What is Sea cucumber?
{{Taxobox | name = Sea Cucumber | image = Sea Cucumber.jpg | image_width = 220px | image_caption = | regnum = [[Animal]]ia | phylum = [[Echinodermata]] | classis = '''Holothuroidea''' <!-- | subdivision_ranks = [[Order (biology)|Orders]] | subdivision = Subclass [[Apodacea]]<br/> &nbsp;[[Apodida]]<br/> &nbsp;[[Molpadiida]]<br/> <br/> Subclass [[Aspidochirotacea]]<br/> &nbsp;[[Aspidochirotida]]<br/> &nbsp;[[Elasipodida]]<br/> <br/> Subclass [[Dendrochirotacea]]<br/> &nbsp;[[Dactylochirotida]]<br/> &nbsp;[[Dendrochirotida]] --> }} '''Sea cucumbers''' are a [[Class (biology)|class]] of [[echinoderm]]s, the '''Holothuroidea'''. They have a longish body, and leathery skin. Sea cucumbers live on the floor of the ocean. Most sea cucumbers are [[scavenger]]s. There are about 1500 [[species]] of sea cucumbers. Sea cucumbers have a unique [[Respiration|respiratory]] system, and effective defences against [[predator]]s. The [[China|Chinese]] people eat them. Like all echinoderms, sea cucumbers have an [[endoskeleton]] just below the skin, [[calcareous]] structures that are usually reduced to isolated ossicles joined by [[connective tissue]]. These can sometimes be enlarged to flattened plates, forming an armour. In [[pelagic]] species the skeleton is absent.<ref>[http://www.answers.com/topic/pelagic-sea-cucumber Pelagic sea cucumber: Information from Answers.com]</ref><ref>{{cite journal|first=Mike|last=Reich|url=http://www.geobiologie.uni-goettingen.de/people/mreich/pdf/PDFs/POST_Dijon_Seegurken1.pdf |title=Cambrian holothurians ? – The early fossil record and evolution of Holothuroidea|editor=Lefebvre B. David B. Nardin E. & Poty E. |journal= Journées Georges Ubaghs |date=2006|publisher= Université de Bourgogne|location= Dijon, France|pages= 36–37}}</ref> == Overview == [[File:Conspicuous Sea Cucumber, Coconut Island, Hawaii.JPG|thumb|right|230px|Sea cucumber, Coconut Island, [[Hawaii]]]] [[File:Sea cucumber defence.JPG|thumb|right|230px|Sea cucumber in the [[Seychelles]] ejects sticky filaments from the anus in self-