Persistence, entrainment, and function of circadian rhythms in polar vertebrates.
Polar organisms must cope with an environment that periodically lacks the strongest time-giver, or zeitgeber, of circadian organization-robust, cyclical oscillations between light and darkness. We review the factors influencing the persistence of circadian rhythms in polar vertebrates when the light-dark cycle is absent, the likely mechanisms of entrainment that allow some polar vertebrates to remain synchronized with geophysical time, and the adaptive function of maintaining circadian rhythms in such environments.
Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska; and.
Cory T
CT
Williams
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska.
Brian M
BM
Barnes
Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska; and clbuck@uaa.alaska.edu.
C Loren
CL
Buck
D000222:Adaptation, Physiological; D000818:Animals; D005075:Biological Evolution; D002940:Circadian Rhythm / Q000528:radiation effects; D003081:Cold Climate; D003080:Cold Temperature; D006801:Humans; D008027:Light; D010775:Photic Stimulation; D017440:Photoperiod; D013045:Species Specificity; D013997:Time Factors; D014714:Vertebrates / Q000502:physiology*