Bioaccumulation of cadmium by Lumbricus terrestris

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Abstract
Two experiments were carried out to determine cadmium bioaccumulation in Lumbricus terrestris (Oligochaeta—Annelida). In the first one cadmium contaminated sewage sludge was added to an earthworm culture. Worms cadmium content has increased, related to culture residence time (up to six months) whereas, in control culture, such an increase was not observed even if the content of worms were greater than soil content. Cadmium was analysed in some groups of organs.1 The results show that cadmium is mainly accumulated in intestinal and associated chloragogenous tissue compartment. From 85 to 95% of total cadmium mass found in worms is located in this organ (control worms as well as contaminated worms). Intestinal cadmium concentration raised to 120ppm in contaminated culture where soil cadmium content was 3 ppm. In the second experiment, earthworms were exposed to intentionally contaminated food. Bioaccumulation was also found to be significant. This observation seems to show that a part of resorbed cadmium comes from the digestive system where it can diffuse in the whole organism as observed. A cadmium increase in excrements has also been observed when the content of worms was sufficiently high.

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