Integrated evaluation of the biological response of the earthworm Eisenia fetida using two glyphosate exposure strategies: soil enriched and soils collected from crops in Southeastern Mexico

Abstract

Abstract Under laboratory conditions, the toxicological effects of pesticides tend to be less variable and realistic than in field studies, limiting their usefulness in environmental risk assessment. In the current study, the earthworm Eisenia fetida was selected as a bioindicator for assessing glyphosate toxic effects in two different trials to solve this question. In Trial 1, the worms were exposed for 7 and 14 days to concentrations of a commercial glyphosate formulation (1 to 500 mg a.i. kg − 1) currently in the field. For Trial 2, the worms were kept in nine soils collected from different plots with crops for 14 days of exposure. In both experiments, glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and acetylcholinesterase (AChE) activities and contents of lipid peroxidation (LPO) were evaluated. In T1, glyphosate formulation produced a 40% inhibition of AChE activity and a significant increase in GST, SOD, CAT, GPx activities, and LPO contents of E. fetida on day 7. In T2, higher concentrations of glyphosate were detected in soils of soybean, papaya, and corn (0.92, 0.87, and 0.85 mg kg − 1), which induced a positive correlation between the levels of glyphosate residues with GST, SOD, CAT, GPx, and LPO, and negative with AChE. These findings indicate that crop soils polluted with glyphosate elicited higher oxidative stress than in laboratory conditions, confirmed by IBRv2, PCA, and AHC analysis.