Editing Tunicate (section)

{{Short description|Marine animals, subphylum of chordates}}
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{{Use dmy dates|date=September 2020}}
{{Automatic taxobox
| name = Tunicates
| fossil_range = <br>[[Cambrian Stage 3]]&ndash;[[Holocene|Present]],<br>{{fossil range|518|0|earliest=557|ref=<ref>{{Cite journal |last1=Yang |first1=Chuan |last2=Li |first2=Xian-Hua |last3=Zhu |first3=Maoyan |last4=Condon |first4=Daniel J. |last5=Chen |first5=Junyuan |date=2018 |title=Geochronological constraint on the Cambrian Chengjiang biota, South China |journal=[[Journal of the Geological Society]] |language=en |volume=175 |issue=4 |pages=659–666 |doi=10.1144/jgs2017-103 |bibcode=2018JGSoc.175..659Y |s2cid=135091168 |issn=0016-7649 |url=http://nora.nerc.ac.uk/id/eprint/521412/1/2018-JGS-Chuan%20Yang%20et%20al.pdf}}</ref>}} (Possible [[Ediacaran]] record, 557 Ma<ref>{{Cite journal |last1=Fedonkin |first1=M. A. |last2=Vickers-Rich |first2=P. |last3=Swalla |first3=B. J. |last4=Trusler |first4=P. |last5=Hall |first5=M. |title=A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians |journal=[[Paleontological Journal]] |volume=46 |pages=1–11 |year=2012 |issue=1 |doi=10.1134/S0031030112010042 |bibcode=2012PalJ...46....1F |s2cid=128415270}}</ref><ref>{{Cite journal |last1=Martyshyn |first1=Andrej |last2=Uchman |first2=Alfred |date=2021-12-01 |title=New Ediacaran fossils from the Ukraine, some with a putative tunicate relationship |journal=PalZ |language=en |volume=95 |issue=4 |pages=623–639 |doi=10.1007/s12542-021-00596-1 |bibcode=2021PalZ...95..623M |s2cid=244957825 |issn=1867-6812 |doi-access=free }}</ref>)
| image = Tunicate komodo.jpg
| image_caption = Gold-mouth sea squirt (''[[Polycarpa aurata]]'')
| image_upright = 1.15
| display_parents = 2
| taxon = Tunicata
| authority = [[Jean-Baptiste Lamarck|Lamarck]], 1816<ref name=WoRMS>{{cite WoRMS |author=Sanamyan, Karen |year=2013 |title=Tunicata |id=146420 |access-date=2013-04-04 }}</ref><ref name="Nielsen2012">{{cite journal |author=Nielsen, C. |date=2012 |title=The authorship of higher chordate taxa |journal=[[Zoologica Scripta]] |volume=41 |issue=4 |pages=435–436 |doi=10.1111/j.1463-6409.2012.00536.x |s2cid=83266247}}</ref>
| subdivision_ranks = Classes and unplaced [[genus|genera]]
| subdivision_ref = <ref name=WoRMS/><ref name="Tatian"/>
| subdivision = * "[[Ascidiacea]]"<ref>{{Cite journal |last=Giribet |first=Gonzalo |date=2018-04-27 |title=Phylogenomics resolves the evolutionary chronicle of our squirting closest relatives |journal=[[BMC Biology]] |volume=16 |issue=1 |pages=49 |doi=10.1186/s12915-018-0517-4 |issn=1741-7007 |pmc=5924484 |pmid=29703197 |doi-access=free }}</ref>
* [[Thaliacea]]
* [[Larvacean|Appendicularia]]
* {{extinct}}''[[Yarnemia]]''?
* {{extinct}}''{{Ill|Megasiphon|ia}}''
* {{extinct}}''[[Shankouclava]]''?
| synonyms = Urochordata <small>Lankester, 1877</small>
}}

A '''tunicate''' is an exclusively marine [[invertebrate]] animal, a member of the [[subphylum]] '''Tunicata''' ({{IPAc-en|ˌ|tj|uː|n|ᵻ|ˈ|k|eɪ|t|ə}} {{respelling|TEW|nih|KAY|tə}}). This grouping is part of the [[Chordata]], a [[phylum]] which includes all animals with [[dorsal nerve cord]]s and [[notochord]]s (including [[vertebrates]]). The subphylum was at one time called '''Urochordata''', and the term '''urochordates''' is still sometimes used for these animals.

Despite their simple appearance and very different adult form, their close relationship to the vertebrates is certain. Both groups are chordates, as evidenced by the fact that during their mobile larval stage, tunicates possess a [[notochord]], a hollow [[dorsal nerve cord]], [[pharyngeal slit]]s, post-anal tail, and an [[endostyle]]. They resemble a [[tadpole]].

Tunicates are the only chordates that have lost their [[Myomere|myomeric]] segmentation, with the possible exception of the seriation of the gill slits.<ref>{{cite journal |pmid=29488055 |doi=10.1007/s12064-018-0260-y |volume=137 |title=The evolutionary origin of chordate segmentation: revisiting the enterocoel theory |year=2018 |journal=Theory Biosci |pages=1–16 |author=Onai T |issue=1 |s2cid=3553695 }}</ref><ref>{{Cite book |url=https://books.google.com/books?id=WXjkBwAAQBAJ&dq=Tunicates+contrast+display+metameric+segmentation+exception+gill+slits&pg=PA163 |title=Before the Backbone: Views on the origin of the vertebrates |first=H. |last=Gee |date=27 July 2007 |publisher=Springer Science & Business Media |isbn=9780585252728 |via=Google Books}}</ref> However, [[Doliolida|doliolids]] still display segmentation of the muscle bands.<ref>{{cite journal |author=Bone, Q., and K. P. Ryan |title=On the Structure and Innervation of the Muscle Bands of Doliolum (Tunicata: Cyclomyaria) |journal=Proceedings of the Royal Society of London. Series B, Biological Sciences |volume=187 |date=1974 |issue=1088 |pages=315–327 |doi=10.1098/rspb.1974.0077 |jstor=76405 |pmid=4154453 |bibcode=1974RSPSB.187..315B |s2cid=20806327 |url=http://www.jstor.org/stable/76405 |access-date=13 May 2023|url-access=subscription }}</ref>

Some tunicates live as solitary individuals, but others replicate by [[budding]] and become [[Colony (biology)|colonies]],<ref>{{Cite journal |last1=Alié |first1=Alexandre |last2=Hiebert |first2=Laurel S. |last3=Scelzo |first3=Marta |last4=Tiozzo |first4=Stefano |date=2020-03-19 |title=The eventful history of nonembryonic development in tunicates |journal=Journal of Experimental Zoology Part B: Molecular and Developmental Evolution |volume=336 |issue=3 |pages=250–266 |language=en |doi=10.1002/jez.b.22940 |pmid=32190983 |bibcode=2021JEZB..336..250A |s2cid=213181394}}</ref> each unit being known as a [[zooid]]. They are marine [[filter feeder]]s with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their [[Aquatic respiration|respiration]] and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Adult ascidian tunicates are [[Sessility (zoology)|sessile]], immobile and permanently attached to rocks or other hard surfaces on the ocean floor. [[Thaliacea]]ns (pyrosomes, doliolids, and salps) and [[larvacean]]s on the other hand, swim in the [[pelagic zone]] of the sea as adults.

Various species of [[Ascidiacea|ascidians]], the most well-known class of tunicates, are commonly known as [[sea squirt]]s, sea pork, sea livers, or [[sea tulip]]s.

The earliest probable species of tunicate appears in the fossil record in the early [[Cambrian period]].