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 ha s 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 signifi cant skin gas exchange. Gas composition was measured in subcutaneous g as pockets. CO2 and O-2 exchange through skin were measured both in vi tro and in vivo. In 7-wk-old gas pockets, the steady state PO2 and PCO 2 values were 50 Torr (where 1 Torr = 133.322 Pa) and 35 Torr, respect ively, compared with PO2 and PCO2 values of 73 Torr and 33 Torr, respe ctively, in l-wk-old gas pockets. These changes are attributed to an i n creased capillary density and a decreased skin thickness after 7 wk. There was no significant gas exchange through skin during in vitro me asurements. In vivo measurements indicated that O-2 uptake was 0.5% an d CO2 loss was 0.9% of total body metabolism at 20 degrees C. At 35 de grees C, skin O-2 uptake and CO2 loss increased to 1.3% and 2.9%, resp ectively. 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 relativel y low PCO2 and high PO2 in the gas pockets is better explained by the relative hyperventilation state exhibited by this shrew.