Integrated computational and experimental evidence of biochemical and physiological perturbations induced by environmentally relevant thallium exposure in Daphnia magna

Thallium (Tl), a highly toxic heavy metal, poses a serious threat to freshwater ecosystems. This study investigated the chronic toxicity of Tl(I) in Daphnia magna using an integrated approach combining network toxicology, molecular docking, and biochemical assays. Network analysis identified 23 candidate enzyme targets, with significant enrichment in pathways related to glutathione metabolism, suggesting a potential involvement of antioxidant regulation in Tl(I)-induced toxicity. Molecular docking indicated energetically favorable spatial associations between Tl(I) and several enzymes, suggesting structurally plausible interaction regions rather than experimentally confirmed binding interactions, implying that Tl(I) may interfere with enzyme function through interactions with multiple targets. Chronic exposure experiments across environmentally detected, contamination-relevant, and high-stress Tl(I) concentration ranges further showed that Tl(I) significantly affected survival, growth, reproduction, and locomotor activity of D. magna. in a concentration-dependent manner. Biochemical measurements revealed alterations in key enzyme activities together with increased oxidative stress markers. Consistent with the docking predictions, several enzymes predicted as potential targets displayed measurable activity changes, indicating agreement between computational predictions and physiological responses observed at the organism level, although direct Tl(I)-enzyme binding was not experimentally validated. The results suggest that Tl(I) exposure may disturb redox balance and ion homeostasis through interactions with multiple enzymatic systems, ultimately contributing to physiological dysfunction and reduced reproductive performance. This study provides mechanistic integrated evidence that helps clarify potential pathways underlying Tl(I) toxicity and offers supports ecological risk assessment of thallium contamination in freshwater environments.