Abstract:Using the toxicity method, we studied the acute toxicity of ammonia nitrogen to Scylla paramamosain and its influence on phenol oxidase (PO), alkaline phosphatase (AKP), acid phosphatase (ACP), superoxide dismutase (SOD) , and lysozyme (LZM) in the conditions of different ammonia nitrogen concentrations of 0 (C0, control group), 10 (C10), 20 (C20), 30 (C30), 40 (C40), 50 mg/L (C50) and different times of 0, 6, 24, 48, and 72 h. The results showed that the semi-lethal concentration (LC50) at 24 and 48 h of ammonia-N were 104.793 and 66.124 mg/L respectively, and the safe concentration (SC) was 7.90 mg/L. The LC50 at 24 and 48 h of NH3-N were 8.396 and 5.298 mg/L respectively, and the SC was 0.63 mg/L. The LZM activity of each treatment group was significantly lower than that of C0 group (P<0.01) at 6, 24, 48, and 72 h. AKP and ACP activity of C10, C20, and C40 groups was significantly higher than that of control group at 24 h (P<0.05), while the SOD activity of the C20 group was significantly lower than that of other stress times (P<0.05). At 72 h, the PO activity of C30, C40, and C50 groups were significantly higher than that of C0 group (P<0.05). Under the experimental conditions, ammonia nitrogen that was lower than 40 mg/L could significantly enhance the AKP and ACP activity of S. paramamosain over a 24 h period, while 50 mg/L ammonia nitrogen had inhibitory effects. Ammonia nitrogen in all groups had significant inhibitory effects on LZM activity of S. paramamosain, which had no significant effect on SOD activity, but had an obvious enhancement effect on activity of PO by 72 h.
