High molecular weight (1,500,000 to 3,000,000) hemoglobins found in the plasma of many polychete and oligochete annelid worms and various mollusks. They bind one mole of oxygen per heme and function as oxygen carriers.
Annelida
A phylum of metazoan invertebrates comprising the segmented worms, and including marine annelids (POLYCHAETA), freshwater annelids, earthworms (OLIGOCHAETA), and LEECHES. Only the leeches are of medical interest. (Dorland, 27th ed)