碳酸盐碱度对达里湖瓦氏雅罗鱼耗氧率、氨氮排泄和排氨基因表达的影响

采用封闭流水式呼吸室法,研究了不同浓度碳酸盐碱度(以下简称CA,10、30、50、70、90、110 mmol/L)对体质量为(84.62±6.70)g的达里湖瓦氏雅罗鱼耗氧率、氨氮排泄率、血氨含量及排氨基因Rh家族(Rhag、Rhbg、Rhcg1和Rhcg2)在鳃组织中表达量的影响。结果表明,随着碱度的升高,瓦氏雅罗鱼的耗氧率和排氨率均表现为先下降后上升的趋势,且都显著低于对照组(P0.05)。在CA90时,耗氧率和排氨率均达到最低值,表明CA90可能是达里湖瓦氏雅罗鱼所能承受的最大碱度胁迫。相反,随着碱度的升高,瓦氏雅罗鱼的血氨含量呈现先上升后下降的趋势,在CA90时达到峰值。然而在CA0~50时,瓦氏雅罗鱼血氨含量无显著差异(P0.05),表明达里湖瓦氏雅罗鱼进化出特殊的排氨机制,使其体内能够保持较低的氨氮含量以此规避氨中毒。定量PCR显示,参与氨转运的4种Rh基因在不同碱度处理组均有不同程度的上调表达;其中Rhcg1和Rhcg2在高碱度(CA110)最为显著(P0.05),表明Rhcg1和Rhcg2可能在达里湖瓦氏雅罗鱼高碱胁迫下的排氨过程中发挥重要作用。能量代谢研究(O∶N)发现,在CA0~70时,雅罗鱼无需消耗过多能源物质即可实现高碱度胁迫下的能量需求;而在碱度为90~110时,则主要消耗脂肪和碳水化合物供能,减少蛋白质耗能,以此降低毒氨的产生。依据上述研究结果,深入探讨了达里湖瓦氏雅罗鱼在高碱胁迫下的排氨策略及其可能的生理和分子机制,为推动达里湖瓦氏雅罗鱼在不同类型盐碱水域的增养殖提供科学依据。

Effects of carbonate alkalinities on oxygen consumption, ammonia excretion and ammonia excretion gene expression in Leuciscus waleckii Dybowski

Effects of different concentrations of carbonate alkalinities on oxygen consumption rate, ammonia excretion rate, plasma ammonia content as well as relative gene expression profile of Rh family in gill of Leuciscus waleckii Dybowski fish were studied using close water flow respiration measurement chamber. Oxygen consumption rate and ammonia excretion rate were significantly inhibited in different alkalinity conditions in comparison with those in control, and the lowest values of them were found in CA90, which indicated CA90 may be the alkalinity limit for this species. Contrarily, the plasma ammonia content showed the opposite trend, first increasing then decreasing, and peaked in CA90. No significant difference was found for plasma ammonia content when CA ranged from 0 to 50 mM, indicating this species has evolved to have specific ammonia excretion mechanism and thus helps maintain the low level of toxic ammonia form. Quantitative real-time PCR showed that Rhcg1 and Rhcg2 out of the four tested genes in Rh family may play an important role in the process of ammonia excretion in high alkaline stress. Energy metabolism (O:N) study found that L. waleckii Dybowsk did not consume too much energy to satisfy the energy needs within tolerance range (CA0-70); however, when the environmental alkalinity was higher between 90 and 110, the body fat and carbohydrates became the main energy sources to reduce protein consumption, which in turn decreased the poisonous ammonia excretion. This study served to elucidate the ammonia excretion strategy and possible physiological and molecular mechanism of ammonia excretion in L. waleckii Dybowski under high alkaline stress and it may provide evidence for aquaculturing L. waleckii Dybowski species in different carbonate alkaline waterbodies.