Title: Exploring the missing link between soil total antioxidant capacity and herbicide-induced stress on the earthworm Eudrilus eugeniae (Kinberg)

Abstract

Herbicide application and residue accumulation in farm soils have deleterious effects on non-target fauna such as earthworms. Although previous studies have documented both positive and deleterious effects of herbicides on soil biota, reports are rare on possible toxicity reduction by raising soil total antioxidant capacity (TAC). Here we review the impact of pretilachlor, a herbicide on the morpho-histology and physiology of the earthworm Eudrilus eugeniae in soil amended with farmyard manure (FYM), poultry manure (PM) and vermi manure (VM), sources of antioxidants over a period of 168 h. The results indicated a significant spike in the TAC of amended soils relative to control. Dermal undulation, setal aberrations, muscular anomaly, protein and lipid peroxidation variations in the activities of lactate dehydrogenase (LDH) and catalase (CAT) were significantly less in animals from amended soils. The maximum percent increase in protein (314%) and reductions in LPX (87%), LDH (87.9%) and CAT (87.3%) were observed in the earthworm from VM-amended soil. The increase in TAC was also maximum (109.9%) in soil amended with VM. A significant negative correlation between soil TAC with the biochemical parameters was observed and confirmed through receiver operator characteristics (ROC) and principal component analysis (PCA). The novelty of the present study includes exploring the missing link between the antioxidant level of organically amended soil and the herbicide-induced oxidative stress in the earthworm E. eugeniae. It was concluded that soils with high levels of antioxidants could reduce oxidative damage in E. eugeniae due to herbicide toxicity.