Their great success is due to their ability to exploit nature's resources during different stages of metamorphosis, such as larvae, nymphs, and pupae. Their ability to disperse by flight allows the utilization of widely ranging food sources. Members include sea stars, sea urchins, brittle stars, and sea cucumbers. Internally, echinoderms are deuterostomes but of simple design. The unique water-vascular system operates the tube feet by contracting the ampulla on each one to achieve a suction useful in locomotion and prey capture.
Sea stars can evert their stomachs when feeding.