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A Study on Daily Torpor in the Korean Striped Field Mouse (Apodemus agrarius)

등줄쥐(Apodemus agrarius)의 일중휴면에 관한 연구

  • Published : 2006.07.31

Abstract

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 $(4^{\circ}C)$ or food deprivation $(23^{\circ}C)$ 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 $6{\sim}12$ AM, but the decrease of body temperature $(T_b)$ began mainly at $4{\sim}6$ AM at any conditions, the time when Ta is lowest. This strategy might be also adopted for reducing heat loss to unpredictable environment. Minimum $T_b$ of both males and females during torpor did not fall below $16.5^{\circ}C$. 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 $(4^{\circ}C\;or\;23{\pm}2^{\circ}C)$ suggests that entering time of torpor might be controlled by the circadian rhythm of the mice rather than by the photoperiod.

등줄쥐에서 일중휴면이 어떤 요인에 의하여 유발되는지를 알기 위하여, 온도, 먹이 및 광주기를 조절하여 등줄쥐의 체온변화를 자동온도기록장치를 이용하여 조사하였다. 등줄쥐 암컷에서는 21개체 중 8개체가 겨울철 및 봄철 실외환경, 저온실$(4^{\circ}C)$과 절식상태$(23^{\circ}C)$에서, 등줄쥐 수컷에서는 23개체 중 2개체가 겨울철 실외환경에서 휴면을 하는 점으로부터, 일중휴면은 일부 암 수 등줄쥐에서 저온이나 먹이결핍 등 갑작스런 환경변화에 대처하기 위한 에너지 절약대책으로 채택되고 있음이 시사되었다. 그러나 수컷에서는 번식기에는 번식 기회를 줄이지 않기 위하여 휴면을 억제하지만 암컷에서는 번식기에도 휴면을 하는 점으로부터 암 수가 서로 다른 전략으로 집단을 유지하고 있다고 생각되었다. 일중휴면은 오전 6시${\sim}$낮 12시 사이에 가장 빈번하게 관찰되었으며, 휴면시의 체온의 하강은 어떠한 조건에서도 주위온도가 가장 낮은 오전 4시${\sim}$6시경에 시작되었는데, 이러한 점은 일중휴면이 열 손실의 억제를 위한 전략임을 시사하고 있다. 휴면시 최저체온은 $16.5^{\circ}C$이었다. 광주기의 영향은 없었으며, 일정온도 하에서 항상 암기$(24D,\;4^{\circ}C)$에 두거나, 절식$(23^{\circ}C)$ 하에 광주기를 변화시켜도(16L:8D 또는 8L:16D) 서로 유사한 시각에 일중휴면이 일어나고 있어, 일중휴면 시각이 광주기에 의해서 조절되지 않으며 활동일주기의 영향을 받고 있다고 생각되었다.

Keywords

References

  1. Bartels, W., B. S. Law and F. Geiser, 1998. Daily torpor and energetics in a tropical mammal, the northern blossom- bat, Macroglossus minimus (Megachiroptera). J. Comp. Physiol. B 168, 233-239 https://doi.org/10.1007/s003600050141
  2. Carpenter, F. L., 1974. Torpor in Andean hummingbird: its ecological significance. Science 183, 545-547 https://doi.org/10.1126/science.183.4124.545
  3. Geiser, F., D. K. Coburn, G. Koertner and B. S. Law, 1996. Thermoregulation, energy metabolism, and torpor in blossom- bats, Syconycteris australis (Megachiroptera). J. Zool., Lond. 239, 583-590 https://doi.org/10.1111/j.1469-7998.1996.tb05944.x
  4. Hainsworth, F. R., B. G. Collins and L. L. Wolf, 1977. The function of torpor in hummingbirds. Physiol. Zool. 50, 215-222 https://doi.org/10.1086/physzool.50.3.30155724
  5. Heldmaier, G., S. Steinlechner, T. Ruf, H. Wiesinger and M. Klingenspor, 1989. Photoperiod and thermoregulation in vertebrates: body temperature rhythms and thermogenic acclimation. J. Biol. Rhythms 4, 251-265
  6. Hohtola, E., R. Hissa, A. Pyornila, H. Rintamaki and S. Saarela, 1991. Nocturnal hypothermia in fasting Japanese quail: the effect of ambient temperature. Physiol. Behav. 49, 563-568 https://doi.org/10.1016/0031-9384(91)90281-R
  7. Lovegrove B. G. and J. Raman, 1998. Torpor patterns in the pouched mouse (Saccostomus campestris; Rodentia): a model animal for unpredictable environments. J. Comp. Physiol. B 168, 303-312 https://doi.org/10.1007/s003600050150
  8. Mika M., C. Koshimoto, K. Tsuchiya, A. Nishiwaki and T. Morita, 2005. Body temperature profiles of the Korean field mouse Apodemus peninsulae during winter aggregation. Mammal Study 30, 33-40 https://doi.org/10.3106/1348-6160(2005)30[33:BTPOTK]2.0.CO;2
  9. Morita T., 1995. Advances in ecophysiological research on mammalian hibernation. Mammalian Science 35(1), 1-20
  10. Morita T., 2000. Wood mouse and daily torpor. pp. 234-253, In Kawamich T., N. Kondo and T. Morita (eds.), Hibernation in Mammals, University of Tokyo Press, Tokyo
  11. Pivorun E. B. and M. G. Tannenbaum, 1984. Naloxone inhibition of stress-induced daily torpor. Life Sci. 34(22), 2145-2150 https://doi.org/10.1016/0024-3205(84)90313-8
  12. Ruby N. F., R. J. Nelson, P. Licht and I. Zucker, 1993. Prolactin and testosterone inhibit torpor in Siberian hamsters. Am. J. Physiol. 264, R123-R128
  13. Taylor, R. E., 1998. Evolution of energetic strategies in shrews. pp. 309-346, In Wojcik J. M. and M. Wolsan (eds.), Evolution of Shrews. Polish Academy of Science, Bialowieza
  14. Walker, L. E., J. M. Walker, J. W. Palca and R. J. Berger, 1983. A continuum of sleep and shallow torpor in fasting doves. Science 221, 194-195 https://doi.org/10.1126/science.221.4606.194
  15. Walton, J. B. and J. F. Andrews, 1981a. Torpor in single and huddled wood mice (Apodemus sylvaticus (L.)). Acta Univ. Carol. Biol. 1979, 181-184
  16. Walton, J. B. and J. F. Andrews, 1981b. Torpor induced by food deprivation in the wood mice (Apodemus sylvaticus (L.)). J. Zool., Lond. 194, 260-263 https://doi.org/10.1111/j.1469-7998.1981.tb05773.x
  17. Won P. H., 1967. Mammals, 659 pp. In Illustrated encyclopedia of fauna and flora of Korea. Vol. 7, Ministry of Education, Seoul
  18. Yoon M. H., S. J. Jung and H. S. Oh, 1997. Population structure and reproductive pattern of the Korean striped field mouse, Apodemus agrarius. Korean J. Biol. Sci. 1, 53-61 https://doi.org/10.1080/12265071.1997.9647348