Acute Exposure to Glyphosate, Arsenic, and Their Mixture in Adults of Cnesterodon decemmaculatus (Cyprinodontiformes: Poeciliidae): Insights From a Multi-Biomarker Approach.
Despite the frequent co-occurrence of glyphosate and arsenic in agricultural freshwater systems, the biochemical mechanisms underlying their combined toxicity in fish remain poorly understood. Here, we evaluated the acute (96 h) individual and joint effects of glyphosate (0.5 mg/L) and arsenic [As(III), 0.5 mg/L] on the Neotropical fish Cnesterodon decemmaculatus using an integrated biomarker approach. Endpoints related to oxidative balance, DNA integrity, neurotoxicity, and energy metabolism were assessed across multiple tissues. Glyphosate exposure induced marked oxidative and metabolic disturbances, including increased catalase activity, glutathione levels, and mitochondrial electron transport system activity, along with reduced cellular energy allocation and glutathione-S-transferase activity. In contrast, arsenic decreased glutathione content, superoxide dismutase activity, lipids, and carbohydrates. Comparable DNA damage levels were observed across single and combined exposures. Co-exposure resulted in non-additive interactions, with mixture effects deviating from the sum of individual responses, leading to either reduced (antagonistic) or enhanced (potentiation) effects depending on the biomarker and its direction of change. Antagonistic interactions predominated for genotoxic and several oxidative stress biomarkers, whereas potentiation was observed for selected metabolic endpoints. Multivariate analysis revealed distinct physiological profiles among treatments, with partial overlap between glyphosate and mixture responses. These findings underscore the complexity of pollutant mixture effects and highlight the need to incorporate combined exposures into ecotoxicological risk assessment.