taxonomic
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
group containing about 2,400 described species of
amoeboid
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 or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
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 ...
pseudopod
A pseudopod or pseudopodium (plural: 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 filamen ...
s and tubular
mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
l
cristae
A crista (; plural cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area f ...
. In traditional and currently no longer supported classification schemes, Amoebozoa is ranked as a
phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
within either the
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 ...
Protista
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 excl ...
or the kingdom
Protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
. In the classification favored by the International Society of Protistologists, it is retained as an unranked "
supergroup Supergroup or super group may refer to:
* Supergroup (music), a music group formed by artists who are already notable or respected in their fields
* Supergroup (physics), a generalization of groups, used in the study of supersymmetry
* Supergroup ...
" within Eukaryota.
Molecular genetic
Molecular genetics is a sub-field of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics often applies an "investigative approach" to determine the ...
analysis supports Amoebozoa as a
monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
. Modern studies of eukaryotic
phylogenetic trees
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...
identify it as the sister group to Opisthokonta, another major clade which contains both
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
and
animals
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
as well as several other clades comprising some 300 species of unicellular eukaryotes. Amoebozoa and Opisthokonta are sometimes grouped together in a high-level
taxon
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 ...
, variously named
Unikonta
Amorphea are members of a taxonomic supergroup that includes the basal Amoebozoa and Obazoa. That latter contains the Opisthokonta, which includes the Fungi, Animals and the Choanomonada, or Choanoflagellates. The taxonomic affinities of the mem ...
, Amorphea or
Opimoda
The Scotokaryotes (Cavalier-Smith) is a proposed basal Neokaryote clade as sister of the Diaphoretickes. Basal Scotokaryote groupings are the Metamonads, the Malawimonas and the Podiata. In this phylogeny the Discoba are sometimes seen as paraph ...
.
Amoebozoa includes many of the best-known amoeboid organisms, such as ''
Chaos
Chaos or CHAOS may refer to:
Arts, entertainment and media Fictional elements
* Chaos (''Kinnikuman'')
* Chaos (''Sailor Moon'')
* Chaos (''Sesame Park'')
* Chaos (''Warhammer'')
* Chaos, in ''Fabula Nova Crystallis Final Fantasy''
* Cha ...
'', ''
Entamoeba
''Entamoeba'' is a genus of Amoebozoa found as internal parasites or commensals of animals.
In 1875, Fedor Lösch described the first proven case of amoebic dysentery in St. Petersburg, Russia. He referred to the amoeba he observed microscopic ...
'', ''
Pelomyxa
''Pelomyxa'' is a genus of giant flagellar amoebae, usually 500-800 μm but occasionally up to 5 mm in length, found in anaerobic or microaerobic bottom sediments of stagnant freshwater ponds or slow-moving streams.Chistyakova, L. V., and A. ...
'' and the genus ''
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 ...
'' itself. Species of Amoebozoa may be either shelled (testate) or naked, and cells may possess
flagella
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 ...
. Free-living species are common in both salt and freshwater as well as soil, moss and leaf litter. Some live as
parasites
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
or
symbionts
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
of other organisms, and some are known to cause disease in humans and other organisms.
While the majority of amoebozoan species are unicellular, the group also includes several clades of
slime molds
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 ...
, which have a macroscopic, multicellular stage of life during which individual amoeboid cells remain together after multiple cell division to form a macroscopic plasmodium or, in cellular slime molds, aggregate to form one.
Amoebozoa vary greatly in size. Some are only 10–20 μm in diameter, while others are among the largest protozoa. The well-known species ''
Amoeba proteus
''Amoeba proteus'' is a large species of amoeba closely related to another genus of giant amoebae, ''Chaos''. As such, the species is sometimes given the alternative scientific name ''Chaos diffluens''.
This protozoan uses extensions called pseu ...
,'' which may reach 800 μm in length, is often studied in schools and laboratories as a representative cell or
model organism
A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...
, partly because of its convenient size.
Multinucleate
Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinat ...
amoebae like ''Chaos'' and ''Pelomyxa'' may be several millimetres in length, and some multicellular amoebozoa, such as the "dog vomit" slime mold ''
Fuligo septica
''Fuligo septica'' is a species of slime mold, and a member of the class Myxomycetes. It is commonly known as scrambled egg slime, or flowers of tan because of its peculiar yellowish appearance. It is also known as dog vomit slime mold, and is ...
