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Echinodermata Klein, 1734 Sea urchins; Sand dollars; Sea cucumbers; Seastars; Cushion stars; Brittle-stars; Basket-stars; Sea lilies; Feather stars

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Higher taxa:  Life   Echinodermata   IDnature guides: Groups_Echinodermata, North_American_Invasives Overview Phylogeny Echinodermata families Links to other sites References Acknowledgements We parsed the following live from the Web into this page. Such content is managed by its original site and not cached on Discover Life. Please send feedback and corrections directly to the source. See original regarding copyrights and terms of use. Animal Diversity Web

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© John Pickering, 2006-2009 Sea star	© John Pickering, 2006-2009 Sea urchins
© John Pickering, 2006-2009 Sea urchins and Starfish	© John Pickering, 2006-2009 Sea urchins and Starfish
© John Pickering, 2006-2009 Sea urchins and Starfish	© John Pickering, 2006-2009 Starfish and Sea urchins
© Copyright GNU Free Documentation License The Passion Flower feather star, Ptilometra australis, a modern crinoid

Kinds

Acanthasteridae Aeropsidae Amphilepididae Amphiuridae Antedonidae Apatopygidae Aporometridae Arachnoididae Arbaciidae Archasteridae Aspidodiadematidae Asteriidae -- Sea Stars Asterinidae -- Blunt-armed sea star Asterodiscididae Asterometridae Asteronychidae Asteropseidae Asteroschematidae Asterostomatidae Astriclypeidae Astropectinidae -- Two-spined sea star Atelecrinidae Bathycrinidae Benthopectinidae Bourgueticrinidae Brisingidae Brissidae Calometridae Calymnidae Cassidulidae Caudinidae Caymanostellidae Chaetasteridae Charitometridae Chiridotidae Cidaridae Clypeasteridae Colobometridae Comasteridae Ctenodiscididae Cucumariidae Deimatidae Dendrasteridae Diadematidae Echinarachniidae Echinasteridae Echinidae Echinolampadidae Echinometridae Echinoneidae Echinothuriidae Elpidiidae Eudiocrinidae Eupyrgidae Euryalidae Fibulariidae Ganeriidae Gephyrothuriidae Goniasteridae Goniopectinidae Gorgonocephalidae Heliasteridae Hemiasteridae Hemieuryalidae Heterothyonidae Himerometridae Holasteridae Holopodidae Holothuriidae -- Five-toothed sea cucumbers Hyocrinidae Isocrinidae Korethrasteridae Laetmogonidae Laganidae Lissodiadematidae Loveniidae Luidiidae Mariametridae Mellitidae Metrodiridae Micropygidae Mithrodiidae Molpadiidae Myriotrochidae Myxasteridae Neolampadidae Notocrinidae Odontasteridae Ophiacanthidae Ophiactidae Ophidiasteridae Ophiocanopidae Ophiocomidae Ophiodermatidae Ophioleucidae Ophiomyxidae Ophionereididae Ophiothricidae Ophiuridae Oreasteridae Palaeostomatidae Paracucumidae Parasaleniidae Pedinidae Pelagothuriidae Pentametrocrinidae Pericosmidae Phormosomatidae Phrynocrinidae Phyllophoridae Phymosomatidae Placothuriidae Platasteriidae Pliolampadidae Poraniidae Porcellanasteridae Porphyrocrinidae Pourtalesiidae Proisocrinidae Psolidae Psychocidaridae Psychropotidae Pterasteridae Ptilometridae Pythonasteridae Radiasteridae Rhopalodinidae Rotulidae Saleniidae Schizasteridae Sclerodactylidae Solasteridae Spatangidae Sphaerasteridae Stichopodidae -- Furry sea cucumbers Stomechinidae Stomopneustidae Strongylocentrotidae Synallactidae Synaptidae Temnopleuridae Thalassometridae Toxasteridae Toxopneustidae Tropiometridae Urechinidae Valvasteridae Vaneyellidae Xyloplacidae Ypsilothuriidae Zoroasteridae Zygometridae

