Echinoderms are sea creatures with multiple limbs that extend from a central body in a symmetric radial pattern. Sea stars are the most recognizable echinoderms, but at least 6,000 known species exist, including sea urchins and sea cucumbers.
Echinoderms rely on their vascular system to move. They absorb sea water through tiny tube feet, which extend as water circulates through different chambers. Echinoderms alternate between extending and retracting their tube feet, enabling a slow walking motion. Echinoderms also use their feet to cling to rocks and ocean surfaces. Many are known for their spiny skin texture and their ability to reproduce damaged or missing limbs.