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Myxogastria/Myxogastrea (myxogastrids,
ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...
) or Myxomycetes ( ICN), is a
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...
of
slime mold Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mu ...
s that contains 5 
orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
, 14 
families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
, 62 
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
, and 888 
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. They are colloquially known as the ''plasmodial'' or ''acellular'' slime moulds. All species pass through several, very different morphologic phases, such as microscopic individual cells, slimy amorphous organisms visible with the naked eye and conspicuously shaped
fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...
. Although they are monocellular, they can reach immense widths and weights: in extreme cases they can be up to across and weigh up to . The class Myxogastria is distributed worldwide, but it is more common in temperate regions where it has a higher biodiversity than in polar regions, the subtropics or tropics. They are mainly found in open forests, but also in extreme regions such as deserts, under snow blankets or underwater. They also occur on the bark of trees, sometimes high in the canopy. These are known as corticolous myxomycetes. Most species are very small.


Taxonomy and classification


Nomenclature

The Latin name ''Myxomycota'' comes from the Ancient Greek words μύξα ', which means "mucus", and μύκης ', which means "fungus". The name ''Myxogastria'' was introduced in 1970 by Lindsay Shepherd Olive to describe the family Myxogastridae, which was introduced in 1899 by
Thomas Huston Macbride Thomas Huston Macbride (July 31, 1848 – March 27, 1934) was the tenth president of the University of Iowa, serving from 1914 to 1916. Macbride was a naturalist and botanist, Macbride Hall at the University of Iowa is named for him. He often c ...
. Swedish mycologist
Elias Magnus Fries Elias Magnus Fries (15 August 1794 – 8 February 1878) was a Swedish mycologist and botanist. Career Fries was born at Femsjö (Hylte Municipality), Småland, the son of the pastor there. He attended school in Växjö. He acquired ...
described numerous slime moulds as Myxogasteres in 1829. Species in the class Myxomycota are colloquially known as
plasmodial A plasmodium is a living structure of cytoplasm that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from slime molds, but are also found in parasitic Myxosporea, and so ...
or
acellular Non-cellular life, or acellular life is life that exists without a cellular structure for at least part of its life cycle. Historically, most (descriptive) definitions of life postulated that an organism must be composed of one or more cells, ...
slime moulds. Some consider the Myxomycota to be a separate
kingdom Kingdom commonly refers to: * A monarchy ruled by a king or queen * Kingdom (biology), a category in biological taxonomy Kingdom may also refer to: Arts and media Television * ''Kingdom'' (British TV series), a 2007 British television drama s ...
, with an unsettled phylogeny because of conflicting molecular and developmental data. The relations among Myxogastrid
orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
are as yet unclear. Eukaryotic microbiology Organisms ...
bezeichnet. -->


Range

The continuous classification of new taxa reveals that the class is not fully described. The class comprises around 900–1000 species. According to a 2000 inquiry, there were 1012 officially accepted
taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
, including 866 on species level. Another study in 2007 stated a number of more than 1000, in which the Myxogastria comprised the biggest group of slime moulds, with over 900 species. On the basis of sequenced environmental samples it is estimated that the group has between 1200 and 1500 species – more than previously estimated. Among the 1012 taxa only a few species are common: 305 species were discovered in a single location or groupings, a further 258 species were found in a few areas between 2–20 times, and only 446 were common in several locations with over 20 discoveries. Reclassifications encounter problems because the Myxogastriae are morphologically very plastic, which is to say susceptible to environmental influences; only a few characteristics are diagnostic for a small number of species. In the past authors have unsuccessfully tried to describe a new taxon based on a small number of examples, but this leads to numerous duplications, sometimes even at genus level. For example, ''Squamuloderma nullifila'' is actually a species from the genus ''
Didymium Didymium ( el, , twin) is a mixture of the elements praseodymium and neodymium. It is used in safety glasses for glassblowing and blacksmithing, especially with a gas ( propane)-powered forge, where it provides a filter that selectively block ...
''.


