Response of the freshwater fish, Oreochromis mossambicus to the environmental pollutant, nonylphenol

Exposure to nonylphenol on adult freshwater fish, Oreochromis mossambicus at sublethal concentration (0.15 mg/ L) for 24 h, 96 h and 7 days did not alter the body weights of the animal when compared with control groups. However, the weight of gill significantly decreased at 7 days of exposure and this was evidenced due to necrosis or atrophy of gill lamellae. Nonylphenol significantly decreased the activities of antioxidant enzymes with concomitant increase in the level of hydrogen peroxide and lipid peroxidation in all treatment groups thereby denoted that nonylphenol upsets the pro-oxidant and antioxidant status in the gills. A significant decrease in the activity of succinate dehydrogenase, a gill marker enzyme, at 96 h could be due to the impairment of aerobic metabolism and stress-related shift towards anaerobiosis at organ level in nonylphenol-treated fishes. Histopathology of gills showed three principal alterations as lamellar fusion, hypertrophy of lamellar epithelium and the mucous deposition over the respiratory epithelium. To summarize, the toxicity of nonylphenol was by the generation of reactive oxygen species in gill of the fresh water fish, Oreochromis mossambicus.