The human version of the respira- tory pigment is called hemo- globin, and the crab version is called hemocyanin. In hemoglobin, when iron binds to oxygen, it absorbs mostly blue light, so it appears bright red.

Can humans have blueblood?

But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion. ... But blue blood does exist elsewhere in the animal world. It's common in animals such as squid and horseshoe crabs, whose blood relies on a chemical called hemocyanin, which contains a copper atom, to carry oxygen.

Do humans have hemocyanin in their blood?

The blue comes from a copper-rich protein called hemocyanin, which carries oxygen from the lungs to the bloodstream and then to the cells of the octopus's body. Hemoglobin, an iron-containing protein found in the blood of other animals—including humans—serves the same oxygen-transporting function but turns blood red.