Overview

The phylum Echinodermata, which means "spiny skin", has about 20,000 species. They are aquatic animals with radial symmetry and inhabit both shallow and deep waters. Echinoderms have an intricate water vascular system which is a network of fluid-filled canals inside their body and functions in locomotion, feeding, and gas exchange. They eat a wide variety of food including molluscs, plankton and algae, and a few species of starfish are even known to eat other starfish. Some echinoderms have suctions cups at the end of their tube feet (a part of their water vascular system) and use them to pry open clams and barnacles. Sea stars actually eat by inserting their stomach into their prey and eating the insides. Echinoderms also have the ability to grow back missing limbs. Two species are currently on the endangered list - Echinus esculentus and Isostichopus fuscus. They have little human value as food, but have some economic value being sold for aquariums.

Phylogeny

Tree of Life web project Scientific name -- Common name Echinodermata -- Sea stars, Brittle stars, Sea urchins, Sand dollars, Sea cucumbers Echinoidea -- Heart urchins, Sand dollars, Sea urchins Holothuroidea -- Sea cucumbers Ophiuroidea -- Basket stars, Brittlestars, Snake stars Stelleroidea -- Star fishes Asteroidea -- Sea stars, Starfishes Crinoidea -- Feather stars, Sea lillies

Links to other sites

Tree of life -- Taxonomy of echinodermata. University of California -- Introduction to echinodermata.

References

Animal Diversity Web

Acknowledgements

I thank John Pickering for his assistance with the development of this page.

