长爪沙鼠的代谢率与器官的关系

我们测定了野生长爪沙鼠（Meriones unguiculatus)的基础代谢率和冷诱导的最大代谢率，分析了动物体内11种器官或组织的大小与代谢率的关系。长爪沙鼠的基础代谢率为118.10mlO2/h，最大代谢率为659.83mlO2/h。经过残差分析表明，基础代谢率并不与任何一种器官或组织相关，而最大代谢率与小肠湿重（n=20，r=-0.478,P=0.033)和消化道全长（n=20,r=-0.487,P=0.030)显著相关，表明体内器官重量的差别并不是造成种内基础代谢率差别的原因；体内存在着与最大代谢率相关的“代谢机器”，消化系统（特别是小肠）是这一代谢机器的重要组成部分，但代谢机器的大小并不能通过基础代谢率反映出来。基础代谢率与最大代谢率不相关，因此不支持“较高的基础代谢率能够产生较高的非基础代谢率（最大代谢率等）”的假设。

RELATIONSHIPS BETWEEN METABOLIC RATES AND BODY COMPOSITION IN THE MONGOLIAN GERBILS (MERIONES UNGUICULATUS)

A central problem of evolutionary physiology concerns the physiological origin and functional significance of the intra and inter specific variation in basal metabolic rate (BMR). Previous studies on laboratory mice suggest that individuals with relatively high basal metabolic rates have relatively large masses of metabolically active tissues; energetically expensive organs that contribute to cold resistance. We measured the BMR and cold induced maximum metabolic rate (MMR) in 20 wild Mongolian gerbils ( Meriones unguiculatus). Then the gerbils were dissected and 11 body parts were weighed. The BMR was 118 10 ml O 2/h and the MMR was 659 83 ml O 2/h (Mean body mass was 65 2 g). We analyzed the relationship between residual variations of BMR, MMR and 11 body parts, and found that none of the variations in body components could be linked to the variation in BMR, however the small intestine wet mass and total digestive tract length were highly correlated with MMR (n=20, r=-0 478, P= 0 033 and n=20, r=-0 487, P =0 030, separately). We used principal component analysis to describe the variation in the morphology and found no components contributed significantly to variations in BMR or MMR. We also pooled body parts into three groups and found that none of them were correlated with variation in BMR or MMR. These data indicate that in vivo variation in BMR is not caused by the variation in the mass of the body parts that we examined. A metabolic mechanism to generate high MMR exists in which the the small intestine plays the major part, but the size of this metabolic machinery is not reflected by BMR. The correlation between variation in BMR and variation in MMR was not significant ( n=20, r=0 059, P= 0 806). Therefore, our results do not support the hypothesis that BMR variation reflects the evolution of metabolic machinery to generate high nonbasal metabolic rates during energetically demanding periods such as cold exposure.