Comparative analysis of antioxidant enzyme activities in Lithoglyphus naticoides and Theodoxus fluviatilis: insights into redox status and environmental adaptation

The study investigates the influence of environmental conditions on redox-regulating enzymes in two freshwater snail species, Lithoglyphus naticoides and Theodoxus fluviatilis, in the Serbian section of the Danube. These species have high population densities and are characterized by their easy accessibility for sampling making them suitable candidates for biomonitoring efforts. Given the increasing concern about pollution of freshwater ecosystems, this study addresses how different concentrations of trace metals (As, Cd, Cu, Hg, Ni, Pb, Zn) at two sites — Stari Slankamen and Novi Sad — affect the antioxidant enzyme responses of snails at different periods of the year. According to the consensus-based sediment quality guidelines, both studied localities show a significant load of trace metals, especially during the summer months. Nickel concentrations are over 36 mg/kg and Zn concentrations are over 200 mg/kg. Furthermore, the NS locality has an additional contamination with Cd of over 3 mg/kg. The study measures key antioxidant enzymes—superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase (GST)—as biomarkers of metal contamination. The results show that enzyme activities are generally higher in spring than in summer, underlining the seasonal influences on physiological responses. Preliminary results indicate that T. fluviatilis is more sensitive to environmental changes than L. naticoides, highlighting the need for species-specific considerations in biomonitoring. Long-term studies are recommended to further investigate the chronic effects of pollution on these species and to improve the understanding of the relationship between environmental conditions and physiological responses in freshwater ecosystems.