How Many Hearts Does an Octopus Have?

An octopus has three hearts. Two of them (branchial hearts) pump blood through the gills to pick up oxygen. The third (systemic heart) pumps oxygenated blood to the rest of the body. The systemic heart actually stops beating when the octopus swims, which is why octopuses prefer crawling to swimming: swimming literally exhausts their circulatory system. Their hearts cannot keep up.

Octopus blood is blue, not red, because it uses copper-based hemocyanin instead of iron-based hemoglobin to carry oxygen. Hemocyanin is less efficient than hemoglobin, which is part of why octopuses need three hearts instead of one. The copper-based system works better in cold, low-oxygen environments (like the deep ocean), which is an evolutionary trade-off: worse overall performance but better cold-water survival.

The three-heart system is just one of the many things that make octopuses seem like aliens that accidentally ended up on Earth. They also have 9 brains (one central brain and one in each arm), blue blood, the ability to change color and texture in milliseconds, no skeleton at all, and they can taste with their suckers. They are the closest thing to extraterrestrial intelligence that exists on this planet, and they live for only 1-5 years, which seems cosmically unfair.

Octopus anatomy compared

Animals with multiple hearts