Starfish

The starfish usually has five arms, and on their undersides are hundreds of tiny tube feet, which it uses to wander across the bottom and pull shells open. If it loses an arm, the arm grows back, and from some arm pieces a whole new starfish can even grow. It has no brain.

For scientists

Sea stars (Asteroidea) move using a water vascular system: water pressure stretches and curls hundreds of tube feet, with which they can even pry open the shells of clams. Many species can push their stomach out of their body and start digesting prey on the outside. They have no central brain, but a ring of nerves and a strong power of regeneration: a whole animal can grow back from one arm with a piece of the central disc.

Source: Smithsonian Ocean

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