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KMID : 0385020030190040247
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Korean Journal of Laboratory Animal Science
2003 Volume.19 No. 4 p.247 ~ p.252
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Cold Adaptation and Absence of Circadian Body Temperature Rhythm in Pikas
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Lee Jeong-Beom
Bae Jun-Sang
Choi Jeong-Hwan
Ham Joo-Hyen
Takaaki Matsumoto
Min Young-Ki
Yang Hun-Mo
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Abstract
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The pika inhabiting in cold zone or in high mountains is thought to be adapted to the cold as well as to the high-altitude. The autonomic characteristics of the high body temperature, high metabolism and poor heat loss ability such as poor panting, small ear pinnae and no thermal salivation and also the behavioral characteristics that the pikas live in the burrows under the ground or in the shelter among rocks and hoard grasses for winter food to survive winters have been reported. However, insulated cold defense in the pikas is not studied and the pika’s circadian activity rhythm is controversial after the field observations. Therefore, the skin thickness and hairs length were histologically studied and the body temperature and locomotive activity were monitored in the freely moving pikas with a biotelemetry system to clarify the pika’s circadian rhythm. In contrast with the robust nocturnal rhythms in the rabbits and the rats, neither diurnal nor nocturnal body temperature rhythm was observed in the pikas, except for a slight rise at dawn and dusk consisting with the previous field observations. The pika is considered to be adaptive to the cold not only ecologically and autonomically but also due to the insulated cold defense mechanisms. Though further investigation should be done, the absence of circadian body temperature rhythm in the pika is quite unique and attractive for the research field of circadian rhythm.
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KEYWORD
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Circadian body temperature, Pikas, Adaptation
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