Wagner E L, Gleeson T T
Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder 80309-0334, USA.
Physiol Behav. 1997 Feb;61(2):175-80. doi: 10.1016/s0031-9384(96)00369-1.
Desert iguanas (Dipsosaurus dorsalis) undergo respiratory recovery more rapidly and incur lower energetic costs when they recover from 40 degrees C burst activity at 20 degrees C than when they recover at 40 degrees C. However, a body temperature of 20 degrees C falls well outside the preferred activity temperature range of this species, and imposes several physiological and behavioral liabilities. To determine if exhausted animals would favor a thermal regimen that allows for rapid and inexpensive respiratory recovery, we exercised lizards to exhaustion and allowed them to recover in a laboratory thermal gradient for 180 min. Recovering animals allowed their body temperatures to cool significantly to a mean temperature of 33.5 degrees C during the first 60 min of recovery, and subsequently rewarmed themselves to an average temperature of 38 degrees C for the remainder of their recovery period. Control animals maintained a constant body temperature of 37.7 degrees C throughout the 180-min recovery period. We then exercised animals to exhaustion at 40 degrees C and allowed them to recover for 180 min under a thermal regimen that mimicked that selected by exhausted animals in the previous experiment. Animals recovering under this thermal regimen returned to rates of O2 consumption, removed exercise-generated blood lactate, and incurred energetic costs that were more similar to data previously collected for animals recovering from exercise at a constant 40 degrees C than to data from animals recovering at 20 degrees C. These results suggested that the energetic benefits associated with recovery at 20 degrees C are not of sufficient biological importance to cause a major shift in thermoregulatory behavior.
沙漠鬣蜥（Dipsosaurus dorsalis）从40摄氏度的爆发性活动中恢复时，在20摄氏度环境下比在40摄氏度环境下呼吸恢复得更快，能量消耗也更低。然而，20摄氏度的体温远低于该物种偏好的活动温度范围，并带来了一些生理和行为上的负担。为了确定精疲力竭的动物是否会倾向于选择一种能实现快速且低成本呼吸恢复的热调节方式，我们让蜥蜴运动至精疲力竭，然后让它们在实验室的温度梯度中恢复180分钟。恢复中的动物在恢复的前60分钟内，体温显著下降至平均33.5摄氏度，随后在剩余的恢复期内将体温重新升高至平均38摄氏度。对照动物在整个180分钟的恢复期内保持37.7摄氏度的恒定体温。然后，我们在40摄氏度的环境下让动物运动至精疲力竭，并让它们在一种模拟前一实验中精疲力竭动物所选择的热调节方式下恢复180分钟。在此热调节方式下恢复的动物，其氧气消耗率、清除运动产生的血乳酸的能力以及能量消耗，与之前收集的在40摄氏度恒定温度下从运动中恢复的动物的数据更为相似，而与在20摄氏度下恢复的动物的数据不同。这些结果表明，在20摄氏度下恢复所带来的能量益处，在生物学上的重要性不足以导致热调节行为发生重大转变。