Classification and phylogeny

The following classification is based on Adl ''et al''. (2005) while the classes and further divisions on Dykstra & Keller (2000) who included the Myxogastria in Mycetozoa. The sister taxon is the subclass Dictyostelia. Together with the
Protostelia Protosteliomycetes/Protosteliales (ICBN) or Protostelea/Protostelia/Protosteliida (ICZN) is a grouping of slime molds from the phylum Mycetozoa. The name can vary depending upon the taxon used. Other names include Protostelea, Protostelia, and Pr ...
they formed the taxon
Eumycetozoa {{Cat main, Protista Eukaryotic microbiology Organisms ...
. Other subclasses differ from the other species mainly in the development of fruit bodies; while Protostelia create a separate fruit body from each single mononuclear cell, Dictyostelia develop cell complexes – the so-called pseudo-plasmodia – from separate cells, which then become fruit bodies. Clade Myxogastria (or myxomycetes) * Class Ceratiomyxomycetes Hawksworth, Sutton & Ainsworth 1983 ** Order
Ceratiomyxida Myxogastria/Myxogastrea (myxogastrids, International Code of Zoological Nomenclature, ICZN) or Myxomycetes (International Code of Nomenclature for algae, fungi, and plants, ICN), is a Class (biology), class of slime molds that contains 5 o ...
Martin 1949 ex Farr & Alexopoulos 1977 ** Order
Protosporangiida Mycetozoa is a polyphyletic grouping of slime molds. It was originally thought to be a monophyletic clade, but recently it was discovered that protostelia are a polyphyletic group within Conosa. Classification It can be divided into dictyosteli ...
Shadwick & Spiegel 2012 * Class Myxomycetes Link 1833 em. Haeckel 1866 ** Subclass Lucisporomycetidae Leontyev et al. 2019 (Clear‑spored acellular slime moulds) *** Superorder Cribrarianae Leontyev 2015 **** Order Cribrariales Macbride 1922 ***** Family Cribrariaceae Rostafinski 1873 *** Superorder Trichianae Leontyev 2015 **** Order Reticulariales Leontyev 2015 ***** Family
Reticulariaceae Reticulariaceae is a family of slime molds recognized by the Integrated Taxonomic Information System The Integrated Taxonomic Information System (ITIS) is an American partnership of federal agencies designed to provide consistent and reliabl ...
Rostafinski 1873 **** Order
Liceales Liceales (also Liceida) is an order of Amoebozoa. References Amoebozoa orders Myxogastria {{Amoebozoa-stub ...
Jahn 1928 ***** Family Liceaceae Rostafinski 1873 **** Order
Trichiales Trichiales ( synonymous with Trichiida) is an order of slime moulds Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage ...
Macbride 1922 ***** Family
Dianemidae Trichiales (synonymous with Trichiida) is an order of slime moulds in the phylum Amoebozoa. Trichiales is one of five orders in the group Myxomycetes (also called Myxogastria), or the true plasmodial slime molds. It is also currently categorized ...
Macbride 1899 ***** Family
Trichiidae Trichiales ( synonymous with Trichiida) is an order of slime moulds in the phylum Amoebozoa. Trichiales is one of five orders in the group Myxomycetes (also called Myxogastria), or the true plasmodial slime molds. It is also currently categoriz ...
Rostafinski 1826 ** Subclass Collumellidia Leontyev et al. 2019 (Dark‑spored acellular slime moulds) *** Order Echinosteliopsidales Shchepin et al. **** Family Echinosteliopsidaceae Olive 1970 *** Superorder Echinostelianae Leontyev 2015 **** Order Echinosteliales Martin 1961 ***** Family
Echinosteliaceae ''Echinostelium'' is a genus of slime mould, and the only genus in the family Echinosteliaceae, or Echinosteliidae. It was discovered by Heinrich Anton de Bary in 1855, apparently near Frankfurt am Main. Some species of Echinostelium have a sexua ...
Rostafinski ex Cooke 1877 *** Superorder Stemonitanae Leontyev 2015 **** Order Clastodermatales Leontyev et al. 2019 ***** Family
Clastodermataceae The Clastodermataceae are a family of slime molds in the order Echinosteliales. The family was circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. ...
Alexopoulos & Brooks 1971 **** Order Meridermatales Leontyev 2015 ***** Family Meridermataceae Leontyev 2015 **** Order
Stemonitales Stemonitidales is an order (biology), order of Amoebozoan slime molds in the class Myxogastria, Myxomycetes. References

