Echinodermata are marine invertebrates with an endoskeleton, or internal skeleton. Echinoderms are all bottom-dwellers. Most can crawl from place to place, few can swim or float. They use a water vascular system that aids in movement, gas exchange, feeding, and excretion; water enters the body and then comes back out through a system of canals in the their bodies. Some are predators often feed on detritus (waste). Reproduction in echinoderms is typically by external fertilization; eggs and sperm are discharged into the water. Most echinoderms go through several larval stages before settling down.
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