Abstract: An acute biological toxicity test of nitriteN (NO₂^--N) on Palaemonetes sinensis (with body weight of 0.28±0.05 g) was carried out in the laboratory at 18±1 ℃ and pH 7.3±0.1. The results showed that the median lethal concentrations of NO₂^--N for 24, 48, 72 and 96 h to P. sinensis were 37.9, 27.3, 24.9, and 23.2 mg·L^-1, respectively, and the safety concentration (SC) for 96 h was 2.32 mg·L^-1. Then the P. sinensis were exposed to five NO₂^--N concentrations (6, 9.5, 13, 16.5 and 20 mg·L^-1) and related nonspecific immunity indicators were measured at 24, 48 and 96 h. After exposure to NO₂^--N for 24 h, no significant difference for superoxide dismutase (SOD) activities in the hepatopancreas and muscles was observed among the different treatments (P>0.05), with the exception of the 20 mg·L^-1 treatment in muscle. At 96 h, the SOD activities in hepatopancreas of the 13, 16.5 and 20 mg·L^-1 groups were significantly lower than that in the control group (P<0.05). In comparison, muscle tissues in the 6 and 9.5 mg·L^-1 groups were significantly higher than that in the control group (P<0.05). At 24 h, there was no significant difference for either acid phosphatase (ACP) or alkaline phosphatase (AKP) activity in hepatopancreas, except that the ACP activity of the 20 mg·L^-1 group and the AKP activity in the 6 mg·L^-1 group were significantly increased. At 96 h, the ACP and AKP activities in the hepatopancreas for the 13, 16.5 and 20 mg·L^-1 groups were significantly decreased. In comparison, after exposure to NO₂^--N for 24 h, the ACP and AKP activities in the muscles showed a “poisonintoxication” effect, and they all increased significantly except the AKP activities in the 13  and 20 mg·L^-1 groups (P<0.05); at 96 h, there was no significant difference among the various treatments (P>0.05) except the 9.5 mg·L-1 group. It was concluded that P. sinensis could tolerate NO₂^--N of relatively high concentrations, but exposure to NO₂^--N for long durations had significant effects on the activities of nonspecific immunerelated enzymes in P. sinensis. Our results provide a better understanding on the healthy aquaculture of P. sinensis.

Key words: waterlogging, mowing, clonal seedling, invasion, plowing, seedling, herbicide