{{Taxonbar, from=Q148806 Amoebozoa orders Myxogastria ...
Macbride 1922 ***** Family Comatrichaceae Leontyev 2015 ***** Family
Stemonitidaceae Stemonitidaceae is an family of slime molds in the order Stemonitidales. It was first circumscribed by Elias Magnus Fries in 1829. Genera *''Leptoderma'' *'' Macbrideola'' *'' Meriderma'' *'' Paradiachea'' *''Stemonitis'' *'' Symphytocarpus'' ...
Fries 1829 **** Order
Physarales Physarales is an order of Amoebozoa in the class Myxomycetes. It contains three families, the Didymiaceae Didymiaceae is a family of plasmodial slime molds in the order Physarales. Genera The family contains the following four genera: * ' ...
Macbride 1922 ***** Family
Didymiaceae Didymiaceae is a family of plasmodial slime molds in the order Physarales. Genera The family contains the following four genera: * '' Diderma'' * '' Didymium'' * '' Lepidoderma'' * ''Mucilago ''Mucilago crustacea'' is a species of slime mou ...
Rostafinski ex Cooke 1877 ***** Family
Lamprodermataceae Lamprodermataceae is a family of slime molds in the order Physarales Physarales is an order of Amoebozoa in the class Myxomycetes. It contains three families, the Didymiaceae Didymiaceae is a family of plasmodial slime molds in the order ...
Leontyev 2015 ***** Family
Physaraceae Physaraceae is a family of slime molds in the order Physarales. Genera The following genera are members of Physaraceae: *''Badhamia'' *'' Craterium'' *''Fuligo'' *'' Kelleromyxa'' *'' Leocarpus'' *'' Physarella'' *'' Physarina'' *''Physarum'' ...
Chevallier 1826 Some classifications place part of the orders above in the subclass Myxogastromycetidae.


Characteristics and life cycle


Monocellular, mononuclear phase


Spores

The spores of Myxogastria are
haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
, mainly round and measure between 5  μm and 20 μm, rarely up to 24 μm in diameter. Their surface is generally reticular, sharp, warty or spiky and very rarely smooth. The typical colour of the spore mass becomes visible through the structure, since the spores themselves are not pigmented. In some species, especially of the genus ''
Badhamia ''Badhamia'' is a genus of slime molds in the family Physaraceae. It was circumscribed by English naturalist Miles Joseph Berkeley Miles Joseph Berkeley (1 April 1803 – 30 July 1889) was an English cryptogamist and clergyman, and one of ...
'', the spores produce lumps. The colour, shape and diameter of spores are important characteristics for identifying species. Important factors for the germination of spores are mainly moisture and temperature. The spores usually remain germinable after several years; there were even spores preserved in
herbarium A herbarium (plural: herbaria) is a collection of preserved plant specimens and associated data used for scientific study. The specimens may be whole plants or plant parts; these will usually be in dried form mounted on a sheet of paper (called ...
specimens which germinated after 75 years. After the spores' development, they first receive a diploid nucleus, and the
meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
takes place in the spore. At the germination, the spore shells open either alongside special germinal pores or chinks, or rip irregularly and then release one to four haploid
protoplast Protoplast (), is a biological term coined by Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by stripping the cell wall from plant, bacterial, or fungal cells by mechanical, chemical or enzy ...
s.


