Vol. 4, Issue 1, Part E (2018)

Abstract
The present study was designed based on the hypothesis that if exposure to octylphenol could alter the antioxidant defense system in the muscle tissue of the fish, Oreochromis niloticus. Fish were exposed to sublethal concentration of octylphenol i.e., 50.6 µg/L for 24, 48, 72 and 96 h durations along with control groups. Octylphenol treatment showed significant (P<0.05) reduction in the activity of antioxidant enzymes as superoxide dismutase, catalase and glutathione reductase in time-dependent manner when compared to the corresponding control groups. However, the levels of lipid peroxidation and hydrogen peroxide generation showed a significant (P<0.05) increase in all treatment groups and this could be due to generation of free radicals in muscle tissues. The activity of acetylcholinesterase showed significant (P<0.05) decrease after 48 h of octylphenol exposure in muscle tissue indicating defect in the neurotransmission at neuromuscular junction. Octylphenol exposure showed alteration in histomorphology of muscle tissues as evidenced by degenerated muscle tissue with split muscle fibres after 24 and 48 h. Complete disorganization of muscle fibres after 72 h, whereas thickened and shortened muscle bundles noted after 96 h of octylphenol treatment. Therefore, the present study suggests that octylphenol altered the antioxidant defense system and also affects the histomorphology of muscle tissues in the freshwater fish, Oreochromis niloticus.