Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals.

Blood volume and body composition measurements were carried out on diving and nondiving harbor seals, Phoca vitulina. There were small, statistically significant differences in several red blood cell parameters between diving and nondiving seals, but the effect was superimposed on uniformly large blood volumes ranging from 11 to 12% of body weight found in all the animals. It is suggested that the large blood oxygen transport and storage capacity is not so much a direct result of the apneic diving experience, but an expression of phylogenetic control. The development of blood volume during early growth was closely related to the increase in lean body mass. In spite of the inherently large blood volume, this marine mammal when exposed to high altitude for 85 days at an elevation of 3.1 km above sea level appeared to exhibit typical mammalian erythropoietic and ventilatory responses to long-term, mild hypoxia. Thus, it probably cannot be considered to be preacclimatized to high altitude.