Contributor: Loren Bahls - December 2013
Length Range: 18.1-48.2 µm
Striae in 10 µm: 6-8
Valves are cylindrical with a transversely undulate central area that occupies about half the valve diameter. One or two central fultoportulae are clearly visible in LM on the convex (raised) portion of the central area. The central area is otherwise colliculate with scattered nodules, or is unornamented. Striae are equal in length and multiseriate near the valve margins. Striae become uniseriate nearest to the valve center, where individual areolae are easily distinguished in LM.
Internally, alveoli are partially occluded by a central lamina, creating a distinct concentric ring (also called a shadow line) through the striae about one-third of the distance from the central area to the valve margin. Another concentric ring near the valve margin represents the distal internal occlusions of the alveoli (Håkansson 2002, Houk et al. 2010, Lowe 1981).
This page is dedicated to Rex Lowe on the occasion of his 70th birthday. Lowe published pioneering descriptions of the ultrastructure, ecology, and distribution of Cyclotella gamma over thirty years ago (Lowe 1981). More recently, Håkansson (2002) and Houk et al. (2010) have also published SEM descriptions and images. These images and descriptions were used above to describe features that cannot be seen in LM.
Basionym: Cyclotella gamma
Author: Sovereign 1963
Length Range: 18-33 µm
Striae in 10 µm: 5-7 alveoli ("costae")
Cells circular, drum-shaped, 18-33 µm in diameter. The marginal zone of the valves has radial costae on the inner side of the membrane (like Pinnularia) 5 to 7 in 10 µm; on the exterior of the membrane are radial rows of poroids upon the interior costae. Openings of the inner compartments of the costae form a small circular band crossing the costae. The median area is about half the diameter of the valve, is tangentially waved and one or more large pores are located at a distance from the center.
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.
Lowe, R.L. (1981). The frustular morphology and distribution of Cyclotella gamma Sov. (Bacillariophyceae). Proceedings of the Iowa Academy of Sciences 88: 82-84.
Sovereign, H.E. (1963). New and rare diatoms from Oregon and Washington. Proceedings of the California Academy of Sciences, series 4, 31(14): 349-368.
Cyclotella gamma is a resident of the benthos of shallow, weedy, mesotrophic lakes at lower elevations in the northern United States. It was described from a lake on Orcas Island, Washington (Sovereign 1963) and subsequently recorded from several lakes in Michigan (Lowe 1981). The specimens shown on this page are from three lakes in the Northern Continental Divide Ecoregion of Montana. The pH of these lakes ranges from 7.2 to 7.8 and specific conductance ranges from 250 to 332 µS/cm. Cyclotella gamma is probably much more widely distributed than these records indicate because it is often confused with C. meneghiniana.
Hidden Meadow Lake, Glacier National Park, Montana: home of Cyclotella gamma.