Cumulative Soil Metal Contamination Reshapes Oxidative and Neuroenzymatic Stress Responses in Ants Across an Industrial Pollution Gradient

Metal(loid) contamination is a persistent environmental stressor in terrestrial ecosystems, yet field-based evidence linking cumulative soil contamination to physiological responses in social insects remains limited. In this study, we investigated an industrial pollution gradient by measuring soil concentrations of potentially toxic elements across multiple sites and integrating multi-element exposure into a cumulative pollution index. Two ant taxa, Lasius niger (Linnaeus, 1758) and Tetramorium cf. caespitum (Linnaeus, 1758), were sampled using a standardized field design, and biochemical endpoints were assessed to characterize antioxidant defense, thiol-based redox status, oxidative damage, and neuroenzymatic responses. Ant homogenates were analyzed spectrophotometrically for antioxidant enzymes, reduced glutathione, lipid peroxidation, protein oxidation, and acetylcholinesterase activity compared with the local low-contamination reference site. In addition, PLI showed positive site-level associations with multiple biomarkers, suggesting coordinated covariation between cumulative soil contamination and biochemical responses. Because these analyses were based on site-level mean values and direct tissue metal burdens were not measured, the findings should be interpreted as field-based associations rather than evidence of direct internal dose–response or metal-specific causality. These findings suggest that cumulative soil metal(loid) contamination is linked to integrated oxidative and neuroenzymatic stress responses in ants and support the use of ant-based biomarkers as informative tools for ecological biomonitoring under field conditions.