Short Communications Foetal and Adult Blood Oxygen Affinities of the Viviparous Seaperch, Embiotoca Lateralis

The high oxygen affinity of foetal versus adult blood is an almost universal characteristic of viviparous vertebrates; a notable exception is the cat (Novy & Parer, 1969). There is also likely to be a difference in the oxygen affinities of foetal and adult blood in the teleostean fish, the seaperch Embiotoca lateralis Agassiz. Our studies of E. lateralis foetal and adult haemoglobins and erythrocytes have shown several mechanisms which are likely to facilitate oxygen transfer to the foetal fish by increasing foetal blood oxygen affinity with respect to that of adult blood. Proposed mechanisms include structurally distinct foetal and adult haemoglobins with foetal haemoglobin having the higher oxygen affinity, lower foetal erythrocyte nucleoside triphosphate (NTP, primarily ATP) concentrations, and possibly, lower mean corpuscular haemoglobin concentrations (MCHC) in foetal cells (Ingermann & Terwilliger, 1981a,6, 1982a). It is necessary, however, to see if the oxygen affinity of foetal whole blood is greater than that of adult blood as predicted from purified haemoglobin oxygen binding and erythrocyte characteristics. Consequently, we have measured the oxygen affinities of foetal and adult whole bloods under comparable conditions.