ORIGINAL ABSTRACT

Copper (Cu) and glyphosate are ubiquitous contaminants in aquatic environments, with well-documented individual toxicological effects. However, the mechanisms underlying their combined toxicity and the dual role of glyphosate remain unclear. In this study, Daphnia magna (D. magna) was used as a model organism to investigate the effects of acute exposure to 10 μg L-1 Cu, 20 mg L-1 glyphosate, and their mixture. An integrated approach was employed, including physiological, histopathological, biochemical, transcriptomic, and metabolomic analyses. Results showed that glyphosate reduced Cu bioaccumulation in D. magna during 24-96 h of exposure, thereby alleviating Cu-induced toxicity. This mitigation was manifested as increased body length at 48-72 h, reduced intestinal damage and apoptosis, and modulated antioxidant enzyme activities. Additionally, glyphosate exerted independent molecular disturbances, including downregulation of genes involved in the neuroactive ligand-receptor interaction pathway and inhibition of amino acid metabolism. Co-exposure induced 1044 differentially expressed genes (DEGs), in contrast to 610 DEGs in the Cu-alone group and 859 DEGs in the glyphosate-alone group. These DEGs were significantly enriched in starch and sucrose metabolism and oxidative phosphorylation pathways. Metabolomic analysis further revealed that Cu partially reversed glyphosate-induced inhibition of amino acid metabolism. Collectively, these findings clarify the interactive effects between Cu and glyphosate, providing valuable insights for the risk assessment of aquatic co-pollutants.