Toxicity and possible food-chain effects of copper, dimethoate and a detergent (LAS) on a centipede (Lithobius mutabilis) and its prey (Musca domestica)

Toxicity of copper (Cu) and two biodegradable chemicalsÐan insecticide (dimethoate) and a detergent (LAS), was tested on a common forest litter invertebrate carnivore Lithobius mutabilis and its prey, Musca domestica. The chemicals were mixed into arti®cial food medium for house ̄y larvae, and the centipedes were kept on contaminated OECD soil and fed contaminated larvae. The concentrations of chemicals were selected to cover the whole range of survival of a prey animal: from no increased mortality (control) up to 100% mortality during development from egg to adult. The house ̄y larvae were signi®cantly more affected than their predators by all three chemicals. The LC50 values for house ̄y from egg to emergence were (in mg kg ÿ1 dry mass food): Cu, 708; dimethoate, 0.330; LAS, 110. In contrast, LC50 values for L. mutabilis for all three chemicals were above the range of concentrations tested: Cu > 1500; dimethoate > 0.8; LAS > 10 000 (nominal concentrations in soil and house ̄y medium). No signi®cant sublethal effects on body weight or respiration rates were found in centipedes. This may suggest that in contaminated areas, except for direct toxicity, a lack of food may be an important factor in reducing centipede populations. The centipede prey, being mostly detritivores feeding directly on and living in a contaminated medium, are more exposed to a toxicant than epigeic species such as centipedes. # 1999 Elsevier Science B.V. All rights reserved.