Xw. Song et al., THERMAL RELATIONS OF METABOLIC-RATE REDUCTION IN A HIBERNATING MARSUPIAL, American journal of physiology. Regulatory, integrative and comparative physiology, 42(6), 1997, pp. 2097-2104
We tested whether the reduction of metabolic rate (MR) in hibernating
Cercartetus nanus (Marsupialia, 36 g) is better explained by the reduc
tion of body temperature (T-b), the differential (Delta T) between T-b
and air temperature (T-a), or thermal conductance (C). Above the crit
ical T-a during torpor (T-tc) of 4.8 +/- 0.7 degrees C, where the T-b
was not regulated, the steady-state MR was an exponential function of
T-b (r(2) = 0.92), and the overall Q(10) was 3.3. However, larger Q(10
) values were observed at high T-b values during torpor, particularly
within the thermoneutral zone (Q(10) = 9.5), whereas low Q(10) values
were observed below T-b 20 degrees C (Q(10) = 1.9). The Delta T did no
t change over T-a 5-20 degrees C, although MR fell, and therefore the
two variables were not correlated. Below the T-tc, T-b was regulated a
t 6.1 +/- 1.0 degrees C and MR increased proportionally to Delta T. Ou
r study suggests that MR in torpid C. nanus is largely determined by t
emperature effects and metabolic inhibition. In contrast, Delta T expl
ains MR only below the T-tc and C appears to affect MR only indirectly
via changes of T-b, suggesting that Delta T and C play only a seconda
ry role in MR reduction during hibernation.