Today

Octopuses Have Three Hearts

An octopus has not one but three hearts! Two pump blood to the gills to pick up oxygen, and the third pumps it to the rest of the body. Even stranger, their blood is blue, not red, because it uses copper instead of iron to carry oxygen. When an octopus swims, its main heart actually stops beating — which may be why they often prefer to crawl. English tip: the standard plural is 'octopuses'; 'octopi' is common but based on a false Latin form. Example: 'We saw two octopuses at the aquarium.'