Is there a significant gas exchange through the skin of the shrew Crocidura russula monacha?

Abstract

Because of its small body mass, the shrew Crocidura russula monacha has a relatively high surface area to volume ratio, thin skin, and high thermal conductance compared with larger mammals. This study was aimed at examining the possibility that such a mammal may exhibit a significant skin gas exchange. Gas composition was measured in subcutaneous gas pockets. CO2 and O2 exchange through skin were measured both in vitro and in vivo. In 7-wk-old gas pockets, the steady-state PO2 and PCO2 values were 50 Torr (where 1 Torr = 133.322 Pa) and 35 Torr, respectively, compared with PO2 and Pco2 values of 73 Torr and 33 Torr, respectively, in 1-wk-old gas pockets. These changes are attributed to an increased capillary density and a decreased skin thickness after 7 wk. There was no significant gas exchange through skin during in vitro measurements. In vivo measurements indicated that O2 uptake was 0.5% and CO2 loss was 0.9% of total body metabolism at 20 degrees C. At 35 degrees C, skin O2 uptake and CO2 loss increased to 1.3% and 2.9%, respectively. These values are only part of the expected skin metabolism; thus, the rest must come from blood. Because gas exchange through the skin of this shrew is within the range of other mammals, the relatively low PCO2 and high PO2 in the gas pockets is better explained by the relative hyperventilation state exhibited by this shrew.