Sundell Erika, Morgenroth Daniel, Brijs Jeroen, Ekström Andreas, Gräns Albin, Sandblom Erik
Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden.
Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Conserv Physiol. 2018 Nov 22;6(1):coy061. doi: 10.1093/conphys/coy061. eCollection 2018.
Greater salinity variations resulting from ongoing climate change requires consideration in conservation management as this may impact on the performance of aquatic organisms. Euryhaline fish exhibit osmoregulatory flexibility and can exploit a wide range of salinities. In seawater (SW), they drink and absorb water in the intestine, which is associated with increased gastrointestinal blood flow. Yet, detailed information on other cardiovascular changes and their control across salinities is scant. Such knowledge is fundamental to understand how fish are affected during migrations between environments with different salinities, as well as by increased future salinity variability. We used rainbow trout () as a euryhaline model species and determined dorsal aortic blood pressure, cardiac output and systemic vascular resistance after chronic freshwater-or SW-acclimation. We also assessed α-adrenergic control of blood pressure using pharmacological tools. Dorsal aortic blood pressure and systemic vascular resistance were reduced, whereas cardiac output increased in SW. α-Adrenergic stimulation with phenylephrine caused similar dose-dependent increases in resistance and pressure across salinities, indicating unaltered α-adrenoceptor sensitivity. α-Adrenergic blockade with prazosin decreased resistance and pressure across salinities, but the absolute reduction in resistance was smaller in SW. Yet, both pressure and resistance after prazosin remained consistently lower in SW. This shows that SW-acclimation lowers systemic resistance through reduced vascular α-adrenergic tone, along with other unknown vasodilating factors. The marked changes in adrenergic regulation of the vasculature across salinities discovered here may have implications for cardiovascular and aerobic performance of fishes, with possible impacts on fitness-related traits like digestion and exercise capacity. Moreover, the evolution of more complex circulatory control systems in teleost fishes compared with elasmobranchs and cyclostomes may have been an important factor in the evolution of euryhalinity, and may provide euryhaline teleosts with competitive advantages in more variable salinity environments of the future.
持续的气候变化导致盐度变化更大，这在保护管理中需要加以考虑，因为这可能会影响水生生物的表现。广盐性鱼类表现出渗透调节的灵活性，能够适应广泛的盐度范围。在海水中，它们通过饮水并在肠道吸收水分，这与胃肠道血流量增加有关。然而，关于其他心血管变化及其在不同盐度下的调控的详细信息却很少。这些知识对于理解鱼类在不同盐度环境之间迁徙以及未来盐度变异性增加时如何受到影响至关重要。我们使用虹鳟作为广盐性模型物种，在长期适应淡水或海水环境后，测定背主动脉血压、心输出量和全身血管阻力。我们还使用药理学工具评估了α-肾上腺素能对血压的控制。在海水中，背主动脉血压和全身血管阻力降低，而心输出量增加。用去氧肾上腺素进行α-肾上腺素能刺激在不同盐度下引起类似的剂量依赖性阻力和压力增加，表明α-肾上腺素能受体敏感性未改变。用哌唑嗪进行α-肾上腺素能阻断降低了不同盐度下的阻力和压力，但在海水中阻力的绝对降低幅度较小。然而，哌唑嗪处理后的压力和阻力在海水中仍持续较低。这表明适应海水环境通过降低血管α-肾上腺素能张力以及其他未知的血管舒张因子来降低全身阻力。此处发现的不同盐度下血管系统肾上腺素能调节的显著变化可能对鱼类的心血管和有氧性能产生影响，可能对消化和运动能力等与适应性相关的性状产生影响。此外，与板鳃类和圆口类相比，硬骨鱼类更复杂的循环控制系统的进化可能是广盐性进化的一个重要因素，并且可能为广盐性硬骨鱼类在未来盐度变化更大的环境中提供竞争优势。
