Octopuses Are Hiding Three Hearts And Blue Blood

The real animal is stranger than anything a cartoon invented.

You'd expect one heart. An octopus casually runs on three, and they don't all do the same job.

Two hearts push blood through the gills. The third sends it around the rest of the body.

Its blood isn't red either. It's blue, because it carries oxygen using copper instead of iron.

When an octopus swims hard, the main heart pauses, which is partly why it prefers to crawl.