Stephanodiscus reimeri

E.C.Ther. and Stoermer 1992      Category: Centric

Stephanodiscus parvus


Stephanodiscus yellowstonensis

LM scalebar = 10 µm = 20 pixels.


Contributor: Phil Woods - June 2011
Diameter: 35-120 µm
Rows of areolae in 10 µm:


Valves disc-shaped and concentrically undulate with a convex, or concave, valve face. Valves are large and robust. Areolae are large, circular to trapezoidal to sub-hexagonal in shape, arranged in uniseriate rows in the valve center, and become fasciculate in the outer 2/3 of the valve radius. Areola foramina have a thick edge and internal domed cribra (SEM feature). Fascicles radiate from the valve center and are separated by hyaline interfascicular costae. Fascicles at the valve margins are biseriate, ending in two or more rarely three (four?) rows of areolae. Multiple fultoportulae are arranged in a loose ring in the valve center. Spines are located at the ends of every two to three costae just inside the valve face margin. A small fultoportula is positioned below each spine and above the valve margin.

Research indicates that this species is endemic, extant only in demonstrably marginal habitats, and that its morphology is highly autapomorphic (Theriot, 1992). However, the species is also found in close proximity to S. niagarae; it is highly probable that the two species are reproductively isolated and that S. reimeri occupies a unique sector of environmental space. More work is necessary to determine the origin and evolutionary histories of both S. niagarae and S. reimeri.

Original Description

Author: E.C.Ther. and Stoermer in E.C.Ther. 1992
Diameter: 30-120 µm
Rows of areolae in 10 µm: 8-12 parallel to a stria

Original Description

Valvae disciformes, diametris 30-120 /tim visis. Area centrali convexa aut concava. Areolae in fasciculis inter costas radiantes, 8-12 in 10 /tim par- allelae ad striam. Foramina externa et cribra interna. Spinae in annulo 3-8 /tm a margine locato. Rimopor- tulae 2-11 in annulo aliquantum ulterius quam annulus spinarum locatae. Fultoportulae in annulo in area centrali et 1 fultoportula inter omnem spinam et marginem.

Valves disc shaped, with diameters 30-120 µm observed. Central area convex or concave. Areolae in fascicles between radiating costae, 8-12 in 10 /µm parallel to a stria. Foramen external and cribra internal. Spines in a ring located 3-8 /µm from the margin. From 2 to 11 labiate processes located in a ring just outside the ring of spines. Strutted processes in a ring in the central area and one strutted process between each spine and the margin.

Original Images

Cite This Page:
Woods, P. (2011). Stephanodiscus reimeri. In Diatoms of the United States. Retrieved April 19, 2018, from

Species: Stephanodiscus reimeri

Contributor: Phil Woods

Reviewer: Mark Edlund


Theriot, E. (1992). Clusters, species concepts, and morphological evolution of diatoms. Systematic Biology 41: 141-157.

Theriot, E. and Stoermer, E.F. (1981). Some aspects of morphological variation in Stephanodiscus niagarae (Bacillariophyceae). Journal of Phycology 17: 64-72.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Stephanodiscus reimeri CAS

NCBI Genbank Taxonomy

Stephanodiscus reimerii NCBI

North American Diatom Ecological Database (NADED)


Autecology Discussion

Stephanodiscus reimeri is thought to be restricted in distribution to West Lake Okoboji and the larger drainage system known as the “Iowa Great Lakes” (Theriot 1992, Theriot and Stoermer 1981). Live samples have been collected at Big Spirit Lake, MN and IA, and West Lake Okoboji, IA (Theriot, 1992).

In late May 2011, S. reimeri was found in Lazy Lagoon, a shallow eutrophic harbor connected to West Lake Okoboji, IA. Slides from the Iowa Lakeside Lab Herbarium include S. reimeri in planktonic, epiphytic, epipelic, and epilithic habitats of West Lake Okoboji. Stephanodiscus reimeri is considered tychoplanktonic, becoming resuspended into the water column during turnover in the spring/fall when the water column becomes unstratified. Most of the recent samples were collected using plankton nets, but other specimens have been retrieved from benthic collections after the large frustules settled on the lake bottom. Historically, abundant benthic populations are collected in West Lake Okoboji by the Iowa Lakeside Lab summer diatom class (Mark Edlund, pers. comm.).


Live Stephanodiscus reimeri collected from Lazy Lagoon with a 35 µm mesh plankton net.

Credit/Source: Phillip Woods

Separated Stephanodiscus reimeri valves.

Credit/Source: Phillip Woods

Live Stephanodiscus reimeri, girdle view.

Credit/Source: Phillip Woods

Lazy Lagoon, West Lake Okoboji, Dickinson Co., Iowa.

Credit/Source: Phillip Woods