Asterionella
| Asterionella | ||||||||||||
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Asterionella formosa (German: Schwebesternchen) |
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| Scientific name | ||||||||||||
| Asterionella | ||||||||||||
| Hassall |
Asterionella is a genus of diatoms (Bacillariophyta) with around 10 species that occur in fresh and marine water.
features
The representatives are slim, rod-shaped algae, which are thickened towards the ends. They have several small plastids that are colored golden brown by fucoxanthin . The cells are united to form star-shaped colonies open on one side. They have the two-part pebble shells typical of diatoms. In the side view this appears rectangular, in the shell view it appears linear with swollen ends. After cell division, the shells remain connected to one another with a jelly and thus form the colonies. The cells can therefore always be seen in side view. The individual cells are between 20 and 160 micrometers in size.
The asexual reproduction is carried out by the typical division of diatoms with concomitant reduction cell. Another option is to break the colonies. Sexual reproduction of Asterionella is not known. The formation of permanent cells directly from vegetative cells has been described. This enables cells to enlarge.
Occurrence and ecology
Asterionella is a component of the phyto plankton . Especially in spring there are larger occurrences. They are often parasitized by Chytridiomycetes , the colonies are empty and have vesicle-shaped appendages.
Due to the mass occurrence in dams and other water reservoirs, Asterionella can lead to clogging of the filter systems.
supporting documents
- Karl-Heinz Linne von Berg, Michael Melkonian u. a .: The Kosmos algae guide. The most important freshwater algae under the microscope. Kosmos, Stuttgart 2004, ISBN 3-440-09719-6 , p. 236.