Stephanodiscus Ehrenberg, 1845

Holotype species: Stephanodiscus niagarae Ehrenberg

Original publication: Ehrenberg, C.G. (1845). Neue Untersuchungen über das kleinste Leben als geologisches Moment.. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin, 1845: 53-87.

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Type designated in: Boyer, C.S. (1927). Synopsis of North American Diatomaceae. Part I. Coscinodiscatae, Rhizosolenatae, Biddulphiatae, Fragilariatae. Proceedings of the Academy of Natural Sciences of Philadelphia 78(Suppl.): 1-228.

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Description: Cells discoid or barrel-shaped, often with delicate organic threads radiating from around the edge of the valve. A ring of spines is present around the valve face. Plastids numerous, discoid. A common freshwater planktonic genus in lakes, rivers and reservoirs. Valves shallow, saucer-like. Valve face concentrically undulate or almost flat; in sibling pairs the elevations of one valve fit into depressions of the other. The areolae are simple round poores occluded internally by domed cribra; they are arranged in files usually containing a single row of areolae at the centre, but become double or multiple towards the edge of the valve face. The areolae of the valve mantle are slightly closer together and often occur in diagonal rows without intervening costae; the mantle edge is often vertically grooved. Spines occur in a single row around the edge of the valve face, where they are attached to small raised pads at the ends of costae; spines simple, except in S. binderanus where they fork. Fultoportulae present, arranged in a ring around the mantle, always occurring beneath certain of the spines; also occurring on the valve face, singly or in a ring. The fultoportulae may have either subsidiary tubes or buttresses. One or a few rimoportulae occur in the mantle and externally have tubular extensions. Copulae numerous, areolate, split, with ligulae.

The most recent alteration to this page was made on 2018-02-20 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Houk, V., Klee, R. & Tanaka, H. (2014). Atlas of freshwater centric diatoms with a brief key and descriptions. Part IV. Stephanodiscaceae B. Stephanodiscus, Cyclostephanos, Pliocaenicus, Hemistephanos, Stephanocostis, Mesodictyon & Spicaticribra. Fottea (Supplement) 14: 1-530.

Comments: This genus has proved exceedingly troublesome especially to ecologists and not all the problems are yet solved. S. binderanus was transferred from Melosira by Round (1972b). Round (1981e) discusses the history of the genus and gives descriptions of three species (S. niagarae, S. rotula, S. minutula) and there is an excellent account of the variability of S. niagarae by Theriot & Stoermer (1981). Håkansson & Locker (1981) also discuss some of these species. It is importnat to note that S. astraea, once thought invalid, has been rediscovered (Håkansson & Locker, 1981 - see also Håkansson, 1986).

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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. 20 February 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 18 June 2024

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