Myxogastria
Myxogastria | |
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Badhamia utricularis (Physarales) | |
Scientific classification | |
Domain: | Eukaryota |
Clade: | Amorphea |
Phylum: | Amoebozoa |
Clade: | Evosea |
Subphylum: | Conosa |
Infraphylum: | Eumycetozoa |
Class: | Myxogastria Macbride (1899) |
Orders | |
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Synonyms | |
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Myxogastria/Myxogastrea (myxogastrids,
They are colloquially known as the plasmodial or acellular slime moulds.All species pass through several, very different
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
Taxonomy and classification
Nomenclature
Myxomycota, now considered a
Range
The continuous classification of new taxa reveals that the class is not fully described. According to a 2000 inquiry, there were 1012 officially accepted taxa, including 866 on species level.[7] 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.[7][8]
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.[10] 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.[10][11]
Classification and phylogeny
Cladogram of the Myxogastria | |||||||||||||||||||||||||||
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This is a traditional classification based on Lister and Lister, made in the early 20th century. Molecular genetical studies confirm and stabilise this classification. The most basal group is Echinosteliida. Other groups further contain two superclades, which are morphologically definable by spore colour.[12] |
Cladogram of Myxogastria[13] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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The following classification is based on Adl et al. (2005)
Clade Myxogastria[17] (or myxomycetes)
- Class Ceratiomyxomycetes Hawksworth, Sutton & Ainsworth 1983
- Order CeratiomyxidaMartin 1949 ex Farr & Alexopoulos 1977
- Order ProtosporangiidaShadwick & Spiegel 2012
- Order
- 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
- Order Cribrariales Macbride 1922
- Superorder Trichianae Leontyev 2015
- Order Reticulariales Leontyev 2015
- Family Reticulariaceae Rostafinski 1873
- Order Liceales Jahn 1928
- Family Liceaceae Rostafinski 1873
- Order Trichiales Macbride 1922
- Family DianemidaeMacbride 1899
- Family TrichiidaeRostafinski 1826
- Family
- Order Reticulariales Leontyev 2015
- Superorder Cribrarianae Leontyev 2015
- 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 EchinosteliaceaeRostafinski ex Cooke 1877
- Family
- Order Echinosteliales Martin 1961
- Superorder Stemonitanae Leontyev 2015
- Order Clastodermatales Leontyev et al. 2019
- Family Clastodermataceae Alexopoulos & Brooks 1971
- Order Meridermatales Leontyev 2015
- Family Meridermataceae Leontyev 2015
- Order StemonitalesMacbride 1922
- Family Comatrichaceae Leontyev 2015
- Family Stemonitidaceae Fries 1829
- Order Physarales Macbride 1922
- Family Didymiaceae Rostafinski ex Cooke 1877
- Family Lamprodermataceae Leontyev 2015
- Family Physaraceae Chevallier 1826
- Order Clastodermatales Leontyev et al. 2019
- Order Echinosteliopsidales Shchepin et al.
- Subclass Lucisporomycetidae Leontyev et al. 2019 (Clear‑spored acellular slime moulds)
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
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 specimens which germinated after 75 years. After the spores' development, they first receive a diploid nucleus, and the meiosis 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 protoplasts.[11]
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.[14] Myxamoebae move like amoebae – that is, crawling on the substrate – and are produced in dry conditions. Myxoflagellates, which are peritrichous 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.[11] 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.[11] 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[14] quiescent states – the so-called microcysts. For that to happen, the myxamoebae assume a round shape and secrete a thin cell wall.[18] In this state they can easily survive one year or longer. If living conditions improve, they become active again.[19]
Zygogenesis
If two cells of the same type meet in this phase, they cross-fertilise to a diploid zygote through the fusion of
Plasmodium
The second trophic phase begins with the development of the plasmodium. The multinucleated organism now absorbs via phagocytosis as many nutrients as possible. These are bacteria, protists, dissolved substances, moulds, higher fungi and small particles of organic material.[11] 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 attained a surface area of 5.5 sq m.[20] 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.[14] 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.[19]
The cell has chemotactic and negative phototactic 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.[11] A resting state, the so-called sclerotium, 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,[14] in this phase.[19]
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Sporangia (pediculated) of Trichia decipiens (Trichiales)
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Plasmodiocarp of Hemitrichia serpula (Trichiales)
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Aethalium of Enteridium lycoperdon (Liceales)
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
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 20 kilograms (44 lb) (
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.[19]
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.[11] The Myxogastria are most commonly found in temperate latitudes, and rarely in the polar regions, the subtropics or tropics.[21] The physical features of the substrate and climatic conditions are the major aspects of the species' presence. Endemism is rare.[22]
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.[23] 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.[21] 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.[22]
In the Antarctic, species were found in the South Shetland Islands,[24] South Orkney Islands, South Georgia and the Antarctic Peninsula.[25] 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,[25] with only individual finds since then.[24] 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 and Tierra del Fuego,[26] and 22 on high ground on Macquarie Island.[27]
Habitats
The majority of Myxogastria species live terrestrially in open forests. The most important microhabitat is deadwood, but also the bark of living trees (corticolous myxomycetes), rotting plant material, soil, and animal excrements.
