Pediastrum duplex
Introduction '''''Pediastrum duplex''''' is a species of fresh water green algae in the genus ''Pediastrum''. It is the type species of the genus ''Pediastrum''. ''Pediastrum duplex'' forms nonmotile coenobia (colonies) with a fixed number of cells. These coenobia are flat and have a circular shape. The colonies usually contain 8 to 32 cells, with examples of 4, 64 or 128 occurring rarely. Colonies have holes between the cells; the holes are smaller in diameter than the cells. The cells are polygonal, distinctly rectangular in outline with concave sides. The outer cells of the coenobium have two triangular lobes that are longer than the cell body. At the tip of the lobes are very short rosettes that may also have fine bristles. The cell wall is usually smooth, but may sometimes have a distinct sculptured texture. It reproduces by forming autocolonies asexually, although sexual reproduction has also been observed. ''Pediastrum duplex'' is a very common component of the freshwater phytoplankton, and has a cosmopolitan distribution. Because the cell wall is resistant to decay, the cell wall has been found in Holocene lake sediments.
Infraspecies Because ''Pediastrum duplex'' is very variable, many infraspecific taxa have been named. A partial list is included below:''Pediastrum duplex brachylobum''''Pediastrum duplex clathratum''''Pediastrum duplex cohaerens''''Pediastrum duplex duplex''''Pediastrum duplex'' f. ''denticulatum''  Isabella & R.J. Patel''Pediastrum duplex gracillimum''''Pediastrum duplex regulosum''''Pediastrum duplex reticulatum''''Pediastrum duplex rotundatum''''Pediastrum duplex'' var. ''asperum''''Pediastrum duplex'' var. ''clathratum'' (A.Braun) Lagerheim, 1882''Pediastrum duplex'' var. ''convexum''  W. Krieger''Pediastrum duplex'' var. ''cornutum''''Pediastrum duplex'' var. ''gracillimum''  W. West & G.S. West''Pediastrum duplex'' var. ''irregulare''  G.R. Hegde & K. Somanna''Pediastrum duplex'' var. ''longicorne''  W. Krieger''Pediastrum duplex'' var. ''reticulatum'' Lagerheim, 1882''Pediastrum duplex'' var. ''rugulosum''  Raciborski''Pediastrum duplex'' var. ''subgranulatum''  RaciborskiOne variety, ''Pediastrum duplex'' var. ''gracillimum'', has been shown to be not closely related to ''Pediastrum duplex'' ''sensu stricto''. It differs by having cells with narrower lobes and comparatively larger gaps between cells in the colonies. This variety has been split off as a new genus, named ''Lacunastrum'' with ''Lacunastrum gracillimum'' as its sole species.
References
Further reading *Cao, X., Strojsová, A., Znachor, P. & Zapomelová, E. (2005). Detection of extracellular phosphatases in natural spring phytoplankton of a shallow eutrophic lake (Donghu, China). European Journal of Phycology 40: 251–258. *Day, S.A., Wickham, R.P., Entwisle, T.J. & Tyler, P.A. (1995). Bibliographic check-list of non-marine algae in Australia. Flora of Australia Supplementary Series 4: vii + 276. *Hu, H. & Wei, Y. (2006). The freshwater algae of China. Systematics, taxonomy and ecology. pp. 4 pls of 16 figs, i-iv, i-xv, 1–1023.China: www.sciencep.com. ****  pdf*Smoliner, C. (1983). Das zähe leben der grünalge Pediastrum duplex. Mikrokosmos 8: 241–245.
External links *  Images of various infraspecies