Lethal and sublethal effects of acetamiprid on Eisenia andrei: Behavior, reproduction, cytotoxicity and oxidative stress

The neonicotinoid acetamiprid has been suggested as a worldwide substitute for organophosphates, due to its lower toxicity. The present study assessed several acetamiprid effects on Eisenia andrei earthworms in acute contact (ranging from 1.6 x 10(-5) to 0.16 mu g cm(-2) acetamiprid), behavioral (0.1, 0.5, 1 mg kg(-1)) and chronic (0.001, 0.01, 0.05 and 0.1 mg kg(-1) acetamiprid) assays carried out in natural soil. Reproduction, cytotoxicity (coelomocyte density and viability), immune cell typing (eleocytes and amoebocytes) and antioxidant defense system (glutathione (GSH), catalase (CAT) and glutathione S-transferase (GST)) responses were determined. The LC50 in the acute contact test was calculated as 1.86 x 10(-2) mu g cm(-2). Acetamiprid concentrations of 0.5 and 1 mg kg(-1) led to earthworm avoidance responses (NR = 61.09 +/- 10.01%) and habitat loss (NR = 78.02 +/- 12.03%), respectively. Reproduction was also affected, with a decreased number of cocoons and hatchlings per cocoon observed at 0.05 and 0.1 mg kg(-1). Amoebocytes were the predominant immune system cells during the 15th and 30th assay days, while eleocytes were the main cells observed at the 45th day. CAT activities on the 30th and 45th day of exposure were increased at the lowest acetamiprid concentrations (0.001 and 0.01 mg kg(-1)) and decreased with increasing pesticide concentration (0.05 and 0.1 mg kg(-1)). Maximum GST activities and GSH levels were noted at 0.01 mg kg(-1) acetamiprid. However, increasing concentrations led to GST inhibition, while GSH levels were maintained. A long-term acetamiprid exposure affected earthworm reproduction, behavior and immune and antioxidant systems, which could affect the ecological soil balance and, consequently, the entire food chain.