Coelastrum Nägeli, 1849

Holotype species: Coelastrum sphaericum Nägeli

Original publication and holotype designation: Nägeli, 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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Description: Thalli forming 4, 8, 16, 32 or 64 (-128) celled coenobia to ca. 100 &m diameter, organized as spherical, pyramidal or cuboid, free-floating colonies. Cells more-or-less densely alligned but usually with empty spaces between wall interstices. Cells globose, ovoid, or pyramidal 2-30 &m in maximum dimension. Cells joined at edges by specialized wall plaques that may also occur on other wall faces, or various elongate wall processes. Cell walls apparently smooth, but ultrastructurally may have wrinkled surface. Cells initially uninucleate becoming multinucleate prior to reproduction mitotis involving centrioles cytokinesis associated with phycoplast. Chloroplast single and parietal with single pyrenoid. Asexual reproduction by formation of daughter colony (coenobium) inside parental cells. During reproduction all mitoses occur prior to cytokinesis and coenobial formation. Mitotic nuclei in C. proboscideum partly isolated by perinuclear ring of endoplasmic reticulum. In this species daughter cells do not move relative to one another prior to adhesion thus cell position in developing coenobia determined by cleavage planes. After coenobial release, parental walls may remain attached, producing more complex and irregular colonies. Flagellated stages and sexual reproduction unknown. Coelastrum planktonic and cosmopolitan in freshwater habitats from arctic to tropical environments often abundant in eutrophic conditions. A number of species available in algal culture collections (CCAP, UTEX, NIES). In culture, colony formation in C. microporum modified by medium composition with additions of sodium citrate and soil extract to medium with 0.25 g l-1 CaCl2 producing highest levels of colonies as opposed to solitary cells. Cells walls with acetoresistant, trilaminar layer resembling sporopollenin. Species distinguished based on cell size and shape, numbers of cell per coenobia and patterns of cell wall ornmentation and nature of wall processes. Several species groups have been distinguished based on cell morphology in lateral view cells with single, snout-like or well-developed free projections that are more or less triangular or 5-6 angled and cells with several processes that are localized in apical portion of cell or distributed around the whole cell surface. Species also distinguished based on physiological and biochemical features in culture. Asterarcys (?Scenedesmaceae) may be synonymous with Coelastrum.

Information contributed by: D. Garbary & A. Comas. The most recent alteration to this page was made on 2012-07-10 by Michael Guiry.

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

Most recent taxonomic treatment adopted: Hegewald, E., Wolf, M., Keller, A. Friedl, T. & Krienitz, L. (2010). ITS2 sequence-structure phylogeny in the Scenedesmaceae with special reference to Coelastrum (Chlorophyta, Chlorophyceae), including the new genera Comasiella and Pectinodesmus. Phycologia 49(4): 325-335.

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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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Michael Guiry in Guiry, M.D. & Guiry, G.M. 10 July 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 03 December 2022

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