Octopuses Have Three Hearts and Blue Blood
Two hearts pump blood through the gills, while a third circulates it to the rest of the body. Their blood contains hemocyanin instead of hemoglobin, turning it blue when oxygenated. When an octopus swims, one heart stops, explaining why these animals prefer crawling.
💡 Fun detail:
Octopuses can taste with their suckers, allowing them to decide if prey is edible before bringing it to their mouth.
Source: Monterey Bay Aquarium