中华绒螯蟹在不同pH值环境下的氮排泄

研究不同pH值环境对中华绒螯蟹（Eriocheir sinensis）氮排泄的影响。本研究采用直接浸浴法测定中华绒螯蟹在pH值4．5，6．0，7．5，9．0和10．5条件下的氮排泄。结果表明，在pH值9．0及其以下时，氨氮排泄无显著变化，当pH值升高到10．5时，氨氮排泄急剧下降，其排泄过程具有不连续性；亚硝酸氮、尿素氮和有机氮的排泄随pH值的升高而增加；硝酸氮的排泄同亚硝酸氮类似，但在pH值10．5时，呈下降状态；总氮的排泄随pH值升高而降低。在pH值4．5时，中华绒螯蟹的氨氮排泄量占总氮排泄量的91．0％，随着pH值上升，氨氮占总氮排泄的比例下降，而包括有机氮在内的其它形式的含氮化合物的排泄比例上升。因此．我们认为当环境pH值在9．0以下的范围波动时，不会对中华绒螯蟹的氨氮排泄带来不利影响，但过高的pH值可能会阻碍氮排泄。

Nitrogenous excretion of Chinese mitten crab at different ambient pH levels

In order to demonstrate the effects of ambient pH on nitrogenous substances excretion by Chinese mitten crab, Eriocheir sinensis, the crab was immersed to pH d. 5, 6. 0, 7.5, 9. 0 and 10. 5 for 2dh. The results indicated that the excretion of ammonia-N remained unchanged at pH 9. 0 or at lower pH conditions. However, at pH 10. 5, the excretion rates decreased dramatically, these phenomena implied discontinuous properties for ammonia excretion. The excretion of nitrite-N, urea-N and organic-N were increased in a pridependent manner. The nitrate-N excretion increased from pH d. 5 to 9. 0 while decreased at pH 10. 5. In contrast, total-N excretion decreased with the increased ambient pH. The ratios between different excreted nitrogenous substances also varied with the changes of the ambient pH. At pH d. 5, ammonia-N excretion accounted for 91.0% of the total nitrogenous excretion. The percentage of ammonia-N excretion dropped with increased pH, while other forms of nitrogenous including the organic-N excretion increased significantly. The results suggested that the fluctuations in ambient pH had no negative effects on ammonia nitrogen excretion when the environmental pH is below 9. 0; however, extremely high pH might impede the nitrogenous excretion of E. sinensis.