(Thwaites) De Toni 1891 Category: Symmetrical biraphid
BASIONYM: Schizonema vulgare Thwaites 1848
Valves are linear-lanceolate-rhomboid with rostrate and rounded apices. Areolae are round or oval and form transverse striae that are radiate at the center of the valve and slightly or strongly convergent near the apices. Striae are circumradiate about the apices. In SEM, a single row of isolated areolae next to either side of the raphe forms a continuous line. This line of areolae forms a boundary to the axial area and ovoid central area. The raphe branches are slightly curved. Internal, longitudinal ribs are parallel to the raphe. The longitudinal ribs fuse with the helictoglossae to form a porte-crayon structure, but are incomplete at the central nodule. The central nodule is relatively flat as compared to other Frustulia species. In SEM, the external proximal and distal raphe ends form a small Y-shape.
Basionym: Schizonema vulgare
Author: Thwaites 1848
Length Range: µm
Striae in 10 µm:
De Toni, G.B. (1891). Sylloge algarum omnium hucusque cognitarum. Vol. II. Bacillarieae; sectio I. Raphideae. Typis Seminarrii, Patavii.
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.