Montana Field Guide

Morphological Category – Symmetric biraphid

Valves linear-lanceolate with protracted and narrowly rostrate to subcapitate apices. Raphe weakly lateral, becoming filiform at the distal and proximal ends. Proximal raphe ends small and straight, not inflated. Axial Area narrow, barely wider than the raphe, flaring slightly at the stauros. Central Area a rectangular stauros, often asymmetric and slightly wider at valve margins. Striae radiate throughout. Short striae are sometimes present at the margins of the stauros. Areolae irregularly spaced and difficult to resolve in LM.

Length: 30-54 µm. Width: 6.0-9.0 µm. Striae in 10 µm: 32-40.

Stauroneis bryocola has lanceolate valves with subtly protracted and broadly rounded apices. Stauroneis gracilior, S. kootenai, and S. pikuni have lanceolate valves with capitate apices and a lower stria and areola density (less than 30 in 10 µm). Stauroneis schroederi has lanceolate valves with gradually attenuated apices and striae and areolae less than 30 in 10 µm.

Small lakes and wetlands.

In Montana waters where S. neohyalina is found, pH ranges from 6.2 to 7.6 and specific conductance ranges from 8 to 109 µS/cm. Lange-Bertalot & Metzeltin (1996) reported this species from an electrolyte-poor, humic-rich lake in Finland. Siver et al. (2005) reported this species (as Stauroneis gracilior) from somewhat acidic ponds on Cape Cod, Massachusetts.

GENERAL LIFE CYCLE
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 is a threat to S. neohyalina.