Histology, toxicity tests, and mortality of zebrafish (Danio rerio) following exposure to Butachlor

Abstract

This study aims to develop an environmental management model for the effects of the agricultural pesticide Butachlor based on an experimental toxicity model using zebrafish. The research is divided into two stages: Stage 1 involves performing laboratory studies, while Stage 2 focuses on developing environmental management strategies to mitigate the effects of Butachlor. The LC₅₀96h level was first determined in a pilot test. Then, in the main experiment, 600 zebrafish were randomly divided into four groups, each with three replications, for 30 days: T1 was exposed to 40% of the LC₅₀96h concentration of Butachlor, T2 to 60%, T3 to 80%, and there was a control group (C). Sampling occurred on days 0, 15, and 30 of the experiment, and histopathological examinations of the fish liver and gills were conducted. The histological results for the gills revealed several issues: hyperemia, swollen epithelium in the secondary lamellae, concentrated chloride cells at the base of the secondary lamellae, vasodilation, hyperemia at the tip of the secondary lamellae, and clubbed tips in the secondary lamellae of the groups exposed to Butachlor. Additionally, liver histology demonstrated changes in liver tissue, including hyperemia and fatty changes due to Butachlor exposure. These results indicate that Butachlor induced an oxidative stress response in the fish in a dose-dependent manner. Simultaneously, tissue damage increased with higher concentrations and longer exposure durations to Butachlor. Given the relevance of using zebrafish as a model for studying human diseases, the findings of this study are likely generalizable to humans and underscore the potential risk that Butachlor, sometimes used in rice fields, poses to human health.                                                                                   

Keywords: Butachlor, zebrafish, oxidative stress, histology.