Cosmocladium Brébisson, 1856: 133
Holotype species: Cosmocladium pulchellum Brébisson
Original publication and holotype designation:Brébisson, [L.] A. de (1856). Liste des Desmidiées, observées en Basse-Normandie. Mémoires de la Société Nationale des Sciences Naturelles et Mathématiques de Cherbourg 4: 113-166, pls I, II.
Taxonomic status: currently recognized as a distinct genus.
Description: Cells smooth-walled, with shallow or deep median constriction (isthmus) where semicell walls overlap. Semicells ellipsoid to elongate-oval in apical view, with one chloroplast per semicell, each with central pyrenoid. Nucleus in isthmus between chloroplasts. Cells in colonies (or filamentous); joined either by connecting strands secreted by special group of pores or by incompletely shed primary walls. Cells often with broad mucilage envelope secreted through scattered cell wall pores. Asexual reproduction by cell division typical of Cosmarium-type desmids (see Cosmarium), and by fragmentation of colonies, which seldom have more than 16 cells. Each pair of daughter cells must form new connecting strands between them; these are produced from basal pore groups on each parental semicell (or from shed primary walls). Cell division within colony produces lateral branch; connecting strands of branch cells converge on the same group of basal pores in main axis cell, indicating that one pore may contribute to formation of more than one connecting strand. Sexual reproduction by conjugation known in two species (both with connecting strands from pores), but no detailed studies have been made. Zygospores spherical with several short, stout, acute spines.
Comments: Cosmocladium species are found in acidic, oligotrophic, aquatic habitats in Europe and North American with isolated records from Asia and New Zealand. Brébisson described C. pulchellum as attached to filamentous Zygnematales, but this would seem to be incorrect as, in almost all subsequent descriptions of various species, colonies are unattached. Later illustrations of attached C. pulchellum seem to be modified from Brébisson. On this basis, Heimans (1935) rejected C. pulchellum as a nomen confusum, and chose C. saxonicum de Bary as the type species. Gerrath (1970) also concluded that species with cells connected by primary walls should be removed to Cosmarium. Prescott et al. (1981), however, reject both Heiman's and Gerrath's treatment of the genus.
NCBI Nucleotide Sequences
Numbers of names and species: There are 11 species (and infraspecific) names in the database at present, of which 7 have been flagged as currently accepted taxonomically.
Names: ('C' indicates a name that is currently 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):
Cosmocladium constrictum (W.Archer) W.Archer C
Cosmocladium hitchcockii (Wolle) G.M.Smith C
Cosmocladium perissum J.Roy & Bisset C
Cosmocladium pulchellum Brébisson C - type
Cosmocladium pusillum L.Hilse S
Cosmocladium saxonicum De Bary C
Cosmocladium subramosum Schmidle C
Cosmocladium tuberculatum Prescott C
Cosmocladium tumidum L.N.Johnson S
Cosmocladium tumidum var. evolutum Scott & Grönblad S
Cosmocladium tumidum var. hallei P.Bourrelly & A.Couté C
Hall, J.D., Karol, K.G., McCourt, R.M. & Delwiche, C.F. (2008). Phylogeny of the conjugating green algae based on chloroplast and mitochondrial nucleotide sequence data. Journal of Phycology 44: 467-477.
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.
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43527
Cite this record as:
Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 24 May 2013.
Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:6871