Scenedesmus
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Scenedesmus is a genus of unicellular green algae ( Chlorophyta ) that are common in freshwater. Scenedesmus species have in common a cell nucleus and a chloroplast with a pyrenoid surroundedby starch . The vegetative cells are without flagella and immobile. Starting from single cells, they form a characteristic, flat aggregation group, a so-called coenobium of 2 - 32 cells, which are arranged in one or two rows. Depending on the type, the cells have a rounded to elongated shape with pointed cell poles. The cell wall consists of a basal layer of hemicellulose with superimposed sporopollenin , which, depending on the type, is smooth or forms characteristic elevations with or without spinous processes.
Reproduction takes place through auto spores . Each cell can form a new daughter coenobium through the aggregation of car spores. Zoospores were observed but not confirmed.
Scenedesmus species occur mainly as plankton in eutrophic fresh water of ponds and lakes, rarely in brackish water , in practically all climatic zones. Their physiology and biochemistry are comparatively uniform. All 28 strains investigated so far have hydrogenases and intensively form secondary carotenoids under nitrogen deficiency. The species differ in the ability to split starch, in the tolerance to increased salt concentrations and pH values. Their guanine-cytosine content in DNA fluctuates between 50 and 69% (85 strains examined). The genus Scenedesmus includes more than 100 species, which are divided into 2–6 subgenera or "groups".
literature
- E. Hegewald, N. Hangata: Phylogenetic studies on Scenedesmaceae (Chlorophyta). In: Algol Stud / Arch Hydrobiol Suppl. 100, 2000, pp. 29-49.
- E. Hegewald: Taxonomy and Phylogeny of Scenedesmus Algae. In: The Korean Journal of Phycology. 12 (4), 1997, pp. 235-246.
Web links
- Agaebase algaebase.org