'', can cover an area of several square meters.
Morphology
Amoebozoa is a large and diverse group, but certain features are common to many of its members. The amoebozoan cell is typically divided into a granular central mass, called
endoplasm
Endoplasm generally refers to the inner (often granulated), dense part of a cell's cytoplasm. This is opposed to the ectoplasm which is the outer (non-granulated) layer of the cytoplasm, which is typically watery and immediately adjacent to the ...
, and a clear outer layer, called ectoplasm. During locomotion, the endoplasm flows forwards and the ectoplasm runs backwards along the outside of the cell. In motion, many amoebozoans have a clearly defined anterior and posterior and may assume a "monopodial" form, with the entire cell functioning as a single pseudopod. Large pseudopods may produce numerous clear projections called subpseudopodia (or determinate pseudopodia), which are extended to a certain length and then retracted, either for the purpose of locomotion or food intake. A cell may also form multiple indeterminate pseudopodia, through which the entire contents of the cell flow in the direction of locomotion. These are more or less tubular and are mostly filled with granular endoplasm. The cell mass flows into a leading pseudopod, and the others ultimately retract, unless the organism changes direction.
While most amoebozoans are "naked," like the familiar ''
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 ...
'' and ''Chaos'', or covered with a loose coat of minute scales, like
Cochliopodium
''Cochliopodium'' is a Himatismenida genus.
It has been found in eyewash stations.
It includes:
* ''C. actinophorum'' (Auerbach 1856) Page 1976
* ?''C. ambiguum'' Penard 1904
* ''C. arabianum'' Tekle, Gorfu & Anderson 2015
* ''C. barki'' Kudry ...
and
Korotnevella
''Korotnevella'' is a genus of Amoebozoa.EOL
EOL or Eol may refer to:
* Encyclopedia of Life, a freely-accessible, online collaborative bio-encyclopedia
* End-of-life (product), a term used with respect to terminating the sale or support of goo ...
, members of the order
Arcellinida
Arcellinid testate amoebae or Arcellinida,http://www.microscopy-uk.org.uk/mag/artjun03/gsamoebae.html Testate amoebae, peat bogs and past climates. accessed 16 march 2007 Arcellacean or lobose testate amoebae are single-celled protists partially ...
form rigid shells, or
tests
Test(s), testing, or TEST may refer to:
* Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities
Arts and entertainment
* ''Test'' (2013 film), an American film
* ''Test'' (2014 film), ...
, equipped with a single aperture through which the pseudopods emerge. Arcellinid tests may be secreted from organic materials, as in ''
Arcella
''Arcella'' is a genus of testate amoebae in the order Arcellinida, usually found in freshwaters and mosses, and rarely in soils. A key characteristic of ''Arcella'' is the circular test with a hole on its center from where finger-like pseudopod ...
'', or built up from collected particles cemented together, as in ''
Difflugia
''Difflugia'' is the largest genus of Arcellinida, one of several groups of Tubulinea within the eukaryote supergroup Amoebozoa. Arcellinida species produce shells or tests from mineral particles or biogeonic elements (e.g. diatom frustules) and ...
. ''
In all amoebozoa, the primary mode of nutrition is
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 ...
, in which the cell surrounds potential food particles with its pseudopods, sealing them into
vacuole
A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...
s within which they may be digested and absorbed. Some amoebozoans have a posterior bulb called a uroid, which may serve to accumulate waste, periodically detaching from the rest of the cell. When food is scarce, most species can form
cyst
A cyst is a closed sac, having a distinct envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac (like the manner in which ...
s, which may be carried aerially and introduce them to new environments. In slime moulds, these structures are called spores, and form on stalked structures called fruiting bodies or
sporangia
A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...
.
The majority of Amoebozoa lack
flagella
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 more generally do not form
microtubule
Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...
-supported structures except during
mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
. However, flagella do occur among the
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 sp ...
, and many slime moulds produce biflagellate
gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...
s . The flagellum is generally anchored by a cone of microtubules, suggesting a close relationship to the
opisthokont
The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and ...
s. The
mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
in amoebozoan cells characteristically have branching tubular cristae. However, among the
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 sp ...
, which are adapted to anoxic or microaerophilic habitats, mitochondria have been lost.
