Asterionella
Hassall 1850 Category: Araphid
TYPE SPECIES: Asterionella formosa Hassall
Image Credit: Megan Otu, Sarah Spaulding
CLASS: Fragilariophyceae
ORDER: Fragilariales
FAMILY: Fragilariaceae
- Valve linear-lanceolate with capitate ends
- Spines present on valve margins
- Cells linked by mucilage pads forming characteristic stellate colonies
- Porefield at headpole
- Single rimoportula at headpole
The valves of Asterionella are symmetrical to the apical axis and asymmetric to the transapical axis. In valve view, the valves are linear-lanceolate in shape, with capitate ends. Living cells attach by mucilage pads at the basal ends, or footpoles, to form characteristic stellate colonies. Living colonies present cells in girdle view, while processed samples break up the colonies so that single valves typically lie in valve view. In processed samples, small spines are visible on the valve margins.
Asterionella is a characteristic planktonic species and the stellate colonies are buoyant and resistant to sinking. It is considered to have one of the slowest sinking rates of the freshwater planktonic diatoms. During blooms of A. formosa, cells may become heavily infested with chytrid fungal parasites, which are colorless, spherical strutures that attach to the frustules by hyphae. Asterionella formosa is common and considered to have a worldwide distribution. The taxon is known to be introduced by humans into new habitats and also to increase with anthropogenic eutrophication of lakes.
Cite This Page:
Spaulding, S., and Edlund, M. (2009). Asterionella. In Diatoms of the United States. Retrieved May 21, 2013, from http://westerndiatoms.colorado.edu/taxa/genus/Asterionella
Contributor: Sarah Spaulding | Mark Edlund - January 2009
Reviewer: Sam Rushforth
Citations
Körner, H. (1970). Morphologie und Taxonomie der Diatomeen Gattung Asterionella. Nova Hedwigia 20: 557-724.
Lund, J.W.G. (1950). Studies on Asterionella formosa Hass. 2. Nutrient depletion and the spring maximum. Journal of Ecology 38: 15-35.
Maberly, S.C., Hurley, M.A., Butterwick, C., Corry, J.E., Heaney, S.I., Irish, A.E., Jaworski, G.H.M., Lund, J.W.G., Reynolds, C.S. and Roscoe, J.V. (1994). The rise and fall of Asterionella formosa in the south basin of Windermere - analysis of a 45 year series of data. Freshwater Biology 31: 19-34.
Mayer, A. (1937). Die Bacillariophyten-Gattungen Fragilaria und Asterionella in Bayern. Ber. Bayerischen Bot. Gesell. 22: 50-85.
Pappas, J.L. and Stoermer, E.F. (2001). Asterionella Hassall (Heterokontophyta, Bacillariophyceae), taxonomic history and quantitative methods as an aid to valve shape differentiation. Diatom 17:47-58.
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