Earthworms play key roles in soils and sublethal effects of environmental toxicants on these organisms should be taken seriously, since they might have detrimental effects on higher ecological levels. Earthworms make important contributions to the breakdown of organic matter, soil fertility, and to the formation of soils. In laboratory experiments we have assessed sub-lethal effects of imidacloprid on two earthworm species commonly found in different agricultural soils (Lumbricus terrestris and Aporrectodea caliginosa). After 7 days of exposure in contaminated soil, a significant loss of body mass was found in both species exposed to imidacloprid concentrations as low as 0.66 mg kg-1 dry soil. These losses ranged from 18.3 to 39% for A. caliginosa and from 7.4 to 32.4% for L. terrestris, respectively. The detected sub-lethal effects were found close to the predicted environmental concentration (PEC) of imidacloprid, which is in the range of 0.33–0.66 mg kg-1 dry soil.
Source: Nils Dittbrenner, Rita Triebskorn, Isabelle Moser, Yvan Capowiez (2010) Ecotoxicology (attached)