Cocconeis
Ehrenberg 1837 Category: Monoraphid
TYPE SPECIES: Cocconeis scutellum Ehrenberg
Image Credit: Sarah Spaulding
CLASS: Bacillariophyceae
ORDER: Achnanthales
FAMILY: Cocconeidaceae
- Valves elliptical to nearly circular in outline
- One valve possess a raphe
- Rapheless valve possesses only a sternum
Cocconeis is heterovalvar, that is, the raphe valve ornamentation differs from that of the rapheless valve. Ornamentation of the raphe valve may differ markedly from that of the rapheless valve. The valve mantle is narrow in relation to the valve face, so cells are rarely (if ever) seen in girdle view. Valves may be flexed, or arched, along the apical axis forming a 'saddle' shape. Striae are often uniseriate, but some taxa possess multiseriate striae composed of loculate areolae. In several taxa, the raphe valve is marked by a region near the edge of the valve that is ornamented with a hyaline ring and a more defined mantle than the rapheless valve. Valvocopula may be closed, or complete, with internal projections of silica.
The genus contains both marine and freshwater taxa. Living cells have a solitary and adnate habit of growth. Cells possess a single plastid that is flat and C-shaped. Species of Cocconeis may be epiphytic on other algae, as well as on hard substrates (e.g. rock, sand). Cells grow with the raphe valve in contact with the substrate.
Cite This Page:
Spaulding, S., and Edlund, M. (2009). Cocconeis. In Diatoms of the United States. Retrieved May 20, 2013, from http://westerndiatoms.colorado.edu/taxa/genus/Cocconeis
Contributor: Sarah Spaulding | Mark Edlund - January 2009
Reviewer: Sam Rushforth
Citations
Gerloff, J. and Rivera, P. (1979). The submicroscopic structure of the valves of Cocconeis pediculus (Bacillariophyceae). Wildenowia 9: 99-110. http://www.jstor.org/stable/3996121
Holmes, R.W. (1985). The morphology of diatoms epizoic on cetaceans and their transfer from Cocconeis to two new genera. British Phycological Journal 20: 43-57.
Holmes, R.W., Crawford, R.M. and Round, F.E. (1982). Variability in the structure of the genus Cocconeis Ehr. (Bacillariophyta) with special reference to the cingulum. Phycologia 21: 370-381.
Jahn, R., Kusber, W.H. and Romero, O.E. (2009). Cocconeis pediculus Ehrenberg and C. placentula Ehrenberg var. placentula (Bacillariophyta): Typification and taxonomy. Fottea 9(2): 275–288.
Kingston, J.C. (2003). Araphid and Monoraphid Diatoms. In: Freshwater Algae of North America. Ecology and Classification (J.D. Wehr and R.G. Sheath, eds). Elsevier Science pp. 595-636.
Kreis, R.G.,Jr. and Stoermer, E.F. (1979). Diatoms of the Laurentian Great Lakes III. Rare and poorly known species of Achnanthes Bory and Cocconeis Ehr. (Bacillariophyta). J. of Great Lakes Research 5:276-291.
Leterme, S.C., Ellis, A.V., Mitchell, J.G., Buscot, M.J., Pollet, T., Schapira, M. and Seuront, L. (2010). Morphological flexibility of Cocconeis placentula (Bacillariophyceae) nanostructure to changing salinity levels. Journal of Phycology 46, (4): 715–719. 10.1111/j.1529-8817.2010.00850.x
Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.