Minnaar Ingrid A, Bennett Nigel C, Chimimba Christian T, McKechnie Andrew E
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; 2South African Research Chair for Mammal Behavioural Ecology and Physiology, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield, 0028 South Africa.
Physiol Biochem Zool. 2014 May-Jun;87(3):475-85. doi: 10.1086/675342. Epub 2014 Apr 10.
The relative contributions of respiratory and cutaneous evaporation to total evaporative water loss (TEWL) and how the partitioning of these two avenues varies with environmental temperature has received little attention in bats. We trained Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) captured in Pretoria, South Africa, to wear latex masks while hanging in respirometry chambers, and we measured respiratory evaporative water loss (REWL) and cutaneous evaporative water loss (CEWL) over air temperatures (Ta) from 10° to 40°C. The bats' normothermic body temperature (Tb) was approximately 36°C, which increased at higher Ta to 40.5° ± 1.0°C at Ta ≈ 40°C. Both TEWL and resting metabolic rate (RMR) increased sharply at Ta >35°C, with a mean TEWL at 40°C equivalent to 411% of that at 30°C. The increase in TEWL was driven by large increases in both CEWL and REWL. CEWL comprised more than 50% of TEWL over the entire Ta range, with the exception of Ta ≈ 40°C, where REWL accounted for 58% of evaporative water loss. Surface area-specific CEWL increased approximately sixfold with increasing Ta. Thermoregulation at Ta approaching or exceeding Tb involved a considerable energetic cost, with RMR at Ta ≈ 40°C exceeding by 24% that measured at Ta ≈ 10°C. Our data do not support recent arguments that respiratory gas exchange across the wing membranes represents 5%-10% of the total in E. wahlbergi.
在蝙蝠中，呼吸蒸发和皮肤蒸发对总蒸发失水量（TEWL）的相对贡献，以及这两种途径的分配如何随环境温度变化，很少受到关注。我们训练了在南非比勒陀利亚捕获的瓦尔伯格氏肩章果蝠（Epomophorus wahlbergi），让它们挂在呼吸测量室中时佩戴乳胶面罩，并测量了10°C至40°C气温（Ta）下的呼吸蒸发失水量（REWL）和皮肤蒸发失水量（CEWL）。蝙蝠的正常体温（Tb）约为36°C，在较高的Ta下会升高，在Ta≈40°C时升至40.5°±1.0°C。在Ta>35°C时，TEWL和静息代谢率（RMR）均急剧增加，40°C时的平均TEWL相当于30°C时的411%。TEWL的增加是由CEWL和REWL的大幅增加驱动的。在整个Ta范围内，CEWL占TEWL的比例超过50%，但Ta≈40°C时除外，此时REWL占蒸发失水量的58%。随着Ta的升高，单位表面积的CEWL增加了约六倍。在Ta接近或超过Tb时进行体温调节涉及相当大的能量消耗，Ta≈40°C时的RMR比Ta≈10°C时测量的值高出24%。我们的数据不支持最近的观点，即通过翼膜进行的呼吸气体交换占瓦尔伯格氏肩章果蝠总量的5%-10%。
