 days, followed by a feeding period of 40-50 days with uncontaminated lettuce. The time-dependent distribution of the four metals during loading and unloading was determined in all major organs. Four general types of response to metal loading have been distinguished. Another general feature is the rhythmic nature of accumulation and de-accumulation of metals in several organs. On the other hand, each metal also elicits specific responses which can be described in terms of acute or delayed reaction and long-term accumulation. Lead is accumulated by most organs and redistributed after loading has stopped, but a single organ, the midgut gland, accumulates about 90% of this metal. Zinc accumulates in most organs during the first part of the loading period and is then redistributed to the midgut gland which may hold up to 70% of the metal at the end of the experiment. Cadmium is not taken up at all by a number of organs but the midgut gland and anterior gut keep accumulating it. After loading has been terminated the metal appears to move from the midgut gland to the gut. Copper is distributed more evenly than the other metals in the organs of the snail, the midgut gland not playing a dominant role in the storage of this metal.