Staurosira Guide
Credit: Eduardo Morales
  1. Striae narrow, composed of small, round or somewhat elongated areolae
  2. Striae do not meet in central sternum

Staurosira valves are elliptic or cruciform in outline. In girdle view, the frustules are rectangular in shape. Cells often form colonies, joined by interlinking spines. The striae are narrow and composed of small, round areolae. Note that, for most species, the areolae are only visible in SEM. Striae do not meet one another in the central sternum. Valves lack rimoportulae.

Staurosira includes the former Fragilaria construens and its relatives. In the light microscope it can be distinguished from Staurosirella based on the structure of the striae. The striae of Staurosira are composed of round areolae, while the striae of Staurosirella are lineolate.