Asterionella formosa
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| Asterionella formosa | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Division: | Ochrophyta |
| Clade: | Bacillariophyta |
| Class: | Fragilariophyceae |
| Order: | Tabellariales |
| Family: | Tabellariaceae |
| Genus: | Asterionella |
| Species: | A. formosa |
| Binomial name | |
| Asterionella formosa Hassall, 1850 | |
| Synonyms[1] | |
|
Asterionella gracillima var. formosa (Hassall) Wislouch 1921 | |
Asterionella formosa is a species of diatom belonging to the family Fragilariaceae.
It has cosmopolitan distribution.[2]
Etymology
Asterionella formosa is the type species of its genus, Asterionella.[1]
The species name "formosa" is derived from the Latin adjective for "beautiful", or "handsome".[1]
Description
Asterionella formosa ranges from 45–68 micrometres (0.0018–0.0027 in) in length and 1.1–4.5 μm in width. Asterionella formosa has valves (siliceous plate that makes up a half of a diatom cell) that are long and narrow, with capitate (enlarged and rounded) apices (tips) unequal in size. The larger apex is known as the footpole. A. formosa has a very narrow sternum (thickened, longitudinal section of the silica valve) and irregularly spaced striae (rows of pores on the valve surface), slightly offset from one another at the sternum. Some A. formosa have irregularly spaced marginal spines between striae. At each end, there is a porefield (area of pores with a different pattern). Rimoportulas (round apertures) have been observed to occur at either or both ends of the valve.[3]
Within each cell is a nucleus at their center and 6–8 golden-brown chromatophores.[4]
Asterionella formosa colonies consist of cells joined at their valve faces' footpoles by mucilage pads.[3] Their colonies consist of 8–20 cells and take on a spiral, star-like shape. They may also occur in a closed ring shape, but this is rare.[4]