Scytonema C.ex É. & C.Flahault, 1886
Lectotype species: Scytonema hofmanii C.Agardh ex Bornet & Flahault
Original publication and holotype designation: Bornet, É. & Flahault, C. (1886 '1887'). Revision des Nostocacées hétérocystées contenues dans les principaux herbiers de France (Troisième fragment). Annales des Sciences Naturelles, Botanique, Septième série 5: 51-129.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Komárek, J., Kastovsky, J., Mares, J. & Johansen, J.R. (2014). Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach. Preslia 86: 295-335.
Description: Filamentous - thallose; solitary branched filaments or mats on the substrate. Filaments free or in fascicles, sometimes densely coiled, creeping on the substrate or with erect branches, commonly falsely branched, with one or (obligatory) two lateral branches. Branching initiates after trichome dissociation by help of necridic cells between two heterocytes, usually not at heterocytes; both branches grow parallel aside or in crossing position; the filaments make sometimes typical loop-like lateral formations before branching, in which tops of the trichomes later divide. Trichomes isopolar, cylindrical, not diversified in basal and apical parts, uniseriate, usually with solitary heterocytes, constricted (rarely not constricted) at cross walls; terminal parts of branches cylindrical or slightly widened, with rounded apical cell; middle parts of trichomes sometimes with elongated, cylindrical cells. Sheaths firm, limited, parallel or diverging, lamellated, usually yellow-brown (colored by scytonemin) in some parts. Cells pale or olive-green, usually with solitary, irregularly disposed granules or with granular content, rarely yellowish or pinkish colored; apical cells sometimes with large vacuoles. Heterocytes intercalary, solitary, rarely in pairs, cylindrical or barrel-shaped. Akinetes were several times mentioned, but not proved and well described. Cells divide crosswise to the trichome axis, mainly in meristematic zones near the ends of branches. Reproduction by hormogonia, which develop at the ends of branches and liberate from sheaths. Hormogonia germinate at both ends and form isopolar filaments. Many Scytonema-species grow aerophytic or subaerophytic on wet rocks, wood, soil, epiphytic on mosses; several species are incrusted by calcium carbonate and represent dominant members of microphytes in travertine springs. Few species are known from atmophytic habitats near thermal waters. The submersed species grow usually in rocky littoral of lakes, rarely among water plants, mainly on alkaline substrate, rarely in moors or acidic waters, few species are marine, occurring on coral reefs or in brackish water. The genus is very common mainly in tropical regions, but particularly the variability of tropical taxa is insufficiently known and many species are arbitrarily misinterpreted.
Information contributed by: J. Komárek. The most recent alteration to this page was made on 3 Mar 2015 by M.D. Guiry.
Numbers of names and species: There are 201 species names in the database at present, as well as 57 infraspecific names. Of the species names, 127 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):
Click here to also show infraspecific names in the list below.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
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.
Created: 28 December 2000 by M.D. Guiry
Verified by: 03 March 2015 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=42978
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 20 November 2019.