1. The octopus is a mollusk and has no bones (all bones have degraded). 2. The octopus is a cephalopod, with eight arms and legs growing on the head. 3. The octopus is The most intelligent of all invertebrates. 4. The skin of the octopus contains highly developed pigment-containing cells, which can change its body color very quickly. The body color of the octopus can be used as a protective color, and it is said that it can also reflect the octopus's mood. 5. The octopus breathes by sucking water into its mantle and expelling the water from the body through the short funnel-shaped body tube. When the octopus is frightened, it will eject water from the body tube and rely on the hydraulic jet to quickly move in the opposite direction to avoid danger. 6. Octopus When in danger, it will spray out an ink-like substance as a smoke screen to avoid danger.