Slime molds

from Wikipedia, the free encyclopedia

The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.

The slime molds ( Mycetozoa or Eumycetozoa ) are a taxon of unicellular organisms that combine the characteristics of animals and fungi in their way of life , but do not belong to either group. So, despite their name, they are not mushrooms.

The group includes just over 1000 species , but the number is considered imprecise. According to the more recent opinion, the slime molds no longer represent a common group. The three contained taxa Myxogastria , also known as Myxomycetes (as the most extensive group), Dictyostelia and Protostelia , are no longer put together.

Within biology , systematic research into slime molds is carried out by botany and mycology .

Features and life cycle

Slime molds go through several morphologically extremely different stages in the course of their life. Their respective appearance is inextricably linked to their life cycle.

features

The fruiting bodies produce spores, which in turn are amoeboid organisms. The amoeba are diverse, but always have tubular cristae and pointed pseudopods . Initially, they are mononuclear amoeboflagellates or amoebas . They give rise to multinucleated plasmodia or - in the case of Dictyostelia - multicellular pseudoplasmodia .

Plasmodium in transition to the formation of a fruiting body

Mature slime molds can develop fruiting bodies under appropriate circumstances, either as a sporocarp arising from a single amoeboid cell in Myxogastria and Protostelia, or as a sorocarp in the subclass of Dictyostelia, which is composed of aggregations of amoeboid single cells.

The actual formation of the fruit bodies can take place in two different ways. On the one hand, as with the species of Myxogastria and Protostelia, in which individual plasmodia change from negative to positive phototaxis, move towards the light and thus seek out a high-altitude location that is exposed to the light and thus at the same time to the wind for the purpose of ideal spore spreading, where they develop the fruiting bodies, the so-called sporocarps .

The processes for the representatives of the subclass Dictyostelia are considerably more complex. This is where the cells that were previously living as individual amoebas collect and form a pseudoplasmodium, a temporary multicellular form of organization that moves like a snail. When it arrives at the right place, it undergoes another metamorphosis: some of the cells form a stalk and others the so-called sorus , which contains the spores. Here the fruiting body, the so-called Sorokarp , is not an expression of a cell, but of a complex of cells.

Habitats

The majority of all slime mold species live terrestrially, only a few species are known to have a completely submerged way of life. However, a distinction can be made between various so-called microhabitats , especially tree microhabitats . The most important microhabitat is dead wood ; the bark of living trees, rotting plant material from the litter horizon, soil and animal excrement are also important. A rare special form, especially of tropical species, is the colonization of living leaves by plants. Slime molds are mostly found in open forests, but if the basic conditions are met, slime molds can also be found in unusual places such as deserts ( 33 species have been identified for the Sonoran Desert alone), in the meltwater of alpine snowdrifts and in regions particularly at high latitudes.

distribution

Slime molds are distributed worldwide with the majority of their species, but occur significantly more frequently and with a higher species diversity in temperate latitudes than in the subtropics and tropics .

The reasons for the lower frequency in the tropics are the lack of light in the local forests (impairment of positive phototaxis), calm (detrimental to the distribution of the spores), mold infestation favoring humidity, very acidic soils, a variety of predators and frequent, extremely heavy rains which can wash off or destroy the cells called.

Systematics

The slime mold class includes around 1000 to 1100 species. In 2007, a study estimated the number of species to be well over 1000, after which the subclass Myxogastria, as by far the largest group of slime molds, comprised well over 900 species, with over 100 species the subclass Dictyostelia was already significantly smaller, while the smallest subclass, the Protostelia , included only 36 species. Estimates based on sequenced environmental samples assume that the group is significantly larger than previously known (Myxogastria: 1200–1500 species, Dictyostelia: approx. 300, Protostelia: 150).

The following system is essentially based on Adl et al. In 2005, however, in the ranks and further subdivision of the largest group, the Myxogastria, it takes up the systematics of Dykstra and Keller 2000. It is unclear whether the genus Guttulinopsis belongs to the slime molds or to the Heterolobosea .

Trichia favoginea , ( Myxogastria )
Pseudoplasmodium of a Dictyostelium species, ( Dictyostelia )
Species of Stemonitida , ( Myxogastria )
Ceratiomyxa fruticulosa , ( Protostelia )

proof

  1. ↑ a b c Sina M. Adl, Alastair GB Simpson, Mark A. Farmer, Robert A. Andersen, O. Roger Anderson, John A. Barta, Samuel S. Bowser, Guy Brugerolle, Robert A. Fensome, Suzanne Fredericq, Timothy Y. James, Sergei Karpov, Paul Kugrens, John Krug, Christopher E. Lane, Louise A. Lewis, Jean Lodge, Denis H. Lynn, David G. Mann, Richard M. McCourt, Leonel Mendoza, Øjvind Moestrup, Sharon E. Mozley-Standridge, Thomas A. Nerad, Carol A. Shearer, Alexey V. Smirnov, Frederick W. Spiegel, Max FJR Taylor: The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists. In: The Journal of Eukaryotic Microbiology. Vol. 52 (5), 2005, pp. 399-451.
  2. ^ Henry Stempen, Steven L. Stevenson: Myxomycetes. A Handbook of Slime Molds . Timber Press, 1994, ISBN 0-88192-439-3 , pp. 15-18 .
  3. ↑ a b Michael J. Dykstra, Harold W. Keller: Mycetozoa. In: John J. Lee, GF Leedale, P. Bradbury (Eds.): An Illustrated Guide to the Protozoa . tape 2 . Allen, Lawrence 2000, ISBN 1-891276-23-9 , pp. 952-981 .
  4. ↑ Uno H. Eliasson: Myxomycetes on living leaves in the tropical rainforest of Ecuador; an investigation based on the herbarium of higher plants. In: Wolfgang Nowotny (Ed.): Wolfsblut and Lohblüte. Life forms between animals and plants = Myxomycetes (=  Stapfia . Band 73 ). Linz 2000, ISBN 3-85474-056-5 , p. 81 (German, English, French, Spanish). PDF on ZOBODAT
  5. ^ A b c Henry Stempen, Steven L. Stevenson: Myxomycetes. A Handbook of Slime Molds . Timber Press, 1994, ISBN 0-88192-439-3 , pp. 49-58 .
  6. ↑ Sina M. Adl, Brian S. Leander, Alastair GB Simpson, John M. Archibald, O. Roger Anderson, David Bass, Samuel S. Bowser, Guy Brugerolle, Mark A. Farmer, Sergey Karpov, Martin Kolisko, Christopher E. Lane, Deborah J. Lodge, David G. Mann, Ralf Meisterfeld, Leonel Mendoza, Øjvind Moestrup, Sharon E. Mozley-Standridge, Alexey V. Smirnov, Frederick Spiegel: Diversity, Nomenclature, and Taxonomy of Protists. In: Systematic Biology. Vol. 56, 2007, pp. 684-689.

Web links

Commons : Slime mold (Mycetozoa)  - Collection of images, videos and audio files