Euastrumex , 1848
Lectotype species: Euastrum ansatum Ehrenberg ex Ralfs
Original publication:Ralfs, J. (1848). The British Desmidieae. pp. [i]-xxii, [i], -226, pls I-XXXV. London: Reeve, Benham & Reeve.
Type designated in Guiry, M.D. (2013). Taxonomy and nomenclature of the Conjugatophyceae (=Zygnematophyceae). Algae. An International Journal of Algal Research 28: 1-29.
Taxonomic status: currently recognized as a distinct genus.
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.
Description: Cells solitary, usually longer than broad, with deep median constriction (isthmus) shere semicell walls overlap. Apical view oval to elliptical (biradiate), often with broadened middle region (rare triangular forms known). Each semicell usually with distinct apical and lateral lobes; apical lobe with emarginate apex or apical incision. Cell wall smooth with scattered pores, or variously ornamented with granules, verrucae or short spinules. Usually one chloroplast per semicell with one or more pyrenoids. Nucleus in isthmus. Asexual reproduction by cell division and new semicell morphogenesis characteristic of Cosmarium-type desmids (see Cosmarium). Sexual reproduction by conjugation. Conjugating cells pair and form gelatinous envelope. Gametes fuse between gametangia. Mature zygospores globose to ellipsoidal with many short, acute spines or mamillate protuberances. Euastrum commonly collected from acidic, oligotrophic, aquatic habitats or from bogs. Several species cosmopolitan. Euastrum cannot be distinguished with absolute confidence from Cosmarium or Micrasterias; placement of certain taxa is arbitrary.
Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 12 Sep 2013 by M.D. Guiry.
Numbers of names and species: There are 647 species names in the database at present, as well as 1318 infraspecific names. Of the species names, 296 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.
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.
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: 11 April 2002 by M.D. Guiry
Verified by: 12 September 2013 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43531
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 19 February 2019.