Staurastrum Meyen ex Ralfs, 1848

Lectotype species: Staurastrum paradoxum Meyen ex Ralfs

Original publication: Ralfs, J. (1848). The British Desmidieae The drawings by Edward Jenner, A.L.S. pp. [i]-xxii, [i], [1]-226, 35 pls. London: Reeve, Benham & Reeve, King William Street, Strand.

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Type designated in: Guiry, M.D. (2013). Taxonomy and nomenclature of the Conjugatophyceae (=Zygnematophyceae). Algae. An International Journal of Algal Research 28: 1-29.

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Description: Cells small to large, 2- to 12-radiate in end view, with shallow or deep median constriction (isthmus) where semicell walls overlap, and two intergrading cell morphologies. Most species with long, hollow processes on each semicell (number related to radiation pattern); processes usually with two or more terminal spinules, and possibly one or more series of denticulations, spines or verrucae along process and on apex and body of central axis of semicell. On other species, semicell angles rounded, truncate or with short processes; cell wall smooth or with rows of small granules or spinules. Chloroplasts usually one per semicell, stellate (lobed) in end view, with axial pyrenoid or with several pyrenoids in lobes extending into cell angles or processes. Nucleus in isthmus. Asexual reproduction by cell division and new semicell formation typical of Cosmarium-type desmids (see Cosmarium). Sexual reproduction by conjugation known for many species. Gametangia come together within broad gelatinous envelope; gametangia fuse in conjugation tube. Mature zygospores usually spherical, with long furcate spines. Many species cosmopolitan; others restricted to tropical areas or certain continents. Species with long processes often planktonic. Most species bethic or periphytic in acidic, oligotrophic lakes, ponds and swamps. Proposals to segregate groups of species into distinct genera generally ignored because of difficulty in establishing clear generic limits. Former Staurastrum taxa with single spine (or thickened cell wall) at each angle now referred to Staurodesmus. Palamar-Mordvintseva (1976) segregated species without long processes into several genera; not generally accepted except in Russian and Ukrainian publications. Cylindriastrum includes species with elongate angular- cylindric cells. Cosmoastrum includres species with smooth wall or with rows of granules or spinules over entire wall or only around cell angles. Raphidiastrum includes species with two or more spines at each angle and those with a single angular spine which also have rows of granules or spinules on cell wall. Placement of some taxa arbitrary since these genera have intergrading forms.

Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 2013-09-12 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Guiry, M.D. (2013). Taxonomy and nomenclature of the Conjugatophyceae (=Zygnematophyceae). Algae. An International Journal of Algal Research 28: 1-29.

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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.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 12 September 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 22 April 2024

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