Plasma and blood volumes in the little brown bat

¹ Department of Zoology, Cornell University, Ithaca, New York

Modifications are described which make T-1824 suitable for plasma volume determinations on small bats. An average plasma volume of 6.5 ml/100 gm body weight has been determined for the active little brown bat, Myotis lucifugus; average blood volume, based on plasma volume and hematocrit, is 13.0 ml/100 gm body weight. Seasonal changes have been observed which apparently result primarily from changes in lean body weight and from pregnancy. Young bats have a proportionately greater blood volume. No significant differences have been found between sexes, nor between determinations made during day and night hours. Plasma and blood levels are changing least at the beginning and end of the hibernating period. Comparisons of previous studies suggest that, while a plasma decrease and unchanged cell volume seem generally characteristic of mammals which have entered hibernation, a concurrent drop in heart blood hematocrit of the hibernating bat suggests a redistribution of erythrocytes as well.