Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal do Amazonas, Manaus, AM, Brazil.
Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal do Amazonas, Manaus, AM, Brazil.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Dec;262:111076. doi: 10.1016/j.cbpa.2021.111076. Epub 2021 Sep 14.
The osmotic physiology of freshwater stingrays was investigated in fifteen species from white (WW), black (BW), and clearwater (CW) rivers of Brazilian hydrographic basins. Regardless of phylogeny, potamotrygonids collected in the BW (Negro, Jutai, Nhamunda, and Manacapuru rivers), and CW (Tapajos, Parana, Mutum, Demeni, and Branco rivers) exhibited lower levels of osmolytes and plasma osmolality than those from WW (Amazon estuary, Solimoes, and Tarauaca rivers). However, the gill and kidney Na/K-ATPase activities were higher in the potamotrygonid species from BW and CW than those from WW. These results may be related to the ability of the potamotrygonids to achieve high ion uptake from ion-poor waters, such as those of BW and/or CW. Additionally, the high kidney Na/K-ATPase activity may help to minimize ion loss and generate diluted urine. Thus, diffusional losses of salts are balanced by uptake of ions in the gill, and reabsorption by the kidney. The physiological traits showed a weak phylogenetic signal, which indicates a strong evolutionary convergence. Multivariate analyses revealed that variations in physiological traits has a significant association with the type of water, as well as its physical and chemical characteristics such as electric conductivity and pH. Therefore, the South American Neotropical freshwater stingrays adjust their osmoregulatory mechanisms according to the environment in which they live.
我们研究了来自巴西流域白水（WW）、黑水（BW）和清水（CW）的 15 种淡水𫚉鱼的渗透生理学。无论系统发育如何，在 BW（内格罗河、朱塔伊河、纳姆unda 河和马纳卡普鲁河）和 CW（塔帕若斯河、巴拉那河、穆图姆河、德梅尼河和布兰科河）中收集的 Potamotrygonids 表现出的渗透溶质和血浆渗透压水平低于来自 WW（亚马逊河口、索利蒙伊斯河和塔劳阿卡河）的 Potamotrygonids。然而，来自 BW 和 CW 的 Potamotrygonids 的鳃和肾脏 Na/K-ATPase 活性高于来自 WW 的 Potamotrygonids。这些结果可能与 Potamotrygonids 从贫水（如 BW 和/或 CW）中摄取高离子的能力有关。此外，高肾脏 Na/K-ATPase 活性可能有助于最小化离子损失并产生稀释尿液。因此，盐的扩散损失通过鳃的离子摄取和肾脏的重吸收来平衡。生理特征显示出微弱的系统发育信号，表明强烈的进化趋同。多元分析表明，生理特征的变化与水的类型以及其物理和化学特性（如电导率和 pH）有显著的关联。因此，南美洲新热带淡水𫚉鱼根据其生活环境调整其渗透调节机制。
