Muscle capillary supply in hind limb and diaphragm of the common shrew (Sorex araneus).

Shrew species of the subfamily Soricinae have unusually high metabolic rates when compared to Crocidurinae shrews and other similar-sized mammals. The aim of this study was to clarify whether the high basal metabolic rate of Soricinae shrews is reflected in a high capillary density in their muscles. To this end, the capillary supply of four limb muscles and diaphragm of the common shrew (Sorex araneus) was quantified from cross-sectioned muscles. The capillary densities of the limb muscles were 2575 +/- 329, 3111 +/- 299, 2812 +/- 197 and 2752 +/- 173 capillaries mm-2 fibre area in gastrocnemius lateralis, g. medialis, plantaris and soleus, respectively. Capillary density of the shrew diaphragm (6691 +/- 1057) was double that of the limb muscles. This value is among the highest ever measured in mammals. In general, the capillary supply in the hind limb of the common shrew is about 3-4 times higher than commonly found in the leg muscles of the laboratory rat or other bigger mammals, but similar to those in Crocidurinae shrews and some small rodents. Thus the high resting metabolism of the common shrew is not associated with an extraordinarily high capillary density. The apparent disparity between basal metabolic rate and muscle capillary supply in S. araneus is probably due to the small aerobic scope of shrews in the subfamily Soricinae.