Visit us at

Diatoms of the United States is now known as Diatoms of North America.
This site has been redesigned and updated, and will be closing soon.

Fragilariforma nitzschioides

(Grunow) Lange-Bert. 2011      Category: Araphid
BASIONYM: Fragilaria nitzschioides Grunow in Van Heurck 1881

Fragilariforma marylandica


Fragilariforma polygonata

LM scalebar = 10 µm = 80 pixels.


Contributor: Kerry Howard | Eduardo A. Morales - June 2012
Length Range: 19-54 µm
Width Range: 3.5-5.5 µm
Striae in 10 µm: 18-25


Valves are linear with parallel or slightly convex sides, although smaller valves may be more linear-elliptical in shape. Apices are slightly rostrate to bluntly rounded. A single rimoportula is present on one or both poles, in line with a stria. Striae are parallel throughout most of the valve, but may be slightly radiate towards the ends. Valves typically have 20-21 striae in 10 µm, but the range is 18-25 in 10 µm. Striae are fine, extend around the margin of the valve onto the valve mantle. A very narrow sternum is present along the apical axis of the valve. The striae on either side of the sternum are slightly offset or alternate (SEM). There is a small apical pore field present at each pole. Frustules form colonies and are observed as rectangular bands in girdle view. Short spines on the margin of the valve are often seen in girdle view. The short spines are flat and slightly rounded (spatulate). In girdle view, 2-3 copulae may also be visible on each frustule. Internal valves are common in specimens from ephemeral habitats.

Note that the transfer of Fragilaria nitzschoides Grunow in Van Heurck was made to Fragilariforma nitzschiodes (Grunow) Lange-Bertalot (Hofmann et al. 2011), but not used in that flora.

Original Description

Basionym: Fragilaria nitzschioides
Author: Grunow in Van Heurck 1881
Length Range: µm
Striae in 10 µm:

Original Description

  1. F. Nitzschioides Grun* 16 1/2 to 17 stries et 8 points marginaux en 0,01 mm

Original Images

Cite This Page:
Howard, K., and Morales, E. (2012). Fragilariforma nitzschioides. In Diatoms of the United States. Retrieved May 24, 2018, from

Species: Fragilariforma nitzschioides

Contributor: Kerry Howard | Eduardo A. Morales

Reviewer: Rex Lowe


Hofmann, G., Werum, M. and Lange-Bertalot, H. (2011). Diatomeen im Süßwasser-Benthos von Mitteleuropa. Koeltz Scientific Books, Königstein, 908 pp.

Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.

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.

Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Van Heurck, H. (1881). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers. pls 31-77.

Williams, D.M. and Round, F.E. (1987). Revision of the genus Synedra Ehrenb. Diatom Research 1(2): 313-339.

Williams, D.M. and Round, F.E. (1988). Fragilariforma, nom. nov., a new generic name for Neofragilaria Williams & Round. Diatom Research 3: 265-267.

Winsborough, B. M. (2000). Pleistocene diatoms from the 602,000 YR BP Lava Creek B Ash. Diatom Research, 15(1): 159-166.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Fragilariforma nitzschioides CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Fragilariforma nitzschioides forms colonies where individual cells are held together by small linking spines and small mucilage pads produced at the apical pore fields of each valve (Round et al, 1990). In live colonies, chloroplasts are numerous, small, discoid, and are either scattered throughout the cell or gathered into the center of the cell. It is abundant in samples collected from the Cayler Prairie pothole in Dickinson Co., Iowa. Live samples were collected from the outflow stream in the marshy area located within the pothole. The prairie pothole experiences both wet and dry periods throughout the year, and numerous F. nitzschioides internal valves are observed in samples of detrital thatch from the marsh and outflow stream. Internal valves are valves that are not part of the regular division of the cell and only one functional valve is produced during mitosis (Round et al, 1990). Internal valves are common in taxa living in subaerial or saline habitats, and are also associated with dormancy in some taxa (Round et al., 1990).

Fossil F. nitzschioides colonies (chains of 10-15 individuals) have been reported in the 602,000 year old Lava Creek B Ash deposit (Yellowstone Caldera eruption) in Smithville, Texas. The autecological preferences of the diatom assemblage (both planktonic and benthic taxa) in the ashfall deposit suggests these taxa were living in a cool, alkaline, moderate to high conductivity, slow-flowing stream or lake (Winsborough, 2000).


Internal valves of Fragilariforma nitzschioides, Cayler Prairie swale, Dickinson Co., Iowa

Credit/Source: Kerry Howard

Live Fragilariforma nitzschioides cells in a colony, Cayler Prairie, Dickinson Co., Iowa

Credit/Source: Kerry Howard

Multiple contracted plastids and internal valves visible in live Fragilariforma nitzschioides colony, Cayler Prairie, Dickinson Co., Iowa

Credit/Source: Kerry Howard

Fragilariforma nitzschioides valves in girdle view

Credit/Source: Kerry Howard

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

Fragilariforma nitzschioides

EMAP Response Plots

Fragilariforma nitzschioides

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.