An octopus is less an animal than a separate experiment in intelligence. It has 3 hearts, blue blood (copper-based, not iron), and around 500 million neurons - as many as a dog - but most of them sit in its 8 arms, which can taste, decide, and act on their own. Scientists treat it as the closest thing to alien biology on Earth, and it can even edit its own RNA. When it jet-swims, its main heart stops beating.
