Lange-Bertalot and Krammer 1999 Category: Symmetrical biraphid
BASIONYM: Stauroneis circumborealis Lange-Bertalot and Krammer 1999
Contributor: Loren Bahls - December 2011
Length Range: 81-148 µm
Width Range: 20-31 µm
Striae in 10 µm: 14-16
Valves are elliptic-lanceolate with short and broadly rounded apices. The axial area is wide, about one-fifth the width of the valve and 4-5 times wider than the raphe. The stauros is also wide and expands towards the valve margins. Short striae are often found at the margins of the stauros. The raphe is lateral and is strongly curved near the proximal ends. Central pores are large and tear drop shaped. Terminal raphe fissures are hooked towards the same side as the proximal ends. Striae are radiate throughout, more so near the apices. Areolae are distinct and number 15-18 in 10 µm.
Basionym: Stauroneis circumborealis
Author: Lange-Bertalot and Krammer 1999
Length Range: 70-130 µm
Width Range: 23-27 µm
Striae in 10 µm: 15-16
Valvae comparate late lanceolatae sive aliquantum elliptico-lanceolatae, in media parte paulatim denique magis attenuatae apicibus curte protractis et late rotundatis, pseudosepta semper absunt. Longitudo circiter 70-130 µm, latitudo 23-27 µm. Fissurae raphis valde laterales sitae inter se extremis centralibus distincte reverse-laterales poris centralibus unilateraliter declinatis. Area axialis satis lata sublinearis sed in media ramorum parum dilatata ad mediam valvae tamen non dilatata. Area centralis fasciam latam formans conspicue dilatata ad margines versus, ibi plerumque cum striis irregulariter abbreviatis. Striae transapicales radiatae in media parte et magis radiantes in partibus distalibus, 15-16 in 10 µm. Puncta striarum satis crassa apparentia, 14-16 in 10 µm.
Bahls, L. (2010). Stauroneis in the Northern Rockies: 50 species of Stauroneis sensu stricto from western Montana, northern Idaho, northeastern Washington and southwestern Alberta, including 16 species described as new. Northwest Diatoms, Volume 4. The Montana Diatom Collection, Helena, 172 pp.
Lange-Bertalot, H. and Genkal, S.I. (1999). Diatoms from Siberia I. Islands in the Arctic Ocean (Yugorsky-Shar Strait). Iconographia Diatomologica 6: 1-292.
Van de Vijver, B., Beyens, L. and Lange-Bertalot, H. (2004). The genus Stauroneis in Arctic and Antarctic Regions. Bibliotheca Diatomologica 50, 312 pp.
Stauroneis circumborealis is widely distributed in small lakes and ponds in the Northern Rockies. In these waters pH ranges from 6.0 to 7.6 and specific conductance ranges from 8 to 117 µS/cm. This taxon has also been reported from the Russian Arctic (Lange-Bertalot & Genkal 1999) and from the Zackenberg area of Greenland (Van de Vijver et al. 2004).
Paradise Pond, Glacier National Park, Montana: home of Stauroneis circumborealis
Credit/Source: Loren Bahls