Eumycetozoa (), or true slime molds, is a diverse group of

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s that behave as

slime mold Slime mold or slime mould is an informal name given to a polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are near-microscopic; those in the Myxogastria ...

s and develop

fruiting 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 ...

, either as

sorocarp A sorocarp (from the Greek word ''soros'' "a heap" + ''karpos'' "fruit") is the fruiting body characteristic of certain cellular slime moulds (e.g., Dictyosteliida). Each sorocarp consists of both a sorophore (stalk) and a sorus.Lawrence, E. 2 ...

s or as sporocarps. It is a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group or

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

within the phylum

Amoebozoa Amoebozoa is a major Taxonomy (biology), taxonomic group containing about 2,400 described species of Amoeba, amoeboid protists, often possessing blunt, fingerlike, Pseudopod#Morphology, lobose pseudopods and tubular mitochondrial cristae. In trad ...

that contains the myxogastrids,

dictyostelid The dictyostelids (Dictyostelia/Dictyostelea, ICZN, Dictyosteliomycetes, ICBN) or cellular slime molds are a group of slime molds or social amoebae. Multicellular behavior When food (normally bacteria) is readily available dictyostelids behave ...

s and protosporangiids.

Characteristics

Eumycetozoa is a

that includes three groups of amoebozoan protists:

Myxogastria Myxogastria/Myxogastrea (myxogastrids, ICZN) or Myxomycetes ( ICN) is a class of slime molds that contains 5 orders, 14 families, 62 genera, and 888 species. They are colloquially known as the ''plasmodial'' or ''acellula ...

, Dictyostelia and Protosporangiida—also known as Myxomycetes, Dictyosteliomycetes and Ceratiomyxomycetes, respectively. It is defined on a node-based approach as the least inclusive clade containing the species ''

Dictyostelium discoideum ''Dictyostelium discoideum'' is a species of soil-dwelling Amoeboid, amoeba belonging to the phylum Amoebozoa, infraphylum Mycetozoa. Commonly referred to as slime mold, ''D. discoideum'' is a eukaryote that transitions from a collection of unic ...

'' (a dictyostelid), ''

Physarum polycephalum ''Physarum polycephalum'', an Multinucleate, 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 s ...

'' (a myxogastrid) and '' Ceratiomyxa fruticulosa'' (a protosporangiid). All known members of Eumycetozoa generate

, either as

s (in dictyostelids) or as sporocarps (in myxogastrids and protosporangiids). Within their life cycle, they may appear as a single

haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ...

amoeboid An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and r ...

cells (in dictyostelids), or as

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and the ...

d amoebae with two

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

that give rise to obligate amoebae with no cilia, from which the sporocarps develop (in myxogastrids and protosporangiids). The flagellated amoebae of myxogastrids and protosporangiids and non-flagellated amoebae of dictyostelids have a flat cell shape. They form wide

pseudopodia A pseudopod or pseudopodium (: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and ...

with acutely pointed subpseudopodia (i.e. smaller pseudopodia that grow beneath). Unlike other amoebae, the pseudopodia lack a prominent streaming of granular

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

. In eumycetozoans where

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

is well studied, the

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

cannibalizes on haploid amoebae.

Evolution

Eumycetozoa is a well supported

within Amoebozoa. In independent

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, it has been consistently recovered as the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

Archamoebae The Archamoebae are a group of protists originally thought to have evolved before the acquisition of mitochondria by eukaryotes. They include genera that are internal parasites or commensals of animals ('' Entamoeba'' and '' Endolimax''). A few ...

. The Eumycetozoa+Archamoebae clade is, in turn, the sister group to

Variosea Conosa is a grouping of Amoebozoa. It is subdivided into three groups: Archamoeba, Variosea and Mycetozoa. In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa (= Eumycetozoa). Conosa includes t ...

. Within Eumycetozoa, Dictyostelia has a basal position while

and Protosporangiida form a clade. Together, these three groups are part of the larger clade

Conosa Conosa is a grouping of Amoebozoa. It is subdivided into three groups: Archamoeba, Variosea and Mycetozoa. In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa (= Eumycetozoa). Conosa includes t ...

