Involved in oxygen transport from the lung to the various peripheral tissues. Heterotetramer of two alpha chains and two beta chains. Red blood cells. Echidnas have a major hemoglobin I (with alpha-1 chain variants A, B, and C) and a minor hemoglobin II (with alpha-2 chain variants A and B). All hemoglobins may have the same beta chain. The sequences of both alpha-1 A and B variants differ from that of the alpha-2 A variant at nine positions. The sequence shown is that of alpha-1 B. Belongs to the globin family.