title: Gyrosigma
text: # Gyrosigma
  
  Gyrosigma is a genus of diatoms belonging to the family Pleurosigmataceae.
  
  The genus has cosmopolitan distribution.
  
  Like other diatoms, Gyrosigma has a siliceous cell 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, which allows the diatom to move.
  
  The valves of Gyrosigma are sigmoid in outline, as well as the raphe. There are striations parallel to the raphe, as well as striations perpendicular to the raphe. This contrasts with the similar genus Pleurosigma, which has striations that lie diagonally to the raphe.
  
  ## Species
  
  Species:
  
  * Gyrosigma acuminatum (Kützing) Rabenhorst, 1853
  * Gyrosigma aestuarium Kisselev, 1925
  * Gyrosigma algoris J.R.Carter, 1981
  