Retention of Carbon Dioxide during Entrance into Torpor in Dormice

Abstract

Metabolic rate (MR), heart rate (HR) and body temperature (Tb) of two edible dormice (Glis glis) were studied during entrance into torpor at two temperature ranges, Ta = 0 to 5ºC and 15 to 20ºC. MR was reduced rapidly from 275 to 84 ml O2 * h-1 within the first hour after onset into torpor at the low temperature range and from 154.5 to 82.2 ml O2 * h-1 at the high temperature range. HR decrease paralleled the reduction of MR. Between 0-5ºC the HR decreased rapidly from 388 to 171 BPM within the first hour and from 284 to 193 BPM in the range of 15-20ºC. After onset of metabolic reduction Tb decreased within one hour from 36.9ºC to 30.8ºC at the low temperature range (cooling rate 6.1ºC*-1). At the high temperature range cooling rate within the first hour was at 2.4ºC*h-1 with a Tb decrease from 37.2ºC to 34.9ºC. A decrease of respiratory quotient (RQ) appeared closely correlated to the reduction of Tb at Ta below 5ºC. The RQ decreased to 0.25 indicating a retention of CO2. In the temperature range of 15 to 20ºC no reduction of RQ could be observed during entry into torpor. The RQ even rose slightly from 0.7 - 0.8 to about 1.0. We suggest that the depression of metabolism and heart acticity is an active downregulation, but the decrease of RQ at low Ta point out a temperature dependent relationship caused by cooling of body fluids.