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A Diatom - Stauroneis akamina
General Description
Morphological Category – Symmetric biraphid
Valves rhomboid-lanceolate with rostrate to subcapitate apices.
Raphe fissures lateral, narrowing centrally. Proximal raphe ends nearly straight with unexpanded pores. Terminal raphe fissures curved, opening towards the secondary side.
Axial Area narrow and linear, widening slightly near the stauros.
Stauros typically narrower towards the valve margin, but may be rectangular in some specimens. Occasionally, short striae are present in the central area.
Striae convergent or parallel at the center, becoming radiate towards the apices.
Areolae elongate and often irregularly spaced, 16-24 in 10 µm.
Size RangeLength 63-140 µm.
Width 16-24 µm.
Striae in 10 µm 16-22.
Useful Link:
Diatom Glossary [Diatoms of North America website]
Diagnostic Characteristics
Stauroneis akamina belongs to a group of medium to large Stauroneis species with oblong areolae that are often irregularly spaced. It differs from S. nobilis by its smooth valve outline and smaller size. Stauroneis alabamae is larger and has a lower stria density. Stauroneis margaritorae is shorter (60-90 µm) with narrower valves (13-16 µm). Stauroneis nobilis var. minima has smaller valves with narrower apices. Stauroneis baconiana has linear valves that are much narrower.
Range Comments
Northern Rocky Mountains: Alberta, Idaho, Montana, Oregon.
Type Locality
Akamina Pools, Waterton Lakes National Park, Alberta, Canada.
Number of Observations in Montana Diatom Collection Database (Bahls 1968-2019): 16;
Montana: 12
Habitat
Pools, ponds and fens in the mountains.
Ecology
Cold, circumneutral waters with low conductivity and nutrients (Bahls 2021).
Water Chemistry
Stauroneis akamina is known from pools in Waterton Lakes National Park, from ponds and fens in Glacier National Park, and wetlands in southwestern Montana. pH of these waters ranges from 6.0 to 7.3 and specific conductance ranges from 25 to 71 µS/cm.
Reproductive Characteristics
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).
Stewardship Responsibility
Threats or Limiting Factors
Stauroneis akamina is at moderate risk of extirpation from Montana as a result of climate change and regional warming (Bahls 2018).
References
- Literature Cited AboveLegend:
View Online Publication
Amato, A. 2010. Diatom reproductive biology: living in a crystal cage. The International Journal of Plant Reproductive Biology 2(1): 1-10.- Bahls, L. 2018. Potential loss of cold-water stenothermal diatoms (Bacillariophyta) from their southern refugia in the western United States. Diatom Research 32: 483-494.
- Bahls, Loren. 1968-Present. Montana Diatom Collection Database. Missoula, Montana.
- Bahls, Loren. 2021. Diatoms of Montana and Western North America: Catalog and Atlas of Species in the Montana Diatom Collection Volume 1. The Academy of Natural Sciences of Philadelphia Special Publication 24. 508pp.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Bahls, Loren. 2023. Diatoms of Montana and western North America: Catalog and atlas of species in the Montana diatom collection Volume 2. The Academy of Natural Sciences of Philadelphia Special Publication 27. 600pp.
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