Myxamoebae and Myxoflagellates

In those species which reproduce sexually, haploid cells bud from the spores. Depending on the environmental conditions, either a myxamoeba or a myxoflagellate buds from the spore. Myxamoebae move like
amoeba An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by extending and ret ...
e – that is, crawling on the substrate – and are produced in dry conditions. Myxoflagellates, which are
peritrichous A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...
and can swim, develop in moist to wet environments. Myxoflagellates almost always have two flagella; one is generally shorter than the other and sometimes only vestigial. The flagella are used for locomotion and to help to move food particles closer. If the humidity changes, cells can switch between the two manifestations. Neither form has a cell wall. This developmental stage (and the next one) serves as a nourishment provider and is also known as the first trophic phase (nourishment phase). In this monocellular phase, the Myxogastria consume bacteria and fungus spores, and probably dissolved substances, and they reproduce through simple
cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...
. If the environmental conditions change adversely in this phase, for example extreme temperature, extreme dryness or food shortage, the Myxogastria may switch to very long-lived, thin-shelled quiescent states – the so-called micro
cysts A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...
. For that to happen, the myxamoebae assume a round shape and secrete a thin cell wall. In this state they can easily survive one year or longer. If living conditions improve, they become active again.


Zygogenesis

If two cells of the same type meet in this phase, they cross-fertilise to a diploid zygote through the fusion of
protoplasm Protoplasm (; ) is the living part of a cell that is surrounded by a plasma membrane. It is a mixture of small molecules such as ions, monosaccharides, amino acid, and macromolecules such as proteins, polysaccharides, lipids, etc. In some defini ...
s and nuclei. The conditions which trigger this are not known. The diploid zygote becomes a multinucleated
plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a vert ...
through multiple nuclear divisions without further cell division. If the resulting cells were peritrichous, they change their shape before the fusion from the peritrichous form to the myxamoeba. The production of a zygote requires two cells of different
mating type Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct Sex, sexes. They also occur in macro-organisms such as fungi. Definition Mating types are the microorganism equivalent ...
s (
heterothallic Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of ...
).


Plasmodium

The second trophic phase begins with the development of the
plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a vert ...
. The multinucleated organism now absorbs via
phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...
as many nutrients as possible. These are bacteria,
protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...
s, dissolved substances, moulds, higher fungi and small particles of organic material. This enables the cell to undergo enormous growth. The nucleus divides multiple times, and the cell soon becomes visible to the naked eye and usually has a surface area – depending on the species – up to one square metre; however, in 1987 one artificially cultivated cell of ''
Physarum polycephalum ''Physarum polycephalum'', an acellular slime mold or myxomycete popularly known as "the blob", is a protist with diverse cellular forms and broad geographic distribution. The “acellular” moniker derives from the plasmodial stage of the lif ...
'' attained a surface area of 5.5 sq m. Myxogastria species have numerous nuclei in their trophic plasmodium phase; the small, non-veined proto-plasmodia have between 8–100 nuclei, while large, veined meshworks have between 100 and 10 million nuclei. All of these remain part of a single cell, which has a viscous, slimy consistency, and may be transparent, white, or brightly coloured in orange, yellow, or pink. The cell has
chemotactic Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemical ...
and negative
phototactic Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive li ...
capabilities in this phase, meaning that it is able to move towards nutrients and away from dangerous substances and light. The movements originate in the grainy cytoplasm, which streams by pulsation in one direction within the cell. In this way the cell reaches a speed of up to 1000 μm per second – the speed in plant cells is 2–78 μm per second. A resting state, the so-called
sclerotium A sclerotium (; (), is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until favo ...
, may occur in this phase. The sclerotium is a hardened, resistant form composed of numerous "macrocysts", which enable the myxogastria to survive in adverse conditions, for example during winter or dry periods, in this phase. File:Trichia decipiens (Pers.)Macbr.jpg, Sporangia (pediculated) of ''
Trichia decipiens ''Trichia decipiens'' is a worldwide widespread slime mould species from the order Trichiida. Characteristics The plasmodium is white, becoming pink to red at maturity. The small- to large-group-forming fruiting bodies are shiny olive to ye ...
'' (
Trichiales Trichiales ( synonymous with Trichiida) is an order of slime moulds Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage ...
) File:Hemitrichia serpula 57955.jpg, Plasmodiocarp of ''
Hemitrichia serpula ''Hemitrichia'' is a genus of slime molds, of the family Trichiidae, found within the order Trichiida. It was first described by Josef Rostafinksi in 1873 and remains a well-defined genus of the slime molds. ''Hemitrichia'' species exhibit either ...
'' (
Trichiales Trichiales ( synonymous with Trichiida) is an order of slime moulds Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage ...
) File:Enteridium lycoperdon 4.jpg, Aethalium of ''
Enteridium lycoperdon ''Enteridium lycoperdon'', the false puffball, is one of the more obvious species of slime mould or Myxogastria, typically seen in its reproductive phase as a white 'swelling' on standing dead trees in the spring, or on large pieces of fallen wo ...
'' (
Liceales Liceales (also Liceida) is an order of Amoebozoa. References Amoebozoa orders Myxogastria {{Amoebozoa-stub ...
)


