Epithemia
Kützing 1844 Category: Epithemioid
TYPE SPECIES: Epithemia turgida (Ehrenberg) Kützing
Image Credit: Rex Lowe, Sarah Spaulding
CLASS: Bacillariophyceae
ORDER: Rhopalodiaceae
FAMILY: Rhopalodiaceae
- Raphe eccentric, positioned along ventral margin
- Raphe opens internally into a canal
- Areolae complex
Epithemia has an eccentric raphe system, positioned along the ventral margin. Each branch of the raphe is arched toward the dorsal margin. Externally, the proximal raphe slits terminate in expanded ends, while internally, the raphe slit is continuous through the central nodule. The raphe is also supported internally by large, transapical costae. The valvocopulum, which is the girdle band next to the valve mantle, often possesses septum-like extensions. Areolae are complex.
Living cells of Epithemia often possess endosymbiotic cyanobacteria capable of fixing atmospheric nitrogen. Species within the genus, therefore, are often tolerant of nitrogen limiting conditions. Epithemia is an exclusively freshwater genus. Cells are epiphytic and epipelic. They are commonly found in carbonate rich (alkaline) waters and can also tolerate relatively high conductivity.
Cite This Page:
Spaulding, S. (2010). Epithemia. In Diatoms of the United States. Retrieved May 26, 2013, from http://westerndiatoms.colorado.edu/taxa/genus/epithemia
Contributor: Sarah Spaulding - December 2010
Citations
Bergey, E.A. (1995). Local effects of a sedentary grazer on stream algae. Freshwater Biology 33: 401–409. 10.1111/j.1365-2427.1995.tb00402.x
Blinn, D.W., Truitt R.E. and Pickart, A. (1989). Feeding ecology and radular morphology of the freshwater limpet Ferissia fragilis. Journal of the North American Benthological Society 8:237-242.
DeYoe, H.R., Lowe, R.L. and Marks, J.C. . (1992). Effects of nitrogen and phosphorus on the endosymbiont load of Rhopalodia gibba and Epithemia turgida (Bacillariophyceae). Journal of Phycology 28: 723–873. 10.1111/j.0022-3646.1992.00773.x
Kelly, M.G. (2003). Short term dynamics of diatoms in an upland stream and implications for monitoring eutrophication. Environmental Pollution 125:117-122 . 10.1016/S0269-7491(03)00075-7
Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.
Sims, P.A. (1983). A taxonomic study of the genus Epithemia with special reference to the type species E. turgida (Ehrenb.) Kütz. Bacillaria 6: 211-235.
You, Q., Liu, Y., Wang, Y. and Wang, Q. (2009). Taxonomy and distribution of diatoms in the genera Epithemia and Rhopalodia from the Xinjiang Uygur Autonomous Region, China. Nova Hedwigia 89:397-430. 10.1127/0029-5035/2009/0089-0397