Editing Gastrotrich (section)

==Etymology and taxonomy==
The  name ''gastrotrich'' comes from [[Greek language|Greek]] γαστήρ, ''gaster'' 'stomach' and θρίξ, ''thrix'' 'hair'.<ref>{{cite web |url=http://www.thefreedictionary.com/gastrotrich |title=Gastrotrich |work=The Free Dictionary |access-date=2014-01-29}}</ref> The name was coined by the Russian zoologist [[Élie Metchnikoff]] in 1865.<ref name=WoRMS/> The common name ''hairyback'' apparently arises from a mistranslation of ''gastrotrich''.<ref>{{cite book |title=Hairybacks Gastrotricha: Bugs Britannica |last=Marren |first=Peter|author-link=Peter Marren |year=2010 |publisher=Random House |isbn=978-0-7011-8180-2 |page=27 |url=https://books.google.com/books?id=Ah62bUZLDOwC&pg=PA27 }}</ref>

The relationship of gastrotrichs to other phyla is unclear. [[Morphology (biology)|Morphology]] suggests that they are close to the [[Gnathostomulid]]a, the [[Rotifer]]a, or the [[Nematode|Nematoda]]. On the other hand, [[phylogenetics|genetic studies]] place them as close relatives of the [[flatworm|Platyhelminthes]], the [[Ecdysozoa]] or the [[Lophotrochozoa]].<ref name=Todaro/>  As of 2011, around 790 species have been described.<ref name=Zhang2011>{{cite journal| author=Zhang, Z.-Q.| title=Animal biodiversity: An introduction to higher-level classification and taxonomic richness | journal=Zootaxa| volume=3148| year=2011| pages=7–12| doi=10.11646/zootaxa.3148.1.3 | url=http://mapress.com/zootaxa/2011/f/zt03148p012.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://mapress.com/zootaxa/2011/f/zt03148p012.pdf |archive-date=2022-10-09 |url-status=live}}</ref> The phylum contains a single class, divided into two orders: the [[Macrodasyida]] and the [[Chaetonotida]].<ref name=Ruppert>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=753–757 }}</ref> Edward Ruppert ''et al.'' report that the Macrodasyida are wholly marine,<ref name="Ruppert"/> but two rare and poorly known species, ''Marinellina flagellata'' and ''Redudasys fornerise'', are known from fresh water.<ref>{{Cite journal | doi = 10.1371/journal.pone.0031740| pmid = 22348127| title = Gastrotricha: A Marine Sister for a Freshwater Puzzle| journal = PLOS ONE| volume = 7| issue = 2| pages = e31740| date = 14 February 2012| last1 = Todaro | first1 = M. A. | last2 = Dal Zotto | first2 = M. | last3 = Jondelius | first3 = U. | last4 = Hochberg | first4 = R. | last5 = Hummon | first5 = W. D. | last6 = Kånneby | first6 = T. | last7 = Rocha | first7 = C. E. F. | pmc=3279426| bibcode = 2012PLoSO...731740T| doi-access = free}}</ref> The Chaetonotida comprises both marine and freshwater species.<ref name="Ruppert"/>