Sovereign 1963 Category: Asymmetrical biraphid
BASIONYM: Cymbella rainierensis Sovereign 1963
REPORTED AS: Cymbella rainierensis (Patrick & Reimer 1975, p. 31, plate 4, fig. 8) | Cymbopleura subaustriaca (Zimmermann et al. 2010, p. 50, plate 63, figs. 8-11)
GENUS CONSIDERED: Cymbopleura
Contributor: Loren Bahls - September 2012
Length Range: 44-82 µm
Width Range: 13.2-16.4 µm
Striae in 10 µm: 8-11 at the valve center, 13-15 near the apices
Valves are lanceolate and slightly dorsiventral with weakly protracted rostrate or apiculate apices. The axial area is narrow and positioned near the central apical axis. The central area is approximately half the width of the valve and rounded rhomboid in shape. The raphe is straight and lateral, becoming filiform at the proximal and distal ends. Proximal raphe ends are displaced ventrally, with slightly expanded ends that are indistinctly hooked toward the ventral side. Distal raphe ends are comma shaped and dorsally deflected. Striae are radiate throughout and indistinctly punctate. In most populations, areola density is 28-34 in 10 µm, although one population had an areola density of 20- 24 in 10 µm.
This species has the characteristics of Cymbopleura and should be considered for transfer to that genus.
Basionym: Cymbella rainierensis
Author: Sovereign 1963
Length Range: 42-79 µm
Width Range: 13-16 µm
Striae in 10 µm: 9-11 in the middle, closer at the ends
Valves naviculoid, almost symmetrical in outline, lanceolate with rounded ends, 42-79 µm long by 13-16 µm wide. Raphe straight, almost on the median line. Axial area narrow lanceolate, central area rhomboidal. Striae lightly radial, at the middle 9 to 11 in 10 µm, closer at the ends, finely lineolate.
Foged, N. (1981). Diatoms in Alaska. Bibliotheca Phycologica, Band 53, J. Cramer, Vaduz, 317 pp.
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.
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.
Zimmermann, C., Poulin, M. and Pienitz, R. (2010). Diatoms of North America: The Pliocene-Pleistocene freshwater flora of Bylot Island, Nunavut, Canadian High Arctic. Iconographia Diatomologica (H. Lange-Bertalot, ed.), Volume 21, A.R.G. Gantner Verlag K.G., Ruggell, 407 pp.
Cymbella rainierensis has been recorded from several lakes, ponds and fens in Glacier National Park, Montana. In these waters it prefers circumneutral pH with low specific conductance. The type locality is Mowich Lake in Mount Rainier National Park, where pH measured 5.8 to 7.2. Sovereign (1963) reports that it is also found in over a dozen high mountain lakes in the Mount Rainier area. In the Montana Diatom Collection, we have two records from Mount Rainier National Park: Dewey Lake and a small pond near Dewey Lake. Zimmermann et al. (2010) reported this species (as Cymbopleura subaustriaca) from the Canadian High Arctic. Foged (1981) reported it from Alaska.
Frog pond near Dewey Lake, Mount Rainier National Park, Washington, home of Cymbella rainierensis.
Credit/Source: Ryan Davis, Adventurers and Scientists for Conservation