Fragilaria crotonensis

Kitton 1869      Category: Araphid

Fragilaria amphicephaloides


Fragilaria mesolepta

LM scalebar = 10 µm = 40 pixels.


Contributor: Eduardo A. Morales | Barry Rosen | Sarah Spaulding - May 2013
Length Range: 60-72 µm
Width Range: 2-3 µm
Striae in 10 µm: 17-18


Valves are lanceolate with capitate ends. The central area is wider than rest of the valve. The valve margins may be undulate, with a central swollen middle of the valve. The valve face is undulate due to raised virgae. The valve face/mantle junction forms a sharp angle. The abvalvar edge of the mantle is shallower toward the valve apices, producing detachment of contiguous cells in girdle view. In girdle view, frustules are lanceolate, wider near the center of the valve. Cells form ribbon-like colonies joined by linking spines. The axial area is lanceolate, with clear fascia at the central area. Striae are distinct, composed of apically elongated areolae (lineolae). Striae are interrupted by spines. Striae are parallel throughout the valve and extend midway onto the valve mantle. Costae are wider than the striae. Spines are dimorphic; spatulate near the valve center and conical near the valve ends. Spines are present along the valve face margin, positioned in line with the striae. Well-developed apical pore fields with round poroids are present on the mantle at both valve ends. One rimoportulae is present on each valve. The rimoportula is located along a stria, close to the axial area. Copulae, or girdle bands, were not observed.

Original Description

Author: Kitton 1869
Length Range: µm
Striae in 10 µm:

Original Description

Fragillaria crotonensis, n.s., F. Kitton.-Frustules linear, inflated at the central part, where they cohere and form ribbon-like filament; valve narrow, acicular; striae faint, moniliform (fig.81).-Croton water, New York, Dr. Edwards.

Original Images

Cite This Page:
Morales, E., Rosen, B., and Spaulding, S. (2013). Fragilaria crotonensis. In Diatoms of the United States. Retrieved April 19, 2018, from

Species: Fragilaria crotonensis

Contributor: Eduardo A. Morales | Barry Rosen | Sarah Spaulding

Reviewer: Sam Rushforth


Canter, H.M. and Jaworski, G.H.M. . (1983). A further study on parasitism of the diatom Fragilaria crotonensis Kitton by chytridiaceous fungi in culture. Annals of Botany 52(4): 549-563 .

Crawford, R.M., Canter, H.M. and Jaworski, G.H.M. . (1985). A study of two morphological variants of the diatom Fragilaria crotonensis Kitton using electron microscopy . Annals of Botany 55(4): 473-485.

Saros, J.E., Michel, T.J., Interlandi, S.J. and Wolfe, A.P. (2005). Resource requirements of Asterionella formosa and Fragilaria crotonensis in oligotrophic alpine lakes: implications for recent phytoplankton community reorganizations. Canadian Journal of Fisheries and Aquatic Sciences 62: 1681-1681. doi:10.1139/f05-077

Spaulding, S.A., Otu, M., Wolfe, A.P. and Baron, J. (2015). Paleolimnological records of nitrogen deposition in shallow, high-elevation lakes of Grand Teton National Park, Wyoming, U.S.A. Arctic, Alpine and Antarctic Research 47(4): 701-715.

Wolfe, A.P., Cooke, C.A. and Hobbs, W.O. (2006). Are current rates of atmospheric nitrogen deposition influencing lakes in the eastern Canadian Arctic?. Arctic, Antarctic, and Alpine Research 38: 465-476.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Fragilaria crotonensis CAS

NCBI Genbank Taxonomy

Fragilaria crotonensis NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 34017

Autecology Discussion

Fragilaria crotonensis is a common species in temperate, mesotrophic lakes of North America. Cells can be joined in large ribbon-like colonies. These colonies are resistant to sinking in the water column and help F. crotonensis maintain position in the phytoplankton.

Fragilaria crotonensis, along with Asterionella formosa, is considered a marker that the levels of reactive nitrogen (Nr) have increased above the threshold in oliogotropic lakes of the western United States where diatom assemblages become more like assemblages in mesotrophic and eutrophic lakes (Saros et al. 2005, Wolfe et al. 2006, Spaulding et al. 2015). See the autecology of A. formosa for further discussion.


Living colony of F. crotonensis.

Credit/Source: S. Spaulding

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

Fragilaria crotonensis

EMAP Response Plots

Fragilaria crotonensis

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.