NDLI: Hibernation and circadian rhythms of body temperature in free-living Arctic ground squirrels.

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Williams, Cory T. Barnes, Brian M. Richter, Melanie Buck, C. Loren
Spatial Coverage	Arctic Regions Alaska
Description	Country affiliation: United States Author Affiliation: Williams CT ( Department of Biological Sciences, University of Alaska, Anchorage, Alaska 99508, USA. cw3@ualberta.ca)
Abstract	In mammals, the circadian master clock generates daily rhythms of body temperature (T(b)) that act to entrain rhythms in peripheral circadian oscillators. The persistence and function of circadian rhythms during mammalian hibernation is contentious, and the factors that contribute to the reestablishment of rhythms after hibernation are unclear. We collected regular measures of core T(b) (every 34 min) and ambient light conditions (every 30 s) before, during, and following hibernation in free-living male arctic ground squirrels. Free-running circadian T(b) rhythms at euthermic levels of T(b) persisted for up to 10 d in constant darkness after animals became sequestered in their hibernacula in fall. During steady state torpor, T(b) was constant and arrhythmic for up to 13 d (within the 0.19°C resolution of loggers). In spring, males ended heterothermy but remained in their burrows at euthermic levels of T(b) for 22-26 d; patterns of T(b) were arrhythmic for the first 10 d of euthermia. One of four squirrels exhibited a significant free-running T(b) rhythm (τ = 22.1 h) before emergence; this squirrel had been briefly exposed to low-amplitude light before emergence. In all animals, diurnal T(b) rhythms were immediately reestablished coincident with emergence to the surface and the resumption of surface activity. Our results support the hypothesis that clock function is inhibited during hibernation and reactivated by exposure to light, although resumption of extended surface activity does not appear to be necessary to reinitiate T(b) cycles.
File Format	HTM / HTML
ISSN	15222152
Issue Number	4
Volume Number	85
e-ISSN	15375293
Journal	Physiological and Biochemical Zoology
Language	English
Publisher	University of Chicago Press
Publisher Date	2012-07-01
Publisher Place	United States
Access Restriction	Subscribed
Subject Keyword	Discipline Physiology Discipline Biochemistry Discipline Zoology Body Temperature Circadian Rhythm Radiation Effects Hibernation Sciuridae Physiology Alaska Animals Arctic Regions Circadian Clocks Light Male Remote Sensing Technology Seasons Time Factors Journal Article Research Support, U.s. Gov't, Non-p.h.s.
Content Type	Text
Resource Type	Article
Subject	Physiology Biochemistry Animal Science and Zoology

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