Didymogenes

{{Short description|Genus of algae}} {{Automatic taxobox | image = Didymogenes palatina Schmidle.JPG | image_caption = ''Didymogenes palatina'' | taxon = Didymogenes | type_species = ''Didymogenes palatina'' | type_species_authority = Schmidle<ref name=AlgaeBase>{{AlgaeBase genus|id= 44254 |title=''Didymogenes'' Schmidle, 1905 |access-date=2025-01-09}}</ref> | authority = Schmidle, 1905 | subdivision_ranks = Species | subdivision_ref = <ref name=AlgaeBase/> | subdivision = * ''Didymogenes anomala'' * ''Didymogenes granulata'' * ''Didymogenes palatina'' * ''Didymogenes soliella'' * ''Didymogenes sphaerica'' }}

'''''Didymogenes''''' is a genus of microscopic green algae in the class Trebouxiophyceae.<ref>See the NCBI [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=247498 webpage on Didymogenes]. Data extracted from the {{cite web | url=https://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=National Center for Biotechnology Information | access-date=2007-03-19}}</ref> It is a planktonic species found in freshwater habitats worldwide.<ref name=AlgaeBase/> Formerly placed in the family Scenedesmaceae,<ref name=AlgaeBase/> molecular studies have placed it in the family Chlorellaceae.<ref>{{cite journal|doi=10.1111/j.1440-1835.2009.00552.x |title=Polyphyletic distribution of bristle formation in Chlorellaceae: ''Micractinium'', ''Diacanthos'', ''Didymogenes'' and ''Hegewaldia'' gen. nov. (Trebouxiophyceae, Chlorophyta) |date=2010 |last1=Pröschold |first1=Thomas |last2=Bock |first2=Christina |last3=Luo |first3=Wei |last4=Krienitz |first4=Lothar |journal=Phycological Research |volume=58 |pages=1–8 }}</ref>

==Description== ''Didymogenes'' consists of colonies of two or four cells, termed coenobia, which may sometimes be united to form compound coenobia (syncoenobia). Cells are attached to each other by their centers, arranged parallel or crosswise. The cells are curved or sigmoid, 4–18 μm long, with apices rounded. The cell walls are smooth or with granules, or with bristles. Inside the cells are a single nucleus and a single parietal chloroplast with a pyrenoid.<ref name=AlgaeBase/><ref name=Shubert2014>{{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= Shubert|first1=Elliot| last2=Gärtner |first2=Georg |chapter= Chapter 7. Nonmotile Coccoid and Colonial Green Algae |url= |location= |publisher= Elsevier Inc. |page= |isbn=978-0-12-385876-4 }}</ref> The ultrastructure of the bristles are similar to that of the closely related ''Micractinium''.<ref>{{cite journal|doi=10.1016/S0003-9365(11)80271-X |title=Didymogenes palatina Schmidle and Didymogenes anomala (G. M. Smith) Hind. (Chlorococcales): Taxonomy, Ultrastructure, Autosporogenesis and Autospore Wall Assembly |date=1993 |last1=Schnepf |first1=E. |last2=Hegewald |first2=E. |journal=Archiv für Protistenkunde |volume=143 |issue=1–3 |pages=41–53 }}</ref>

In 2013, two additional species of ''Didymogenes'', ''D. soliella'' and ''D. sphaerica'', were described. The morphologies of these two species are dissimilar from ''Didymogenes'' as traditionally defined, and are similar to ''Chlorella'', consisting of solitary, spherical cells. Their placement in ''Didymogenes'' is based on molecular data.<ref>{{cite journal|doi=10.1111/pre.12010 |title=Molecular characterization of ''Chlorella'' cultures of the National Institute for Environmental Studies culture collection with description of ''Micractinium inermum'' sp. nov., ''Didymogenes sphaerica'' sp. nov., and ''Didymogenes soliella'' sp. nov. (Chlorellaceae, Trebouxiophyceae) |date=2013 |last1=Hoshina |first1=Ryo |last2=Fujiwara |first2=Yuko |journal=Phycological Research |volume=61 |issue=2 |pages=124–132 }}</ref>

Reproduction occurs asexually via the formation of autospores, arranged into coenobia. The autospores are released by the rupture of the parent cell wall, and daughter cells may have remnants of the cell walls attached. Sexual reproduction or zoospores have not been observed in this genus.<ref name=AlgaeBase/>

==References== {{Reflist|1}}

Category:Trebouxiophyceae genera Category:Chlorellaceae Category:Freshwater algae