Here's a fun fact: Octopuses have three hearts, and two of them stop beating when they swim. That’s right—swimming literally tires them out so much that their bodies partially shut down circulation. Because of this, they prefer crawling along the ocean floor rather than swimming through open water. Even crazier, their blood is blue instead of red because it uses a copper-based molecule called hemocyanin to transport oxygen, which works better in cold, low-oxygen environments. Oh, and about their

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