Grunow 1867      Category: Symmetrical biraphid
TYPE SPECIES: Craticula perrotetii Grunow




Image Credit: Lauren Fuelling, Pat Kociolek

CLASS: Bacillariophyceae
  ORDER: Naviculales
    FAMILY: Stauroneidaceae

  1. Striae parallel, or nearly parallel
  2. Valves lanceolate, with narrowly rostrate or capitate poles
  3. Distinct internal valves may be present

The valves of Craticula are lanceolate, with narrowly rostrate or capitate poles. The striae are distinctly parallel, or nearly parallel. The genus is polymorphic, forming different valve morphologies. Distinct internal valves, called craticula, are formed in response to osmotic stress. Note that these craticular stages are not always present. Living cells possess two elongate, plate-like chloroplasts appressed to the girdle.

Craticula is a term applied to internal valves that are formed within frustules that are normal in morphology. The craticular valves consist of a raphe-sternum and robust transverse bars. The genus Craticula occurs in epipelic habitats across North America, in fresh to brackish waters.

Cite This Page:
Spaulding, S., and Edlund, M. (2008). Craticula. In Diatoms of the United States. Retrieved May 28, 2015, from

Contributor: Sarah Spaulding | Mark Edlund - December 2008