Investigating the toxic effects of ethoprophos on Eisenia fetida: Integrating light microscopy, scanning electron microscopy, and biochemical analysis

Abstract

This research investigated the ecological impact of exposing Eisenia fetida, an essential component of soil ecosystems, to the organophosphate pesticide ethoprophos, widely used in agriculture. With a focus on understanding the specific effects on earthworms, we employed three concentrations (7.5, 15, and 30 mg/kg) over 28 days, considering the pesticide's short half-life and existing data on environmental concentrations. We aimed to contribute to a broader understanding of how these pesticides affect soil health. Histological analysis, including staining with Hematoxylin-eosin, Mallory Trichrome, Periodic acid-Schiff, and Alcian blue methods, was conducted on control and treatment groups. The histological and histopathological results were evaluated using the light microscopy, revealing various degenerations in the epithelial and muscle layers. Scanning electron microscopy analysis detected concentration-related notable compaction of the body surface, asymmetry, and distortion in the body segments. In the exposed groups, especially those subjected to higher ethoprophos concentrations, the grid-like appearance of the clitellum was visibly disturbed. This disturbance in the grid-like pattern is indicative of structural changes and disruptions at the microscopic level. Furthermore, total protein, carbohydrate, lipid analyses, as well as acid phosphatase and alkaline phosphatase enzyme activities, were also evaluated for earthworms from each experimental group. The analyses showed a concentration-related decrease in all biochemical measurements, except acid phosphatase enzyme activity. In conclusion, our study reveals that the environmentally realistic concentrations of ethoprophos, an effective and widely used pesticide in pest control, have detrimental effects on the health and physiology of E. fetida. These effects are manifested through histological deformities, altered biochemical profiles, and observable physiological disturbances. These results shed light on the harmful effects of ethoprophos on earthworms, underlining the necessity to restrict its usage in agricultural practices and thereby support environmental sustainability.