Lange-Bertalot in Rumrich et al. 2000 Category: Symmetrical biraphid
BASIONYM: Berkella linearis Ross and Sims 1978
REPORTED AS: Frustulia spicula var. alpina (Amossé 1972, p. 307, figs 23:2-6)
Contributor: Loren Bahls - February 2016
Length Range: 28-61 µm
Width Range: 5.8-8.3 µm
Striae in 10 µm: 30-34
Valves are linear, sometimes with undulate or slightly concave margins. The apices are rostrate to subrostrate. The central area is linear and elongate. Raphe branches are distinctly curved and bordered by longitudinal ribs that do not extend into the central area. Proximal ends of the longitudinal ribs are blunt; distal ends are narrow and indistinct. Striae are parallel at the valve center, slightly convergent towards the ends, and radiate around the apices. Areolae number 28-32 in 10 μm.
Basionym: Berkella linearis
Author: Ross and Sims 1978
Length Range: 27-48 µm
Width Range: 5-6.5 µm
Striae in 10 µm: about 30
Valve broadly linear, or with slightly concave margins, tapering towards the broad or slightly subcapitate obtuse apices, mantle shallow, 27-48 µm long, 5-6.5 µm broad. Central and axial areas forming a linear space, appearing slightly constricted at some levels of focus, and slightly narrowed towards the elliptical and slightly widened terminal areas. Striae parallel in the central part of the valve, slightly convergent in the distal parts, and radiating around the terminal nodules, about 30 in 10 µm; areolae about 30 in 10 µm, in irregular longitudinal rows that tend to be concave towards the branches of the raphe. Outer fissures of the raphe slightly reflexed at the centre and the apices, slightly widened at the centre to form a central pore on either side of which is a minute depression in the valve surface. Central nodule elongate-elliptic, occupying about half the width of the central area.
Lange-Bertalot, H. (2001). Navicula sensu stricto, 10 genera separated from Navicula sensu lato, Frustulia. Diatoms of Europe 2: 1-526.
Ross, R. and Sims, P.A. (1978). Notes on some diatoms from the Isle of Mull, and other Scottish localities. Bacillaria 1:151-168.
Rumrich, U., Lange-Bertalot, H. and Rumrich, M. (2000). Diatoms of the Andes. From Venezuela to Patagonia/Tierra del Fuego and two additional contributions. Lange-Bertalot, H. (ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 9. Phytogeography-Diversity-Taxonomy. Koeltz Scientific Books, Königstein, Germany, 9:673 pp.
There are four records of F. amosseana in the Montana Diatom Collection, two from streams, and one each from a fen and a pond. All of these waters are along the Rocky Mountain Front in north-central Montana and southwestern Alberta, Canada. The largest population was found in Pine Butte Fen (photos below). Pine Butte Fen is fed by the headwaters of the Teton River, which drain a region of limestone geology in the Bob Marshall Wilderness. Ross and Sims (1978) report this species from several waters in the U.K. with alkaline pH and moderate conductivity. Lange-Bertalot (2001) considers this species to be cosmopolitan, but infrequent, particularly in intermittent alkaline waters with higher electrolyte content.
Pine Butte Fen, Teton County, Montana, home of Frustulia amosseana. This view is looking east from the Rocky Mountain Front towards Pine Butte.
Credit/Source: Loren Bahls
Pine Butte Fen looking west from the top of Pine Butte towards Ear Mountain on the Rocky Mountain Front.
Credit/Source: Loren Bahls