Octopus and horseshoe crabs hàve blue blood due to presence of copper their blood. It is called as Heamocyanin. Instead of Iron , copper is the carrier of oxygen and hence it's blue in colour when oxygenated. read more
Hemoglobin, an iron-containing protein found in the blood of other animals—including humans—serves the same oxygen-transporting function but turns blood red. Spiders, molluscs and other crustaceans have blue blood too. read more
10 Animals That Bleed Blue Turns out blue bloods are pretty gross even without the inbreeding. Without iron-rich hemoglobin turning their blood a recognizable red, these animals have had to make do with copper-based hemocyanin. read more