Classification
Place of Amoebozoa in the eukaryote tree
It appears (based on molecular genetics) that the members of Amoebozoa form a
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 t ...
to animals and fungi, diverging from this lineage after it had split from the other groups,
as illustrated below in a simplified diagram:
Strong similarities between Amoebozoa and
Opisthokont
The opisthokonts () are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and ...
s lead to the hypothesis that they form a distinct clade. Thomas Cavalier-Smith proposed the name "unikonts" (formally, Unikonta) for this branch, whose members were believed to have been descended from a common ancestor possessing a single emergent flagellum rooted in one
basal body
A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a eukaryotic undulipodium (cilium or flagellum). The basal body was named by Theodor W ...
.2] However, while the close relationship between Amoebozoa and Opisthokonta is robustly supported, recent work has shown that the hypothesis of a uniciliate ancestor is probably false. In their Revised Classification of Eukaryotes (2012), Adl et al. proposed Amorphea as a more suitable name for a clade of approximately the same composition, a sister group to the
Diaphoretickes
Diaphoretickes () is a major group of eukaryotic organisms, with over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes.
Diaphoretickes includes:
* Archaeplastida (comprising red alg ...
. More recent work places the members of Amorphea together with the malawimonids and
collodictyon
''Collodictyon'' is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids. Due to their mix of cellular components, Collodictyonids do not belong to any well-known kingdom (biology), kingdom-l ...
ids in a proposed clade called Opimoda, which comprises one of two major lineages diverging at the root of the eukaryote tree of life, the other being
Diphoda
A bikont ("two flagella") is any of the eukaryotic organisms classified in the group Bikonta. Many single-celled members of the group, and the presumed ancestor, have two flagella.
Enzymes
Another shared trait of bikonts is the fusion of two ge ...
.
Subphyla within Amoebozoa: Lobosa and Conosa
Traditionally all amoebozoa with lobose pseudopods were grouped together in the class
Lobosea
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
, placed with other amoeboids in the phylum Sarcodina or
Rhizopoda
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 ...
, but these were considered to be unnatural groups. Structural and genetic studies identified the
percolozoa
The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages.
Characteristics
Most Percolozoa are found as bacterivores in soil, fresh water and occasional ...
ns and several archamoebae as independent groups. In phylogenies based on
rRNA
Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosoma ...
their representatives were separate from other amoebae, and appeared to diverge near the base of
eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
evolution, as did most slime molds.
However, revised trees by
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 ...
and Chao in 1996 suggested that the remaining lobosans do form a monophyletic group, to which the Archamoebae and Mycetozoa were closely related, although the percolozoans were not. Subsequently, they emended the phylum Amoebozoa to include both the subphylum Lobosa and a new subphylum
Conosa
Conosa is a grouping of Amoebozoa. It is subdivided into three groups – Archamoebae, Variosea (paraphyletic) and Mycetozoa (polyphyletic).
In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa. ...
, comprising the Archamoebae and the
Mycetozoa
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 dictyostelid ...
.
Recent molecular genetic data appear to support this primary division of the Amoebozoa into Lobosa and Conosa. The former, as defined by Cavalier-Smith and his collaborators, consists largely of the classic Lobosea: non-flagellated amoebae with blunt, lobose pseudopods (''Amoeba'', ''Acanthamoeba, Arcella, Difflugia etc.''). The latter is made up of both amoeboid and flagellated cells, characteristically with more pointed or slightly branching subpseudopodia (Archamoebae and the Mycetozoan slime molds).
Discosea
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a ...
Cavalier-Smith 2004 stat. nov. Adl et al. 2018
** Order ? Stereomyxida Grell 1971
** Order ?
Stygamoebida
The Flabellinia are a subclass of Amoebozoa. During locomotion the cells are flattened and have a clear layer called ''hyaloplasm'' along the front margin. Some form slender subpseudopodia projecting outward from the hyaloplasm, but the cell m ...
Smirnov & Cavalier-Smith 2011
** Class
Centramoebia
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a ...
Cavalier-Smith et al. 2016
*** Order
Centramoebida
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a ...
Rogerson & Patterson 2002 em. Cavalier-Smith 2004
*** Order
Himatismenida
Himatismenida is an Amoebozoa order, in the class Discosea, along with Glycostylida and Dermamoebida. It contains species such as ''Cochliopodium
''Cochliopodium'' is a Himatismenida genus.
It has been found in eyewash stations.
It includes ...
Pellitida
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, ...
Flabellinia
The Flabellinia are a subclass of Amoebozoa. During locomotion the cells are flattened and have a clear layer called ''hyaloplasm'' along the front margin. Some form slender subpseudopodia projecting outward from the hyaloplasm, but the cell ma ...
