Van de Vijver and Lange-Bertalot 2004 Category: Symmetrical biraphid
BASIONYM: Stauroneis acidoclinatopsis Van de Vijver and Lange-Bertalot 2004
REPORTED AS: Stauroneis anceps (Krammer and Lange-Bertalot 1986)
Contributor: Loren Bahls - December 2011
Length Range: 57-61 µm
Width Range: 10-12 µm
Striae in 10 µm: 23-25
Valves are linear-lanceolate with abruptly protracted, capitate apices. The axial area is narrow, becoming more narrow near the valve ends. It is slightly wider near the central area, a rectangular stauros. External raphe fissures are weakly lateral and nearly straight. Proximal raphe ends are weakly curved and slightly expanded. Striae are gently radiate near the valve middle, becoming more strongly radiate towards the apices. Areolae are easily distinguished in LM and number 24–28 in 10 µm.
Basionym: Stauroneis acidoclinatopsis
Author: Van de Vijver and Lange-Bertalot 2004
Length Range: 50-54 µm
Width Range: 9-10 µm
Striae in 10 µm: 24-27
Valves linear to linear-lanceolate with broadly rounded, abruptly protracted ends. Length 50-54 µm, breadth 9-10 µm. Pseudosepta absent. Axial area fairly narrow, linear, slightly widening towards the central area. Central area forming an almost rectangular fascia, hardly expanded towards the margins. Raphe fissures almost straight, slightly lateral. Central raphe pores very weakly curved, slightly expanded. Striae weakly radiate in the middle, becoming more radiate towards the ends, 24-27 in 10 µm. Puncta of the striae easily discernible in LM, 23-26 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.
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 acidoclinatopsis has been recorded from five lakes and wetlands in the Northern Rockies, where it prefers circumneutral waters of low conductance. These waters have a pH range of 5.5 to 8.5 and a conductivity range of 10 to 257 µS/cm. This species was described from material collected at Qeqertarsuaq, West Greenland (69 degrees north latitude), where it was found in a small shallow pool with slightly acid water (pH 6.0), low conductance (<50 µS/cm), and very low nutrient levels (Van de Vijver et al. 2004).
Drosera Fen, Indian Meadows Research Natural Area, Helena National Forest, Montana: home of Stauroneis acidoclinatopsis.
Credit/Source: Loren Bahls