Decussata placenta
(Ehrenberg) Lange-Bertalot and Metzeltin in Lange-Bertalot 2000 Category: Symmetrical biraphid
BASIONYM: Navicula placenta Ehrenberg 1854
LM scalebar = 10 µm = 40 pixels.
Observations
Contributor: Pat Kociolek - January 2011
Length Range: 24-50 µm
Width Range: 13-18 µm
Striae in 10 µm: 22-27
Description
Valves are elliptical with rostrate to rostrate-apiculate to capitate-apiculate apices. The axial area is narrow, expanded at the center to form a transapically oval to circular central area. The raphe is filiform, straight to slightly undulate, with prominent, dilated external proximal raphe ends. Areolae from neighboring striae are slightly offset, producing a quincunx pattern; areolae are circular. Striae are arranged in three patterns: radiate and two crossing oblique patterns.
This is a distinctive species. Our observations expand the size range of this taxon beyond that reported by Patrick & Reimer (1966), although the valve apices are typically more capitate-apiculate than the illustrated population (Edlund et al. 2006).
Original Description
Basionym: Navicula placenta
Author: Ehrenberg 1854
Length Range: µm
Striae in 10 µm:
Original Description
Original Images
Cite This Page:
Kociolek, P. (2011). Decussata placenta. In Diatoms of the United States. Retrieved June 19, 2013, from http://westerndiatoms.colorado.edu/taxa/species/decussata_placenta
Species: Decussata placenta
Contributor: Pat Kociolek
Reviewer: Mark Edlund
Image Credit: Pat Kociolek
- Axial area narrow
- Proximal raphe ends prominent
- Areaolae slightly offset
Valves elliptical with rostrate to rostrate-apiculate apicies. Axial area narrow, expanded at the center to form a circular central area. The raphe is filiform and straight to slightly undulate, with prominent, dilated external proximal raphe ends. Areolae from neighboring striae slightly offset, producing a quincunx pattern.
Compare
This uniquely shaped and structured species is not easily confused with other species.
Citations
Edlund, M.B., Brant, L.A., Levkov, Z. and Nakov, T. (2006). An emended description of Decussata (Patrick) Lange-Bertalot & Metzeltin that includes protoplast organization and detailed valve and cingulum ultrastructure. Diatom Research 21: 269-280.
Krammer, K. and Lange-Bertalot, H. (1986). Bacillariophyceae. 1. Teil: Naviculaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Susswasserflora von Mitteleuropa, Band 2/1. Gustav Fisher Verlag, Jena. 876 pp.
Lange-Bertalot, H. (2000). Transfer to the generic rank of Decussata Patrick as a subgenus of Navicula Bory. Iconographia Diatomologica 9: 670-673.
Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.
Links & ID's
Index Nominum Algarum (INA)
California Academy of Sciences (CAS)
North American Diatom Ecological Database (NADED)
NADED ID: 219001
Autecology Discussion
Widely distributed, found commonly in aerophilous conditions
EMAP Assessment
Sampling for 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). Streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming). Over 1200 sites on 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.
EMAP Distribution
Decussata placenta
Distribution
The distribution map represents the relative abundance of this Decussata placenta in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Decussata placenta was not recorded, or with a red circle indicating the relative abundance of Decussata placenta.
Note that the size of the proportional symbols varies between species to help show both abundant and rare species.
Scale for the map to the left
EMAP Response Plots
Decussata placenta
EMAP citations
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.