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KMID : 0613820060160040618
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Journal of Life Science
2006 Volume.16 No. 4 p.618 ~ p.625
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A Study on Daily Torpor in the Korean Striped Field Mouse (Apodemus agrarius).
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Yoon Myung-Hee
Han Chang-Wook
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Abstract
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Patterns of induced daily torpor were measured in the striped field mouse, Apodemus agrarius, in response to low temperature, food deprivation and various photoperiods using implanted data loggers. A total of 8 of 21 females entered daily torpor in response to low outside ambient temperature (Ta) during winter and spring, constant low Ta (4℃) or food deprivation (23℃) during summer, but 2 of 23 males did only in response to low outside Ta during winter. This fact indicates that torpor is an adaptive hypothermia to unpredictable environment in both some males and females, as well as that torpor was inhibited in males in the reproductive season as in other mammals, which is regarded as a strategy not to reduce the chance of copulation. As for females, however, torpor was employed in response to unpredictable environment even in the reproductive season, suggesting that alternative strategies other than keeping the chance of copulation maybe hired by females to keep the population. Torpor bout generally began at 6～12 AM, but the decrease of body temperature (Tb) began mainly at 4～6 AM at any conditions, the time when Ta is lowest. This strategy might be also adopted for reducing heat loss to unpredictable environment. Minimum Tb of both males and females during torpor did not fall below 16.5℃. Photoperiod had no influence on the incidence and timing of daily torpor in either males and females. The similar timing of torpor bout in response to the 3 different photoperiods (24D, 16L:8D or 8L:16D) under the constant temperatures (4℃ or 23±2℃) suggests that entering time of torpor might be controlled by the circadian rhythm of the mice rather than by the photoperiod.
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KEYWORD
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Apodemus agrarius, body temperature, daily torpor
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