(Ehrenberg) Williams and Round 1987 Category: Araphid
BASIONYM: Fragilaria pinnata Ehrenberg 1843
Contributor: Eduardo Morales - October 2010
Length Range: 4-10 µm
Width Range: 3-4 µm
Striae in 10 µm: 11-14
Valves are ovoid, 3-4 µm wide and 4-10 µm long with rounded ends. Valve face flat, or slightly undulate due to raised costae. In girdle view, frustules are rectangular and form ribbon-like colonies, joined by linking spines. Colonies are attached to the substratum at one end by a frustule with a a mucilage pad, or colonies may be planktonic. Axial area is linear to lanceolate. Striae are distinct, 11-14 in 10 µm. Lineolae are long forming wide striae . Striae vary from parallel in the valve center to radiate toward the valve ends. Striae extend onto the valve mantle. Costae are more slender than the striae. Spines are positioned on costae along the valve margin, except at the apices. Spines are conical at the base and spatulate towards the terminus. A single apical pore field with round poroids is present, displaced toward valve mantle. Girdle bands are open and do not bear perforations.
Samples collected from North America exhibit several morphological variants that are often included under the name Staurosirella pinnata. Since the type of this taxon has not been studied in detail, it is difficult to determine which of these variants corresponds to the “true” S. pinnata. We consider the specimens depicted in this page closely resemble the iconotype specimens presented by Ehrenberg (1843).
Basionym: Fragilaria pinnata
Author: Ehrenberg 1843
Length Range: µm
Striae in 10 µm:
F. pinnata, lineari-oblonga striis validis in 1/100 lin. 15, apicibus simpliciter rotundatis. Affinis striolatae et syricae. Icon!
Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.
Williams, D.M. and Round, F.E. (1987). Revision of the genus Fragilaria. Diatom Research 2: 267-288.
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.