Different Sensitivities of Biomarker Responses in Two Epigeic Earthworm Species After Exposure to Pyrethroid and Organophosphate Insecticides

Abstract

In many studies that investigate the toxic effects of pollutants on earthworms, experiments are performed using only one species of earthworms, most commonly the Eisenia species. However, the differences in sensitivities of different earthworm species could potentially lead to an underestimation of environmental aspects of pollutants. Therefore, the aim of this study was to compare the sensitivity of biomarker responses of Eisenia andrei, an epigeic compost species commonly used in laboratory experiments, with those of Lumbricus rubellus, an epigeic species widely distributed in temperate regions. The earthworms were exposed to the three commonly used insecticides: organophosphates dimethoate (0.03, 0.3, and 3 mg kg(-1)) and pirimiphos-methyl (0.02, 0.2, and 2 mg kg(-1)), as well as pyrethroid deltamethrin (0.01, 0.1, and 0.5 mg kg(-1)), for 1 and 15 days using an artificial soil test. The effects of the pesticides were assessed by measuring the activities of acetylcholinesterase (AChE), carboxylesterase (CES), catalase (CAT), glutathione S-transferase (GST) as well as the concentration of glutathione (GSH). The pesticides caused a significant inhibition of AChE and CES activities and significant changes in activities of CAT, GST, and GSH concentration in both earthworm species. A comparison of biomarker responses between E. andrei and L. rubellus showed significant differences; E. andrei proved to be less susceptible to pesticide exposure than L. rubellus. In addition, the results from the filter-paper contact test mortality experiments showed that lethal concentrations were lower for L. rubellus compared with the E. andrei, further showing a greater sensitivity of L. rubellus. The difference in sensitivities of these epigeic species should be taken into account when conducting toxicity studies.