Fructification

Mature plasmodia can produce fruit bodies under appropriate circumstances, the exact triggers for this process are unknown. According to laboratory researchers, changes in humidity, temperature or
pH value In chemistry, pH (), historically denoting "potential of hydrogen" (or "power of hydrogen"), is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of ions) are ...
as well as starvation periods were thought to be the triggers in some species. The plasmodia abandon their nutrient intake and crawl, attracted by light – a positive phototaxis – towards a dry, light area, to get an optimal spread of the spores. Once the fructification begins, it cannot be stopped. If disturbances occur, malformed spore-bearing fruit bodies are often produced. The plasmodium or parts of the fruit bodies can be smaller than one millimetre, in extreme cases they are up to a square metre and weigh up to (''
Brefeldia maxima ''Brefeldia maxima'' is a species of non-parasitic plasmodial slime mold, and a member of the class Myxogastria, Myxomycetes. It is common name, commonly known as the tapioca slime mold because of its peculiar pure white, tapioca pudding-like app ...
''). Their shape is often pediculated or unstiped sporangia with non-cellular stems, but can also appear as veined or netted
plasmodiocarp A plasmodiocarp is a special form of fruit bodies of slime moulds. It is produced if the plasmodium concentrates during the fructification and pull back into the venetion of the plasmodium, from which the fruit body is created. The fruit body trac ...
s, pincushion-shaped aethaliae or seemingly pincushion-shaped pseudo-aethaliae. The fruit bodies almost always have a hypothallus on the edge. The abundantly produced spores are stored in a reticular or filamentous structure – the so-called
capillitium Capillitium (pl. capillitia) is a mass of sterile fibers within a fruit body interspersed among spores. It is found in Mycetozoa (slime molds) and gasteroid fungi of the fungal subdivision Agaricomycotina The subdivision Agaricomycotina, also kn ...
– and are found on nearly all species except
Liceida Liceales (also Liceida) is an order of Amoebozoa Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In ...
and other species from the genus '' Echinostelium''. When the open fruit bodies have dried, the spores are dispersed by wind or by small animals such as woodlice, mites or beetles, which either pick up the spores through contact with the fruit bodies or ingest and then excrete them. Dispersal by running water is also possible, but it plays a minor role.


Asexual forms

Some Myxogastria species may produce asexually. These are continuously diploid. There is no meiosis before the germination of the spores and the production of the plasmodium proceeds without germination of two cells.


