(Grunow) Krammer 1991 Category: Centric
BASIONYM: Melosira distans var. alpigena Grunow in Van Heurck 1882
REPORTED AS: Aulacoseira distans var. septentrionalis (Camburn & Charles 2000)
Contributor: Marina Potapova - May 2009
Length Range: 4-15 µm
Width Range: 4-7 µm
Striae in 10 µm: 15-22
Frustules are cylindrical and 4-15 µm in diameter, with a mantle height of 4-7 µm. The ratio of the mantle height to valve diameter is less than 1. The mantle has convex sides and the valve face is flat. Rows of pervalvar areolae are curved to the right (dextrorse) and number 15-22 in 10 µm. The valve face is unornamented except for one row of marginal areolae. Spines are located at the end of each pervalvar costa. Spines are thin and have an ‘anchor’ shape at the end. The ringleiste is small.
Some valves of A. alpigena have almost straight rows of mantle areolae that also may be almost parallel to the pervalvar axis. Such specimens have been often misidentified as A. distans (Ehrenberg) Simonsen. Crawford and Likhoshway (1999) examined the type material of A. distans and showed that it is characterized by numerous rimportulae that internally form short tubes, situated close to a very deep ringleiste. These rimportulae are easily observed in LM in valve views. A. alpigena does not have such prominent and numerous rimoportulae and differs from A. distans also by having higher density of mantle areolae, shallow ringleiste, and plain valve face.
Basionym: Melosira distans var. alpigena
Author: Grunow in Van Heurck 1882
Length Range: µm
Striae in 10 µm:
Krammer, K. (1991). Morphology and taxonomy of some taxa in the genus Aulacoseira Thwaites (Bacillariophyceae). I. Aulacoseira distans and similar taxa. Nova Hedwigia 52(1-2):89-112.
The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.
Results are published in:
Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.
Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.
Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.