grooves are arranged little feet which act like suckers
These are used both for moving about and as organs of smell.
Sea star cannot travel very fast with their little tube-like feet,but sucking disk of their feet to either half of the oyster shell and pull at i untill the oyster mouth,and wraps it about the oyster.
Starfish can also eat by taking food into their mouths in the ordinary way. They can also replace broken arms. In fact, they may even grow a whole new body from one arm. There should be at least on starfish in Ripley’s “Believe it or not” museum!