Maina John N, McCracken Kevin G, Chua Beverly, York Julia M, Milsom William K
Department of Zoology, University of Johannesburg, Johannesburg, South Africa.
Department of Biology and Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Coral Gables, Florida, United States of America.
PLoS One. 2017 Mar 24;12(3):e0174395. doi: 10.1371/journal.pone.0174395. eCollection 2017.
High altitude flight in rarefied, extremely cold and hypoxic air is a very challenging activity. Only a few species of birds can achieve it. Hitherto, the structure of the lungs of such birds has not been studied. This is because of the rarity of such species and the challenges of preparing well-fixed lung tissue. Here, it was posited that in addition to the now proven physiological adaptations, high altitude flying birds will also have acquired pulmonary structural adaptations that enable them to obtain the large amounts of oxygen (O2) needed for flight at high elevation, an environment where O2 levels are very low. The Andean goose (Chloephaga melanoptera) normally resides at altitudes above 3000 meters and flies to elevations as high as 6000 meters where O2 becomes limiting. In this study, its lung was morphologically- and morphometrically investigated. It was found that structurally the lungs are exceptionally specialized for gas exchange. Atypically, the infundibulae are well-vascularized. The mass-specific volume of the lung (42.8 cm3.kg-1), the mass-specific respiratory surface area of the blood-gas (tissue) barrier (96.5 cm2.g-1) and the mass-specific volume of the pulmonary capillary blood (7.44 cm3.kg-1) were some of the highest values so far reported in birds. The pulmonary structural specializations have generated a mass-specific total (overall) pulmonary morphometric diffusing capacity of the lung for oxygen (DLo2) of 0.119 mlO2.sec-1.mbar-1.kg-1, a value that is among some of the highest ones in birds that have been studied. The adaptations of the lung of the Andean goose possibly produce the high O2 conductance needed to live and fly at high altitude.
在稀薄、极度寒冷且缺氧的空气中进行高空飞行是一项极具挑战性的活动。只有少数几种鸟类能够做到。迄今为止，此类鸟类的肺部结构尚未得到研究。这是因为这类物种稀少，且制备固定良好的肺组织存在挑战。在此，有人提出，除了现已证实的生理适应性外，高空飞行的鸟类还会获得肺部结构适应性，使其能够在氧气水平极低的高海拔环境中获取飞行所需的大量氧气（O₂）。安第斯鹅（Chloephaga melanoptera）通常栖息在海拔3000米以上的高度，并能飞到高达6000米的海拔高度，在那里氧气变得有限。在本研究中，对其肺部进行了形态学和形态计量学研究。结果发现，其肺部在结构上特别适合气体交换。不同寻常的是，肺漏斗血管丰富。肺的质量比体积（42.8 cm³·kg⁻¹）、血气（组织）屏障的质量比呼吸表面积（96.5 cm²·g⁻¹）以及肺毛细血管血的质量比体积（7.44 cm³·kg⁻¹）是迄今为止鸟类中报道的一些最高值。肺部结构特化产生了肺对氧气的质量比总（整体）肺形态计量扩散容量（DLo₂）为0.1 mlO₂·sec⁻¹·mbar⁻¹·kg⁻¹，这一数值在已研究的鸟类中处于最高水平。安第斯鹅肺部的适应性可能产生了在高海拔地区生存和飞行所需的高氧气传导率。
