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Corethron Castracane, 1886

Empire Eukaryota
Kingdom Chromista
Phylum Bacillariophyta
Subphylum Coscinodiscophytina
Class Coscinodiscophyceae
Subclass Corethrophycidae
Order Corethrales
Family Corethraceae

Lectotype species: Corethron criophilum Castracane

Currently accepted name for the type species: Corethron pennatum (Grunow) Ostenfeld

Original publication:Castracane, [C.A.] F. (1886). Report on the Diatomaceae collected by H.M.S. Challenger during the years 1873-76. In: Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873-76. Botany - Vol. II. (Murray, J. Eds), pp. [1]-178.
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Type designated in Boyer, C.S. (1927). Synopsis of North American Diatomaceae. Part I. Coscinodiscatae, Rhizosolenatae, Biddulphiatae, Fragilariatae. Proceedings of the Academy of Natural Sciences of Philadelphia 78(Suppl.): 1-228.
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Taxonomic status: currently recognized as a distinct genus.

Gender: This genus name is currently treated as neuter.

Most recent taxonomic treatment adopted: Crawford, R.M., Hinz, F. & Honeywill, C. (1998). Three species of the diatom genus Corethron Castracane: structure, distribution and taxonomy. Diatom Research 13(1): 1-28, 59 figs.

Description: Cells solitary (reported rarely in short filaments), usually seen in girdle view, which is cylindrical with dome-shaped valves and numerous discoid plastids. A cosmopolitan marine planktonic genus occurring in vast numbers, especially around Antarctica (see Fryxell & Hasle, 1971). The complex heterovalvy partly explains the perplexing variety of 'phases' illustrated by Hendey (1937) and first revealed with the EM by Fryxell & Jasle (1971). One valve is domed with a wide, upturned and scalloped brim. Within this brim are deep sockets with peg-like projections at either side. Into these sockets are inserted the bases of long, tapering, toothed spines which are T-shaped in section with the top of the T lying adjacent to the valve brim. Hair-like filaments are often found on this valve. In the intact cell the spines on the valve just described point away from the girdle. The other valve has a ring of spines of two types. Spines similar to those in the first described valve alternate with shorter spines that have distinctive claw-like tips described in detail by Fryxell & Hasle (1971). Interestingly, there are right- and left-handed versions of these spines. Near their base there is an expansion to form an oar-shaped blade before the spine enters the socket which itself is smaller than that of the long spine. Compare the two interiors. The short spines point up and away from the valve rim but the long spine is inserted with the stem of the T towards the brim which is downturned in this valve. Consequently the large spines of both valves of an intact cell point in the same direction. When the spines are released from the constraint of the cingulum as the cells divide, they swivel in their socklets to adopt an acute angle with the valve. Corethron is thus a unique diatom with moveable valve components. There are no tube-processes. Both the valve and the scale-like girdle bands are finely areolate.

The most recent alteration to this page was made on 12 Jan 2021 by M.D. Guiry.

Comments: Scott & Thomas (2005: 48) record this genus as being a member of the Family Leptocylindraceae. The scale-like nature of the bands led Fryxell & Hasle to place Corethron in the Rhizosoleniaceae. We cannot agree with this and equally see no justification for placing it in the Melosiraceae as Simonsen (1979) has done. We prefer to allocate this remarkable monospecific genus to its own family. Further detail is provided in Crawford & Round, 1989.

Numbers of names and species: There are 14 species names in the database at present, as well as 2 infraspecific names. Of the species names, 7 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.

Scott, F.J. & Thomas, D.P. (2005). Diatoms. In: Antarctic marine protists. (Scott, F.J. & Marchant, H.J. Eds), pp. 13-201. Canberra & Hobart: Australian Biological Resources Study; Australian Antarctic Division.

Verification of data
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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.

Created: 23 April 2002 by M.D. Guiry

Verified by: 12 January 2021 by M.D. Guiry

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=44372

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 04 August 2021.

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