Editing Spirotrich

{{Short description|Class of single-celled organisms}}
{{Automatic taxobox
| image = Euplotes.jpg
| image_caption = Euplotes, a spirotrich
| fossil_range = {{fossil range|444|0|ref=<ref name="Parfrey2011">{{cite journal|author-link1=Laura Wegener Parfrey|last1=Parfrey|first1=Laura Wegener|last2=Lahr|first2=Daniel J. G.|last3=Knoll|first3=Andrew H.|last4=Katz|first4=Laura A.|author-link4=Laura A. Katz|title=Estimating the timing of early eukaryotic diversification with multigene molecular clocks|journal=Proceedings of the National Academy of Sciences of the United States of America|date=August 16, 2011|volume=108|issue=33|pages=13624&ndash;13629|doi=10.1073/pnas.1110633108|pmid=21810989|pmc=3158185|doi-access=free}}</ref>}}
| display_parents = 2
| taxon = Spirotrichea
| authority = [[Otto Bütschli|Bütschli]] 1889<ref name=Lynn>{{cite book|title=The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature |author=Lynn DH |date=2008-06-24 |edition=3 |publisher=Springer |isbn=978-1-4020-8239-9 |page=122}}</ref>
| subdivision_ranks = Subclasses
| subdivision = 
[[Choreotrich]]ia<br>
[[Euplotia]]<br>
[[Hypotrichia]]<br>
[[Licnophoria]]<br>
[[Oligotrich]]ia<br>
[[Phacodiniidea]]<br>
[[Protohypotrichia]]<br>
}}

The '''spirotrichs''' are a large and diverse group of [[ciliate]] protozoa.<ref name=Lynn7>{{cite book|title=The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature |author=Lynn DH |edition=3 |publisher=Springer |isbn=978-1-4020-8239-9 |chapter=Intramacronucleata: Class 1. Spirotrichae - Ubiquitous and Morphologically Complex |date=2008-06-24 |pages=141–173}}</ref>  They typically have prominent oral cilia in the form of a series of polykinetids, called the adoral zone of [[membranelle]]s, beginning anterior to the oral cavity and running down to the left side of the mouth.  There may also be one or two paroral membranes on its right side.  The body cilia are fused to form polykinetids called cirri in some, and are sparse to absent in others.

Forms with cirri are common throughout soil, freshwater, and marine environments.  Individuals tend to be flattened, with cirri confined to the ventral surface.  These are variously used for crawling over objects, acting as feet, swimming, or assisting in food capture.  They are generally divided into [[hypotrich]]s and [[stichotrich]]s, but were originally all considered hypotrichs.

Forms with sparse or absent body cilia tend to be smaller and are mostly marine, but a few are common in freshwater.  Again, they are generally divided into [[oligotrich]]s and [[choreotrich]]s, but were originally all considered oligotrichs.  The latter group includes the [[tintinnid]]s, which produce loricae or shells and are the predominant fossil ciliates.

As first defined by [[Otto Bütschli|Bütschli]] in 1889 the spirotrichs were one of two orders, together with the now-abandoned [[holotrich]]s, and included all ciliates with prominent oral cilia: [[heterotrich]]s, hypotrichs, oligotrichs, and [[peritrich]]s, although the last were soon separated.  The heterotrichs have an adoral zone of membranelles, but molecular and ultrastructure studies have shown they are a separate group that diverged from most other ciliates early on.  A few of the smaller groups included with them may be genuine spirotrichs, however, such as the [[Protocruziida]].

The remaining spirotrichs form a [[monophyletic]] group, but their relationships are uncertain.  For the most part the oligotrichs and choreotrichs appear to form closely related, natural groups.  However ''Halteria'' and its close relatives, originally considered oligotrichs, form a separate group and may even be modified stichotrichs.  Studies also suggest the hypotrichs are [[paraphyletic]] to the stichotrichs, and possibly to the oligotrichs and choreotrichs as well.  This stands in contrast to the earlier belief that they were the most advanced of all protozoa.

==See also==
*[[Ciliate MDS/IES database]]

==References==
{{Reflist}}

{{Alveolata}}
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[[Category:Spirotrichea| ]]