Körtner G, Song X, Geiser F
School of Biological Sciences, University of New England, Armidale NSW, Australia.
J Comp Physiol B. 1998 Dec;168(8):631-8. doi: 10.1007/s003600050186.
Circadian rhythms have been observed in most mammals, but their importance and function remain controversial with respect to daily cycles during hibernation. We investigated the timing of arousals from and entries into hibernation for both free-living and captive mountain pygmy-possums (Burramys parvus). Under both natural and laboratory conditions most arousals and entries were entrained with the light-dark cycle. Entries occurred mainly during the night and arousals preferably around dusk, which coincides with the onset of the normal activity phase for the nocturnal pygmy-possums. This entrainment prevailed throughout the hibernation season although only the laboratory animals were constantly subjected to photoperiodic stimuli, whereas under natural conditions hibernacula are shielded from photic cues and diurnal temperature fluctuations. Nevertheless, possums left their hibernacula frequently throughout winter and were occasionally trapped close to the snow surface suggesting that during the periods of post-arousal normothermia they can be exposed to environmental stimuli. It thus appears that the synchronisation with the photocycle was governed by a temperature-compensated circadian clock which was reset periodically during short activity periods. For the mountain pygmy-possum, entrainment with the photocycle probably has two functions: 1. Entrainment ensures that foraging bouts during the hibernation season remain synchronised with the dark phase. 2. Information about the prevailing climatic conditions sampled during short activity periods enables them to time final spring emergence from hibernation when snow melt begins and ensures that the breeding season can commence as early as possible.
大多数哺乳动物都存在昼夜节律，但就冬眠期间的日常周期而言，其重要性和功能仍存在争议。我们研究了自由放养和圈养的山地侏儒负鼠（Burramys parvus）进入和脱离冬眠的时间。在自然和实验室条件下，大多数进入和脱离冬眠的行为都与明暗周期同步。进入冬眠主要发生在夜间，脱离冬眠则最好在黄昏前后，这与夜行性侏儒负鼠正常活动阶段的开始时间一致。尽管只有圈养动物持续受到光周期刺激，而在自然条件下，冬眠场所会屏蔽光信号和昼夜温度波动，但这种同步在整个冬眠季节都普遍存在。然而，负鼠在整个冬季经常离开它们的冬眠场所，偶尔会被困在靠近雪面的地方，这表明在苏醒后的正常体温期间，它们可能会受到环境刺激。因此，与光周期的同步似乎是由一个温度补偿的生物钟控制的，该生物钟在短暂的活动期会定期重置。对于山地侏儒负鼠来说，与光周期同步可能有两个功能：1. 同步确保冬眠季节的觅食活动与黑暗阶段保持同步。2. 在短暂活动期获取的有关当前气候条件的信息，使它们能够在雪开始融化时确定最终从冬眠中苏醒的时间，并确保繁殖季节能尽早开始。
