(Kützing) Compère 2001      Category: Araphid
TYPE SPECIES: Bacillaria ulna Nitzsch




Image Credit: Sarah Spaulding

CLASS: Fragilariophyceae
  ORDER: Fragilariales
    FAMILY: Fragilariaceae

  1. Narrow, elongate valves
  2. Narrow central sternum
  3. Central area present, may possess ghost striae
  4. Rimoportulae 1-2

Valves are linear and elongate, with some species near 50 µm in length, others reaching greater than 500 µm in length. A narrow central sternum is present, with striae that meet from each side of the valve or are slightly offset. A central area may be present, varying from small and oval to rectangular and extending to the valve margins. The central area may contain “ghost striae”, or faint striae that are present over part, or all, of the central area. One to two rimoportulae are present, at one or both apices. In many species, the apices are distinctly rostrate. Striae are punctate and may be uniseriate or biseriate.

Living cells are common in rivers and lakes. They are attached to the substrate by a mucilage pad secreted by an apical porefield.

The genus Ulnaria was proposed to include species within the species complex surrounding Fragilaria ulna, that is, Fragilaria subgenus Alterasynedra Krammer and Lange-Bertalot 1991. It includes Ulnaria biceps (Kützing) Compère, U. capitata (Ehrenberg) Compère, U. lanceolata (Kützing) Compère, U. ulna (Nitzsch) Compère and U. ungeriana (Grunow) Compère.

Cite This Page:
Spaulding, S. (2013). Ulnaria. In Diatoms of the United States. Retrieved March 30, 2015, from http://westerndiatoms.colorado.edu/taxa/genus/ulnaria

Contributor: Sarah Spaulding - March 2013