(Grunow) Lemmermann 1900 Category: Centric
BASIONYM: Cyclotella comta var. radiosa Grunow in Van Heurck 1882
SYNONYM(S): Cyclotella radiosa (Grunow in Van Heurck) Lemmermann
REPORTED AS: Puncticulata radiosa (Tanaka 2007, p. 45, plates 60-63)
Contributor: Loren Bahls - December 2013
Length Range: 10.9-23.8 µm
Striae in 10 µm: 14-18
Cells are cylindrical with shallow mantles. The valve face is concentrically undulate, with a marginal ring of striae that occupy slightly more than one-half of the valve diameter. At the center of the valve, coarse areolae of equal size are arranged in a radiate pattern. One to several areolae are scattered in the clear area at the center of the valve. The marginal striae are slightly unequal in length. Every fourth or fifth interstria, also called a costa, is thickened. These thickened costae appear in LM as shadow lines, or Schattenlinien, which number about 4 in 10 µm.
Håkansson (2002), Houk et al. (2010) and Tanaka (2007) published SEM images and written observations of this taxon, although they are not of North American specimens. External views show a concentrically undulate and radially wrinkled valve face. The slightly convex central area is surrounded by a shallow depression. Radial lines of areolae and central fultoportulae lie in grooves separated by low ridges, on which small granulae are scattered or also arranged in radial lines. At least one rimoportula opens to the outside at the end of a shortened stria. The striated marginal area consists of multiseriate striae that continue onto the mantle. Areolae in the striae are much finer than those in the central area. A ring of marginal fultoportulae occurs at the junction of the valve face and mantle.
Internally, striae are expressed as short, oblong alveoli separated by costae. The costae are sometimes divided, with every fourth or fifth costa is thickened and bearing a marginal fultoportula. The marginal fultoportula consists of a short tube with two lateral satellite pores. At least one rimoportula with is located between the central area and the marginal alveoli. The central area is concentrically undulate with areolae and several central fultoportulae arranged in radial rows. Each central areola is covered with a domed cribrum. Central fultoportulae consist of a short tube surrounded by three satellite pores.
Basionym: Cyclotella comta var. radiosa
Author: Grunow in Van Heurck 1882
Length Range: µm
Striae in 10 µm:
Ellis, B.K., Stanford, J.A., Craft, J.A., Chess, D.W., Hauer, F.R. and Whited, D.C. (2002). Plankton communities of alpine and subalpine lakes in Glacier National Park, Montana, U.S.A., 1984-1990. Verh. Internat. Verein. Limnol. 28:1542-1550.
Håkansson, H. (2002). A compilation and evaluation of species in the genera Stephanodiscus, Cyclostephanos and Cyclotella with a new genus in the family Stephanodiscaceae. Diatom Research 17: 1-139.
Houk, V., Klee, R. and Tanaka, H. (2010). Atlas of freshwater centric diatoms with a brief key and descriptions, Part III. Stephanodiscaceae A. Cyclotella, Tertiarius, Discostella. Fottea 10 (Supplement): 1-498.
Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.
Lemmerman, E. (1900). Beiträge zur Kenntnis der Planktonalgen. III. Neue Schwebalgen aus der Umgegend von Berlin. Bericht der Deutschen Botanischen Gessellschaft 18: 24-32.
Tanaka, H. (2007). Taxonomic studies of the genera Cyclotella (Kützing) Brébisson, Discostella Houk et Klee, and Puncticulata Håkanson in the family Stephanodiscaceae Glezer et Makarova (Bacilariophyta) in Japan. Bibliotheca Diatomologica 53: 1-205.
Van Heurck, H. (1880). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers.
Cyclotella radiosa is a planktonic diatom of the pelagic zone of oligotrophic to mesotrophic alpine and subalpine lakes. It was described from Lake Mondsee in Austria and has since been reported from several lakes in Germany and from a lake in the High Tetras of Slovakia (Houk et al. 2010). Tanaka (2007) reported C. radiosa as living in Lake Biwa, Japan, and from fossil deposits in Japan. The specimens shown here were collected from two high elevation lakes in Glacier National Park, Montana (Ellis et al. 2002). Beaver Woman Lake (elev. 1789 m) has a pH of 7.77, a conductivity of 83 µS/cm, total phosphorus of 4.1 µg/L, and total nitrogen of 67 µg/L; Stoney Indian Lake (elev. 1928 m) has a pH of 7.96, a conductivity of 126 µS/cm, total phosphorus of 5.9 µg/L, and total nitrogen of 65 µg/L. Values for other chemical variables are provided by Ellis et al. (2002).
Beaver Woman Lake, Glacier National Park, Montana: home of Cyclotella radiosa.