{{Short description|Genus of algae}} {{Distinguish|Paradoxa (disambiguation){{!}}Paradoxa}} {{Automatic taxobox | image = Paradoxia multiseta 404845814.jpg | image_caption = ''Paradoxia multiseta'' | taxon = Paradoxia | authority = Svirenko, 1928<ref name=AB_g44573/> | type_species = ''Paradoxia multiseta'' | type_species_authority = Svirenko<ref name=AB_g44573/> | subdivision_ranks = Species | subdivision = }}
'''''Paradoxia''''' is a genus of microscopic green algae, in the family Coccomyxaceae.<ref name=AB_g44573>{{AlgaeBase genus|name=Paradoxia|id=44573|access-date=2022-02-23}}</ref> It is found in freshwater habitats as phytoplankton worldwide, but species are rare.<ref name=Matthews/>
==Description== ''Paradoxia'' consists of individual cells or pairs of cells. Individual cells are club-shaped or fusiform in outline, 18–45 μm long and 3–8 μm wide. When paired, the two cells are joined at the base by spines or leaf-like appendages that twist together. These leaf-like appendages have many fine curved ridges on one face. The cell wall is smooth and covered with thin spines up to 24 μm long. Cells are uninucleate (i.e. with one nucleus) and one chloroplast containing a single pyrenoid.<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><ref name=AB_g44573/>
Reproduction occurs asexually via the formation of autospores or zoospores which form a coenobium while still in the mother cell wall. Resting spores have also been reported. Sexual reproduction has not been observed in this genus.<ref name=AB_g44573/>
''Paradoxia'' species are distinguished by the morphology of the cells, and whether or not they are paired. The genus may be closely related to others with leaf-like appendages at the cell ends, in particular ''Ankyra''.<ref name=AB_g44573/>
==Taxonomy== Sources disagree on where to place ''Paradoxia'' taxonomically. In their 1983 monograph, Jiří Komárek and Bohuslav Fott placed ''Paradoxia'' in the family Characiaceae.<ref name=KomarekFott1983>{{cite book | title= Chlorophyceae (Grünalgen), Ordnung Chlorococcales | last1=Komárek | first1=J. | last2=Fott | first2=B. | date=1983 | publisher= E. Schweizerbart'sche Verlagsbuchhandlung | series=Das Phytoplankton des Süßwassers | language=German | pages=1044 }}</ref> A strain labeled as ''Paradoxia multiseta'' in the UTEX-Austin culture collection was found to have a close phylogenetic relationship to ''Coccomyxa''; however, the morphology of the strain (having spherical cells) does not appear to match that of ''Paradoxia'', making the identity suspect.<ref>{{cite journal|doi=10.1007/s10750-012-1079-z |title=Present state of the systematics of planktonic coccoid green algae of inland waters |date=2012 |last1=Krienitz |first1=Lothar |last2=Bock |first2=Christina |journal=Hydrobiologia |volume=698 |issue=1 |pages=295–326 |bibcode=2012HyBio.698..295K }}</ref>
==References== {{Reflist}}
==External links== * [http://www.algaterra.org/ATDB/Names/NamesMain.cfm AlgaTerra database] * [https://web.archive.org/web/20070819165523/http://ravenel.si.edu/botany/ing/ingForm.cfm Index Nominum Genericorum]
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Category:Trebouxiophyceae genera Category:Trebouxiophyceae Category:Enigmatic algae taxa Category:Freshwater algae
{{Green alga-stub}}