Distribution and ecology


Distribution

Myxogastria are distributed worldwide; species were found by early researchers on all continents. However, as many parts of the world were yet not discovered or explored, the exact distribution is not fully known. Europe and North America are often considered the basic habitat of the Myxogastria species. According to recent research, the majority of species are not widely distributed. The Myxogastria are most commonly found in temperate latitudes, and rarely in the polar regions, the subtropics or tropics. The physical features of the substrate and climatic conditions are the major aspects of the species' presence.
Endemism Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
is rare. In the northern areas, the species can be found in Alaska, Iceland, northern Scandinavia, Greenland and Russia. These are not only particular, specialised species; according to an overview study, more than 150 species were found in the arctic and subarctic regions of Iceland, Greenland, northern Russia and Alaska. These distinctly exceed the tree line. In Greenland, the habitat may reach the 77th latitude line. The Myxogastria species reach their largest biodiversity and highest frequency in forests of temperate regions, which are ideal habitats because of the amount of rich organic material, suitable humidity (not too high) and long-lasting snow cover for snow-inhabiting species. Few Myxogastria species are found in the tropics and subtropics, mainly because of the high humidity which prevents the necessary dehydration of the fruit bodies to permit spore dispersal and promotes infestation by moulds. Other factors are low light levels under the forest canopy which reduces phototaxis, light winds, poor soils, natural enemies and heavy rainfall which can wash away or destroy cells. Species living in soil or deadwood decrease as humidity increases. In a study from Costa Rica, 73% of the total findings were in the relatively dry Tropical Moist Forest, while 18% were in the very moist Tropical Premontane Wet Forests and only 9% in Lower Premontane Rain Forest. In the Antarctic, species were found in the
South Shetland Islands The South Shetland Islands are a group of Antarctic islands with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the nearest point of the South Orkney Islands. By the Antarctic Treaty of 195 ...
,
South Orkney Islands The South Orkney Islands are a group of islands in the Southern Ocean, about north-east of the tip of the Antarctic PeninsulaSouth Georgia South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east ...
and the
Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...
. Species from the Antarctic or subantarctic regions are rarer than specimens in the Arctic regions, although lack of access may be a factor. Until 1983, only 5 records were made, with only individual finds since then. According to two studies of the myxomycete flora of these regions, more species were discovered in the subantarctic forests, for example 67 species in Argentinian
Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...
and
Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla G ...
, and 22 on high ground on
Macquarie Island Macquarie Island is an island in the southwestern Pacific Ocean, about halfway between New Zealand and Antarctica. Regionally part of Oceania and politically a part of Tasmania, Australia, since 1900, it became a Tasmanian State Reserve in 197 ...
.


Habitats

The majority of Myxogastria species live terrestrially in open forests. The most important microhabitat is deadwood, but also th
bark of living treescorticolous myxomycetes
, rotting plant material, soil, and animal excrements. Slime moulds may be found in numerous unusual locations. The comprehensive group of the nivicol Myxogastria populate closed snow blankets, to quickly fructificate at exposure – for example during thaws – and release their spores. Other habitats are deserts – 33 species were found in the
Sonora desert The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and ecoregion that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the southwestern United States (in Arizona ...
, for example – or living on leaves from plants in the tropics. Some species live in aquatic environments, such as those of the genera ''
Didymium Didymium ( el, , twin) is a mixture of the elements praseodymium and neodymium. It is used in safety glasses for glassblowing and blacksmithing, especially with a gas ( propane)-powered forge, where it provides a filter that selectively block ...
'', ''
Physarum ''Physarum'' is a genus of mycetozoan slime molds in the family Physaraceae. It contains the following species: *''Physarum albescens'' *'' Physarum album'' *'' Physarum andinum'' *'' Physarum bivalve'' *'' Physarum bogoriense'' *'' Physarum c ...
'', '' Perichaena'', ''
Fuligo ''Fuligo'' is a widespread genus of plasmodial slime mold in the family Physaraceae. These organisms are protozoans rather than fungi, but for historical reasons are sometimes treated as part of mycology. Species The following species are acce ...
'', ''
Comatricha ''Comatricha'' is a genus of slime molds in the family Amaurochaetaceae. As of 2015, Index Fungorum ''Index Fungorum'' is an international project to index all formal names (scientific names) in the fungus kingdom. the project is based at th ...
'' and ''
Licea ''Licea'' is a genus of slime molds belonging to the family Liceidae. The genus was species description, first described by Heinrich Schrader (botanist), Heinrich Schrader in 1797. The genus has a cosmopolitan distribution. Species: * ''Licea ...
'', which were found living underwater as myxoflagelletes and plasmodia. All but one species, '' Didymium difforme'', fructificated only when the water ebbed or when they left it.


