Water vascular systemThe water vascular system or hydrovascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract.
StarfishStarfish or sea stars are a class of echinoderms generally shaped like a star polygon. (In common usage, these names are also often applied to ophiuroids, which are correctly referred to as brittle stars or basket stars.) Starfish are also known as asteroids because they form the taxonomic classAsteroidea (). About 1,900 species of starfish live on the seabed, and are found in all the world's oceans, from warm, tropical zones to frigid, polar regions.
Brittle starBrittle stars, serpent stars, or ophiuroids (from Latin ophiurus'brittle star'; from Ancient Greek (óphis)'serpent' and (ourá)'tail'; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.
HydraulicsHydraulics (from Ancient Greek (húdōr)'water' and (aulós)'pipe') is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. Rooted in fluid mechanics, hydraulics is used to govern the use of energy via pressurized liquids. It has been part of human history since ancient times. Hydraulic topics range through some parts of science and most engineering modules.
Sea urchinClass of marine invertebratesSea urchins or urchins () are the classEchinoidea within the echinoderms. Approximately 950 species live on the seabed, inhabiting all oceans and depths from the intertidal zone to the deep sea. They typically have a globular body covered by spiny protective tests (hard shells), typically from 3 to 10 cm (1 to 4 in) across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines.
EchinodermAn echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry (pentamerous symmetry), and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone.
Sand dollarSand dollars (also known as sea cookies or snapper biscuits in New Zealand, or pansy shells in South Africa, and sometimes as sand urchins) are species of flat, burrowing sea urchins belonging to the orderClypeasteroida. NamesThe term "sand dollar" derives from the appearance of the tests (skeletons) of dead individuals after being washed ashore. The test lacks its velvet-like skin of spines and has often been bleached white by sunlight.
Sea cucumberSea cucumbers are echinoderms from the classHolothuroidea ( ). They are benthicmarine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number being in the Asia–Pacific region. Sea cucumbers serve a useful role in the marine ecosystem as detritivores who help recycle nutrients, breaking down detritus and other organic matter, after which microbes can continue the decomposition process.
ComatulidaComatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters. TaxonomyBourgueticrinida, the sea lilies, has traditionally been viewed as an order of Articulata and a sister taxon to Comatulida.*As an Amazon Associate I earn from qualifying purchases.