Octopuses have three hearts
Two pump blood to the gills, one drives it to the rest of the body — and it stops when they swim.
Verified · Smithsonian Ocean
An octopus runs on three hearts. Two branchial hearts push blood through the gills to pick up oxygen, and one systemic heart sends that oxygenated blood out to the rest of the body.
There’s a catch: the systemic heart stops beating when the octopus swims. That’s part of why these animals prefer to crawl — swimming literally exhausts them.
Their blood is blue, not red. Instead of iron-based hemoglobin, octopuses use copper-based hemocyanin, which moves oxygen more efficiently in the cold, low-oxygen water of the deep.
Sources & references
2 referencesWell-established. Corroborated by 2 independent sources.
1 Smithsonian Ocean Museum / research “An octopus has three hearts and blue, copper-based blood.” ocean.si.edu ↗
2 National Geographic Science media “Two branchial hearts pump blood through the gills; a systemic heart circulates it to the body.” nationalgeographic.com ↗
✓ Last reviewed Jun 6, 2026
