Response and Movement

Nervous and sensory systems are generally poorly developed in echinoderms. There is a simple nervous system sensitive to temperature, light, and vibrations. They lack specialized sense organs nose, eyes, and ears. No brain, or head but they do have a nerve net and a nerve ring. Their nerve cells can detect light and touch. Starfish have eyespots (which are a cluster of nerve cells) at the tips of each arm that sense each ray for light.
The water-vascular system supplies water through canals of small muscular tubes to the tube feet (ambulacral feet). As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is released. Sea stars, sea cucumbers, and sea urchins move by alternately extending and retracting groups of tube feet, gripping with the suction cups and pulling themselves along. The resulting locomotion is generally very slow, but effective.