Agardh 1830 Category: Asymmetrical biraphid
TYPE SPECIES: Cymbella cymbiformis Agardh
The valves of Cymbella are slightly to strongly dorsiventral, or asymmetric to the apical axis. Valves are symmetric to the transapical axis. The terminal raphe fissures are deflected to the dorsal side, an important diagnostic feature. Apical pore fields are present at both poles. Striae are uniseriate. One or more stigmata may be present. If a stigma or stigmata are present, they are located on the ventral side of the central area. Internally, the stigmata are convoluted internal occlusions. Also internally, the proximal raphe may be continuous across central area. Cymbella cells grow predominately in benthic habitats, and often produce mucilaginous stalks that are secreted through the apical porefield.
Historically, Cymbella has been a large, heterogenous group and is not considered to be a natural, or monophyletic group of species. Recently, a number of genera have been split from Cymbella, including Cymbopleura, Delicata and Encyonopsis.
Cite This Page:
Spaulding, S., and Edlund, M. (2008). Cymbella. In Diatoms of the United States. Retrieved October 25, 2014, from http://westerndiatoms.colorado.edu/taxa/genus/Cymbella