Planktosphaeria | |
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Scientific classification | |
(unranked): | Viridiplantae |
Division: | Chlorophyta |
Class: | Chlorophyceae |
Order: | Sphaeropleales |
Family: | Schizochlamydaceae |
Genus: | Planktosphaeria G.M.Smith [1] |
Species | |
Planktosphaeria is a genus of green algae, specifically of the Chlorophyceae. [1] It was first described by the phycologist Gilbert Morgan Smith in 1918, with Planktosphaeria gelatinosa as its type species. Species of Planktosphaeria are commonly found in freshwater plankton around the world. [2]
Planktosphaeria consists of solitary cells or in clusters of 8 to 16. Cells are spherical, usually surrounded by a layer of mucilage, sometimes with multiple layers. Young cells have a single chloroplast with a pyrenoid. [3] Mature cells have numerous angular chloroplasts that are parietal, with one or several pyrenoids. [2]
Distinguishing Planktosphaeria from other nonmotile coccoid, spherical algae is difficult. Often, Planktosphaeria forms loose ring-like aggregations shortly after vegetative reproduction; when this happens, the mother cell wall may remain, which is a useful identification trait. [3]
The taxonomy of Planktosphaeria has been muddled in confusion, particularly with regards to the similar genus Follicularia . [4] Follicularia is a genus that produces zoospores, while Planktosphaeria was characterized by reproduction via autospores only. The phycologist Richard C. Starr redefined Planktosphaeria to include Follicularia and subsequently described several species under the name Planktosphaeria; all of these were isolated from soil samples and produced zoospores. [4]
Phylogenetic analysis of the strains isolated by Starr has revealed that zoospore-producing "Planktosphaeria" species were separate from autospore-producing algae, and therefore the name Follicularia has been reapplied to zoospore-producing algal strains. However, zoospore-producing "Planktosphaeria" are also polyphyletic, with the strains falling into two separate clades. Strains from one clade were reclassified in a new genus, named Herndonia . The nature and classification of "true" Planktosphaeria gelatinosa is still uncertain, because no authentic strain of Planktosphaeria gelatinosa matching the genus-level characteristics exists. [4]
The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.
Sphaeropleales is an order of green algae that used to be called Chlorococcales. The order includes some of the most common freshwater planktonic algae such as Scenedesmus and Pediastrum. The Sphaeropleales includes vegetatively non-motile unicellular, colonial, or filamentous taxa. They have biflagellate zoospores with flagella that are directly opposed in direction : Sphaeroplea, Atractomorpha, Neochloris, Hydrodictyon, and Pediastrum. All of these taxa have basal body core connections. Motile cells generally lack cell walls or have only a very fine layer surrounding the cell membrane. Other common characteristics include a robust vegetative cell wall, cup-shaped chloroplasts with large pyrenoids, and relatively large nuclei.
Selenastraceae is a family of green algae in the order Sphaeropleales. Members of this family are common components of the phytoplankton in freshwater habitats worldwide. A few species have been found in brackish and marine habitats, such as in the Baltic Sea.
Ankistrodesmus is a genus of green algae in the family Selenastraceae. It is one of the most common types of phytoplankton in freshwater habitats around the world.
Ankyra is a genus of green algae in the family Characiaceae. This genus of algae is closely related to Atractomorpha and Sphaeroplea. They are found in stagnant waters.
Dictyochloris is a genus of green algae in the class Chlorophyceae. It is the sole genus of the family Dictyochloridaceae. It is commonly found in terrestrial and subaerial habitats.
Golenkinia is a genus of green algae first described in 1894 by Robert Chodat. The genus is named for the Russian phycologist Mikhail Iljitsch Golenkin. Golenkinia species live in fresh water and are found around the world.
Lagerheimia is a genus of green algae in the family Oocystaceae. It is commonly found in freshwater habitats all over the world, although some species are rare and have only been recorded from Europe or the United States.
Lobocharacium is a genus of green algae in the family Characiosiphonaceae. It contains the single species Lobocharacium coloradoense. It has been isolated from a pond in Colorado, United States.
Palmellopsis is a genus of green algae, specifically of the Palmellopsidaceae. They are either planktonic or attached to substrates in fresh water, or in aeroterrestrial habitats.
Podohedriella is a genus of green algae in the family Selenastraceae. It is found in freshwater habitats or on damp wood.
Pseudomuriella is a genus of green algae, specifically of the class Chlorophyceae. It is the sole genus of the family Pseudomuriellaceae. It is a terrestrial alga that inhabits soils.
Selenastrum is a genus of green algae in the family Selenastraceae. It is common in freshwater habitats around the world. Most species prefer temperate or warm-temperate waters.
Treubaria is a genus of green algae, the sole genus in the family Treubariaceae. Treubaria is found in freshwater habitats and has a cosmopolitan distribution.
Nephrocytium is a genus of green algae in the class Chlorophyceae. Formerly placed in the family Oocystaceae, it is currently placed in its own family, Nephrocytiaceae.
Sphaerocystis is a genus of green algae, specifically of the class Chlorophyceae. It is found as plankton in freshwater habitats.
Deuterocharacium is a genus of green algae in the family Characiaceae. It is found in freshwater habitats, attached to algae or detritus. It is rare and has only been recorded from Europe.
Chlorotetraedron is a genus of green algae, in the family Neochloridaceae. The name may also be written as Chlorotetraëdon. It is found as freshwater plankton or in soil.
Follicularia is a genus of green algae, in the family Schizochlamydaceae. It is found in terrestrial habitats, mainly soil.
Bracteamorpha is a genus of green algae in the order Sphaeropleales, and is the only genus in the family Bracteamorphaceae. It contains a single species, Bracteamorpha trainorii.