• Erythrocruorins are highly cooperative giant extracellular respiratory complexes found in annelids, where they serve the same function as red blood cells. (umassmed.edu)
  • In contrast to the vertebrate hemoglobin, where oxygen affinity is decreased by organic phosphates packaged in the red blood cells, the affinity of the high molecular-weight extracellular annelid respiratory proteins, termed either erythrocruorins (Ers) or hemoglobins, is increased by inorganic divalent cations. (bioone.org)