Scientists have finally solved the puzzle of starfish’s unique bodies. As it turns out, sea stars and other echinoderms are essentially walking heads with little to no body.
Echinoderms — sea stars, sea urchins, sea cucumbers, and their relatives — have unique bodies that have long puzzled evolutionary biologists. These animals evolved from bilateral organisms — those that have two symmetrical sides — but somehow they evolved a radial body plan, meaning their body parts are arranged around a central axis. In the case of adult sea stars, five (or more) arms emanate from a central structure.