Starfish lack an actual brain and instead use a complex nervous system to sense the environment. Nerves run from its mouth down each arm to eyespots at the ends of those arms. This allows starfish to distinguish between light and dark.
Starfish belong to the family of echinoderms. Other echinoderms are sea cucumbers, sand dollars and sea urchins. Using sensors in their many tube feet, starfish are able to find food by sensing chemical trails in the water. They live in seas around the world, both in shallow water and deep on the ocean floor. Most starfish have the ability to regenerate whole limbs when needed.