Daily rhythms of nonshivering thermogenesis and responses to photoperiod manipulations in Apodemus mystacinus from two different ecosystems
✍ Scribed by M. Spiegel; A. Haim
- Publisher
- Elsevier Science
- Year
- 2004
- Tongue
- English
- Weight
- 200 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0306-4565
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✦ Synopsis
Comparative physiology is an important tool for understanding adaptation to environment. Regulatory nonshivering thermogenesis (NST) is an essential mechanism in small mammals for coping with low ambient temperatures. Because of its geographical location and its sharp climatic changes across short distances, Israel offers conducting comparative studies between different populations of the same species. The aims of this study were: (1) to compare NST-capacity daily rhythms, between the two populations of the broad-toothed field mouse Apodemus Mystacinus-that of Mount Carmel (Mediterranean) and that of Mount Hermon (Subalpinic), (2) to compare the thermoregulatory daily rhythms response to photoperiod manipulations of mice from the two populations.
Mice were acclimated for at least 3 weeks to long scotophase (16D:8L-LS) and then to long photophase (16L:8D-LP) at a constant ambient temperature (T a ) of 2471 1C. The following variables were compared at four different times of the day (06, 12, 18, 24 h): minimal body temperature (T b Min), minimal oxygen consumption (VO 2 Min) measured at the lower critical point and their response to noradrenaline (NA), 1.5 mg/1 kg.W b injected s.c., (VO 2 NA and T b NA). NSTcapacity was calculated as the ratio between VO 2 NA and VO 2 Min. The measurements were carried out at T a of 28 1C and in light conditions matching those of acclimation. NA was injected after establishing VO 2 Min and T b Min. The values mean7SD are given for each measurement for n ¼ 6:
A three-way ANOVA revealed a significant difference between the two populations. Significant differences were revealed at different hours within populations under the different photoperiod regimes for different measured variables.