Montana Field Guide

Morphological Category – Symmetric biraphid

Valves lanceolate with narrow rostrate apices. A pseudoseptum occupies both apices. Axial Area wide, about three times the width of the raphe. Central Stauros shaped like a bow tie. Raphe lateral, becoming thread-like near the proximal and distal ends. Proximal raphe ends bent to one side and tipped with inflated pores. Distal raphe ends curved to one side. Striae radiate throughout. Areolae distinct, 12-14 in 10 µm.

Size Range
Length 56-90 µm. Width 13-17 µm. Striae in 10 µm 16-18.

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

Distinguished from S. superhyperborea by its smaller size and narrower apices. Distinguished from S. subhyperborea by its more strongly curved proximal raphe ends, lower striae density and narrower apices.

Lakes on the subarctic tundra, Nunavut.

Cold, circumneutral waters with low pH and conductivity.

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).

In Canada, Stauroneis hyperborea is considered to be a rare to uncommon cold-water stenotherm that is threatened by climate change and regional warming (Bahls personal communication).