(Lund) Håkansson 2002 Category: Centric
BASIONYM: Cyclotella praetermissa Lund 1951
REPORTED AS: Puncticulata praetermissa (Tanaka 2007, p. 43, plates 56-59)
Contributor: Loren Bahls - December 2013
Length Range: 10.8-15.7 µm
Striae in 10 µm: 19-20
Cells are cylindrical with shallow mantles. The valve face is nearly flat, with a marginal ring of short striae and a central area of many scattered, uniform-sized and evenly-spaced areolae. The areolae may be arranged in a weakly radiate pattern in some specimens. The short marginal striae are slightly unequal in length and composed of very fine areolae. Every fourth or fifth costa is thickened. The costae appear in LM number about 5 in 10 µm.
Håkansson (2002), Houk et al. (2010), Krammer and Lange-Bertalot (1991) and Tanaka (2007) published SEM images and descriptions of P. praetermissa from regions outside of North American. External views show a domed central area, with external openings of areolae and central fultoportulae surrounded by a slight depression. Surrounding the central area are 1 to 5 rimoportula. The 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 and every fourth or fifth costa is thickened and bears a marginal fultoportula. The fultoportula which consist of a short tube with two lateral satellite pores. One to 5 rimoportulae are located between the central area and the marginal alveoli. The central area is concentrically undulate, with many areolae and central fultoportulae scattered or 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.
Note that stria density is variously reported in the literature as 15-18 in 10 µm (Houk et al. 2010), 13-15 in 10 µm (Håkansson 2002), and 13-19 in 10 µm (Krammer & Lange-Bertalot 1991). The stria density of Montana specimens ranges from 19 to 20 in 10 µm. This variability may be due, in part, to different measurement techniques employed by various investigators.
Basionym: Cyclotella praetermissa
Author: Lund 1951
Length Range: µm
Striae in 10 µm:
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.
Lund, J.W.G. (1951). Contributions to our knowledge of British Algae. XII. A new planktonic Cyclotella (C. praetermissa n. sp.): Notes on C. glomerata Bachmann and C. catenata Brun and the occurence of setae in the genus. Hydrobiologia 3(1): 93-100.
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.
Cyclotella praetermissa may occur as solitary cells or in short chains of 2-8 cells enclosed in a mucous sheath (Houk et al. 2010). The species was described from material collected at Blelham Tarn in the English Lake District (Lund 1951). Houk et al. (2010) report it from two oligotrophic/mesotrophic lakes in Germany, where it occurs in the plankton and the littoral zone. Tanaka (2007) reports C. praetermissa from several mesotrophic and eutrophic lakes and ponds in Japan. Specimens shown here are from Bowman Lake (photo below) and Kintla Lake in Glacier National Park, Montana. It has also been reported from Waterton Lake in the Waterton/Glacier International Peace Park. In these waters pH ranges from 8.25 to 8.53 and specific conductance from 122 to 149 µS/cm.
Bowman Lake, Glacier National Park, Montana: home of Cyclotella praetermissa.
Credit/Source: Loren Bahls