Echinoderm is pronounced eh-KIE-no-derm; Echinodermata is pronounced eh-KIE-no-der-MA-ta (or eh-kie-no-DER-ma-ta, if you like). Both terms are derived from Greek words for spiny (echinos) and skin (derma).
The echinoderms are a group of animals consisting of over 6,500 known species that have the following features unique to themselves: (1) an internal skeleton composed of crystalline limestone bones; (2) fluid-filled, hydraulically powered organs (comprising a "water vascular system"); (3) tendons ("mutable collagenous tissue") controlled by nerves, which can rapidly transform from rocky rigidity to puddinglike pliancy; and (4) a radial body plan that is five-sided ("pentamerous symmetry").
Some sea anemones (related to corals and jellyfish) and the sea slugs (related to snails) may look like wannabe echinoderms, but their appearance is deceiving. Echinoderms are more closely related to us (vertebrates) than to most other animals, since we both belong to the same ancient branch of life.
Nemo and Jaws are fish stars. Sea stars, also known as starfish, are neither fish nor stars. Rather, they are what echinoderm geeks call Asteroidea, which not surprisingly means starlike animals.
You could suggest to your neighbor to move his garden inland. Although echinoderms are restricted to salt water, they are more ubiquitous than tomatoes. Echinoderms live in every ocean on Earth, and they occur from ankle deep water to abyssal depths (record to date, over 7,000 m [23,000 feet]).
In nature, where most echinoderms are eaten by predators or die of other natural causes, individuals of some species live for a year or less, and others survive for decades. The red sea urchin of California can live for well over 100 years without looking a day over 80.
Because echinoderms are immensely important! Huge numbers of sea stars, sea urchins, and their spiny relatives occur from shallow tide pools to the deepest ocean trenches, often in immense numbers. Their appetite for corals, clams, and kelp has a massive impact on marine ecosystems, and echinoderms themselves are key items on the menus of fishes, lobsters, sea otters, and people. Every year, tons of sea urchins and sea cumbers are harvested; many of them are served in the world’s best restaurants. Other echinoderms are indispensable “lab rats,” and the subjects of cutting edge research in biology and medicine. On top of that, echinoderms are immensely beautiful, which is one of the reasons that sea stars and sand dollars are icons of the ocean.
Echinoderm collections are libraries of specimens, representing 6 to 7 thousand known species, and many more species that are still unnamed. The collections are used by scientists and students who come from nearby and around the world. Information obtained through the examination of specimens in the collections is used in studies of biodiversity, ecology, and paleontology. Specimens in our collections have even been used by law enforcement, to identify species found in illegal shipments of seafood.