Navicula gregaria

Donkin 1861      Category: Symmetrical biraphid
BASIONYM: Navicula gregaria Donkin 1861

Navicula goersii

 

Navicula harmoniae
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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 July 24, 2017, from http://westerndiatoms.colorado.edu/taxa/species/navicula_gregaria

Species: Navicula gregaria

Contributor: Marina Potapova

Reviewer: Mark Edlund

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Image Credit: Marina Potapova

  1. Valves lanceolate with protracted apices
  2. Central area asymmetric
  3. External proximal raphe ends bent toward primary side
  4. Striae slightly radiate around the center
  5. 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)

Original INA

California Academy of Sciences (CAS)

Navicula gregaria CAS

NCBI Genbank Taxonomy

Navicula gregaria NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 46023

Autecology Discussion

Habits

Size Range

101-1000 µm3 (ie Amphora veneta)

Motility

highly motile (e.g. a large cell like Surirella AND extensive raphe)

Attachment

unattached

Habitat

benthic

Colony

solitary

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

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Navicula gregaria from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.

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.