Relationship to other creatures

The relationships of the Myxogastria to other creatures have not been thoroughly researched as of 2012. Their natural predators include many
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s, including
mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
s and
springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...
s, and especially beetles such as the
rove beetle The rove beetles are a family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With roughly 63,000 species in thousands of genera, the ...
s,
round fungus beetle Leiodidae is a family of beetles with around 3800 described species found worldwide. Members of this family are commonly called round fungus beetles due to the globular shape of many species, although some are more elongated in shape. They are g ...
s, wrinkled bark beetles,
Eucinetidae Eucinetidae is a family of beetles, notable for their large coxal plates that cover much of the first ventrite of the abdomen, sometimes called plate-thigh beetles. The family is small for beetles, with about 50 species in 11 genera, but are ...
, Clambidae, Eucnemidae (false click beetles), Sphindidae, Cerylonidae, and minute brown scavenger beetles. Various
Nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
s have also been observed to be their predators; they attach their posterior portion on the
cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells (intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
of the plasmodia or even live within the strands. Certain
Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
species have evolved to specialise in this way: these are mostly representatives of the
Mycetophilidae The Mycetophilidae are a family of small flies, forming the bulk of those species known as fungus gnats. About 3000 described species are placed in 150 genera, but the true number of species is undoubtedly much higher. They are generally found ...
,
Sciaridae The Sciaridae are a family of flies, commonly known as dark-winged fungus gnats. Commonly found in moist environments, they are known to be a pest of mushroom farms and are commonly found in household plant pots. This is one of the least studie ...
and Drosophilidae. The species ''Epicypta testata'' was especially frequently found, especially on ''Enteridium lycoperdon'', ''Enteridium splendens'', ''Lycogala epidendrum'', and ''Tubifera ferruginosa''. Some true fungi specialise in the colonisation of the Myxogastriae: almost all of these are species of sac fungi. The most common such fungus is ''Verticillium rexianum'' – mainly species from ''Comatricha'' or ''Stemonitis''. ''Gliocladium album'' and ''Sesquicillium microsporum'' are often found on Physaridae, while ''Polycephalomyces tomentosus'' is often found on certain species of Trichiidae. ''Nectriopsis violacea'' specialises on ''Fuligo septica''. Bacterial associates, mainly from the family Enterobacteriaceae, were discovered on plasmodia. The combination of plasmodia and bacteria can bind atmospheric nitrogen or produce enzymes which make possible the decomposition of e.g. lignin, carboxymethylcellulose, or xylan. In a few cases, the plasmodia acquired salt tolerance or Phenotypic plasticity, tolerance of heavy metals through this association. Some myxomycetes (''
Physarum ''Physarum'' is a genus of mycetozoan slime molds in the family Physaraceae. It contains the following species: *''Physarum albescens'' *'' Physarum album'' *'' Physarum andinum'' *'' Physarum bivalve'' *'' Physarum bogoriense'' *'' Physarum c ...
'') cause disease in plants such as turfgrasses, but no control is usually necessary against them.


