Imagine a creature with such a radically different body plan that we, bilateral humans, can’t really fathom how they have been so successful. Sea stars, and other echinoderms, move and feed like no other animals. They are animals that followed a different evolutionary path after evolving from the same bilateral ancestors as us.
Many still call sea stars “starfish”, but they certainly aren’t fish. No head, no tail, all arms –sea stars are just that: stars. Based on five-part radial symmetry (though some sea stars have many more arms), key functions are coordinated in the center of their bodies, then passed down the arms. The sea star has no brain, but a nerve ring in its center, like a relay station that coordinates the movement of its arms. This nervous system relays impulses from light, touch and chemical sensors around its body.