Developmental Toxicity and Environmental Risk Assessment of Chlorothalonil: A Comprehensive Study Using Biomphalaria as a Model Gastropod

The threat of pesticide pollution to aquatic ecosystems is severe. Chlorothalonil, a broad-spectrum fungicide, causes toxic effects on non-target organisms. While previous studies have focused on mussels, clams, and fish, research on gastropods remains limited despite their critical ecological roles. This study systematically evaluated the toxicity of chlorothalonil across different developmental stages of B. glabrata, with B. straminea (Red) adults serving as a comparative reference. Results showed that the median lethal concentration (LC₅₀) was 0.3396 mg/L for B. glabrata embryos and 3.598 mg/L for adults, while the LC₅₀ for B. straminea (Red) adults was 2.315 mg/L. Chronic exposure (21 days) to sublethal concentrations significantly inhibited shell growth, reduced egg production, and increased abnormal egg masses concentration-dependently. Histopathological analysis revealed severe tissue damage at 0.8 mg/L, including reduced hemocyte density, hepatopancreatic acinar disintegration, and ovotestis vacuolation. These findings provide critical evidence of chlorothalonil’s environmental risks and emphasize the importance of evaluating pesticide effects on different developmental stages of non-target organisms.