The Freshwater Ciliate <i>Coleps hirtus</i> as a Model Organism for Metal and Nanoparticle Toxicity: Mixture Interactions and Antioxidant Responses.

ABSTRACT: Heavy metals (HMs) and metal-oxide nanoparticles (NPs) frequently co-occur in freshwater systems, yet their combined effects on microbial predators remain poorly understood. Here, the freshwater ciliate Coleps hirtus was used to evaluate the cytotoxicity of single and binary mixtures of HMs (Cd, Cu, Zn) and NPs (ZnO, CuO, TiO₂, SiO₂), and to characterize associated antioxidant responses. Acute toxicity was assessed after 24 h by estimating LC₂₀ and LC₅₀ values, while mixture toxicity for Cd + Zn and Cd + ZnO was analyzed using the Toxic Unit approach and the MixTOX framework. Non-enzymatic (TPC, DPPH, HRSA) and enzymatic (CAT, GST, GPx, SOD) antioxidants were quantified as sublethal biomarkers at concentrations below lethal thresholds. HMs

SUBMITTER: Varatharajan GR 

PROVIDER: S-EPMC12922124 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature