Metabolic, respiratory and cardiac activity in the shrew Crocidura russula

Abstract

Oxygen consumption, respiratory rate, heart rate and body temperature of resting common white-toothed shrews ( Crocidura russula, x = 11.4 g ), have been determined at ambient temperatures (Ta) between 0 and 37 °C. Mean basal oxygen consumption (Ta = 30 °C, Tb = 35.4 °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 °C oxygen consumption was 4.2 times that in the thermal neutral zone (TNZ) which is located at Ta of about 30 °C. The mean basal respiratory rate was 103 min −1 (Ta = 30 °C), fully 40% below the predicted value. The respiratory rate increased at 0 °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 μl (Ta = 30 °C) to 4.9 μl (Ta = 0 °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 °C), in agreement with the expected value. Heart rate increased only 1.75-fold at an ambient temperature of 0 °C. Oxygen pulses depend very strongly on ambient temperature, increasing from 0.98 μl (Ta = 30 °C) to 2.5 μl at 0 °C. Beat frequency and stroke volume regulation are salient features of heart function.