Octopuses are ocean creatures that are most famous for having eight arms and bulbous heads. Some other fun facts: They have three hearts and blue blood; they squirt ink to deter predators; and being boneless, they can squeeze into (or out of) tight spaces. They are quite intelligent and have been observed using tools.

And sadly, for them, sex is a death sentence.An octopus has three hearts. One pumps blood through its organs; the two others pump blood through its gills, according to the World Animal Foundation. Octopus blood is blue because it has a copper-based protein called hemocyanin. Octopuses come in many different sizes. The common octopus (Octopus vulgaris) is 12 to 36 inches (30.5 to 91.4 centimeters) long and weighs 6.6 to 22 lbs. (3 to 10 kilograms). Octopuses live in oceans all over the world. Most are pelagic, meaning they live near the water's surface in shells, reefs and crevices. Some species live on the floor of the ocean, making their homes out of caves.