Here's why:
* Three Hearts: Octopuses have three hearts. Two branchial hearts pump blood through the gills, and the third, systemic heart pumps blood throughout the rest of the body.
* One Bone: Octopuses are invertebrates, meaning they don't have a backbone or internal skeleton. The only "bone" they have is a beak-like structure made of chitin, which is a hard, tough substance found in the exoskeletons of insects and crustaceans.