{{Short description|Genus of algae}} {{Automatic taxobox | image = Actidesmium hookeri.jpg | image_caption = | taxon = Actidesmium | authority = Reinsch | type_species = ''Actidesmium hookeri'' | type_species_authority = Reinsch | subdivision_ranks = Species | subdivision_ref = <ref name="Algaebase">{{cite web | url = http://www.algaebase.org/browse/taxonomy/#6073 | publisher = AlgaeBase version 4.2 World-wide electronic publication, National University of Ireland, Galway | access-date = 2023-05-25 | title = Genus: ''Actidesmium'' taxonomy browser |author1=Guiry, M.D. |author2=Guiry, G.M. | year = 2023 }}</ref> | subdivision = * ''Actidesmium hookeri'' * ''Actidesmium sphaericum'' }}
'''''Actidesmium''''' is a small genus of green algae in the family Characiaceae. It was described by the German phycologist Paul Friedrich Reinsch in 1875.<ref name="Algaebase"/>
''Actidesmium'' consists of microscopic colonies of numerous cells. Cells are in clusters of four, eight, or 16 at the end of long gelatinous strands, which are the remains of the old cell wall. One chloroplast is present, lacking a pyrenoid.<ref name=Hall2014>{{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> ''Actidesmium'' reproduces by zoospores formed by successive division. Zoospores each have two flagella, and are released at the apex of the cell. After release, the mother cell gelatinizes and the zoospores mature into new vegetative cells.<ref>{{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>
Two species are known: ''Actidesmium hookeri'' and ''Actidesmium sphaericum'' (formerly known as ''Actidesmium globosum'').<ref name=Algaebase/> The two differ in the size and shape of their cells, the latter being smaller and globose.<ref>{{cite journal | last1=Steinecke | first1=F | date=1923 | title=Actidesmium globosum, eine neue Characiaceae | journal=Botanisches Archiv | volume=3 | issue=6 | pages=316–317 | url=https://www.biodiversitylibrary.org/item/110777#page/318/mode/1up }}</ref>
''Actidesmium'' has been reported from freshwater habitats in North America and Europe, and is rare.<ref>{{cite journal | jstor=23302189 | title=Notes on New England Algae I: Cyclonexis and Actidesmium | last1=Whelden | first1=R. M. | journal=Rhodora | year=1939 | volume=41 | issue=484 | pages=133–137 }}</ref>
==References== {{Reflist}}
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Category:Sphaeropleales Category:Sphaeropleales genera Category:Freshwater algae
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