Rhoicosphenia
Grunow 1860 Category: Asymmetrical biraphid
TYPE SPECIES: Rhoicosphenia abbreviata (Agardh) Lange-Bertalot
Image Credit: Marina Potapova
CLASS: Bacillariophyceae
ORDER: Cymbellales
FAMILY: Rhoicospheniaceae
- One valve with complete raphe
- One valve with small raphe branch (rudimentary raphe)
- Pseudosepta at both poles
- Frustule curved in girdle view
Frustules of Rhoicosphenia are clavate in valve view and heterovalvar. In girdle view, valves are flexed, and curved. As a result of the asymmetry to the transverse axis, the valve face is curved. One valve has a complete raphe with two distinct raphe branches. The other valve has a very small raphe branch on the footpole. Pseudosepta are present and distinct at both poles. In contrast with species in Gomphonema, valves lack apical pore fields.
Cells grow on short stalks in streams and wave zones of lakes. Rhoicosphenia is common in western North America. A single extant freshwater species is found in North America,R. abbreviata (an earlier homonym of R. curvata). Morphology has been documented by Mann (1982a, 1982b). A number of species appear to be present in North America, currently included within R. abbreviata.
Cite This Page:
Spaulding, S., and Edlund, M. (2009). Rhoicosphenia. In Diatoms of the United States. Retrieved May 24, 2013, from http://westerndiatoms.colorado.edu/taxa/genus/Rhoicosphenia
Contributor: Sarah Spaulding | Mark Edlund - January 2009
Reviewer: Sam Rushforth
Citations
Levkov, Z., Mihalić K.C. and Ector, L. (2010). A taxonomical study of Rhoicosphenia Grunow (Bacillariophyceae) with a key for identification of selected taxa. Fottea 10(2): 145–200.
Mann, D.G. (1982). Structure, life history and systematics of Rhoicosphenia (Bacillariophyta) I. The vegetative cell of Rh. curvata. Journal of Phycology 18: 162-176.
Mann, D.G. (1982). Structure, life history and systematics of Rhoicosphenia (Bacillariophyta) II. Auxospore formation and perizonium structure of Rh. curvata. Journal of Phycology 18: 264-274.