Desmodesmus is a genus of green algae in the family Scenedesmaceae. [1] It is the only chlorophyll-containing organism known to have caused human infections in immunocompetent individuals. All known cases involved open injuries occurring in fresh water. [2]
Desmodesmus consists of colonies of two, four, eight or 16 cells arranged in a row. Cells are ellipsoidal to ovoid, joined to each other by their longer sides. The terminal cells of a colony (and sometimes the medial cells as well) are usually armed with spines. Cell walls may also be covered in ridges, warts, and net-like structures. Cells contain one parietal chloroplast, containing one pyrenoid. [3]
Desmodesmus species usually produce colonies of more than one cell, but single cells (unicells) may be found as well. [4] These single cells may be confused with Lagerheimia , a genus of single-celled algae. [5]
The cell wall of Desmodesmus consists of an outer layer with a net-like structure, with "rosettes" of tubes underneath. [6] These structures are not visible under light microscopy, and only become visible under a scanning electron microscope (SEM) or transmission electron microscope. [7]
Desmodesmus typically reproduces asexually by forming autospores. [4] Sexual reproduction has been observed a few times. [4]
Species in the genus Desmodesmus have long been placed in the related genus Scenedesmus . [4] However, Scenedesmus was found to be polyphyletic, and was split up into several genera (corresponding to the subgenera within Scenedesmus). Desmodesmus has ornamented cell walls, while Scenedesmus sensu stricto lacks ornamentation. [7]
A factor that has long complicated the taxonomy of Scenedesmus and its related taxa is the fact that these algae show considerable phenotypic plasticity. This plasticity has led taxonomists in the past to designate thousands of infraspecific names based on minute changes in spine morphology or cell shape. [4] However, in laboratory conditions the same strain may produce an array of different morphologies. [4]
Currently, Desmodesmus species are delimited using a combination of ultrastructural features and molecular data. In particular, the locus ITS-2 provides enough variability to distinguish between species. [8]
Desmodesmus is found in the plankton of habitats such as ponds and lakes, particularly in eutrophic waters. [6] It is one of the most common types of freshwater plankton. [3] They can also be found in soils and biological soil crusts. [9]
Desmodesmus species tolerate a wide range of habitats and conditions; this also makes them easy to culture. In response to herbivory from predators such as Daphnia , Desmodesmus may develop spines or other defensive features. [4]
Scenedesmaceae is a family of green algae in the order Sphaeropleales. Scenedesmus algae are commonly found in freshwater plankton. The former family Coelastraceae is considered a synonym of Scenedesmaceae.
Coelastrum is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus has a more or less cosmopolitan distribution, although some species appear to have more restricted geographical distributions.
Eustigmatophytes are a small group of eukaryotic forms of algae that includes marine, freshwater and soil-living species.
Scenedesmus is a genus of green algae, in the class Chlorophyceae. They are colonial and non-motile. They are one of the most common components of phytoplankton in freshwater habitats worldwide.
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.
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.
Dimorphococcus is a genus of fresh water green algae in the family Scenedesmaceae. It is found as a component of the phytoplankton of freshwater ponds, lakes, and peat bogs. It is widespread, but usually not very common.
Hariotina is a genus of green algae in the family Scenedesmaceae. They are classified in the subfamily Coelastroideae.
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.
Monactinus is a genus of green algae in the family Hydrodictyaceae. It is very common in freshwater regions throughout the world.
Pseudopediastrum is a genus of green algae in the family Hydrodictyaceae. It is very common in freshwater regions throughout the world.
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.
Tetradesmus is a genus of green algae in the family Scenedesmaceae. Species of Tetradesmus are found in a variety of habitats, including fresh water and biological soil crusts in deserts.
Tetraedron is a genus of green algae in the family Hydrodictyaceae. It may also be spelled as Tetraëdron.
Pediastrum duplex is a species of fresh water green algae in the genus Pediastrum.
Mallomonas lacuna is a species of heterokont algae. It is a tiny free-living cell, about the width of a human hair. It has ornate scales and bristles, as well as long spines. It is a relatively common part of lake or pond plankton. It differs from its cogenerates by the number, distribution, and size of its base plate pores, the secondary structures on the scale surfaces, together with characteristics of its bristles.
Mallomonas hexareticulata is a species of heterokont algae. It is a tiny free-living cell, about the width of a human hair. It has ornate scales and bristles, as well as long spines. It is a relatively common part of lake or pond plankton. It differs from its cogenerates by the number, distribution, and size of its base plate pores, the secondary structures on the scale surfaces, together with characteristics of its bristles.
Mallomonas pseudomatvienkoae is a species of heterokont algae. It is a tiny free-living cell, about the width of a human hair. It has ornate scales and bristles, as well as long spines. It is a relatively common part of lake or pond plankton. It differs from its cogenerates by the number, distribution, and size of its base plate pores, the secondary structures on the scale surfaces, together with characteristics of its bristles.
Mallomonas sorohexareticulata is a species of heterokont algae. It is a tiny free-living cell, about the width of a human hair. It has ornate scales and bristles, as well as long spines. It is a relatively common part of lake or pond plankton. It differs from its cogenerates by the number, distribution, and size of its base plate pores, the secondary structures on the scale surfaces, together with characteristics of its bristles.
Mallomonas pleuriforamen is an extinct species of heterokont algae. It was first found in Middle Eocene lacustrine deposits from northwestern Canada. It was a tiny free-living cell, about the width of a human hair. It had ornate scales and bristles, as well as long spines. It was a relatively common part of lake or pond plankton. It differs from its cogenerates by the number, distribution, and size of its base plate pores, the secondary structures on the scale surfaces, together with characteristics of its bristles.
