Closterium Nitzsch ex Ralfs, 1848

Lectotype species: Closterium lunula Ehrenberg & Hemprich 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: Silva, P.C. (1952). A review of nomenclatural conservation in the algae from the point of view of the type method. University of California Publications in Botany 25: 241-323.

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Description: Cell solitary (rarely aggregated), small to large (72-1700 um), usually elongate-cylindric to elongate-fusiform, straight or, more commonly, curved (at least at ends). Cells usually tapering toward both ends; ends acute, rounded or truncate. Cell wall smooth or with longitudinal striae or costae, wall colorless, yellowish or brown (sometimes only at ends of cell). Cell wall ultrastructurally with outer, electron-dense amorphous layer and inner microfibrillar layer. Perforations in outer layer associated with less dense fibrillar areas in inner layer, but continuous pores similar to those in Desmidiaceae not present. Girdle bands (extra wall sections) present in some species. Chloroplasts two (rarely four) per cell, axial, elongate, stellate in end view, with one to many, axial or scattered pyrenoids. Pyrenoids usually numerous, except in very small species, and in axial row or scattered throughout chloroplast. Nucleus at middle between chloroplasts. Each end of cell with vacuole containing one or more granules of calcium sulfate. Asexual reproduction by transverse cell division. Daughter cell morphogenesis involves formation new semicells by gradual expansion from severed end, and in one species group, also involves formation of extra pieces of wall (girdle bands). Aplanospores and parthenospores observed in some species. Sexual reproduction by homothallic or heterothallic conjugation. Gametangia come together in mucilaginous envelope. Gametangia often immature sister cells from recent division. Both cells split at median suture; gametes partially or completely move out to fuse between gametangia. Zygospores spherical, ellipsoid, quadrate or irregular; some with scattered, broad conical protuberances or with long lobes surrounded by empty gametangial wall pieces. Zygospore wall smooth, with pits, scrobiculations, ridges or spines. Karyogamy during germination, followed by meiosis.

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.

Comments: Closterium is cosmopolitan, in periphyton of acidic, oligotrophic lakes and ponds; rarely in in more alkaline, eutrophic environments. Some species (e.g. C. aciculare) planktonic. Experimental studies on host range of parasitic phycomycetes may help in delimiting certain species groups. Several reproductively isolated mating groups (biological species) known in two morphological species complexes (in C. ehrengergii these are polyploids).

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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 18 June 2024

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