Sadauskas-Henrique Helen, Wood Chris M, Souza-Bastos Luciana R, Duarte Rafael M, Smith Donald S, Val Adalberto L
Laboratory of Ecophysiology and Molecular Evolution, National Institute for Amazonian Research, Manaus, Brazil.
Santa Cecília University (Unisanta), Santos, Brazil.
J Fish Biol. 2019 Apr;94(4):595-605. doi: 10.1111/jfb.13943.
To assess how the quality and properties of the natural dissolved organic carbon (DOC) could drive different effects on gill physiology, we analysed the ionoregulatory responses of a native Amazonian fish species, the tambaqui Colossoma macropomum, to the presence of dissolved organic carbon (DOC; 10 mg l ) at both pH 7.0 and pH 4.0 in ion-poor water. The DOC was isolated from black water from São Gabriel da Cachoeira (SGC) in the upper Rio Negro of the Amazon (Brazil) that earlier been shown to protect a non-native species, zebrafish Danio rerio against low pH under similar conditions. Transepithelial potential (TEP), net flux rates of Na , Cl and ammonia and their concentrations in plasma and Na , K ATPase; v-type H ATPase and carbonic anhydrase activities in gills were measured. The presence of DOC had negligible effects at pH 7.0 apart from lowering the TEP, but it prevented the depolarization of TEP that occurred at pH 4.0 in the absence of DOC. However, contrary to our initial hypothesis, SGC DOC was not protective against the effects of low pH. Colossoma macropomum exposed to SGC DOC at pH 4.0 experienced greater net Na and Cl losses, decreases of Na and Cl concentrations in plasma and elevated plasma ammonia levels and excretion rates, relative to those exposed in the absence of DOC. Species-specific differences and changes in DOC properties during storage are discussed as possible factors influencing the effectiveness of SGC DOC in ameliorating the effects of the acid exposure.
为了评估天然溶解有机碳（DOC）的质量和特性如何对鳃生理产生不同影响，我们分析了一种亚马逊本土鱼类——巨脂鲤（Colossoma macropomum）在离子贫乏水体中，于pH 7.0和pH 4.0条件下对溶解有机碳（DOC；10 mg/l）存在时的离子调节反应。DOC是从巴西亚马逊州上里奥内格罗的圣加布里埃尔-达卡舒埃拉（SGC）的黑水分离出来的，先前研究表明，在类似条件下，这种DOC能保护非本土物种斑马鱼（Danio rerio）免受低pH的影响。我们测量了跨上皮电位（TEP）、Na⁺、Cl⁻和氨的净通量率及其在血浆中的浓度，以及鳃中Na⁺, K⁺-ATP酶、V型H⁺-ATP酶和碳酸酐酶的活性。在pH 7.0时，DOC的存在除了降低TEP外，影响可忽略不计，但它阻止了在无DOC情况下pH 4.0时发生的TEP去极化。然而，与我们最初的假设相反，SGC DOC并不能保护鱼类免受低pH的影响。与未接触DOC的巨脂鲤相比，在pH 4.0条件下接触SGC DOC的巨脂鲤经历了更大的Na⁺和Cl⁻净损失、血浆中Na⁺和Cl⁻浓度降低、血浆氨水平和排泄率升高。我们讨论了物种特异性差异以及储存期间DOC特性的变化，这些可能是影响SGC DOC缓解酸暴露影响有效性的因素。