Fossil records

Fossil records of ''Myxogastria'' are extremely rare. Due to their short lifespan and the fragile structures of the plasmodia and the fruit body, fossilisation and similar processes are not possible. Only their Spore (mycology), spores can be mineralised. The few known examples of fossilised living states are preserved in amber. three fruit bodies, two spores and one plasmodium have been described. Two older taxa – Charles Eugène Bertrand's ''Myxomycetes mangini'' and ''Bretonia hardingheni'' from 1892 – are now considered dubious and are today often disregarded. Friedrich Walter Domke described in 1952 a 35 to 40 million year old find in Baltic amber of ''Stemonitis splendens'', an extant species. The state and completeness of the fruit bodies are remarkable, enabling accurate determination. From the same period, location and material is an ''Arcyria sulcata'', first described in 2003 by Heinrich Dörfelt and Alexander Schmidt, a species very similar to today's ''Arcyria denudata''. Both discoveries imply that the fruit bodies of the ''Myxogastria'' have changed only slightly in the last 35–40 million years. However, the ''Protophysarum balticum'' from Baltic amber, first described by Dörfelt and Schmidt in 2006, is considered questionable. The fossil was inconsistent with the typical characteristics of the genus and it was not a valid publication because no Latin name was identified with it. Also, important details of its fruit bodies were not visible or contradicted the identification. Today it is assumed that the fossil belongs to a lichen similar to the genus ''Chaenotheca''. The only known discovery of a preserved plasmodium was found in Dominican amber, and was then grouped into the Physarida. However, this claim is also considered doubtful as the publication was later classified as insufficient due to lack of evidence. In 2019 sporocarps belonging to ''Stemonitis'' was described from Burmese amber, considered to be of a Mid Cretaceous age around 99 million years old. The sporocarps are indistinguishable from extant taxa, suggesting a long morphological stasis. The only known mineralised fossils are the two spore findings from 1971, one of which, ''Trichia favoginea'', is assumed to be from the postglacial period. In palynology, palynologian researches, by absorbing ''Myxogastria'' spores, the fossil was not recognised.


History of research

Because of their unprepossessing nature, the Myxogastriae were for a long time not well researched. Thomas Panckow first named the mould ''Lycogala epidendrum'' as "''Fungus'' cito crescentes" (fast-growing fungus) in his 1654 book ''Herbarium Portatile, oder behendes Kräuter- und Gewächsbuch''. In 1729, Pier Antonio Micheli thought that fungi are different from moulds, and Heinrich Friedrich Link agreed with this hypothesis in 1833. Elias Magnus Fries documented the plasmodial stage in 1829, and 35 years later Anton de Bary observed the germination of the spores. De Bary also discovered the cyclosis in the cell for the movement, he saw them as animal-like creatures and reclassified them as ''Mycetozoa'', which literally translates "''Fungus animals''". This interpretation prevailed until the second half of the 20th century. From 1874 to 1876, Józef Rostafiński, Józef Tomasz Rostafiński, a student of Anton de Bary, published the first extensive monograph on the group. Three monographs by Arthur Lister and Guilielma Lister were published in 1894, 1911, and 1925. These were groundbreaking works about the Myxogastria, as was the 1934 book ''The Myxomycetes'' by Thomas H. Macbride and George Willard Martin. Important works in the late 20th century were the 1969 monographs by George Willard Martin and Constantine John Alexopoulos, and the 1975 monograph by Lindsay Shepherd Olive. The first is perhaps the most notable, as with it "the modern era of the taxonomy of the Myxogastria began". Other notable researchers were Persoon, Rostafinski, Lister, Macbridge, and Martin and Alexopoulos, who discovered and classified many species.


Notes


References

{{Taxonbar, from1=Q46309, from2=Q19830063, from3=Q23892105, from4=Q10334205 Myxogastria, Amoebozoa classes