Calothrix C.Agardh ex Bornet & Flahault, 1886

Lectotype species: Calothrix confervicola C.Agardh ex Bornet & Flahault

Original publication: Bornet, É. & Flahault, C. (1886). Revision des Nostocacées hétérocystées contenues dans les principaux herbiers de France. Annales des Sciences Naturelles, Botanique, Septième série 3: 323-381.

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Type designated in: Geitler, L. (1942). Schizophyta: Klasse Schizophyceae. In: Die natürlichen Pflanzenfamilien, Sweite Auflage. (Engler, A. & Prantl, K. Eds) Vol.1b, pp. 1-232. Leipzig: Wilhelm Engelmann.

Description: Filaments heteropolar, differentiated into basal (usually joined to the substrate) and apical parts, simple, solitary or in small groups, separated one from another (not in common mucilage), rarely with single, lateral false branches, oriented more or less in direction of the original growth; the filaments sometimes creeping on the substrate. Trichomes always with basal, more or less spherical or hemispherical heterocytes, and occasionally with intercalary cylindrical heterocytes; at intercalary heterocytes sometimes division of trichomes and their subsequent dissociation; trichomes sometimes with widened basal part, constricted or unconstricted at the crosswalls, ending by the hair-like apical part composed from narrow, long, hyaline cells; the hair formation is dependent on phosphorus-metabolism; (trichomes in several species obligatory without hairs - they represent probably a special genus different from both Calothrix and Microchaete). Sheaths always present, usually firm, sometimes lamellated and yellow-brownish colored, or funnel-shaped widened at the ends; cells cylindrical or barrel-shaped. Aerotopes in vegetative cells absent, but occur in hormogonia (always ?). Akinetes rarely in basal parts (known in few species only). Probably capable of chromatic adaptation (all species ?). Cell division perpendicularly to the long axis of trichomes (probably always with subapical meristematic zones). Trichomes dissociate at heterocytes and separately develop into new trichomes. Reproduction by motile hormogonia, which divide from the trichome, but help of the necridic cells and liberate from the sheath after separation of the terminal hair; hormogonia of several species with aerotopes (in all species ?; maybe an intergeneric feature). Only periphytic species, growing on aquatic plants, other algae, on stones and wooden substrates in different aquatic habitats, particularly in unpolluted habitats. Several species known from the marine littoral (inc. type species).

Information contributed by: J. Komárek. The most recent alteration to this page was made on 2020-02-17 by M.D. Guiry.

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

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Komárek, J., Kaštovský, J., Mares, J. & Johansen, J.R. (2014). Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach. Preslia 86: 295-335.

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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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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 17 February 2020. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 04 October 2022

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