UPTAKE AND TOXICITY OF COPPER AND ZINC FOR THE AFRICAN EARTHWORM, EUDRILUS-EUGENIAE (OLIGOCHAETA)

Growth rate change in earthworms is considered to be a suitable endpoi nt when determining sublethal effects. In this study we evaluated grow th and maturation in the vermicomposting earthworm species Eudrilus eu ge niae as marker of sublethal toxicity of copper and zinc. We also co mpared routes of uptake. Apart from exposing worms experimentally for 73 days to contaminated food, a series of contact filter paper tests w as also performed to determine LD(50) for copper and zinc. Both copper and zinc at sublethal concentrations affected growth and maturation i n worms exposed to contaminated food. These worms had a copper content of 34.5 mu g g(-1) after 73 days and a zinc content of 184.9 mu g g(- 1), showing a differential uptake. Copper was more toxic than zinc. Al so in the contact test worms did take up more zinc than copper and the LD(50) (48 h) for copper was 0.011 mg cm(-2) and for zinc 0.066 mg cm (-2), which translated to body burdens of 6 mu g g(-1) for copper and 131 mu g g(-1) for zinc. Indications were that a regulatory mechanism existed for both metals. Both metals were taken up through the body wa ll at a relatively fast rate. This study indicated that the skin was t he major route of metal uptake. This study also showed a poor relation between the two types of tests for purposes of evaluating lethality o f zinc and copper.