# Microthamnion

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{{Short description|Genus of algae}}
{{Automatic taxobox
| image=Microthamnion.jpg
| image_caption=''Microthamnion'' sp.
| taxon = Microthamnion
| authority = Nägeli
| type_species = ''Microthamnion kuetzingianum''
| type_species_authority = Nägeli ex Kützing<ref name=AlgaeBase/>
| subdivision_ranks = Species
| subdivision = 
* ''[Microthamnion kuetzingianum](/source/Microthamnion_kuetzingianum)''
}}

'''''Microthamnion''''' is a [genus](/source/genus) of [green algae](/source/green_algae) in the family [Microthamniaceae](/source/Microthamniaceae).<ref>{{AlgaeBase taxon|name=''Microthamnion'' taxonomy|id=87976}}</ref><ref name=AlgaeBase>{{AlgaeBase genus|name=Microthamnion|id=42758}}</ref> It is found in [freshwater](/source/freshwater) habitats around the world, preferably with low levels of pollution;<ref name=AlgaeBase/> it is typically attached to solid substrates.<ref name=Matthews/>

==Description==
''Microthamnion'' consists of a microscopic, branched system of erect filaments. The filaments are uniseriate, with cylindrical cells; terminal cells are obtuse. Cells range from 1-5 μm wide and 2-15 times longer than wide.<ref name=Reder/> New branches form just underneath the cross-walls connecting cells. Cells are uninucleate (i.e. with one [nucleus](/source/cell_nucleus) with a parietal [chloroplast](/source/chloroplast) and no visible [pyrenoid](/source/pyrenoid)s.<ref name=AlgaeBase/><ref name=Matthews>{{cite journal | date = 2016 | last1=Matthews | first1=Robin A. | title=Freshwater Algae in Northwest Washington, Volume II, Chlorophyta and Rhodophyta | url= https://cedar.wwu.edu/cedarbooks/1/ | journal = A Collection of Open Access Books and Monographs | publisher = Western Washington University | doi=10.25710/fctx-n773 }}</ref>

Reproduction occurs [asexually](/source/asexual_reproduction) via the formation of bottle-shaped [zoospore](/source/zoospore)s, which are formed in vegetative cells that develop into [sporangia](/source/sporangia). Typically this occurs in the terminal cells, but any cell except for the most basal may produce zoospores.<ref name=Reder/> The zoospores have two flagella and up to 32 are produced per sporangial cell.<ref name=John2014>{{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= John|first1=David M.| last2=Rindi |first2=Fabio |chapter= Chapter 8. Filamentous (Nonconjugating) and Plantlike Green Algae |url= |location= |publisher= Elsevier Inc. |page= |isbn=978-0-12-385876-4 }}</ref>

==Taxonomy==
''Microthamnion'' was first described by [Carl Nägeli](/source/Carl_N%C3%A4geli) in 1849 in [Friedrich Traugott Kützing](/source/Friedrich_Traugott_K%C3%BCtzing)'s work ''Species algarum''. It is recognized as a well-defined genus, but its placement has varied. Initially placed in the family [Ulotrichaceae](/source/Ulotrichaceae), at times, it has been placed in [Trentepohliaceae](/source/Trentepohliaceae) and [Chaetophoraceae](/source/Chaetophoraceae) until finally being placed in its own family. Currently, it is placed within its own family and order in the class [Trebouxiophyceae](/source/Trebouxiophyceae).<ref name=Reder>{{cite thesis|title=A case study of species delimitation with molecular methods: the algal genus Microthamnion (Microthamniales, Trebouxiophyceae)|last1= Reder|first1=T.|date=2019|location= Köln|publisher= Universität zu Köln|pages= i-xii, 1-109 |url=https://kups.ub.uni-koeln.de/10406/}}</ref>

The species-level taxonomy of this genus is unclear, since individuals display a wide range of morphological variation. Many names have been given to forms which may be mere growth forms and not taxonomically informative.<ref name=John2014/><ref name=AlgaeBase/> As a consequence, opinions on the number of species vary widely, ranging from as few as one very polymorphic species<ref>{{cite journal|doi=10.1016/S0003-9365(11)80269-1 |title=A Molecular and Morphological Analysis of Microthamnion (Chlorophyta, Microthamniales) |date=1993 |last1=John |first1=D.M. |last2=Bhoday |first2=R. |last3=Russell |first3=S.J. |last4=Johnson |first4=L.R. |last5=Gacesa |first5=P. |journal=Archiv für Protistenkunde |volume=143 |issue=1–3 |pages=33–39 }}</ref> to as many as fourteen putative species.<ref name=Reder/>

==References==

{{Reflist|1}}

{{Taxonbar|from=Q300550}}

Category:Microthamniales
Category:Trebouxiophyceae genera
Category:Freshwater algae

{{green algae-stub}}

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Adapted from the Wikipedia article [Microthamnion](https://en.wikipedia.org/wiki/Microthamnion) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Microthamnion?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.