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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of hibernation, estivation and daily torpor in the edible dormouse, Glis glis (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 511-521 
    Details
    ISSN: 1432-136X
    Keywords: Key words Circadian clock ; Conductance ; Energy saving ; Metabolic rate ; Metabolic depression ; AbbreviationsADMR average matabolic rate ; BM body mass ; C conductance ; MR metabolic rate ; RMR resting metabolic rate ; Ta ambient temperature ; Tb body temperature ; VO2 rate of oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Three major forms of dormancy in mammals have been classified: hibernation in endotherms is characterised by reduced metabolic rate (MR) and body temperature (T b) near ambient temperature (T a) over prolonged times in the winter. Estivation is a similar form of dormancy in a dry and hot environment during summertime. Daily torpor is defined as reduced MR and T b lower than 32 °C, limited to a duration of less than 24 h. The edible dormouse (Glis glis) is capable for all three distinct forms of dormancy. During periods of food restriction and/or low T a, daily torpor is displayed throughout the year, alternating with hibernation and estivation in winter and summer respectively. We recorded T b, O2-consumption and CO2-production in unrestrained dormice at different T a's for periods of up to several months. Cooling rate and rate of metabolic depression during entrance into the torpid state was identical in all three forms of dormancy. The same was true for thermal conductance, maximum heat production, duration of arousal and cost of an arousal. The only difference between hibernation and daily torpor was found in the bout duration. A daily torpor bout lasted 3–21 h, a hibernation bout 39–768 h. As a consequence of prolonged duration, MR, T b and also the T b − T a gradient decreased to lower values during hibernation bouts when compared to daily torpor bouts. Our findings suggest that all three forms of dormancy are based on the same physiological mechanism of thermal and metabolic regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600000129
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolism and temperature regulation during daily torpor in the smallest primate, the pygmy mouse lemur (Microcebus myoxinus) in Madagascar (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 59-68 
    Details
    ISSN: 1432-136X
    Keywords: Key words Body temperature ; Metabolic rate ; Torpor ; Pygmy mouse lemur, Microcebus myoxinus ; Environmental conditions ; Madagascar ; AbbreviationsANOVA analysis of variance ; AMR metabolic rate during active arousal ; MR metabolic rate ; RMR resting metabolic rate ; SD standard deviation ; Ta ambient temperature ; Tb body temperature ; TMR torpid metabolic rate ; VO2 rate of oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Thermoregulation, energetics and patterns of torpor in the pygmy mouse lemur, Microcebus myoxinus, were investigated under natural conditions of photoperiod and temperature in the Kirindy/CFPF Forest in western Madagascar. M. myoxinus entered torpor spontaneously during the cool dry season. Torpor only occurred on a daily basis and torpor bout duration was on average 9.6 h, and ranged from 4.6 h to 19.2 h. Metabolic rates during torpor were reduced to about 86% of the normothermic value. Minimum body temperature during daily torpor was 6.8 °C at an ambient temperature of 6.3 °C. Entry into torpor occurred randomly between 2000 and 0620 hours, whereas arousals from torpor were clustered around 1300 hours within a narrow time window of less than 4 h. Arousal from torpor was a two-step process with a first passive climb of body temperature to a mean of 27 °C, carried by the daily increase of ambient temperature when oxygen consumption remained more or less constant, followed by a second active increase of oxygen consumption to further raise the body temperature to normothermic values. In conclusion, daily body temperature rhythms in M. myoxinus further reduce the energetic costs of daily torpor seen in other species: they extend to unusually low body temperatures and consequently low metabolic rates in torpor, and they employ passive warming to reduce the energetic costs of arousal. Thus, these energy-conserving adaptations may represent an important energetic aid to the pygmy mouse lemur and help to promote their individual fitness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050008
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