Schoeman 1969 Category: Symmetrical biraphid
BASIONYM: Navicula libonensis Schoeman 1970
Contributor: Marina Potapova - February 2011
Length Range: 27-35 µm
Width Range: 5.9-7.0 µm
Striae in 10 µm: 12-13
Valves are lanceolate with rounded or very slightly drawn-out ends. The axial area is narrow and linear. The central area is transversely elliptical or irregular-rectangular, often slightly asymmetrical. The proximal raphe ends are straight, slightly expanded. Terminal raphe fissures are hooked towards the secondary side. The lineolate striae are radiate, becoming convergent at the valve apices, 12-13 in 10 µm. The areolae are easily observed under LM, 28-32 in 10 µm.
Note that this concept of Navicula libonenesis follows Lange-Bertalot (2001), but the type material of this species have not been photographed. Therefore it is not clear at present whether North American, European, and South African populations represent the same species.
Basionym: Navicula libonensis
Author: Schoeman 1970
Length Range: 24-32 µm
Width Range: 5-7 µm
Striae in 10 µm: 11-14
The valves are lanceolate with regularly rounded ends which are not produced, 24-32 μ long and 5-7 μ wide. The raphe is straight and filiform bending sharply near the poles towards the same side of the valvar margin; the terminal fissures were observed in only a few cases and appeared to run alongside the valvar margin, thus bending towards the valvar poles; the central poles are small but definite, fairly close together, The axial area is narrow and linear with definite polar areas, and widens into a central area due to the regular or irregular shortening of the central striae. The transapical striae are radial becoming parallel or convergent near the poles, 11-14 in 10 μ (13-14 in 10 μ near the poles of the valve), clearly lineolate. Lineolae form longitudinal striae, 28-30 in 10 μ.
Lange-Bertalot, H. (2001). Navicula sensu stricto, 10 genera separated from Navicula sensu lato, Frustulia. Diatoms of Europe 2: 1-526.
Schoeman, F.R. (1969). Diatoms from the Orange Free State (South Africa) and Lesotho. No. 2. Revista de Biologia 7(1-2):35-74,.
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.