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Overview  News  Technology  Conditions of Use  Privacy Policy  Partners & Contributors  Awards & Recognition  ADW Staff  Contact Us  Spinning Skulls  About Mammals  Frog Calls  Resources for College Instructors  Resources for K-12 Instructors  Contribute to ADW  What's in a Scientific Name?  Authority Lists: Where We Get Our Names  Name, Rank, and Serial Number  Organismal classification: evolutionary relationships & ranks  Glossary  Search Guide  Related Links  Contact Us  Report an Error Structured Inquiry Search — preview Home Kingdom Animalia Phylum Echinodermata Phylum Echinodermata echinoderms Information Pictures Specimens Classification 2009/11/15 02:43:17.424 US/Eastern By Renee Sherman Mulcrone Kingdom: Animalia Phylum: Echinodermata Members of this Phylum Diversity Echinodermata has approximately 7000 described living species and about 13,000 extinct species known from the fossil record. This phylum is the largest without any freshwater or terrestrial forms. ( Brusca and Brusca, 2003 ; Waggoner, 1999 ) Geographic Range Mainly a marine group, echinoderms are found in all the oceans. ( Brusca and Brusca, 2003 ) Biogeographic Regions: arctic ocean ; indian ocean; atlantic ocean ; pacific ocean ; mediterranean sea. Habitat Except for a few species which inhabit brackish waters, all echinoderms are benthic organisms found in marine environments. Echinoderms inhabit depths ranging from shallow waters at tide lines to the deep sea. ( Barnes, 1987 ; Brusca and Brusca, 2003 ; University of Alabama Center for Communication and Educational Technology, 2000 ; Waggoner, 1999 ) These animals are found in the following types of habitat: temperate ; tropical ; polar ; saltwater or marine . Aquatic Biomes: brackish water . Other: intertidal or littoral . Systematic and Taxonomic History Echinoderm means "spiny skin.". Because of its abundant fossil record, up to 25 classes have been recognized. A traditional hypothesis of the Echinodermata using only extant taxonomic groups places the Asteroidea and Ophiuroidea as sister groups based on the shared derived characteristic of a five-rayed body plan. An alternative hypothesis including fossil groups places Asteroidea as a more primitive group with the derived characteristic of five arms connected to a central disc. Ophiuroidea is grouped with Echinoidea and Holothuroidea based on the closed ambicular grooves. In both hypotheses, Echinoidea and Holothuroidea are considered sister groups, having two synapomorphies: 1) an extended ambiculacral groove along the sides of the body from the oral to aboral pole and 2) the reduced aboral surface. Echinoderms are considered to be derived from sessile ancestors. Crinoidea , considered the more primitive forms, are mainly sessile. Asteroidea and Ophiuroidea are sometimes considered classes, instead of subclasses. ( Barnes, 1987 ; Brusca and Brusca, 2003 ; University of Paisley, 1998 ; Waggoner, 1999 ) Synapomorphies Pentaradial symmetry in adults Water vascular system Calcareous internal skeleton Deuterostome embryology Complete gut except where secondarily lost No excretory organs Diffuse nervous system Physical Description Larvae range from a few millimeters to a few decimeters, while adults can range from less than 1 cm to 2 m. While adult forms are radially symmetrical, larval forms are always bilateral. The radial symmetry is secondarily derived. The pentaradial form, whether it has arms or not, has a central disc. An internal skeleton is present throughout members of the phylum. Ossicles, which make up the skeleton, are below an outer dermal layer. The skeletal and muscular arrangement varies among groups. Pedicellariae produced by the skeleton, are pincer-like structures. Found mainly in echinoids and asteroids, their function is debatable. They may be used to capture prey, clean, or hold items to disguise from predators. Echinoderms have a water vascular system consisting of a network of radial canals, which extend through each of the five extensions (arms or rays) of the animal. Each canal has a lateral connection which leads to a tube foot, which may be composed of three parts. Internally is the ampulla and externally is the podia. At the end of the podia is usually a sucker. Grooves with rows of podia extending from the mouth are called the ambiculacra . Between each ambiculacra is the interambulacrum. For groups of animals with "arms" (sea stars, for example), the interambulacrum is just the space between the ambiculacra. For other animals without furrows (sea cucumbers, for example), the areas are like the ambiculacra, but usually lack holes for the tube feet. The water vasuclar system opening, called a madreporite, lies on a particular interambulacrum. Letters are used to describe parts of echinoderms. The ambulacrum opposite the madreporite is section A. Moving clockwise, other parts are coded B through E. Sections C and D are termed the bivium while all the others are collectively termed the trivium. Interambulacrum sections are named using the letters of the ambulacra sections they are between (e. g. AB). ( Barnes, 1987 ; Brusca and Brusca, 2003 ; Waggoner, 1999 ) Some key physical features: ectothermic ; heterothermic ; bilateral symmetry ; radial symmetry . Development Echinoderms are deuterostomes. The larvae, which are planktotrophic or lecithotrophic, have 3-part paired coeloms. Embryonic coelomic structures have specific fates as the bilaterally symmetrical larvae metamorphose into radially symmetric adults. Adult pheromones may attract larvae, which tend to settle near conspecific adults. Metamorphosis in some species is triggered by adult pheromones. ( Barnes, 1987 ; Brusca and Brusca, 2003 ) Special features of growth: metamorphosis . Reproduction Echinoderms are mainly gonochoristic (having separate sexes), with exceptions among the asteroids , holothurians and ophuroids . Holothurians possess a single gonad, crinoids lack distinct