Octopuses have three hearts: two pump blood to the gills, while the third pumps it to the rest of the body. The heart pumping to the body stops beating when the octopus swims.
Sources
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- https://spacedaily.com/t-octopuses-have-three-hearts-and-blue-blood-that-carries-oxygen-using-a-copper-based-protein-rather-than-iron-and-because-the-heart-that-supplies-the-body-stops-beating-whenever-they-swim-many-bottom/ (spacedaily.com)
- https://www.smithsonianmag.com/science-nature/ten-wild-facts-about-octopuses-they-have-three-hearts-big-brains-and-blue-blood-7625828/ (smithsonianmag.com)
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