There’s nothing half-hearted about cephalopods. These tentacular marine creatures, including the octopus, squid and cuttlefish, have three hearts apiece.Two brachial hearts on either side of the cephalopod’s body oxygenate blood by pumping it through the blood vessels of the gills, and the systemic heart in the center of the body pumps oxygenated blood from the gills through the rest of the organism, said Michael Vecchione.
Cephalopods are also literally blue-blooded because they have copper in their blood. Human blood is red because of the iron in hemoglobin. “Just like rust is red, the iron in our hemoglobin is red when it’s oxygenated,” Vecchione said. But in cephalopods, oxygenated blood turns blue.