Copper and nutrition in Helix pomatia (L.)

Summary

• 1. In Helix pomatia the efficiency of assimilation of both food (lettuce) and copper is always high, even when the food has been artificially enriched with copper. In short-term feeding experiments with lettuce containing 1390 (±420)ppm copper about 97% of the metal ingested remains in the snail.

• 2. The availability of copper in the faeces is independent of the type of food and does not differ much from the availability of the metal in untreated lettuce. About half of the metal can be extracted by 0.1 M HCl, whereas the other half is liberated only by ashing.

• 3. The concentration of copper in the organs of a natural population of H. pomatia varied between 20 and 120 ppm (dry weight). Being by far the largest organ the foot contains most of this copper. After the snails have fed on copper-enriched food for three weeks the concentration of copper increases mainly in the alimentary tract and in the midgut gland, but no one organ is capable of concentrating copper to a much higher degree than another. In winter animals which had been feeding on copper-enriched food prior to hibernation, the concentration of copper in several organs may reach values that are from 10 to 40 times higher than those in summer animals.

• 4. When snails begin to feed on copper-enriched food the concentration of the metal increases quickly in the anterior alimentary tract. After three days a striking increase in the midgut gland takes place, followed, after five days, by a further accumulation of copper in the tissues of the alimentary tract, mainly of the intestine. In the albumen gland and in the foot the concentration of copper remains more or less constant.

• 5. In midgut and albumen gland more than 90% of the total copper is so tightly bound that it can be liberated only by ashing, whereas in the walls of the alimentary tract between 55 and 70% of the copper can be extracted with 0.1 M HCl.

• 6. If gastropods and isopods are compared with regard to the efficiency of their assimilation of copper it can be shown that this remains high as long as the ingestion of food (dry weight) does not exceed approximately 3% of fresh body weight per day.