The Icefish is the only known vertebrate with no Hemoglob... | funfact.wiki | funfact.wiki
The Icefish is the only known vertebrate with no Hemoglobin or red blood cells at all, surviving on oxygen-rich frigid water and an enlarged heart and gills instead.
The Octopus's blood is blue, not red. Human blood is red because the iron-based protein Hemoglobin carries its oxygen; in octopuses that job falls to Hemocyanin, a Copper-based protein. Hemocyanin turns blue when it binds oxygen, and carries it better in the cold, low-oxygen sea.