Scenedesmus Meyen, 1829: 774

Classification:
Empire Eukaryota
Kingdom Plantae
Phylum Chlorophyta
Class Chlorophyceae
Order Sphaeropleales
Family Scenedesmaceae
Subfamily Scenedesmoidea

Lectotype species: Scenedesmus obtusus Meyen

Original publication:Meyen, F.J.F. (1829). Beobachtungen über einige niedere Algenformen. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae 14: 768-778, pl. XLIII.
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Type designated inNägeli, C. (1849). Gattungen einzelliger Algen, physiologisch und systematisch bearbeitet. Neue Denkschriften der Allg. Schweizerischen Gesellschaft für die Gesammten Naturwissenschaften 10(7): i-viii, 1-139, pls I-VIII.
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Taxonomic status: currently recognized as a distinct genus.

Description: Thalli single celled or colonial, forming 2- to 32-celled, usually 4- or 8-celled coenobia; surrounding mucilaginous matrix present or absent. Cells arranged linearly, alternating or in 2-3 rows, touching with the lateral walls or in subpolar region only. Cells 3-78 x 2-10 µm, nearly spherical to ellipsoidal, elongate or fusiform to elongate fusiform; cell poles capitate, obtuse, acute or long tapering. Cell wall with hemicellulosic and sporopolleninic layer, usually smooth in subgenus Acutodesmus and Scenedesmus, with submicroscopical structures in subgenus Desmodesmus, partly light microscopically visible as ribs, granulations or dents. Cells spineless or in subgenus Desmodesmus partly with sporopolleninic spines. Excretion of proteinaceous bristles. Cells uninucleate; chloroplast single and parietal with single pyrenoid. Asexual reproduction by autospores; 2-32 per sporangium, usually organized in one coenobium or disintegrated into singe cells; spore release by rupture of parental cell wall. Sexual reproduction reported for S. obliquus in subgenus Acutodesmus, but apparently extremely rare. Gametes biflagellate and isogamous; if syngamy does not occur gametes disintegrate. Chromosome numbers rarely reported, in S. quadricauda n = 11 or 13. Scenedesmus planktonic mainly in eutrophic freshwater ponds and lakes, rarely in brackish water; reported world-wide in all climates. Physiology and biochemistry relatively uniform, with all 28 investigated strains having hydrogenase and producing secondary carotenoids in nitrogen deficient conditions; species differ in ability to hydrolyze starch, growth under acidic conditions and guanine-cytosine content of DNA varies between 50-69% (85 investigated strains). Outer cell wall and nearly all cell wall ornamentation sporopolleninic, inner cell wall hemicellulosic. Species tolerate or prefer eutrophic water with slight acidity but only low salinity. Temperature optima at 28-30%C, but with some strains or taxa at 36%C or above. Some species of Scenedesmus highly polymorphic in culture with variation induced by various culture conditions. Culture variants may be similar to "Dactylococcus" or Lagerheimia spp. Polymorphism has been studied for about 100 years but remains incompletely understood. Variability includes cell number per coenobium/single cells, cell arrangement, cell size and especially expression of ornamentation (spines, ribs, granulation). Some species change ultrastructural features of cell walls from generation to generation based on nutrition. Genus with well defined subgeneric or infrageneric classification with many hundreds of described varieties and forma. Species distinguished mostly on differences in cell size and shape, coenobial morphology and patterns of cell wall ornamentation. Some authors include Tetradesmus as a synonym. Scenedesmus obliquus and sporadically S. obtusus are produced in mass culture and used as food because of their protein and mineral content, or used for other purposes in biochemical industry.

NCBI Nucleotide Sequences

Numbers of names and species: There are 447 species (and infraspecific) names in the database at present, of which 74 have been flagged as currently accepted taxonomically.

Names: ('C' indicates a name that is currently accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43474

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 25 May 2013.

Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:6918