Sodium Dodecylbenzenesulfonate-Induced Oxidative Stress and Tissue Damage in Tubifex tubifex: A Comprehensive Toxicological Study

: In this study, the acute and sublethal toxicity of SDBS was assessed using Tubifex tubifex. In an acute toxicity bioassay, the 96-hour LC₅₀ value for SDBS was determined to be 13.358mg/L. The survival probability of the test organism under elevated SDBS concentrations was further assessed using General Unified Threshold models of Survival (GUTS), where the GUTS-Individual Tolerance (IT) model was applied over the GUTS-Stochastic Death (SD) model. T. tubifex was exposed for 14 days to concentrations equivalent to 10% and 20% of the 96-hour LC₅₀ value (1.33mg/L and 2.67mg/L). Significant alterations were observed in total protein content, antioxidant enzyme activities, and histopathological markers. Specifically, levels of proteins, superoxide dismutase (SOD), and catalase (CAT) decreased, while glutathione S-transferase (GST), glutathione peroxidase (GPx), and malondialdehyde (MDA) increased, indicating oxidative stress. These findings suggest exposure to sublethal levels of SDBS may compromise physiological integrity and antioxidative defense mechanisms in invertebrates.