Chronic acephate exposure disrupts neuroimmune and oxidative balance in Eisenia andrei: A multi-biomarker and histopathological approach

The chronic effects and mechanisms of action of acephate on terrestrial organisms remain poorly understood. In this sense, this study evaluated the sublethal effects of chronic acephate exposure in Eisenia andrei earthworms, focusing on neurotoxicity, oxidative stress, cyto-genotoxicity and histopathological biomarkers. Earthworms were exposed to soils containing 20, 40, and 90 mg a.i. kg⁻¹ acephate for 14, 28, 42, and 56 days. Acephate and its biologically active metabolite, methamidophos, were quantified in soil through Liquid Chromatography-Tandem Mass Spectrometry (LC–MS/MS). Acetylcholinesterase (AChE) activity in exposed earthworms decreased by over 50%, while antioxidant enzyme activities, namely superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), significantly increased (26–348%) at 42 and 56 days. Oxidative damage was evident from increased malondialdehyde (MDA) levels (48–147%) from day 28 onwards and higher protein carbonyl (PTC) content (21–80%) across all time points. Immune responses were also affected, with increased coelomocyte density and viability observed at day 14, followed by decreased viability at the highest acephate concentration. A shift in coelomocyte composition was observed, favoring amoebocytes over eleocytes throughout the exposure period. Significant DNA damage was detected, of up to 535% and 249% increases at day 56 for the 40 and 90 mg kg⁻¹ treatments, respectively. A histopathological analysis revealed irreversible damage to earthworm body walls after 56 days. These findings provide new insights into the chronic sublethal effects of acephate on E. andrei , emphasizing the importance of chronic studies using molecular biomarkers to assess the impacts of pesticides on non-target soil organisms. • Acephate rapidly degrades, but its metabolite methamidophos poses ecotoxic risks. • Chronic acephate exposure inhibits AChE and triggers oxidative stress in earthworms. • DNA damage and immune modulation are observed after long-term acephate exposure. • Histopathological damage can affect ecological earthworm functions, • Chronic multi-biomarker studies help predict ecological pesticide exposure impacts.