(W. Smith) Krammer 2003 Category: Asymmetrical biraphid
BASIONYM: Navicula angustata W. Smith 1853
SYNONYM(S): Cymbella angustata (W. Smith) Cleve 1894
REPORTED AS: Cymbella angustata (Hustedt 1930, p. 351, fig. 639) | Cymbella angustata (Patrick & Reimer 1975, p. 22, plate 3, figs. 3-5)
Contributor: Loren Bahls - August 2012
Length Range: 33-42 µm
Width Range: 6.5-8.3 µm
Striae in 10 µm: 16-18 at the valve center, 18-20 at the valve ends
Valves are lanceolate, subtly triundulate, and very slightly dorsiventral. Apices are rostrate in small specimens and subcapitate in larger specimens. The axial area is narrow and slightly arched with the concave margin towards the ventral margin. The central area is small and asymmetric with irregular borders. The raphe is lateral and follows the arch of the axial area. Proximal raphe ends are close and filiform, displaced slightly to the ventral margin. Distal raphe fissures are comma-shaped and deflected dorsally. Striae are parallel at the valve center, becoming radiate and then strongly radiate towards the apices. Areolae in the striae are not easily distinguished in LM and number 30-35 in 10 µm.
Basionym: Navicula angustata
Author: W. Smith 1853
Length Range: µm
Striae in 10 µm:
Cleve, P.T. (1894). Synopsis of the Naviculoid Diatoms, Part I. Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2):1-194, 5 pls.
Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.
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.
Smith, W. (1853). Synopsis of British Diatomaceae. John Van Voorst, London 1853. 89 pp., pls 1-31.
Cymbopleura angustata is found infrequently in oligotrophic headwaters of the northern Rocky Mountains. These waters are circumneutral to alkaline (pH range: 6.98 to 9.10) with low to moderate levels of dissolved solids (specific conductance range: 71-460 µS/cm). Patrick and Reimer (1975) report this species from cool to cold water habitats in New England states, east central states, Iowa, Michigan, and Montana. Krammer (2003) reports it as widely distributed in oligotrophic waters with low to moderate electrolyte content in nordic, subarctic, and temperate regions, including the Alps.
Redrock Lake, Glacier National Park, Montana: home of Cymbopleura angustata.
Credit/Source: Loren Bahls