(Kützing) Petersen 1938 Category: Araphid
BASIONYM: Exilaria vaucheriae Kützing 1833
REPORTED AS: Synedra socia (Patrick and Reimer 1966)
Contributor: Eduardo Morales - October 2010
Length Range: 6–30 µm
Width Range: 4-5 µm
Striae in 10 µm: 14-16
Valves are linear and narrow, 4-5 µm wide and 14-31 µm long. Valves with rostrate to subcapitate ends. The central margin is unilaterally expanded. Valve face flat, or slightly undulate due to raised costae. The valve face mantle junction forms a sharp angle. In girdle view, frustules are rectangular and form ribbon-like colonies, joined by linking spines. The colonies are attached to the substratum at one end, by a frustule attached by a mucilage pad, or planktonic. The central area clear across the valve in large specimens or a one-sided clear area in medium-sized to small specimens. Ghost striae may be present in the central area devoid of ornamentation. The striae are distinct and composed of long lineolae giving the impression of thick striae, 14-16 in 10 µm, and the costae are broad. The lineolae bear finely branched volae. The striae are mostly parallel, to slightly radiate toward the valve ends. Striae alternate. Striae extend onto the valve mantle, interrupted by spines at the valve face/mantle junction. The spines are spatulate, fine and delicate. They are present along the valve face edge, except at the apices. The spines may be absent, especially in small specimens. Well-developed, ocellulimbus type, apical pore ﬁelds with round poroids are present. A single rimoportula is present on each valve, aligned with the first stria at the valve face apex. The rimoportula is located on, or just off the central sternum, and is parallel or slightly inclined in a counterclockwise fashion with respect to the transapical axis. Scab-like structures, or blisters, are present along the abvalvar portion of the mantle. Copulae, or girdle bands, bear small, unoccluded perforations located just beneath the previous girdle element’s abvalvar edge. Plastids are unknown.
Researchers in North America may have also referred this taxon (especially individual valves) to Synedra socia Wallace based on treatment of this taxon in Patrick and Reimer (1966). Additional study is needed to determine the relationship of S. socia to F. vaucheriae. Several described varieties of Fragilaria capucina with thickened and expanded central areas also deserve closer scrutiny.
Basionym: Exilaria vaucheriae
Author: Kützing 1833
Length Range: µm
Striae in 10 µm:
Frustulis aut solitariis aut fasciculatis, minutissimus, linearibus, utrinque obtusis, altero latere apicem versus subattenuatis et rotundato-obtusis, viridi-lutescentibus et maculatis.
Kützing, F.T. (1833). Algarum aquae dulcis Germanicarum. Decas III. Collegit Fridericus Traugott Kutzing, Cocit. Bot. Ratisbon. Sodalis. Halis Saxonum in Commissis C.A. Schwetschkii et Fil.; p. 3, fig. 24.
Petersen, J.B. (1938). Fragilaria intermedia-Synedra vaucheriae. Botaniska Notiser 1938(1-3):164-170.
Benthic, forming palisade colonies attached to substratum by one end, or attached singly to substratum by a mucilage pad.
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.