Physiological characteristics of pikas as the animal adapted to extreme environments of "cold and high-altitude"

1)野外遥测记录野生鼠兔的体温节律表明，无论是夏季还是冬季，鼠兔基本上都是昼夜活动的。2)对洞穴和外界温度的全年监测表明，洞穴(地下洞网或岩石之间的空间)不仅对天敌具有重要的防御作用，而且对夏热冬寒也具有重要的作用。3)冬季对野生鼠兔体温的监测表明，鼠兔具有强烈的非冬眠特性。4)冬季除低氧外，心脏重量(右/左心脏重量比)总体上是增加的，但与其他生活在地下的动物一样，冬季与夏季相比，心脏重量并没有增加。5)鼠兔耗氧量在20℃时达到最低值，在0~30℃温度范围内低于大鼠。6)通过对野生鼠兔棕色脂肪组织(BAT)产热能力的比较，阐明了BAT在鼠兔耐冷性中的重要作用。7)在温暖环境中饲养的鼠兔，光镜下可见蝙蝠呈白色脂肪组织状，由大的脂滴组成。急性冷暴露的鼠兔，胞浆主要分布在小细胞内。BAT解偶联蛋白(UCP1)在所有鼠兔中均有表达，急性冷暴露后，UCP1的表达强度增强。部分碱基序列分析表明，鼠兔UCP1与兔UCP1同源性最高。

1) Recording the body temperature rhythm of wild pikas by field telemetry method showed clearly that a pika is essentially diurnal both in summer and in winter. 2) Whole year monitoring of burrow and outside temperatures showed that the burrow (an underground tunnel network or the space between the rocks) play an important role as a shelter not only against for natural enemies but also for summer heat and winter cold. 3) Monitoring the body temperature of the wild pika in winter suggested the un-hibernating nature of pikas strongly. 4) Generally, cardiac weight (right/left heart weight ratio) increased by cold in addition to low oxygen in winter, but it did not increase in winter compared with the value of a summer in the wild pika, as same as in the other animals living under ground. 5) The oxygen consumption of the pika became the minimum value at 20 ℃, and was lower than that of the rat at the temperatures between 0 and 30 ℃. 6) As a result of comparing the heat production ability of the brown adipose tissue (BAT) of wild pikas with rats, it was clarified that BAT play an important role in cold-tolerance in pikas. 7) In the pikas reared in the warm, BAT was whitish like white adipose tissue and was composed of a large lipid droplet in electro-microscopic observation. In the pikas exposed to acute cold, most cytoplasm was seen in the small cells. BAT uncoupling protein (UCP1) mRNA was identified in all pikas, and the intensity of UCP1mRNA become strong by acute cold exposure. As a result of the partial analysis of the base sequence of UCP1mRNA, pika UCP1 showed the highest homology with rabbit UCP1.