Like other diatoms, Gyrosigma has a siliceouscell wall called a frustule. The frustule is composed of two sections called valves, with one valve fitting inside the other valve similar to the two halves of a Petri dish. Gyrosigma has valves with a central slit called a raphe, a structure that allows movement of these diatoms.
The valves of Gyrosigma are sigmoid in outline, as well as the raphe. Striations could be parallel or perpendicular to the raphe. This contrasts to a similar genus Pleurosigma, which has striations that lie diagonally to the raphe.
↑Kociolek, J. Patrick; Theriot, Edward C.; Williams, David M.; Julius, Matthew; Stoermer, Eugene F.; Kingston, John C. (2014). "Chapter 15. Centric and Araphid Diatoms". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2ed.). Elsevier Inc. ISBN978-0-12-385876-4.
12Kociolek, J. Patrick; Spaulding, S. A.; Lowe, R. L. (2014). "Chapter 16. Bacillariophyceae: The Raphid Diatoms". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2ed.). Elsevier Inc. ISBN978-0-12-385876-4.