Advantages and limits of autometallography: application to the earthworm Eisenia fetida typica

In order to evaluate the degree of contamination of soil fauna by heavy met als, we used autometallography. Earthworms (Eisenia fetida) maintained in a cadmium-contaminated soil (an horticultural mould containing 80 mg/kg of c admium) were used as test animals. Autometallographic procedures were appli ed on paraffin sections (7 mu m) as well as on frozen sections (approximate ly 10 mu m), the later in order to prevent the loss of metal due to the his tological procedure (fixation, dehydration, paraffin embedding, etc.). Both controls and intoxicated animals showed silver deposits on chloragocytes. This labelling was correlated with the presence of iron in this cell type. The only differences observed in cadmium intoxicated animals concerned firs tly, a weak reaction over the cuticle and secondly, the presence of cadmium -contaminated soil in the digestive tract. The presence of soil in the dige stive tract was never observed in controls and could be attributed to a dis turbance in the physiology of intoxicated worms. in conclusion, autometallo graphy not being metal specific and due to the amount of iron always presen t in chlorogocytes, the autometallographic procedure cannot be used as a di agnostic tool for soil contamination in the earthworm Eisenia fetida.