• The Korean Journal of Zoology
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• v.39 no.1
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• pp.98-105
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• 1996

Studies on thermal adaptation postulate that optimal temperature of physiological properties matches a usually experienced body temperature (Tb) of organisms. Hibernating bats maintain Tb's that are slighdy higher than ambient temperatures (9$^{\circ}$-12$^{\circ}$C) of their wintering sites. To test the hypothesis that muscle function is adjusted to the Tb range of the hibernating animals, we examined contractile function of the biceps brachil muscle of Korean greater horseshoe bats, Rhinolophus ferrumequlnum korai (n = 5) at tissue temperatures between 1O$^{\circ}$ and 35$^{\circ}$C. Relative tetanic force (% of maximum force) was highest at temperatures of 1O$^{\circ}$-15$^{\circ}$C, which match well their Tb's during hibernation. Because non-hibernating endotherms with Tb of around 37$^{\circ}$C show the optimal temperature for muscle force over 30$^{\circ}$-40$^{\circ}$C, our results strongly suggest that the flight muscle of the bats may exhibit thermal adjustments according to their seasonal Tb's. The capacity to generate strong force at such low body temperatures may be adaptive, because bats must have muscles functioning to fly for occasional watering or excretion, or to move away from potential predators during hibernation.