Department of Biology II, Biocenter, University of Munich (LMU), Großhadernerstr. 2, D-82152 Planegg-Martinsried, Germany.
Zoology (Jena). 2012 Aug;115(4):245-54. doi: 10.1016/j.zool.2012.02.003. Epub 2012 Jul 5.
This study aims at a functional and morphological characterization of the lung of a boid snake. In particular, we were interested to see if the python's lungs are designed with excess capacity as compared to resting and working oxygen demands. Therefore, the morphological respiratory diffusion capacity of ball pythons (Python regius) was examined following a stereological, hierarchically nested approach. The volume of the respiratory exchange tissue was determined using computed tomography. Tissue compartments were quantified using stereological methods on light microscopic images. The tissue diffusion barrier for oxygen transport was characterized and measured using transmission electron micrographs. We found a significant negative correlation between body mass and the volume of respiratory tissue; the lungs of larger snakes had relatively less respiratory tissue. Therefore, mass-specific respiratory tissue was calculated to exclude effects of body mass. The volume of the lung that contains parenchyma was 11.9±5.0mm(3)g(-1). The volume fraction, i.e., the actual pulmonary exchange tissue per lung parenchyma, was 63.22±7.3%; the total respiratory surface was, on average, 0.214±0.129m(2); it was significantly negatively correlated to body mass, with larger snakes having proportionally smaller respiratory surfaces. For the air-blood barrier, a harmonic mean of 0.78±0.05μm was found, with the epithelial layer representing the thickest part of the barrier. Based on these findings, a median diffusion capacity of the tissue barrier ( [Formula: see text] ) of 0.69±0.38ml O(2)min(-1)mmHg(-1) was calculated. Based on published values for blood oxygen concentration, a total oxygen uptake capacity of 61.16mlO(2)min(-1)kg(-1) can be assumed. This value exceeds the maximum demand for oxygen in ball pythons by a factor of 12. We conclude that healthy individuals of P. regius possess a considerable spare capacity for tissue oxygen exchange.
本研究旨在对蟒科蛇类的肺进行功能和形态学特征分析。特别是，我们想知道与休息和工作时的氧气需求相比，蟒蛇的肺是否具有多余的容量。因此，我们采用了一种基于体视学的、层次嵌套的方法，研究了球蟒（Python regius）的呼吸扩散能力。使用计算机断层扫描确定呼吸交换组织的体积。使用体视学方法在光镜图像上对组织隔室进行量化。使用透射电镜对氧传输的组织扩散屏障进行了特征描述和测量。我们发现，体质量与呼吸组织体积之间存在显著的负相关；较大的蛇肺具有相对较少的呼吸组织。因此，计算了质量特异性呼吸组织，以排除体质量的影响。包含实质的肺体积为 11.9±5.0mm(3)g(-1)。肺实质的体积分数，即每单位肺实质的实际肺交换组织，为 63.22±7.3%；总呼吸表面积平均为 0.214±0.129m(2)，与体质量呈显著负相关，较大的蛇具有相对较小的呼吸表面。对于气-血屏障，发现其调和均值为 0.78±0.05μm，上皮层是屏障最厚的部分。基于这些发现，计算出组织屏障的中位扩散能力（ [Formula: see text] ）为 0.69±0.38ml O(2)min(-1)mmHg(-1)。基于文献中血液氧浓度的值，可以假设球蟒的总耗氧量为 61.16mlO(2)min(-1)kg(-1)。这个值超过了球蟒的最大氧气需求的 12 倍。我们得出结论，健康的 P. regius 个体具有相当大的组织氧交换备用能力。
