Talbot C, Stagg R M, Eddy F B
Freshwater Fisheries Laboratory, Pitlochry, Perthshire, UK.
J Comp Physiol B. 1992;162(4):358-64. doi: 10.1007/BF00260764.
Atlantic salmon may return to the sea after spawning in fresh water. These fish, known as kelts, reportedly show a limited ability to hypoosmoregulate. However, this study shows that fresh-water-adapted kelts exposed to seawater demonstrate rapid adaptation (within 48 h) in osmoregulatory parameters to values characteristics of seawater-adapted salmonids. The urine flow rate falls from 1.2 to 0.2 ml.kg-1.h-1 within 24 h. Over the same period, urine osmolality increases from 48 mosmol.kg-1 to become isosmotic with the plasma, and Mg2+ secretion by the kidney tubules elevates the urine concentration from 0.5 to 100 mmol.l-1. As is characteristic for marine teleosts, kelts drink seawater and process the ingested water in the gut to replace body water lost by osmosis to the hyperosmotic medium. Seawater exposure causes a marked hypoxia, arterial oxygen tension falling by 43% within minutes and persisting for at least 4 days at this low level. This is associated with large changes in blood pH and acid-base balance. The physiological mechanisms involved in adaptation to a hyperosmotic external medium are discussed, and the osmoregulatory capacity of kelts is compared with that of salmon at other stages of the life cycle.
大西洋鲑鱼在淡水中产卵后可能会返回大海。这些鱼被称为产后亲鱼，据报道其低渗调节能力有限。然而，本研究表明，暴露于海水中的适应淡水的产后亲鱼在渗透调节参数方面迅速适应（48小时内）至适应海水的鲑科鱼类的特征值。尿流率在24小时内从1.2降至0.2毫升·千克⁻¹·小时⁻¹。在同一时期，尿渗透压从48毫摩尔·千克⁻¹增加到与血浆等渗，肾小管分泌的Mg²⁺使尿液浓度从0.5毫摩尔·升⁻¹提高到100毫摩尔·升⁻¹。正如海洋硬骨鱼的特征那样，产后亲鱼饮用海水并在肠道中处理摄入的水，以补充因渗透作用而流失到高渗介质中的身体水分。暴露于海水中会导致明显的缺氧，动脉氧分压在几分钟内下降43%，并在这个低水平持续至少4天。这与血液pH值和酸碱平衡的巨大变化有关。文中讨论了适应高渗外部介质所涉及的生理机制，并将产后亲鱼的渗透调节能力与生命周期其他阶段的鲑鱼进行了比较。
