Navicula gregaria
Donkin 1861 Category: Symmetrical biraphid
BASIONYM: Navicula gregaria Donkin 1861
LM scalebar = 10 µm = 80 pixels.
Observations
Contributor: Marina Potapova - February 2011
Length Range: 16-35 µm
Width Range: 4.1-7.0 µm
Striae in 10 µm: 14-18 in the center valve
Description
Valves are lanceolate with protracted apices. The axial area is narrow and straight. The central area is asymmetric and elliptical. The raphe is straight, with external proximal raphe ends sharply bent toward primary side of the valve. Striae are slightly radiate around the center, becoming parallel, then convergent at the apices. The areolae are clearly visible under LM, numbering 25-32 in 10 μm.
Note that the concept presented here is broad. Others (Lange-Bertalot 2001) report that two distinct morphologies are present on the original Donkin microslide. There is additional discussion on N. gregaria and N. supergregaria in Lange-Bertalot (2001, pg. 85-86, figs. 8-25).
Original Description
Basionym: Navicula gregaria
Author: Donkin 1861
Length Range: µm
Striae in 10 µm:
Original Description
Navicula gregaria, n. sp.-Form on S. V. broadly lanceolate, apiculate; striæ obscure.
Original Images
Cite This Page:
Potapova, M. (2011). Navicula gregaria. In Diatoms of the United States. Retrieved September 23, 2017, from http://westerndiatoms.colorado.edu/taxa/species/navicula_gregaria
Species: Navicula gregaria
Contributor: Marina Potapova
Reviewer: Mark Edlund
Image Credit: Marina Potapova
- Valves lanceolate with protracted apices
- Central area asymmetric
- External proximal raphe ends bent toward primary side
- Striae slightly radiate around the center
- Areolae clearly visible under LM
Valves are lanceolate with protracted apices, 4.1-7.0 µm wide. The central area is asymmetric and elliptic. The external proximal raphe ends are sharply bent toward primary side of the valve. Striae are slightly radiate around the center, numbering 14-18 in 10 µm and are convergent at the apices. The areolae are clearly visible under LM, numbering 25-32 in 10 μm.
Compare
Navicula gregaria is smaller than N. germainii and has distinct areolae. Navicula subrostellata possesses straight proximal raphe ends and a symmetric central area. Navicula canalis is more linear than N. gregaria, that is, it has a smaller length to width ratio. Nevertheless, small specimens of N. canalis may be confused with specimens of N. gregaria.
Navicula germainii
Navicula subrostellata
Navicula canalis
Citations
Cox, E.J. (1995). Taxonomic studies on the diatom genus Navicula Bory VII. The identity and typification of Navicula gregaria Donkin, N. cryptocephala Kutz. and related taxa. Diatom Research 10: 91-111.
Donkin, A.S. (1861). On the marine Diatomaceae of Northumberland with a description of several new species. Quarterly Journal of Microscopical Science, new series, London 1:1-15.
Links & ID's
Index Nominum Algarum (INA)
California Academy of Sciences (CAS)
NCBI Genbank Taxonomy
North American Diatom Ecological Database (NADED)
NADED ID: 46023
Autecology Discussion
EMAP Assessment
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.
EMAP Distribution
Navicula gregaria
Distribution
The distribution map represents the relative abundance of this Navicula gregaria 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 Navicula gregaria was not recorded, or with a red circle indicating the relative abundance of Navicula gregaria.
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
Navicula gregaria
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.