Montana Field Guide

Morphological Category – Symmetric biraphid

Valves lanceolate with capitate apices. Raphe slightly lateral, becoming filiform at the distal and proximal ends. Proximal raphe ends straight, not inflated. Axial Area narrow and linear, barely wider than the raphe, flaring slightly into the central area. Central Area a narrow stauros. Striae radiate throughout. Areolae fine, round to oblong, irregularly spaced, 20-26 in 10 µm.

Size Range
Length 34-52 µm. Width 8.1-10.3 µm. Striae in 10 µm 20-28.

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

Stauroneis kootenai may be distinguished from Stauroneis gracilior by the lack of hyaline areas adjacent to the stauros. It differs from Stauroneis pikuni by having more robust valves and a smaller size. Stauroneis bryocola has rostrate apices. Stauroneis neohyalina has linear-lanceolate valves, rostrate to subcapitate apices and much finer striae and areolae. Stauroneis schroederi has very narrow rostrate to subcapitate apices.

Pools and marshes in the mountains (Bahls 2021).

Cold, circumneutral waters with low nutrients and conductivity (Bahls 2021).

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.