Micrasterias C.ex , 1848
Lectotype species: Micrasterias furcata C.Agardh 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.
There is no clear distinction between Micrasterias and Euastrum, and placement of a few taxa is arbitrary. - (21 Jul 2009) - M.D. Guiry
Description: Cells small to large (up to 400 µm long), usually solitary (M. foliacea is filamentous), much compressed, with very deep median constriction (isthmus) where semicell walls overlap. Other shallow or deep incisions divide each semicell into apical lobe and two lateral lobes, each usually further subdivided. Several species with small or large protuberances or hollow processes, either near base or middle of each semicell, or on one or more of peripheral lobes.
Cell wall smooth with scattered pores, or with numerous granules or spinules, either covering most of cell, restricted to certain lobes or restricted to margins of incisions. Usually one chloroplast per semicell, with few to numerous scattered pyrenoids. Nucleus in isthmus.
Asexual reproduction by cell division and new semicell morphogenesis typical of Cosmarium-type desmids; each daughter cell receives one parental semicell with its secondary wall. The division septum at isthmus splits to become primary walls, these remaining on new semicells until mature form reached. By gradual expansion new semicells form complex outline of new semicell, with initial formation of three main lobes and later formation of mature lobing pattern. Mature secondary wall, with pores and wall ornamentation, produced beneath primary wall, the latter shed in small pieces.
Sexual reproduction by homothallic or heterothallic conjugation known for several species and studied ultrastructurally. Conjugating cells come together within broad gelatinous envelope. Gametangial semicells separate and conjugation tube with thin wall formed. Gametes move together, fusing within conjugation tube. Mature zygospores spherical, with long, simple or furcate spines. Meiosis during zygospore germination forming two gones, initially resembling Cosmarium but producing Micrasterias morphology with subsequent cell divisions.
Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 12 Sep 2013 by M.D. Guiry.
Comments: Micrasterias has several cosmopolitan species; planktonic or periphytic in acidic, oligotrophic or dystrophic lakes and ponds, or in swamps or mires. Several species used as experimental organisms for studies on effects of various treatments (chemicals, various types of radiation, changes in turgor pressure, enucleation, polyploidy, etc.) on morphogenesis of new semicells following cytokinesis.
Micrasterias is most studied among desmids for chromosome numbers and karyotype analysis. Chromosome numbers from 24-230 among 18 species; strains of single species may have different numbers. Morphological variants in culture are aneuploids.
Numbers of names and species: There are 223 species names in the database at present, as well as 753 infraspecific names. Of the species names, 76 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.
Agardh, C.A. (1827). Neue Gattungen und Arten von Algen. Flora 10(41): 641-646.
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=43536
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 21 November 2018.