Montana Field Guide

Morphological Category – Symmetric biraphid

Valves lanceolate with subtly protracted, broadly rounded apices. A shallow pseudoseptum occupies each apex. Axial Area wide, about twice the width of the raphe. Central Stauros wide, bow-tie shaped. Raphe lateral, becoming thread-like at the proximal and distal ends. Proximal raphe ends strongly hooked and tipped with inflated pores. Distal raphe ends curved to one side. Areolae distinct, 13-19 in 10 µm, becoming larger and more distant near the valve margins.

Size Range
Length 70-100 µm. Width 17-20 µm. Striae in 10 µm 14-18.

TAXONOMY & NOMENCLATURE
Stauroneis superhyperborea was originally described in 2004 based on a specimen from Greenland and given the name of Stauroneis obtusa var. lapponica (Bahls 2021).

Useful Link:
Diatom Glossary [Diatoms of North America website]

Stauroneis superhyperborea is distinguished from S. hyperborea and S. subhyperborea by its larger size, wider apices, and more strongly hooked proximal raphe ends.

Subalpine lake in the mountains of northwest Montana and a tundra pool in subarctic Canada (Bahls 2021).

Cool, alkaline waters with low nutrients and conductance (Bahls 2021).

Water Chemistry
pH in Upper Wolverine Lake measured 8.83 and conductance measured 107 µS/cm.

Diatoms typically reproduce by cell division (mitosis) and occasionally by meiosis—sexual reproduction in which female and male gametes combine to form a specialized zygote called an auxospore. Repeated divisions result in cells of a population becoming progressively smaller and smaller. When cells reach a critically small size, sexual reproduction is initiated, resulting in an auxospore and initial cells that are the largest attainable for the species, after which cell division and size reduction resume (Amato 2010).

Climate change and regional warming.