gonads, while asteroids and echinoids have multiple gonads. Echinoderm reproductive strategies vary from free spawning and indirect development to brooding and direct development. Spawning is probably a noctural event. ( Barnes, 1987 ; Brusca and Brusca, 2003 ) Key reproductive features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); simultaneous hermaphrodite; sequential hermaphrodite; sexual ; fertilization ( external ); oviparous . Parental investment ranges from no care after the release of eggs for free spawning to brooding the young. Brooding is found in polar and boreal echinoderms and some deep sea echinoderms, where environments are more difficult for the larvae. ( Barnes, 1987 ; Brusca and Brusca, 2003 ) Parental investment: pre-fertilization (provisioning); pre-hatching/birth (provisioning: female, protecting: female). Behavior Most radially symmetric animals are sessile, however, echinoderms are able to move. The water vascular system originally functioned for collection and transport of food, but evolved to function for locomotion as well. ( Barnes, 1987 ; Brusca and Brusca, 2003 ) Key behaviors: diurnal ; nocturnal ; motile ; sedentary . Communication and Perception The non-centralized nervous system allows echinoderms to sense their environment from all sides. Adult pheromones may attract larvae, which tend to settle near conspecific adults. Metamorphosis in some species is triggered by adult pheromones. ( Brusca and Brusca, 2003 ) Communicates with: chemical . Other communication keywords: pheromones . Perception channels: tactile ; chemical . Food Habits Different groups have different feeding habits. Members of the Crinoidea sit with arms outstretched parallel to the currents and filter feed on passing particles. Most Asteroidea are predators or scavengers, everting their stomach (called a cardiac stomach), which secretes digestive enzymes on their prey. Some asteroids are also suspension feeders. Brittle stars of the Ophiuroidea are predators, deposit feeders, scavengers, and suspension feeders, which feed by outstretching their arms to capture prey. Ophiuroids lack an intestine and anus, and therefore have an incomplete digestive system. The members of Echinoidea are suspension feeders, herbivores, detritivores, and predators. Many have a group of hard plates which retract and grasp like teeth, commonly called Aristotle's lantern. This allows most sea urchins to graze on algae. Most Holothuroidea are suspension or deposit feeders. Holothurians may also eviserate their digestive and other organs in response to predation or seasonal events. ( Brusca and Brusca, 2003 ; Waggoner, 1999 ) Primary Diet: carnivore ( scavenger , molluscivore , eats non-insect arthropods); omnivore ; planktivore ; detritivore . Behaviors: filter-feeding . Predation Known predators otters ( Lutrinae ) flounders ( Pleuronectidae ) haddock ( Melanogrammus ) Echinoderms in general are most vulnerable in their larval stage. As adults, asteroids have an anti-predator adaptation where they can lose an arm to a predator and the arm is later regenerated. Holothurians discharge sticky tubules, known as Cuvierian tubules , at a potential predator. Otters prey mainly on sea urchins . ( Brusca and Brusca, 2003 ) Ecosystem Roles Echinoderms are usually intricate parts of their ecosystems. Many asteroids are keystone species. Sea urchins , if not controlled by predators, may overgraze their habitat. Asteroids have several commensals, including polychaetes that feed on leftovers from the sea star's prey items. ( Barnes, 1987 ; Brusca and Brusca, 2003 ) Key ways these animals impact their ecosystem: keystone species . Economic Importance for Humans: Positive Research on echinoderms has contributed to the overall knowledge of animal fertilization and development. Many echinoderms are easy to culture and maintain in a lab setting, and produce a large amount of eggs. Sea urchin eggs are also edible and often served in sushi bars. ( Brusca and Brusca, 2003 ; University of Alabama Center for Communication and Educational Technology, 2000 ) Ways that people benefit from these animals: food ; research and education. Conservation The European edible sea urchin, Echinus esculentus , is listed as endangered by the IUCN. Isostichopus fuscus , a holothurian, is listed by CITES. It occurs on the coasts of Ecuador, Galapagos, Mexico and Peru. ( UNEP-WCMC, 2005 ; World Conservation Monitoring Centre, 2004 ) Contributors Renee Sherman Mulcrone (author). References Barnes, R. 1987. Invertebrate Zoology . Orlando, Florida: Dryden Press. Brusca, R., G. Brusca. 2003. Invertebrates . Sunderland, Massachusetts: Sinauer Associates, Inc.. UNEP-WCMC, 2005. "Isostichopus fuscus" (On-line). UNEP-WCMC Species Database: CITES-Listed Species. Accessed January 21, 2005 at http://www.cites.org/eng/resources/species.html . University of Alabama Center for Communication and Educational Technology, 2000. "Phylum Echinodermata – echinoderms" (On-line). Accessed January 16, 2005 at http://www.ccet.ua.edu/expedition/scsstarsurcbrit.htm . University of Paisley, 1998. "Echinodermata" (On-line). Accessed January 16, 2005 at http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/units/echi1.htm . Waggoner, B. 1999. "Introduction to the Echinodermata" (On-line). Accessed January 16, 2005 at http://www.ucmp.berkeley.edu/echinodermata/echinodermata.html . World Conservation Monitoring Centre, 2004. "Echinus esculentus" (On-line). 2004 IUCN Red List of Threatened Species. Accessed January 21, 2005 at http://www.iucnredlist.org/search/details.php?species=7011 . 2009/11/15 02:43:20.058 US/Eastern To cite this page: Mulcrone, R. 2005. "Echinodermata" (On-line), Animal Diversity Web. Accessed November 21, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Echinodermata.html. Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students . ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control. 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