Programa de Pós-Graduação em Biologia Comparada, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901, Ribeirão Preto, São Paulo, Brazil; Departamento de Ciências Fisiológicas, Universidade Federal de São Carlos, 13565-905, São Carlos, São Paulo, Brazil.
Departamento de Ciências Fisiológicas, Universidade Federal de São Carlos, 13565-905, São Carlos, São Paulo, Brazil.
Respir Physiol Neurobiol. 2021 Dec;294:103747. doi: 10.1016/j.resp.2021.103747. Epub 2021 Jul 21.
Ventilation and gas exchange have been studied in relatively few species of snakes, especially regarding their response to environmental hypoxia or hypercarbia. We exposed Crotalus durissus (N = 6) and Boa constrictor (N = 6) to decreasing levels of oxygen (12, 9, 6, 3 % O) and increasing levels of carbon dioxide (1.5, 3.0, 4.5, 6.0 % CO) and analyzed the effect of the different gas mixtures on ventilation and gas exchange using open-flow respirometry. Neither hypoxia nor hypercarbia significantly altered the duration of expiration or inspiration, nor their proportions. Both hypoxia and hypercarbia increased minute ventilation, but the decrease in oxygen had a less pronounced effect on ventilation. Gas exchange under normoxic conditions was low and was not significantly affected by hypoxia, but hypercarbia decreased gas exchange significantly in both species. While B. constrictor maintained its respiratory exchange ratio (RER) under hypercarbia between 0.5 and 1.0, C. durissus showed a RER above 1.0 during hypercarbia, due to a significantly greater CO excretion. The overall responses of both species to hypercarbia and especially to hypoxia were very similar, which could be associated to similar lifestyles as ambush hunting sit-and-wait predators that are able to ingest large prey items. The observed differences in gas exchange could be related to respiratory systems with macroscopically different structures, possessing only a tracheal lung in C. durissus, but two functional lungs in B. constrictor.
我们用开放气流呼吸测量法，在相对较少的蛇种（尤其是响尾蛇属和王蛇属）中研究了通气和气体交换，尤其是它们对环境缺氧或高碳酸血症的反应。我们使 6 条响尾蛇和 6 条王蛇分别暴露在氧含量（12、9、6、3%）递减和二氧化碳含量（1.5、3.0、4.5、6.0%）递增的环境中，并分析了不同气体混合物对通气和气体交换的影响。低氧和高碳酸血症都没有显著改变呼气或吸气的持续时间及其比例。低氧和高碳酸血症都增加了分钟通气量，但氧气减少对通气量的影响较小。在正常氧条件下，气体交换量较低，低氧血症并没有显著影响气体交换，但高碳酸血症使两种蛇的气体交换量都显著降低。虽然王蛇在高碳酸血症下维持其呼吸交换率（RER）在 0.5 到 1.0 之间，但响尾蛇在高碳酸血症下的 RER 超过 1.0，这是由于 CO 的排泄量显著增加。这两种蛇对高碳酸血症和低氧血症的整体反应非常相似，这可能与它们相似的生活方式有关，都是伏击狩猎的坐等捕食者，能够摄入大型猎物。观察到的气体交换差异可能与呼吸系统的宏观结构不同有关，响尾蛇只有一个气管肺，但王蛇有两个功能肺。
