Konarzewski Marek, Diamond Jared
Physiology Department, University of California Medical School, Los Angeles, California, 90024-1751.
Evolution. 1995 Dec;49(6):1239-1248. doi: 10.1111/j.1558-5646.1995.tb04450.x.
Animal species of similar body mass vary widely in basal metabolic rate (BMR). A central problem of evolutionary physiology concerns the anatomical/physiological origin and functional significance of that variation. It has been hypothesized that such interspecific differences in wild animals evolved adaptively from differences in relative sizes of metabolically active organs. In order to minimize confounding phenotypic effects and maximize relevant genetic variation, we tested for intraspecific correlations between body-mass-corrected BMR and masses of four organs (heart, kidney, liver, and small intestine) among six inbred strains of mice. We found significant differences between strains in BMR and in masses of all four organs. Strains with exceptionally high (or low) BMR tended to have disproportionately large (or small) organs. The mass of each organ was correlated with the masses of each of the other three organs. Variation in organ masses accounted for 52% of the observed variation in BMR, of which 42% represented between-strain variation, and 10% represented within-strain variation. This conclusion is supported by published measurements of metabolic rates of tissue slices from the four organs. The correlation between BMR and intestine or heart mass arose exclusively from differences between strains, while the correlation between BMR and liver or kidney mass also appeared in comparing individual mice within the same strain. Thus, even though the masses of the four examined organs account for no more than 17% of total body mass, their high metabolic activities or correlated factors account for much of the variation in BMR among mice. We suggest that large masses of metabolically active organs are subject to natural selection through evolutionary trade-offs. On the one hand, they make possible high-energy budgets (advantageous under some conditions), but on the other hand they are energetically expensive to maintain.
体重相似的动物物种，其基础代谢率（BMR）差异很大。进化生理学的一个核心问题涉及这种差异的解剖学/生理学起源及其功能意义。据推测，野生动物种间的这种差异是从代谢活跃器官相对大小的差异适应性进化而来的。为了尽量减少混杂的表型效应并最大化相关的遗传变异，我们在六个近交系小鼠中测试了体重校正后的基础代谢率与四个器官（心脏、肾脏、肝脏和小肠）重量之间的种内相关性。我们发现不同品系在基础代谢率以及所有四个器官的重量方面存在显著差异。基础代谢率异常高（或低）的品系往往具有不成比例的大（或小）器官。每个器官的重量与其他三个器官的重量都相关。器官重量的变异占基础代谢率观测变异的52%，其中42%代表品系间变异，10%代表品系内变异。这一结论得到了已发表的这四个器官组织切片代谢率测量结果的支持。基础代谢率与小肠或心脏重量之间的相关性完全源于品系间的差异，而基础代谢率与肝脏或肾脏重量之间的相关性在同一品系内的个体比较中也存在。因此，即使所检查的四个器官的重量占总体重不超过17%，它们的高代谢活性或相关因素却占了小鼠基础代谢率变异的很大一部分。我们认为，代谢活跃器官的大质量是通过进化权衡而受到自然选择的。一方面，它们使得高能量预算成为可能（在某些条件下是有利的），但另一方面，维持它们的能量成本很高。