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
Some true fungi specialise in the colonisation of the Myxogastriae: almost all of these are species of
Some myxomycetes (
Fossil records
Fossil records of Myxogastria are extremely rare. Due to their short lifespan and the fragile structures of the
As of 2010[update] three fruit bodies, two spores and one plasmodium have been described. Two older
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
The only known discovery of a preserved plasmodium was found in
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.[38]
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 palynologian researches, by absorbing Myxogastria spores, the fossil was not recognised.[36]
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,
From 1874 to 1876, 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".[7] Other notable researchers were Persoon, Rostafinski, Lister, Macbridge, and Martin and Alexopoulos, who discovered and classified many species.[11][7][a]
Notes
- ^
In addition to the monographs dealing with the group worldwide, some local populations are also important, especially since the group has significantly less regional variation, due to its erratic method of wide dispersion. For example, R. Hagelstein (1944) The Mycetozoa of North America, and M. Farr's volume (1973) for the Flora Neotropica series are important regional descriptions. Other, more recent regional publications are Bruce Ing's The Myxomycetes of Britain and Ireland,[3] L. Band & P. Band (1997) Flora Mycologica Iberica, and Yamamoto (1998) The Myxomycete Biota of Japan.
The three-volume work Die Myxomyceten Deutschlands und des angrenzenden Alpenraumes unter besonderer Berücksichtigung Österreichs[5] (The Myxomyceta of Germany and bordering Alpine regions, with special consideration of Austria) was written from 1993 to 2000 by H. Neubert, W. Nowotny, and K. Baumann, which [Baumann] self-published. Although academically they were amateurs, their work was well received by scholars, and has become a frequently-cited standard work.
References
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- ^ Lindsay S. Olive, 1970: "The Mycetozoa: A revised classification", Botanical Review, 36(1), 59–89.
- ^ ISBN 3929822008
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- ^ a b c d Schnittler, M.; Mitchell, D.W. (2000). "Species Diversity in Myxomycetes based on the morphological species concept – a critical examination". Wolfsblut und Lohblüte.[9]: 39–53
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- ^ ISBN 978-3854740568
- ^ a b Clark, Jim (2000). "The species problem in the myxomycetes". Wolfsblut und Lohblüte.[9]: 39–53
- ^ a b c d e f g h i j k l m n Nowotny, Wolfgang (2000). "Myxomyceten (Schleimpilze) und Mycetozoa (Pilztiere)". Wolfsblut und Lohblüte (in German).[9]: 7–37
- ^ A.-M. Fiore-Donno, C. Berney, J. Pawlowski, S.L. Baldauf, 2005: "Higher-order phylogeny of plasmodial slime molds (Myxogastria) based on elongation factor 1-A and small subunit rRNA gene sequences". Journal of Eukaryotic Microbiology, 52, 201–210.
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- ^ Anna Maria Fiore-Donno, Sergey I. Nikolaev, Michaela Nelson, Jan Pawlowski, Thomas Cavalier-Smith, Sandra L. Baldauf, 2010: "Deep phylogeny and evolution of slime moulds (Mycetozoa)". Protist, 161(1), 55–70
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- ^ a b Steven L. Stephenson, Martin Schnittler, & Carlos Lado, 2004: "Ecological characterization of a tropical myxomycete assemblage – Maquipucuna Cloud Forest Reserve, Ecuador". Mycologia, 96, 488–497.
- ^ Steven L. Stephenson, Yuri K. Novozhilov, & Martin Schnittler, 2000: "Distribution and Ecology of Myxomycetes in High-Latitude Regions of the Northern Hemisphere". Journal of Biogeography, 27(3), 741–754.
- ^ a b J. Putzke; J.A.B. Pereira & M.T.L. Putzke (2004). "New record of Myxomycetes to the Antarctica" (PDF). Actas del V Simposio Argentino y I Latinoamericano de Investigaciones Antarticas. V Simposio Argentino y I Latinoamericano de Investigaciones Antarticas. Vol. 1. Buenos Aires, Argentina. pp. 1–4. Archived from the original (PDF) on 14 October 2012.
- ^ a b B. Ing & R.I.L. Smith, 1983: "Further myxomycete records from South Georgia and the Antarctic peninsula". British Antarctic Survey Bulletin, 59, 80–81.
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- ^ S.L. Stephenson, G.A. Laursen, & R.D. Seppelt: "Myxomycetes of subantarctic Macquarie Island". Australian Journal of Botany, 55, 439–449
- ^ Eliasson, Uno H. (2000). "Myxomyceten auf lebenden Blättern im tropischen Regenwald Ecuadors; eine Untersuchung basierend auf dem Herbarmaterial höherer Pflanzen". Wolfsblut und Lohblüte (in German).[9]: 81
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- ^ ISBN 978-3110190755
- ^ Courtney M. Kilgore & Harold W. Keller, 2008: "Interactions between Myxomycete Plasmodia and Nematodes". Inoculum, 59(1), 1–3
- ^ Indira Kalyanasundaram, 2004: "A Positive Ecological Role for Tropical Myxomycetes in Association with Bacteria". Systematics and Geography of Plants, 74(2), 239–242
- ^ Agrios, George N. (2005). Plant Pathology. 5th ed. Academic Press. link.
- ^ a b c d Harold W. Keller & Sydney E. Everhart, 2008: "Myxomycete species concepts, monotypic genera, the fossil record, and additional examples of good taxonomic practice". Revista Mexicana de Micología, 27, 9–19
- ^ a b Alan Graham, 1971: "The role of myxomyceta spores in palynology (with a brief note on the morphology of certain algal zygospores)". Review of Palaeobotany and Palynology, 11(2), 89–99.
- ^ B.M. Waggoner, G.O. Poinar, 1992: "A fossil Myxomycete plasmodium from Eocene-Oligocene amber of the Dominican Republic". Journal of Eukaryotic Microbiology, 39, 639–642.
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