Metabolic, respiratory and cardiac activity in the shrew Crocidura russula

Oxygen consumption, respiratory rate, heart rate and body temperature of resting common white-toothed shrews (Crocidura russula, mean = 11.4 g), have been determined at ambient temperatures (Ta) between 0 and 37 degrees C. Mean basal oxygen consumption (Ta = 30 degrees C, Tb = 35.4 degrees C) was 2.3 ml.g-1.h-1 and was about 12% above the value expected on the basis of the allometric relationship applying for mammals. At 0 degree C oxygen consumption was 4.2 times that in the thermal neutral zone (TNZ) which is located at Ta of about 30 degrees C. The mean basal respiratory rate was 103 min-1 (Ta = 30 degrees C), fully 40% below the predicted value. The respiratory rate increased at 0 degree C to 3.8 times that in TNZ. The amount of oxygen consumed per breath was rather constant, increasing from a mean of 4.3 microliters (Ta = 30 degrees C) to 4.9 microliters (Ta = 0 degree C) which was only 15% above the basal value. Comparing the great changes of respiratory rate with the small alterations of oxygen consumed per breath, a dominant influence of respiratory rate in the regulation of respiration is shown. Basal heart rate was 444 min-1 (Ta = 30 degrees C), in agreement with the expected value. Heart rate increased only 1.75-fold at an ambient temperature of 0 degree C. Oxygen pulses depend very strongly on ambient temperature, increasing from 0.98 microliters (Ta = 30 degrees C) to 2.5 microliters at 0 degree C. Beat frequency and stroke volume regulation are salient features of heart function.