chlorocruorin

The affinity of chlorocruorin for oxygen is equivalent to the haemoglobin. It is interesting that within the same family of worms like [S]abellidae, [S]erpulidae and [A]mphotritidae same^([sic]) species have chlorocruorin while others have haemoglobin.

2003, Ashok Kumar, Animal Physiology, Discovery Publishing House, page 192

1992, N. B. Terwilliger, Chapter 8: Molecular Structure of the Extracellular Heme Proteins, Ch. P. Mangum (editor), Advances in Comparative & Environmental Physiology 13: Blood and Tissue Oxygen Carriers, Springer-Verlag, 1992 softcover reprint, page 203, It was earlier thought that chlorocruorin was very different from hemoglobin based on a subunit structure with a mass of 34-35 kDa (Antonini et al. 1962; Guerratore and Zito 1977). […] Some writers have questioned the value of drawing a distinction between the chlorocruorins and hemoglobins, especially from an evolutionary point of view (Mangum 1985; see also Toulson, Chap. 9, this Vol.). The visual phenomenon of green blood has perhaps led to a stronger distinction between chlorocruorin and hemoglobin than warranted.