Ammonia-induced and Withdrawal-dependent Neurotoxic (Acetylcholinesterase) and Antioxidative (Catalase) Responses in Catfish, Clarias batrachus (Linnaeus, 1758)

Ammonia-induced and its withdrawal-dependent changes in acetylcholinesterase (AChE) and catalase (CAT) of liver, gill and skeletal muscle of Clarias batrachus (Linnaeus, 1758) were investigated. AChE activity declined gradually in these tissues up to 35 days of ammonia exposure. In contrast, CAT activity increased up to 7 days and thereafter, it declined to some extent. Maximum effects of ammonia on CAT and AChE were on 7th and 35th day of treatment respectively. AChE activity declined maximally in gills (61%), but CAT activity enhanced maximally in liver (1.6 fold). Withdrawal of ammonia from water for 14 days after 35 days of exposure indicated incomplete recovery in AChE activity. However, withdrawal of ammonia showed complete reversal in CAT. Removal of ammonia from water may help in damage control. Since ammonia-induced neurotoxic (AChE) effect was more pronounced than antioxidative (CAT) response, AChE may be used as an indicator of ammonia toxicity in aquaculture.