Which animal has three hearts?

The octopus is just one of many creatures that has three hearts. Most cephalopods have three hearts and blue blood.

Octopuses have three hearts, nine brains and the ability to grow back a leg when lost in battle, according to the National Oceanic and Atmospheric Association. Two of the three hearts pump blood to the gills, while the third heart delivers blood to the rest of the octopus' body.

Squid and cuttlefish are two other cephalopods that have three hearts. According to the Smithsonian National Zoological park, the blood of these three-hearted marine animals is blue due to the presence of a protein called hemocyanin, which contains copper and gives the blood its bluish color.