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Name derivation:

Greek fragil meaning brittle; aria meaning connected to something.


Fragilaria  Lyngbye  1819;  43 of 890 species descriptions are currently accepted taxonomically (Guiry and Guiry 20132).

Order Fragilariales   Family Fragilariaceae


Cells are oblong and swollen in the center in girdle view where they are linked together to form a ribbon like colony. Valves are linear and elliptical with rounding at the edges. There is often a space between each cell on each side of the swollen center where cell is connected. Most common in girdle view. Two large chloroplasts per cell.

Similar genera:

Eunotia is a similar colonial "ribbon" with cells that taper toward both ends, but have no space between each cell.

Trachysphenia Petit in Folin et Périer, 1877 is not separated from Fragilaria in PhycoKey.


Found in freshwater sediments with few species in the plankton. Marine classifications of Fragilaria suggest a placing in other taxa.


Guiry, M.D. G.M. Guiry  2013.  AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 02 August 2013. Round, F. E., Crawford, R. M., Mann, D. G. 1990. The Diatoms. Cambridge University Press. New York, NY.

Hasle, G et al. Identifying Marine Phytoplankton. Academic Press (1997).

Lyngbye, H.C.  1819.  Tentamen hydrophytologiae danicae continens omnia hydrophyta cryptogama Daniae, Holsatiae, Faeroae, Islandiae, Groenlandiae hucusque cognita, systematice disposita, descripta et iconibus illustrata, adjectis simul speciebus norvegicis. pp. [i]-xxxii, [1]-248, 70 pls. Hafniae [Copenhagen]: typis Schultzianis, in commissis Librariae Gyldendaliae.

Petit, P.  1877.  Catalogue des Diatomées. In: Les fonds de la mer.  Étude sur les particularités nouvelles des régions sous-marines. Tome Troisième contenant environ 115 figures hors texte, représentant 75 formes animales ou végétales inédites foraminifères, mollusques, diatomées) et plus de 300 pages de texte. 1875-1879. (Folin, L. De & Périer, L Eds), pp. 168-198. Paris: Savy, Libraire-Éditeur.