Influences of different standardised test methods on biochemical responses in the earthworm Eisenia fetida andrei

Studies were carried out to determine the effects on the metabolic activities of earthworms of experimental conditions used in toxicity assays. Earthworms (Eisenia fetida andrei) were maintained under constant environmental conditions, in the absence of toxic agents, using three standard toxicology assay procedures (the artisol, contact filter paper and artificial soil tests) for two periods of time. Two controls were used: (1) earthworms taken directly from stock cultures for analysis and (2) earthworms treated as in soil test but exposed only to the culture medium rather than artificial soil. Biotransformation markers (methoxyresorufin-O-deethylase, NADH and NADPH cytochrome reductases and glutathione-S-transferase activities) and indicators of oxidative stress (catalase activity, lipid peroxides and peroxidisable lipids) were investigated. The results demonstrated that substrates and handling can induce significant biochemical changes in worms maintained in uncontaminated media. None of the substrates were better than others in avoiding these artefacts. Hence, although the soil test is closer to the natural conditions for the worms than the contact or the artisol tests, it still had significant effects on the worms in the absence of toxic chemical. Great care must therefore be taken when comparing results from different ecotoxicological assay procedures.