Krammer 2002 Category: Asymmetrical biraphid
BASIONYM: Cymbella neocistula var. islandica Krammer 2002
REPORTED AS: Cymbella cistula var. gibbosa (Patrick and Reimer 1975, p. 63, Plate 11, Figs 5-7)
Contributor: Loren Bahls - June 2016
Length Range: 44-109 µm
Width Range: 13.5-26.0 µm
Striae in 10 µm: 8-11
Valves are dorsiventral, with broadly rounded apices. The dorsal margin is strongly arched. In larger valves, the ventral margin is concave with a distinctly gibbous center. In smaller valves, the ventral margin is somewhat convex to nearly flat. The axial area located just ventral to the valve mid line. The central area is small and elliptic. The raphe is lateral, becoming reverse-lateral near the proximal ends. Proximal raphe ends are deflected ventrally and terminate in slightly expanded pores. Three to seven stigmata are present on the ventral side of the central area. Striae are radiate throughout. Areolae are distinct in LM and number 16-21 in 10 µm.
Patrick and Reimer (1975) report similar specimens from Lake Michigan (pl. 11, figs 5-7) as Cymbella cistula var. gibbosa. That taxon was described by Brun (1895) from Lake Geneva, Switzerland and was later elevated to species rank (Meister 1912) as Cymbella gibbosa. That name, however, is a later homonym of a species described by Pantocsek (1901). Krammer (2002, p. 79) proposed that the Brun taxon represents initial cells of C. cymbiformis and is not related to C. cistula. We therefore conclude that the specimens shown here from Montana, and those reported by Patrick and Reimer from Lake Michigan probably belong to C. neocistula var. islandica and not to the Brun taxon.
Reimer comments that stigmata may also be present on the dorsal side of the central area, and that valves may be up to 26 µm wide (Patrick and Reimer 1975, p. 63).
Basionym: Cymbella neocistula var. islandica
Author: Krammer 2002
Length Range: 64-114 µm
Width Range: 19-23 µm
Striae in 10 µm: 9-11
Breadth larger [than the nominate variety], puncta coarser and more striae/10 µm. Length 64-114 µm, breadth 19-23 µm, striae 9-11/10 µm, puncta 13-16/10 µm.
Brun, J. (1895). Diatomées Miocènes. Le Diatomiste 2 (24): 229-247.
Krammer, K. (2002). The genus Cymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 3: 1-584.
Meister, F. (1912). Die Kieselalgen der Schweiz. Beiträge zur Kryptogamenflora der Schweiz, 4/1, 1–254.
Pantocsek, J. (1902). Kieselalgen oder Bacillarien des Balaton. Resultate der Wissenschaftlichen Erforschung des Balatonsees, herausgegeben von der Balatonsee-Commission der Ung. Geographischen Gesellschaft. Commissionsverlag von Ed. Hölzel. Wien. 2(2): 112 pp., 17 pls.
Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.
This taxon is less widely distributed than C. neocistula. It has been collected from several lakes in Glacier National Park, Montana, including Lake Josephine in the Many Glacier area (photo below). In these lakes pH ranges from 7.59 to 8.04 and specific conductance ranges from 94 to 129 µS/cm. Patrick and Reimer (1975) illustrate similar specimens from Lake Michigan (Pl. 11, Figs 5-7). Krammer (2002) reports this taxon from Iceland and other nordic and subarctic regions, in oligotrophic waters with lower electrolyte content.
Lake Josephine, Glacier National Park, Montana: home of Cymbella neocistula var. islandica
Credit/Source: Loren Bahls