Corethron Castracane, 1886
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.
Request PDFType 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.
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.
Information contributed by: Various. The most recent alteration to this page was made on 2024-10-01 by G.M. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
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.
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.
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Contributors
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: https://www.algaebase.org/search/genus/detail/?genus_id=44372
Citing AlgaeBase
Cite this record as:
G.M. Guiry in Guiry, M.D. & Guiry, G.M. 01 October 2024. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 21 November 2024
