Circadian Organization of a Subarctic Rodent, the Northern Red-Backed Vole (Clethrionomys Rutilus)

Circadian Organization of a Subarctic Rodent, the Northern Red-Backed Vole (Clethrionomys Rutilus)

Arctic and subarctic environments are exposed to extreme light: dark (LD) regimes, including periods of constant light (LL) and constant dark (DD) and large daily changes in day length, but very little is known about circadian rhythms of mammals at high latitudes. The authors investigated the circad...

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Bibliographic Details
Published in:Journal of biological rhythms Vol. 19; no. 3; pp. 238 - 247
Main Authors: Tavernier, Ronald J., Largen, Angela L., Bult-Ito, Abel
Format: Journal Article
Language:English
Published: Thousand Oaks, CA Sage Publications 01-06-2004
SAGE PUBLICATIONS, INC
Subjects:
Activity patterns
Animals
Arctic Regions
Arvicolinae - physiology
Biology
Circadian rhythm
Circadian Rhythm - physiology
Circadian rhythms
Clethrionomys
Clethrionomys rutilus
Darkness
Exposure
Ice environments
Laboratories
Light
Lighting
Male
Motor Activity - physiology
Nocturnal
Phenotypic variations
Photoperiod
Polar environments
Random Allocation
Rodents
Wheel running
Arctic Regions
Arctic region
light-induced phase shift
circadian rhythms
Arctic
wheel-running activity
northern red-backed vole (Clethrionomys rutilus)
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Summary:Arctic and subarctic environments are exposed to extreme light: dark (LD) regimes, including periods of constant light (LL) and constant dark (DD) and large daily changes in day length, but very little is known about circadian rhythms of mammals at high latitudes. The authors investigated the circadian rhythms of a subarctic population of northern red-backed voles (Clethrionomys rutilus). Both wild-caught and third-generation laboratory-bred animals showed predominantly nocturnal patterns of wheel running when exposed to a 16:8 LD cycle. In LL and DD conditions, animals displayed large phenotypic variation in circadian rhythms. Compared to wheel-running rhythms under a 16:8 LD cycle, the robustness of circadian activity rhythms decreased among all animals tested in LLand DD (i.e., decreased chi-squared periodogram waveform amplitude). A large segment of the population became noncircadian (60% in DD, 72% in LL) within 8 weeks of exposure to constant lighting conditions, of which the majority became ultradian, with a few individuals becoming arrhythmic, indicating highly labile circadian organization. Wild-caught and laboratory-bred animals that remained circadian in wheel running displayed free-running periods between 23.3 and 24.8 h. A phase-response curve to light pulses in DD showed significant phase delays at circadian times 12 and 15, indicating the capacity to entrain to rapidly changing day lengths at high latitudes. Whether this phenotypic variation in circadian organization, with circadian, ultradian, and arrhythmic wheel-running activity patterns in constant lighting conditions, is a novel adaptation to life in the arctic remains to be elucidated.
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content type line 23
ISSN:0748-7304
1552-4531
DOI:10.1177/0748730404264200