Jørgensen 1948 Category: Symmetrical biraphid
BASIONYM: Navicula leptostriata Jørgensen 1948
REPORTED AS: Navicula heimansii (Van Dam and Kooyman 1982)
Contributor: Loren Bahls - March 2012
Length Range: 33-39 µm
Width Range: 4.9-5.7 µm
Striae in 10 µm: 19-20
Valves are narrowly lanceolate with acutely rounded, subtly protracted apices. Valves are lightly silicified and features tend to be faint and difficult to resolve. The raphe is filiform. Proximal raphe ends are very close and deflected to the primary side. The axial area is very narrow. The central area is small, transversely widened, and asymmetrical with irregular borders. Striae are curved and strongly radiate near the valve middle, becoming strongly convergent near the apices. Areolae are very close together and cannot be distinguished in LM.
Basionym: Navicula leptostriata
Author: Jørgensen 1948
Length Range: 18.5-31.5 µm
Width Range: 4-5 µm
Striae in 10 µm: 20-23, 25 towards the apex
N. leptostriata nov. sp., pl. II, fig. 25. The frustule narrow lanceolate with slightly prominent ends. Length 18.5-31.5 µ, 4-5 µ. Axial area very narrow, central area small, round. Transversal striae very faint, radial, convergent towards the apex, 20-23 in 10 µ, 25 towards the apex.
Østrup (1910) found a species in Madum Sø which, on examining his original slide, I have convinced myself is identical with N. leptostriata. Østrup placed his find to N. nuda Pant. in Pantocsek 1886-93 II p. 51; table VI, fig. 108. In my opinion N. leptostriata has nothing to do with this one. N. nuda is somewhat larger, 37.5 µ long and 7 µ wide and lacks striae. The striae on N. leptostriata are very faint in styrax but more distinct in realgar. N. nuda is also stated as having been found in brackish water.
Dominant in Madum Sø, in smaller numbers in Skørsø, Grovsø and Øjesø. pH: 5.0-6.8, acidophilous.
Jørgenson, E.G. (1948). Diatom communities in some Danish lakes and ponds. Det Kongelige Danske Videnskabernes Selskab, Biologiske Shrifter 5(2): 1-140.
Navicula leptostriata has been recorded from eight streams and small lakes in the northern Rocky Mountains, where it is typically associated with Navicula notha. The mean pH at these locations is 7.5 and the mean specific conductance is 154 µS/cm.
Summit Lake, Waterton Lakes National Park, Alberta: home of Navicula leptostriata.
Credit/Source: Photo courtesy of Barb Johnston, Parks Canada.