氨氮急性胁迫对日本沼虾(Macrobrachium nipponensis)死亡率、耗氧率及窒息点的影响

ACUTE EFFECTS OF AMMONIA EXPOSURE ON MORTALITY, OXYGEN CONSUMPTION, AND SUFFOCATION POINT IN FRESHWATER SHRIMP MACROBRACHIUM NIPPONENSIS

采用静水停食法,在水温(24.0±0.2)°C、p H(7.61±0.04)条件下开展了氨氮对日本沼虾(Macrobrachium nipponensis)[体长(4.29±0.32)cm,体质量(1.80±0.12)g]的急性毒性实验,并以此为基础测定了不同氨氮质量浓度胁迫下日本沼虾的耗氧率与窒息点。结果表明:(1)氨氮对日本沼虾24h、48h、72h、96h的半致死质量浓度依次为7.922、6.034、4.237和3.371mg/L;(2)鳃是氨氮攻毒日本沼虾的重要靶器官,氨氮对日本沼虾耗氧率的影响具毒物兴奋效应,0.225mg/L为该效应达到峰值的氨氮质量浓度,0.337mg/L为该效应被终止的氨氮质量浓度临界阈;(3)在对日本沼虾耗氧率的影响具毒物兴奋效应的氨氮质量浓度范围内,日本沼虾的窒息点随氨氮质量浓度的梯次升高渐次呈稳定、略增、再稳定之态势,氨氮质量浓度0.112mg/L为致该虾窒息点发生显著改变的临界阈,该实验组窒息点含氧量与对照组无差异(P<0.05)。

The acute toxicity experiment of ammonia to freshwater shrimp Macrobrachium nipponensis in total length(4.29±0.32)cm and weight(1.80±0.12)g was carried out in static water without feeding at water temperature(24.0±0.2)°C and p H(7.61±0.04). Oxygen consumption rate and the suffocation point of M. nipponensis exposed to different concentrations of ammonia were measured. The results are followed.(1) The LC50 of ammonia on shrimp at 24, 48, 72, and 96 h were 7.922, 6.034, 4.237, and 3.371 mg/L, respectively.(2) Ammonia affected the hormesis on oxygen consumption of M. nipponensis. The highest average oxygen consumption rate was obtained at a concentration of 0.225mg/L(P<0.05). The hormesis terminated at the concentration of 0.337mg/L.(3) Gill was the important target through which ammonia invaded. Within the concentration range of ammonia hormesis, the effect of ammonia on the suffocation point of M. nipponensis experienced from no-change, to slight increase, and to no-change again with the increase of ammonia concentration. The threshold ammonia concentration at which remarkable change in average suffocation point of M. nipponensis stopped was 0.112mg/L, and the oxygen consumption in that group showed no significant difference from that of the control group(P>0.05).