. The following cladogram is based on a 2022 analysis:

Taxonomy

The name Eumycetozoa was first used by German

mycologist Mycology is the branch of biology concerned with the study of fungi, including their taxonomy, genetics, biochemical properties, and use by humans. Fungi can be a source of tinder, food, traditional medicine, as well as entheogens, poison, and ...

Friedrich Wilhelm Zopf Friedrich (or Friederich) Wilhelm Zopf (12 December 1846 – 24 June 1909) was a well-known German botanist and mycologist. He dedicated to his whole life with fungal biology, particularly in classification of fungi and dye production in fungi an ...

in 1884, although no formal

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

was given. In 1975, mycologist Lindsay Shepherd Olive reintroduced the name Eumycetozoa as a

class Class, Classes, 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 d ...

containing the three groups of fruiting amoebae traditionally included in this taxon:

, Dictyostelia and

Protostelia ''Protostelium'' is a genus of protosteloid amoebozoans, i.e., amoebae capable of forming simple fruiting bodies composed of a stalk and a ball of spores. It contains numerous species, including '' P. aurantium'', which was initially classified i ...

. Olive hypothesized that all fruiting amoebae were grouped by this monophyletic taxon, and that the Myxogastria and Dictyostelia were also monophyletic taxa that evolved from a paraphyletic

grade Grade most commonly refers to: * Grading in education, a measurement of a student's performance by educational assessment (e.g. A, pass, etc.) * A designation for students, classes and curricula indicating the number of the year a student has reach ...

of Protostelia. This definition of Eumycetozoa, which included protostelids, was maintained in the 2005

cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

classification of eukaryotes, where the name was synonymized with

Mycetozoa Mycetozoa is a polyphyletic grouping of slime molds. It was originally thought to be a monophyletic clade, but in 2010 it was discovered that protostelia are a polyphyletic group within Conosa. Classification It can be divided into dictyoste ...

. *

** Eumycetozoa Mycetozoa ***

( P) ***

Myxomycetes *** Dictyostelia ***

Incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

Eumycetozoa: '' Copromyxa'', '' Copromyxella'', ''

Fonticula ''Fonticula'' is a genus of cellular slime mold which forms a fruiting body in a volcano shape. As long ago as 1979 it has been known to not have a close relationship with either the Dictyosteliida or the Acrasidae, the two well-established group ...

'' However, studies in the 2000s decade disproved this hypothesis. Both morphological and

molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

studies showed that Eumycetozoa includes a number of non-fruiting amoeboid groups. More importantly, the

were discovered to be

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

. The protosteloid type of fruiting body formation, initially considered the ancestral feature shared between all Eumycetozoa, has evolved independently at least in eight lineages within

(e.g. soliformoviids, cavosteliids, schizoplasmodiids, protosporangiids). This discovery lead to the conclusion that the entirety of Amoebozoa became a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of Eumycetozoa, and was treated as such in the 2012 cladistic classification of eukaryotes. The term Amoebozoa was conserved as a familiar well-established name of popular usage, despite the term Eumycetozoa having priority as the older name. To preserve this widely used name, biologist Seungho Kang and his coauthors redefined Eumycetozoa in 2017 to include only one group of protosteloid amoebae, the Protosporangiida (also known as Ceratiomyxomycetes), which are a monophyletic taxon. This usage corresponds to the 1975 hypothesis from Olive that postulates a

of exclusively fruiting protists that includes myxogastrids, dictyostelids, and some protosteloid amoebae (in this case, the protosporangiids). As of 2019, this renewed definition is accepted by the scientific community and appears in the modern cladistic classification of eukaryotes, revised by the International Society of Protistologists. The name Macromycetozoa was suggested earlier, but Eumycetozoa was chosen for being the oldest term. *

Evosea Evosea is a diverse clade of amoeboid protists discovered through molecular analyses. Along with Tubulinea and Discosea, Evosea is one of the three major groups within Amoebozoa, an important clade of eukaryotic organisms. It contains unicel ...

*** Eumycetozoa Macromycetozoa **** Dictyostelia ****

Myxomycetes **** Protosporangiida The name

was maintained in traditional classifications by some authors like

Thomas Cavalier-Smith Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford. His research has led to discov ...

, who also used a renewed definition to include only protosporangiids. However this scheme did not acquire wide usage.

Notes

References

External links

Eumycetozoa
at UniEuk Taxonomy App. {{taxonbar, from=Q25448563 Protists Taxa described in 1884