Integrated Ecotoxicological Assessment of Pymetrozine and Cartap Hydrochloride: Acute, Chronic, Biochemical, and Temperature Mediated Toxicity in Pheretima posthuma

Abstract

Acute, chronic, biochemical, and temperature mediated effects of Pymetrozine and Cartap hydrochloride were evaluated in Pheretima posthuma, a sentinel species for soil health. Dose dependent mortality was observed, with Cartap showing greater toxicity (LC50: 142 mg/kg soil) than Pymetrozine (185 mg/kg soil). Behavioral alterations including coiling, mucus secretion, and paralysis intensified with concentration, reflecting neuromuscular stress. Sub‑lethal exposure significantly reduced growth and reproduction, with declines in body weight, cocoon production, and juvenile emergence, particularly under Cartap. Biochemical assays revealed marked depletion of protein, carbohydrate, and lipid reserves after 60 days, indicating metabolic disruption and energy exhaustion; lipid reduction was most pronounced. Elevated temperature (26 ± 2 °C) synergistically enhanced toxicity, increasing mortality, biomass loss, and reproductive suppression compared to lower temperature (20 ± 2 °C). Findings confirm that earthworms are highly vulnerable to combined chemical and thermal stressors, underscoring their role as bioindicators and highlighting ecological risks of pesticide residues under changing climatic conditions.