THE BLOOD OF CARNIVOROUS MARSUPIALS - LOW HEMOGLOBIN OXYGEN-AFFINITY

We examined the blood of four dasyurid marsupials, all small, active i nsectivores and/or carnivores, to establish if there were any speciali zations in oxygen transport. All four species had hemoglobins with a l ow affinity for oxygen. This was demonstrated by high P-50's (the part ial pressure of oxygen [Po-2] at which the hemoglobin is half-saturate d with oxygen) of the whole blood (means of 38.3-59.8 mmHg) and of red cells suspended in a physiological buffer (means of 41.6-49.0 mmHg) a t a CO2 tension of 43 mmHg. There was a strong correlation between inc rease in body mass over three orders of magnitude and increase in the oxygen affinity of the whole blood. The effects of changing CO2 tensio ns on the oxygen affinity of whole blood were measured as Delta log P- 50/Delta log Pco(2); means values ranged from 0.25 to 0.373. Values fo r Delta log P-50/Delta pH were measured for red-cell suspensions; mean s values ranged from -0.40 to -0.481. The introduction of 2,3-diphosph oglycerate significantly decreased the oxygen affinity of the hemoglob in of Dasyuroides byrnei. The blood of D. byrnei and Dasyurus viverrin us had high hematocrits and high concentrations of hemoglobin. We conc lude that hemoglobins with a low affinity for oxygen, an adaptation to an active lifestyle, are a characteristic of dasyurid marsupials gene rally.