Smirnov & Cavalier-Smith 2011 em. Kudryavtsev et al. 2014
*** Order
Thecamoebida
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a ...
Schaeffer 1926 em. Smirnov & Cavalier-Smith 2011
*** Order
Dermamoebida
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, ...
Cavalier-Smith 2004 em. Smirnov & Cavalier-Smith 2011
*** Order
Vannellida
The Vannellidae are a family of Amoebozoa, which are found in soil, fresh- and salt water. The most common genus is ''Vannella''.
Description
''Vannellidae'' tend to be flattened and fan-shaped during motion, although some are long and narrow, a ...
Smirnov et al. 2005
*** Order
Dactylopodida
Dactylopodida is an Amoebozoa grouping.
References
Amoebozoa orders
Discosea
{{Amoebozoa-stub ...
Smirnov et al. 2005
* Clade Tevosa Kang et al. 2017
** Clade
Tubulinea
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and ''Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical for ...
Smirnov et al. 2005 stat. nov. Adl et al. 2018
*** Class Corycidia Kang et al. 2017 stat. nov. Adl et al. 2018
***** Order
Trichosida
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
Moebius 1889
***** Family
Microcoryciidae
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
de Saedeleer 1934
*** Class Echinamoebia Cavalier-Smith 2016 stat. nov. Adl et al. 2018
**** Order
Echinamoebida
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
Cavalier-Smith 2004 em. 2011
*** Class Elardia Kang et al. 2017 stat. nov. Adl et al. 2018
**** Subclass Leptomyxia Cavalier-Smith 2016
***** Order
Leptomyxida
Leptomyxida is an order of Amoebozoa.
It includes species such as '' Flabellula citata'', '' Paraflabellula hoguae'', '' Paraflabellula reniformis'', '' Rhizamoeba saxonica'' and '' Leptomyxa reticulata''.
Taxonomy
The taxonomy of Leptomyxida ...
Pussard & Pons 1976 em. Page 1987
**** Subclass
Eulobosia
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
Cavalier-Smith 2016
***** Order
Euamoebida
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and '' Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical f ...
Lepşi 1960 em. Cavalier-Smith 2016
***** Order
Arcellinida
Arcellinid testate amoebae or Arcellinida,http://www.microscopy-uk.org.uk/mag/artjun03/gsamoebae.html Testate amoebae, peat bogs and past climates. accessed 16 march 2007 Arcellacean or lobose testate amoebae are single-celled protists partially ...
Kent 1880
** Clade Evosea Kang et al. 2017 stat. nov. Adl et al. 2018
*** Clade
Cutosa
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 traditional and currently no longer supported classif ...
Cavalier-Smith 2016 stat. nov.
**** Class
Cutosea
Lobosa is a Taxon, taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded Pseudopodia, pseudopods, although one genus in the group, the recently discovered ''Sapocribrum,'' has slender and threadlike (fi ...
Cavalier-Smith 2016
***** Order
Squamocutida
Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered ''Sapocribrum,'' has slender and threadlike (filose) pseudopodia. ...
Cavalier-Smith 2016
*** Subphylum
Conosa
Conosa is a grouping of Amoebozoa. It is subdivided into three groups – Archamoebae, Variosea (paraphyletic) and Mycetozoa (polyphyletic).
In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa. ...
Cavalier-Smith 1998 stat. nov.
**** Infraphylum
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 sp ...
Cavalier-Smith 1993 stat. n. 1998
***** Class Archamoebea Cavalier-Smith 1983 stat. n. 2004
****** Family
Tricholimacidae
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 ...
Cavalier-Smith 2013
****** Family
Endamoebidae
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 ...
Calkins 1926
****** Order
Entamoebida
Entamoebidae is a family of Archamoebae.
It includes ''Entamoeba
''Entamoeba'' is a genus of Amoebozoa found as internal parasites or commensals of animals.
In 1875, Fedor Lösch described the first proven case of amoebic dysentery in S ...
Cavalier-Smith 1993
****** Order
Pelobiontida
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 ...
Page 1976 emend. Cavalier Smith 1987
**** Infraphylum
Semiconosia
Conosa is a grouping of Amoebozoa. It is subdivided into three groups – Archamoebae, Variosea (paraphyletic) and Mycetozoa (polyphyletic).
In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa.
...
