Hassall 1845      Category: Symmetrical biraphid
TYPE SPECIES: Gyrosigma hippocampus (Ehrenberg) Hassall




Smallest to largest - 2 taxa sorted by maximum length

Image Credit: Meredith Tyree, Joana Gauthier, Michelle Chaput

CLASS: Bacillariophyceae
  ORDER: Naviculales

  1. Valve sigmoid
  2. Raphe sigmoid
  3. Striae in perpendicular and parallel rows

Valves are sigmoid. The axial area is narrow and also sigmoid, containing a sigmoid raphe. The striae are comprised of punctate areolae and form rows that are perpendicular and parallel to the apical and transapical axes. The central area is round to elliptic. External proximal raphe ends are deflected in opposite directions from one another. In living cells, two plastids are present.

Gyrosigma is characteristic of epipelic and endopelic habitats. The genus is widely distributed in freshwaters, with some species found in brackish waters.

Cite This Page:
Spaulding, S., and Edlund, M. (2009). Gyrosigma. In Diatoms of the United States. Retrieved March 24, 2018, from

Contributor: Sarah Spaulding | Mark Edlund - January 2009
Reviewer: Sam Rushforth - June 2010