Dol'nik V P
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, 199034 St.-Petersburg.
Zh Obshch Biol. 2003 Nov-Dec;64(6):451-62.
The analysis of allometric dependence of energy expenditure on body mass among reptiles, birds and mammals has shown that standard metabolic rate of reptiles when they are warmed up to the temperature of homoiothermic animals is an order of magnitude lower than that of birds and mammals. Basal metabolism is originated as special feature historically related to the metabolism during active behavior, rather than thermal regulation. Facultative endothermy was not advantageous for large animals because of long time needed to warm up the body. The ancestors of birds and animals escaped negative consequences of van't-Hoff equation by choosing constant body temperature. Heat conductivity of reptile's covers is so great, that it cannot keep endogenous warm of resting animal at any temperature of the body. Reptile "dressed" in covers of bird or mammal would be able to keep warm under conditions of maximal aerobic muscular activity and body temperature similar to that of homoiothermic animals. The base of chemical thermoregulation in birds and mammals is a thermoregulatory muscle tonus which remains unknown. One can suppose that during evolution of birds and mammals the saltation-liked origin of endothermy "fixed" the level of metabolism typical for running reptile and transformed in into the basal metabolism. This event took place at the cell and tissue level. The absence of palaeontological evidences and intermediate forms among recent species does not allow easy understanding of homoiothermy origin.
对爬行动物、鸟类和哺乳动物能量消耗与体重之间的异速生长依赖性分析表明，当爬行动物被加热到恒温动物的温度时，其标准代谢率比鸟类和哺乳动物低一个数量级。基础代谢作为一种特殊特征，在历史上与活跃行为期间的新陈代谢有关，而不是与体温调节有关。兼性体温调节对大型动物不利，因为身体升温需要很长时间。鸟类和哺乳动物的祖先通过选择恒定体温避免了范特霍夫方程的负面影响。爬行动物体表的热导率非常高，以至于在任何体温下都无法保持静止动物的内热。身披鸟类或哺乳动物体表覆盖物的爬行动物在最大有氧肌肉活动和与恒温动物相似的体温条件下能够保暖。鸟类和哺乳动物化学体温调节的基础是一种未知的体温调节肌肉紧张度。可以推测，在鸟类和哺乳动物的进化过程中，类似跳跃式的恒温起源“固定”了典型奔跑爬行动物的代谢水平，并将其转化为基础代谢。这一事件发生在细胞和组织层面。由于缺乏古生物学证据以及现存物种之间的中间形式，恒温起源难以理解。
