Jørgensen C B
Zoophysiological Laboratory, August Krogh Institute, Copenhagen, Denmark.
Biol Rev Camb Philos Soc. 1997 May;72(2):153-237. doi: 10.1017/s0006323196004963.
In the 1790s, Robert Townson established the main features of the water economy of terrestrial amphibians: rapid evaporative water loss in dry surroundings, 'drinking' by absorption of water through the abdominal skin pressed against moist substrates, and use of the urinary bladder as a reservoir from which water is reabsorbed on land. This knowledge was of little interest to the establishment in the first half of the nineteenth century of experimental physiology as a basic medical discipline, when frogs became models in the elucidation of general physiological processes. Townson's pioneer contributions to amphibian physiology were forgotten for 200 years (Jørgensen 1994b). During (1901) and particularly Overton (1904) restored knowledge about amphibian water economy to the level reached by Townson, but the papers had little impact on the young science of animal physiology because they primarily aimed at elucidating the transport of fluids across membranes. Frog skin remained a model preparation in such studies throughout the century. With the establishment of terrestrial ecology early in the century, the relations of animals, including amphibians, to water became a central theme. Concurrently with comparative studies of amphibian water economy in an ecological setting, the subject proceeded as an aspect of animal osmoregulation. Adolph (1920-1930) and Rey (1937a) established the highly dynamic nature of water balance in amphibians in water and on land. Their observations indicated functional links between environment, skin and kidneys, the nature of which remained to be explored. Thorson & Svihla (1943) reopened the ecological approach in a comparative study of the relations between amphibian habitat and tolerance of dehydration. By mid-century, the central themes of amphibian adaptations to terrestrial modes of life were re-established, except for the function of the bladder as a water-depot. During the following decades, a rich literature appeared, particularly focusing on adaptations of amphibians to arid environments. Thus, in the 1970s, it was found that 'waterproofing' of the highly permeable skins by means of skin secretions had evolved independently in several families of tropical arboreal frogs, and that a number of amphibians that aestivate whilst burrowed in dry soil could reduce evaporation by forming cocoons from shed strata cornea. In 1950-1970 the role of bladder urine as a water depot in terrestrial amphibians was recognized: this did not change the established view of water balance in terrestrial amphibians as alternating between dehydration on land and rehydration in response to the deficit in body water. Amphibians may, however, maintain normal water balance whether the ambient medium is water or air by means of little understood integrated mechanisms in control of cutaneous drinking behaviour, water permeability of the skin and bladder wall, and urine production.
18世纪90年代，罗伯特·汤森确立了陆生两栖动物水分代谢的主要特征：在干燥环境中水分快速蒸发散失，通过紧贴潮湿基质的腹部皮肤吸收水分进行“饮水”，以及利用膀胱作为储水器，在陆地上重新吸收水分。在19世纪上半叶，当青蛙成为阐明一般生理过程的模型时，这一知识对于将实验生理学确立为一门基础医学学科的机构来说兴趣寥寥。汤森对两栖动物生理学的开创性贡献被遗忘了200年（约根森，1994b）。杜林（1901年），尤其是奥弗顿（1904年）将关于两栖动物水分代谢的知识恢复到了汤森所达到的水平，但这些论文对年轻的动物生理学科学影响甚微，因为它们主要旨在阐明液体跨膜运输。在整个世纪中，蛙皮在这类研究中仍然是一种典型的实验标本。随着本世纪初陆地生态学的建立，包括两栖动物在内的动物与水的关系成为了一个核心主题。在对两栖动物水分代谢进行生态环境下的比较研究的同时，该主题作为动物渗透调节的一个方面继续发展。阿道夫（1920 - 1930年）和雷伊（1937a）确立了两栖动物在水中和陆地上水分平衡的高度动态性质。他们的观察表明了环境、皮肤和肾脏之间的功能联系，但其本质仍有待探索。索尔森和斯维赫拉（1943年）在一项关于两栖动物栖息地与脱水耐受性之间关系的比较研究中重新开启了生态研究方法。到本世纪中叶，除了膀胱作为储水器的功能外，两栖动物适应陆地生活方式的核心主题得以重新确立。在接下来的几十年里，出现了大量文献，尤其聚焦于两栖动物对干旱环境的适应。因此，在20世纪70年代，人们发现，热带树蛙的几个科通过皮肤分泌物对高渗透性皮肤进行“防水”的现象是独立进化而来的，并且一些在干燥土壤中夏眠的两栖动物可以通过用脱落的角质层形成茧来减少水分蒸发。在1950 - 1970年期间，膀胱尿液作为陆生两栖动物储水器的作用得到了认可：这并没有改变已确立的关于陆生两栖动物水分平衡的观点，即其在陆地脱水和因身体水分亏缺而重新补水之间交替变化。然而，两栖动物无论周围介质是水还是空气，都可能通过控制皮肤饮水行为、皮肤和膀胱壁的水渗透性以及尿液生成等鲜为人知的综合机制来维持正常的水分平衡。
