Octopuses have three hearts, blue blood, and distributed brains

An octopus has three hearts — two pump blood to its gills, one pumps it around the body — and its blood is blue because it uses copper-based haemocyanin instead of iron-based haemoglobin to carry oxygen (haemocyanin is more efficient at low temperatures). More remarkably, roughly two-thirds of an octopus's 500 million neurons are distributed in its eight arms, which can act semi-independently, taste and smell through their suckers, and solve problems without instructions from the central brain. Each arm can continue searching for food for an hour after being severed.

Source: Godfrey-Smith, Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness (2016)