{{Short description|Genus of algae}} {{Automatic taxobox | image = Hydrianum ovale in Rabenhorst 1868.jpg | image_caption = ''Hydrianum ovale'' | taxon = Hydrianum | authority = Rabenhorst, 1868 | type_species = ''Hydrianum ovale'' | type_species_authority = Rabenhorst<ref name=AB_g43383/> | subdivision_ranks = Species | subdivision_ref = <ref name=AB_g43383/> | subdivision = {{Linked species list |Hydrianum coronatum|Fott |Hydrianum crassiapex|Korshikov |Hydrianum diogenes|(F.W.Jane) Fott |Hydrianum ellipticum|Korshikov |Hydrianum gracile|Korshikov |Hydrianum lageniforme|Korshikov |Hydrianum ovale|Rabenhorst |Hydrianum pyrenoidiferum|Massjuk }} | synonyms = * ''Chlororhabdion'' {{au|F.W.Jane}}<ref>{{AlgaeBase genus|id=51465|name=Chlororhabdion|access-date=2024-11-30}}</ref> }}
'''''Hydrianum''''' is a genus of green algae, in the order Chlamydomonadales. It is found in freshwater habitats such as marshes and bogs, as an epiphyte on plants or other algae.<ref name=AB_g43383>{{AlgaeBase genus|name=Hydrianum|id=43383|access-date=2022-02-25}}</ref> It is common, but most likely overlooked due to its similarity with similar genera such as ''Characium''.<ref name=Chlorococcales>{{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>
==Description== ''Hydrianum'' consists of solitary or clustered cells attached to a substrate, via a mucilaginous pad or a stipe. Cells are cylindrical, oval, or spindle-shaped; in some species they are distinctly curved. Cells are uninucleate (with a single nucleus), they contain a single parietal chloroplast (or multiple when older). Pyrenoids are generally absent but may be present in a few species.<ref name=AB_g43383/>
Asexual reproduction occurs via the formation of zoospores; the zoospores are released through a rupture near the apex of the cell wall, while one zoospore stays behind and develops into a new vegetative cell. Zoospores have two flagella and a single chloroplast. After swimming, the zoospores settle and develop into a new cell. Sexual reproduction has not been observed in this genus.<ref name=AB_g43383/>
Members of ''Hydrianum'' with a pyrenoid can be confused with ''Characium'', but in ''Hydrianum'' the zoospores exit subapically or apically, while in ''Characium'' the zoospores exit through a lateral opening. Additionally, in ''Hydrianum'' a zoospore may remain in the sporangium and develop into a new cell. The genus is also similar to ''Characiopsis'', which generally lacks pyrenoids, but is unrelated.<ref name=Chlorococcales/> ==References== {{Reflist}}
==External links== * [https://web.archive.org/web/20070928163719/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]
{{Taxonbar|from=Q5954528}}
Category:Chlamydomonadales genera Category:Chlamydomonadales Category:Freshwater algae
{{Chlorophyceae-stub}}