title: Metabolism, thermogenesis and daily rhythm of body temperature in the wood lemming, Myopus schisticolor.
abstract: Wood lemmings (Myopus schisticolor) were captured during their autumnal migration in September and October. The animals were maintained at 12 degrees C and under 12L:12D photoperiod. Basal metabolic rate and thermogenic capacity of the wood lemming were studied. Basal metabolic rate was 3.54 ml O2.g-1.h-1, which is 215-238% of the expected value. The high basal metabolic rate seems to be typical of rodents living in high latitudes. The body temperature of the wood lemming was high (38.0-38.8 degrees C), and did not fluctuate much during the 24-h recording. The high basal metabolic rate and the high body temperature are discussed with regard to behavioural adaptation to a low-quality winter diet. Thermogenic capacity, thermal insulation and non-shivering thermogenesis of the wood lemming displayed higher values than expected: 53.0 mW.g-1, 0.53 mW.g-1.degrees C-1 and 53.2 mW.g-1, respectively. Brown adipose tissue showed typical thermogenic properties, although its respiratory property was fairly low, but mitochondrial protein content was high compared to other small mammals. The 24-h recording of body temperature and motor activity did not reveal whether the wood lemming is a nocturnal animal. Possibly, the expression of a circadian rhythm was masked by peculiar feeding behaviour. It is concluded that the wood lemming is well adapted to living in cold-temperature climates.
authors.affiliation: University of Oulu, Department of Zoology, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Saarela
authors.forename: R
authors.initials: R
authors.lastname: Hissa
mesh_terms: D000064:Acclimatization / Q000502:physiology; D002001:Adipose Tissue, Brown / Q000502:physiology; D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D001481:Basal Metabolism; D001833:Body Temperature Regulation / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003081:Cold Climate; D009043:Motor Activity / Q000502:physiology; D012377:Rodentia / Q000502:physiology; D013045:Species Specificity; D013814:Thermal Conductivity