Anurans have an exceptional capacity for maintaining vascular volume compared with other groups of vertebrates. They can mobilize interstitial fluids via lymphatic return at rates that are ten-fold higher than mammals. This extraordinary capacity is the result of coordination of specialized skeletal muscles and pulmonary ventilation that vary volume and pressure of subcutaneous lymph sacs, thus moving lymph to dorsally located lymph hearts that return lymph to the vascular space. Variation in the capacity to mobilize lymph within anurans varies with the degree of terrestriality, development of skeletal muscles, lung volume and lung compliance, and lymph heart pressure development. This ability enable anurans, which have the highest rates of evaporative water loss among terrestrial vertebrates, to withstand levels of dehydration far exceeding that of other vertebrates, and to successfully occupy virtually all terrestrial environments during their evolution. Maintenance of vascular fluid volume for all vertebrates can be achieved primarily by moving fluid from the interstitial space to the vascular space by transcapillary uptake and mobilization of interstitial (lymphatic) fluid. Transcapillary fluid uptake at the capillary level has been analyzed historically by Krogh and others from a Starling perspective and involves a balance of hydrostatic and oncotic forces. A complete evaluation of blood volume homeostasis also incorporates pressures and compliances of the vascular and interstitial spaces, but has been applied to only a few species. In this review we outline the current understanding of how anurans and other vertebrates maintain blood volume during hypovolemic challenges such as dehydration and hemorrhage which is crucial for maintaining cardiac output.

与其他脊椎动物群相比，无尾目动物在维持血管容量方面具有非凡的能力。它们可以以比哺乳动物高十倍的速率通过淋巴回流来调动间质液。这种非凡的能力是特殊骨骼肌和肺通气协调的结果，这些通气会改变皮下淋巴囊的体积和压力，从而将淋巴移至背侧的淋巴心脏，使淋巴返回血管空间。无尾类内淋巴动员能力的变化随陆地的程度、骨骼肌的发育、肺容量和肺顺应性以及淋巴心脏压力的发展而变化。这种能力使无尾目动物成为陆生脊椎动物中蒸发失水率最高的动物，承受远远超过其他脊椎动物的脱水程度，并在它们的进化过程中成功占据几乎所有的陆地环境。所有脊椎动物的血管液体量的维持主要是通过经毛细血管摄取和动员间质（淋巴）液将液体从间质空间移动到血管空间来实现的。历史上，Krogh 和其他人从 Starling 的角度分析了毛细血管水平的经毛细血管液体摄取，涉及静水力和渗透力的平衡。血容量稳态的完整评估还包括血管和间质空间的压力和顺应性，但仅适用于少数物种。