M. Schmidt in A. Schmidt 1899 Category: Asymmetrical biraphid
TYPE SPECIES: Didymosphenia geminata (Lyngbye) M. Schmidt in A. Schmidt
Frustules of Didymosphenia are asymmetrical to the transapical axis and symmetrical to the apical axis (although some populations may be slightly to strongly asymmetrical to the apical axis). One to several stigmata are present, a feature that may be variable within a given species. A large apical porefield is present at the footpole. The terminal raphe fissures are deflected prior to reaching the apical porefield. Frustules are wedge shaped in girdle view. A marginal ridge of silica extends along the valve, terminating at the headpole in small spines.
D. geminata is common in North America and in the Upper Great Lakes. It is locally abundant in some lakes and streams, at times producing high biomass. The large volume of mucilaginous stalks of D. geminata may cover surfaces and foul water intake pipes, reaching nuisance proportions. It is invasive in New Zealand and expanding its range in regions of the Northern Hemisphere. This genus is more closely allied to the cymbelloid diatoms than to the gomphonemoid groups, as has been previously reported. Lake Baikal, in Siberia is considered a hotspot of diversity for Didymosphenia.
Cite This Page:
Spaulding, S., and Edlund, M. (2008). Didymosphenia. In Diatoms of the United States. Retrieved November 24, 2014, from http://westerndiatoms.colorado.edu/taxa/genus/Didymosphenia