2025-04-10https://repository.covenantuniversity.edu.ng/handle/123456789/47696Background: Amphibians are subjected to a variety of natural and artificial stresses that can compromise physiological balance. This study explored the variations in oxidative stress markers in Cosmocercan parasitized and non-parasitized Amietophrynus regularis in diverse conditions. The toad specimens were collected from natural habitats and dumpsites of three (3) major areas of Lagos. 15 g wet weight of the liver, intestine, and parasites were separately prepared and analyzed for oxidative stress parameters including; SOD, CAT, GSH, and MDA activities according to well-established protocols. Result: Based on stations, there were significant differences in the SOD levels in the liver and intestine of infected and uninfected toads obtained at the dumpsite and the natural habitat at p < 0.001. Also, the concentration of SOD in the parasites (238.86 ± 7.72 min/mg prot.) recovered from the toads at the dumpsite was very much significantly higher than the concentration in those recovered from the toads in the natural habitat (p < 0.001). The study has shown that the level of SOD released by the antioxidant defense system in response to the oxidative stress in the organism makes it a reliable tool for ecotoxicological assessment. All the oxidative stress markers except for MDA showed significant differences at p < 0.05 between the host tissues and the parasites irrespective of sampling locations indicating both organisms were stressed either due to the host-parasite relationship or from other environmental contaminants. Conclusions: The toad’s antioxidant defense system was typically sensitive and adaptable to environmental conditions, suggesting that it could be used in future research on effective ecotoxicological evaluation tools.application/pdfQH Natural history, QH301 BiologyArticle