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.
Basionym: Fragilaria crotonensis
Author: Kitton 1869
Length Range: µm
Striae in 10 µm:
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.
Cite This Page:
Morales, E., Rosen, B., and Spaulding, S. (2013). Fragilaria crotonensis. In Diatoms of the United States. Retrieved May 29, 2015, from http://westerndiatoms.colorado.edu/taxa/species/fragilaria_crotonensis
Species: Fragilaria crotonensis
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
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.
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 of the onset of threshold levels of nitrogen (N), altering diatom assemblages in oliogotropic lakes of the western United States (Saros et al. 2005, Wolfe et al. 2006).
Living colony of F. crotonensis.
Credit/Source: S. Spaulding