{{Short description|Genus of green algae}} {{Speciesbox | image = The-Simplest-Integrated-Multicellular-Organism-Unveiled-pone.0081641.s003.ogv | image_caption = ''Tetrabaena socialis'' swimming | genus = Tetrabaena | parent_authority = Fromentel | species = socialis | authority = (Dujardin) H.Nozaki & M.Itoh |synonyms = * ''Cryptomonas socialis'' <small>Dujardin 1841</small> * ''Gonium sociale'' <small>(Dujardin) Warming 1876</small> * ''Tetrabaena dujardinii'' <small>Fromentel 1874; heterotypic</small> * ''Tetragonium lacustre'' <small>West & G.S.West 1896; heterotypic</small> }}
'''''Tetrabaena''''' is a monotypic genus of green algae containing the species '''''Tetrabaena socialis'''''.<ref>{{Cite journal |last=Laber |first=Bernd |date=January 6, 2006 |title=Green Algae from a Garden Pond: ''Tetrabaena socialis'' |url=http://www.microscopy-uk.org.uk/index.html?http://www.microscopy-uk.org.uk/mag/artjan06/blalgae.html |journal=Micscape Magazine |access-date=January 27, 2015}}</ref><ref name=":0" /><ref name=":1">{{Cite journal |last1=Lindsey |first1=Charles Ross |last2=Knoll |first2=Andrew H. |last3=Herron |first3=Matthew D. |last4=Rosenzweig |first4=Frank |date=2024-04-10 |title=Fossil-calibrated molecular clock data enable reconstruction of steps leading to differentiated multicellularity and anisogamy in the Volvocine algae |journal=BMC Biology |volume=22 |issue=1 |page=79 |bibcode=2024BMCB...22...79L |doi=10.1186/s12915-024-01878-1 |issn=1741-7007 |pmc=11007952 |pmid=38600528 |doi-access=free}}</ref> It primarily occurs in freshwater, although it has been found in saltwater on at least one occasion.<ref name=":1" /> Although rare, it has a cosmopolitan distribution and has even been found from Antarctica.<ref name=Nakada2014/>
== Description == ''Tetrabaena'' are colonial organisms, consisting of four cells. The four cells are arranged in a square, and attached to each other by the extensions of their cellular sheaths. Cells are ovoid, somewhat asymmetrical in shape. It is a motile flagellate, possessing two equal flagella per cell<ref name=":0" /><ref name=":1" /> and two contractile vacuoles at the base of the flagella. Cells also contain a single cup-shaped chloroplast with a basal pyrenoid.<ref name=Nakada2014>{{cite book |editor-first1=John D.|editor-last1=Wehr|editor-first2=Robert G.|editor-last2=Sheath|editor-first3=J. Patrick|editor-last3=Kociolek |date= 2014 |edition=2 |title= Freshwater Algae of North America: Ecology and Classification |last1= Nakada|first1=Takashi| last2=Nozaki |first2=Hisayoshi |chapter= Chapter 6. Flagellate Green Algae |url= |location= |publisher= Elsevier Inc. |pages=265–313|isbn=978-0-12-385876-4 }}</ref> Although ''Tetrabaena'' possess an eyespot, it does not appear to function as a photoreceptor.<ref>{{cite journal|doi=10.1371/journal.pone.0259138|doi-access=free |title=The four-celled Volvocales green alga Tetrabaena socialis exhibits weak photobehavior and high-photoprotection ability |date=2021 |last1=Tanno |first1=Asuka |last2=Tokutsu |first2=Ryutaro |last3=Arakaki |first3=Yoko |last4=Ueki |first4=Noriko |last5=Minagawa |first5=Jun |last6=Yoshimura |first6=Kenjiro |last7=Hisabori |first7=Toru |last8=Nozaki |first8=Hisayoshi |last9=Wakabayashi |first9=Ken-Ichi |journal=PLOS ONE |volume=16 |issue=10 |article-number=e0259138 |pmid=34699573 |pmc=8547699 |bibcode=2021PLoSO..1659138T }}</ref>
''Tetrabaena'' are capable of sexual reproduction, and are isogamous.<ref name=Nakada2014/>
== Research significance == ''Tetrabaena'' is a member of the order Chlamydomonadales, a model lineage used in the study of the origins of multicellular organisms from single-celled ancestors.<ref name=":0">{{Cite journal |last1=Arakaki |first1=Yoko |last2=Kawai-Toyooka |first2=Hiroko |last3=Hamamura |first3=Yuki |last4=Higashiyama |first4=Tetsuya |last5=Noga |first5=Akira |last6=Hirono |first6=Masafumi |last7=Olson |first7=Bradley J. S. C. |last8=Nozaki |first8=Hisayoshi |date=2013-12-11 |title=The Simplest Integrated Multicellular Organism Unveiled |journal=PLOS ONE |language=en |volume=8 |issue=12 |article-number=e81641 |doi=10.1371/journal.pone.0081641 |doi-access=free |issn=1932-6203 |pmc=3859500 |pmid=24349103|bibcode=2013PLoSO...881641A }}</ref><ref name=":1" /> Within Chlamydomonadales, it is notable for being the colonial species with the smallest number of cells (4), placing it at the boundary between single- and multi-cellularity. As such, it has been characterized as the "simplest integrated multicellular organism."<ref name=":0" />
Genomic data and molecular clock analysis suggest that ''Tetrabaena socialis'' may contain cryptic species.<ref name=":1"/>
==References== {{Reflist}}
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Category:Articles containing video clips Category:Chlamydomonadales Category:Monotypic algae genera Category:Chlorophyta species
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