Haemacyanin
Haemacyanin (-sī"ȧ*nin) , noun
[Haema- + Greek ky`anos a dark blue substance.]
(Physiology Chemistry) A substance found in the blood of the octopus, which gives to it its blue color.
When deprived of oxygen it is colorless, but becomes quickly blue in contact with oxygen, and is then generally called oxyhaemacyanin. A similar blue coloring matter has been detected in small quantity in the blood of other animals and in the bile.