Physical Responses of Lates calcarifer to Acute Nitrite Stress

Abstract

Abstract_The acute toxicity of nitrite (133.33, 266.66, 399.99mg/L) to 15 days posthatched Lates calcarifer (barramundi) was studied by semi-static bioassay method; 0 mg/L nitrite was used as control. Samples were obtained at 0, 6, 12, 24, 36, 48, 72 and 96 h respectively to measure and analyze the activity of antioxidant, digestive enzymes, and concentration of serum cortisol. Nitrite concentration and exposure time significantly affected the antioxidant and digestive enzymes activities. By the end of the experiment, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the experimental group were significantly higher than in the control group, while peroxidase (POD) and catalase activities were significantly lower than in the control group except for in higher concentrations. Differing from POD and catalase, the acid phosphatase (ACP) activity of sub-concentration treatment was significantly higher than in the control group. Amylase activity in the nitrite stressed group was significantly lower than the control group, while the results of protease and lipase activity were reversed. Cortisol activity was delayed because of acute nitrite stress in the barramundi. Lates calcarifer showed certain short-term tolerance to nitrite stress. Results from the present study indicate that nitrite stress stimulates the responses of antioxidant and digestive enzyme activity and cortisol in fish, and these parameters can be used as physical indicators of stress.