(Ehrenberg) Hamilton 1992 Category: Araphid
BASIONYM: Fragilaria binodis Ehrenberg
Contributor: Eduardo Morales - October 2010
Length Range: 7-21 µm
Width Range: 4-6 µm
Striae in 10 µm: 13-16
Valves are biundulate in larger specimens and lanceolate to cruciform in smaller ones, 4-6 µm wide and 7-21 µm long. Valves with rostrate to subcapitate ends. The central margin is constricted in larger specimens or inflated in smaller specimens. The valve face is flat, or slightly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. The abvalvar edge of mantle is parallel to the valve face/mantle junction. In girdle view, frustules are rectangular. Cells form ribbon-like colonies joined by linking spines. One frustule within a colony is attached to the substratum by a mucilage pad. Cells may also be planktonic. The axial area is broad and linear or slightly lanceolate. The striae are distinct, alternate, and composed of lineolae which decrease in size from the valve face/mantle edge to both the central sternum and the valve mantle; 13-16 in 10 µm. Lineolae bear finely branched volae. The striae are parallel to radiate in the central area. Near the valve ends, the striae are slightly radiate to parallel. Striae extend deep onto the valve mantle. Costae are broad. Spines are spatulate, hollow and some possess terminal digitations that attach to neighboring valve lineolae. Spines are present along the valve face edge, except at the apices, and always located on the costae between striae. Well-developed, ocellulimbus type, apical pore ﬁelds with round poroids are present. Apical pore fields are located on the valve mantle. Rimoportula are absent. Scab-like structures, or blisters, are present along the abvalvar side of valve mantle. Copulae lack perforations. Valvocopulae wider than copulae.
Basionym: Fragilaria binodis
Length Range: µm
Striae in 10 µm:
Sr. construens, testula minima laevis, angulis productis subaequalibus.
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.
Ehrenberg, C.G. (1854). Mikrogeologie. Einundvierzig Tafeln mit über viertausend grossentheils colorirten Figuren, Gezeichnet vom Verfasser. Voss, Leipzig., Pl. 5, II, fig. 23 (iconotype).
Hamilton, P.B., Poulin, M., Charles, D.F., and Angell, M. (1992). Americanarum Diatomarum Exsiccata: CANA, Voucher Slides from Eight Acidic Lakes in Northeastern North America. Diatom Research 7(1):25-36.
Cells form ribbon-like colonies.
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.