''Asterionella formosa'' is a species of

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

belonging to the family Fragilariaceae. It has

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

Taxonomy

''Asterionella formosa'' is the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of its genus, '' Asterionella''.

Etymology

The species name "''formosa''" is derived from the Latin adjective for "beautiful", or "handsome".

Description

''Asterionella formosa'' ranges from in length and 1.1–4.5 μm in width. ''Asterionella formosa'' has

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, ...

(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. Within each cell is a

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

at their center and 6–8 golden-brown

chromatophores Chromatophores are cells that produce color, of which many types are Biological pigment, pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals an ...

. ''Asterionella formosa'' colonies consist of cells joined at their valve faces' footpoles by

mucilage Mucilage is a thick gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion, with the direction of their movement always opposite to that of the secretion of ...

pads. 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.

Habitat and distribution

''Asterionella formosa'' is common in mesotrophic and

eutrophic Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

lakes and slow-moving river

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

around the world, and is especially common in the northern hemisphere. It has become increasingly common in

oligotrophic An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates o ...

(low-nutrient) mountainous lakes.

Ecology

''Asterionella formosa'' colonies may be colonized by small, sessile (non-mobile)

choanoflagellates Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and t ...

, or infested by '' Zygorhizidium planktonicum'', a parasitic

chytrid Chytridiomycota are a division of zoosporic organisms in the kingdom (biology), kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zo ...

fungus. To prevent the fungus from spreading, affected cells in the colony usually induce

cell death Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as di ...

. ''A. formosa'' laboratory models have been observed to have dynamic

microbiomes A microbiome () is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupying a reasonably we ...

with many

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

l species, mostly from the phyla

Proteobacteria Pseudomonadota (synonym "Proteobacteria") is a major phylum of gram-negative bacteria. Currently, they are considered the predominant phylum within the domain of bacteria. They are naturally found as pathogenic and free-living (non-parasitic) ...

and Bacteroidetes. Most of the bacteria were

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

and more than half could

metabolize Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the ...

glycolate Glycolic acid (or hydroxyacetic acid; chemical formula ) is a colorless, odorless and hygroscopic crystalline solid, highly soluble in water. It is used in various skin-care products. Glycolic acid is widespread in nature. A glycolate (sometimes s ...

Changes in population

When the amount of

reactive nitrogen Reactive nitrogen ("Nr"), also known as fixed nitrogen, refers to all forms of nitrogen nitrogen cycle, present in the environment except for molecular nitrogen (). While nitrogen is an essential element for life on Earth, molecular nitrogen is c ...

increases in a body of oligotrophic water, diatom populations increase as well. Such increases in ''A. formosa'' populations have been used by North American researchers to determine whether a nitrogen disposition rate in a given lake can cause significant ecological effects. Another study found that ''A. formosa'' population changes follow climate-warming-related changes, such as: longer open water periods (as opposed to frozen), changed lake mixing regimes, and changed lake thermal properties.

References

{{Taxonbar, from=Q49600081 Fragilariophyceae