The epigeic earthworm Eisenia fetida is often used as the standard species in soil toxicological tests of pollutants; however, it does not present in mineral soil. Metaphire guillelmi, an anecic species, is a soil-dwelling species that occurs widely in China and has distinct differences in ecological characteristics from E. fetida. Using tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant, as a representative of organic pollutants, we studied the different behaviors of E. fetida and M. guillelmi in accumulating and transforming the pollutants and the different distribution of residues of the pollutants in the two earthworms. When exposed to TBBPA, both species had a similar toxic sensitivity to soil TBBPA. By means of radioactive tracer 14C-TBBPA, it was shown that M. guillelmi accumulated more TBBPA than E. fetida, evidenced by a 2.7-fold higher 14C-uptake rate and a 1.3-folds higher biota-soil accumulation factor. 14C accumulated mostly in the gut of M. guillelmi and in the skin of E. fetida, suggesting that 14C uptake in M. guillelmi mainly via ingestion of soil and in E. fetida mainly via epidermal adsorption. TBBPA was transformed to a large extent in M. guillelmi than in E. fetida; however, the major metabolites in both earthworms were TBBPA mono- and dimethyl ethers (O-methylation products of TBBPA). O-methylation of TBBPA in and depuration of O-methylation products from M. guillelmi were both rapid processes. Acute toxicity assessments showed that earthworms used O-methylation to detoxify TBBPA, and M. guillelmi had higher detoxification ability than E. fetida. However, at high concentration of TBBPA, the ability of M. guillelmi to transform TBBPA was greatly reduced, while the metabolizing ability of E. fetida was not affected, which was attributed to the higher tolerance of E. fetida to TBBPA. The results provide first insights into species-specific sensitivity of earthworms to soil pollutants and suggest that native earthworm species should be taken into account in soil risk assessments of pollutants.

Species-specific sensitivity of two ecologically different earthworms to TBBPA in soil

256th National Meeting (2018)

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