Toxicity Assessment of Pretilachlor and Bispyribac Sodium on Eisenia fetida through Acute Reproductive Biochemical and Temperature Dependent Effects

Abstract

Soil ecosystems are fundamental to agricultural sustainability, with earthworms serving as keystone species and reliable bio-indicators of chemical stress. This study evaluated the ecotoxicological effects of two widely used rice field herbicides, Pretilachlor and Bispyribac Sodium on Eisenia fetida under controlled laboratory conditions. Acute toxicity assays revealed that Pretilachlor was more potent, with a lower LC50 (0.085 mg/cm²) compared to Bispyribac Sodium (0.142 mg/cm²), and induced pronounced morpho-behavioral alterations. Growth and reproduction studies demonstrated concentration dependent declines in biomass, cocoon production, juvenile emergence, and hatchability, with Pretilachlor exerting stronger inhibitory effects. Biochemical analyses confirmed metabolic disruptions, including depletion of carbohydrate, lipid, and protein reserves, elevated malondialdehyde (MDA) levels, and suppressed catalase (CAT) activity, indicating oxidative stress and impaired antioxidant defense.

Temperature dependent assays further highlighted that elevated thermal conditions intensified herbicide toxicity, reducing LC50 values and exacerbating mortality and reproductive failure. The Eisenia fetida as a sensitive bioindicator for herbicide toxicity and underscore the ecological risks posed by Pretilachlor and, to a lesser extent, Bispyribac Sodium. The integration of acute, chronic, biochemical and environmental endpoints provides a holistic framework for soil ecotoxicology. The study emphasizes the need for sustainable agricultural practices, including bio-pesticide adoption and integrated pest management, to safeguard soil biodiversity and ecosystem resilience under increasing chemical and climatic stress.