(Kützing) Brébisson 1838      Category: Centric
TYPE SPECIES: Cyclotella distinguenda Hustedt




Image Credit: Kalina Manoylov

CLASS: Coscinodiscophyceae
  ORDER: Thalassiosirales
    FAMILY: Stephanodiscaeae

  1. Valve with differential ornamentation between the central and marginal area
  2. Central area flat to tangentially undulate
  3. Single rimoportula - usually

Like the genera Cyclostephanos, Puncticulata and Discostella, the valve face of Cyclotella has differential ornamentation between the central and marginal areas. The central area of the valve face may be flat to tangentially undulate and smooth to colliculate. Valves usually have a single rimoportula. If a single rimoportula is present on the valve mantle, the valve face fultoportulae will be located on the opposite side of the central area. Numerous marginal fultoportulae are present.

Cyclostephanos, Puncticulata, and Discostella were recently separated from this group of diatoms. Still, features within the remaining species in Cyclotella are variable, indicating that the genus continues to be an unnatural group. That is, Cyclotella is not an evolutionary lineage, but represents a mixed grouping of taxa. Cyclotella is a genus that is recognized as an important environmental indicator, across a broad range of environments.

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

Contributor: Sarah Spaulding | Mark Edlund - December 2008


October 3rd, 2012 - Name of type species

The type of the genus Cyclotella is changed on this website from C. tecta (Kützing) Brébisson to C. distinguenda Hustedt based on the following:

In 1984, Håkansson and Ross recognized a nomenclatural problem and proposed that the name of the genus Cyclotella be conserved with Kützing’s material of “Frustulia operculata (C. Agardh) sensu Kütz Taennstaedt 1834” as the type. Because the name Cyclotella operculata was based on Rhopalodia, Håkansson and Ross had to propose a new name for Kützing’s “Frustulia operculata (C. Agardh) Kütz. sensu Taennstaedt 1834” and chose to recognize Kützing’s taxon as a new species: Cyclotella tecta Håkansson et Ross (1984) sp. nov. This proposal was approved by the IAPT (Greuter et al. 1988)

Håkansson (1989) next decided to investigate the type material with LM and SEM of several taxa that seemed related to their new C. tecta. In her 1989 analysis, she determined that C. tecta was a later synomym for a taxon that Hustedt described in 1927 from Lunz, Cyclotella distinguenda, that is, C. distinguenda was identical to C. tecta and clearly C. distinguenda was an earlier and validly published name.

So with that background, what is the type species of Cyclotella? Does it remain C. tecta based on Håkansson and Ross (1984) proposal for conservation that was accepted, or does the generitype switch to C. distinguenda because it is the earlier published name for C. tecta?

We propose that the correct generitype for Cyclotella is thus C. distinguenda Hustedt 1927 based on:

Cyclotella (Kütz.) Bréb. , Brebisson, A. de. 1838. Considerations sur les Diatomees. 20 pp. Falaise, Paris.. (nom. cons.) Typus: Cyclotella tecta Hakannson et Ross (typ. cons.). Currently accepted name for the type species: Cyclotella distinguenda Hustedt 1927

Genus conserved and type designated in: Håkansson and Ross (1984)

  • Mark Edlund