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

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, 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 the O₂ uptake was 0.5% and CO₂ loss was 0.9% of total body metabolism at 20°C. At 35°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.