Cavalier-Smith 2013
***** Class
Variosea
Conosa is a grouping of Amoebozoa. It is subdivided into three groups – Archamoebae, Variosea (paraphyletic) and Mycetozoa (polyphyletic).
In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa. ...
Phalansteriida
''Phalansterium'' is a genus of single-celled flagellated organisms comprising several species, which form colonies. ''Phalansterium'' produces tetraspores.
''Phalansterium'' is hard to classify; it has a distinctive ultrastructure of its peric ...
Mycetozoa
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 dictyostelid ...
de Bary, 1859 ex Rostafinski, 1873
****** Class
Dictyostelea
The dictyostelids (Dictyostelia/Dictyostelea, ICZN, or Dictyosteliomycetes, ICBN) are a group of cellular slime molds, or social amoebae.
Multicellular behavior
When food (normally bacteria) is readily available dictyostelids behave as individ ...
Hawksworth et al. 1983
******* Order Acytosteliales Baldauf, Sheikh & Thulin 2017
******* Order
Dictyosteliales
The dictyostelids (Dictyostelia/Dictyostelea, International Code of Zoological Nomenclature, ICZN, or Dictyosteliomycetes, ICBN) are a group of cellular slime molds, or social amoebae.
Multicellular behavior
When food (normally bacteria) is rea ...
Lister 1909 em. Olive 1970
****** Class Ceratiomyxomycetes Hawksworth, Sutton & Ainsworth 1983
******* 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
******* 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 1961 ex Farr & Alexopoulos
****** Class Myxomycetes Link 1833 em. Haeckel 1866
******* Subclass Lucisporomycetidae Leontyev et al. 2019
******** Superorder Cribrarianae Leontyev 2015
********* Order Cribrariales Macbr. 1922
******** Superorder Trichianae Leontyev 2015
********* Order Reticulariales Leontyev 2015
********* Order
Liceales
Liceales (also Liceida) is an order of Amoebozoa.
References
Amoebozoa orders
Myxogastria
{{Amoebozoa-stub ...
Jahn 1928
********* 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 ...
Echinosteliales
The Echinosteliales are an order of Amoebozoa in the class Myxomycetes. It contains two families, the Clastodermataceae and the Echinosteliaceae. Echinosteliales was circumscribed by George Willard Martin
George Willard Martin (October 27, 18 ...
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
********* Order
Physarales
Physarales is an order of Amoebozoa in the class Myxomycetes. It contains three families, the Didymiaceae, the Lamprodermataceae, and the Physaraceae. Physarales was circumscribed by Thomas Huston Macbride
Thomas Huston Macbride (July 31, 1848 ...
Macbride 1922
Fossil record
Vase-shaped
microfossils
A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...
(VSMs) discovered around the world show that amoebozoans have existed since the
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago.
It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...
Era. The fossil species ''Melanocyrillium hexodiadema'', ''Palaeoarcella athanata'', and ''Hemisphaeriella ornata'' come from rocks 750 million years old. All three VSMs share a hemispherical shape, invaginated aperture, and regular indentations, that strongly resemble modern arcellinids, which are shell-bearing amoeboids. ''P. athanata'' in particular looks the same as the extant genus ''Arcella''.
List of amoebozoan protozoa pathogenic to humans
*''
Entamoeba histolytica
''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...
''
*''
Acanthamoeba
''Acanthamoeba'' is a genus of amoeboid, amoebae that are commonly recovered from soil, fresh water, and other habitat (ecology), habitats.
''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resi ...
''
*''
Balamuthia mandrillaris
''Balamuthia mandrillaris'' is a free-living amoeba that causes the rare but deadly neurological condition granulomatous amoebic encephalitis (GAE). ''B. mandrillaris'' is a soil-dwelling amoeba and was first discovered in 1986 in the brain of ...
''
*''
Endolimax
''Endolimax'' is a genus of amoebozoa that are found in the intestines of various animals, including the species ''E. nana'' found in humans. Originally thought to be non-pathogenic, studies suggest it can cause intermittent or chronic diarrhea ...
''
Meiosis
The recently available ''
Acanthamoeba
''Acanthamoeba'' is a genus of amoeboid, amoebae that are commonly recovered from soil, fresh water, and other habitat (ecology), habitats.
''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resi ...
''
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
sequence revealed several
orthologs
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spec ...
of genes employed in
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 ...
of sexual
eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
s. These genes included ''
Spo11
Spo11 is a protein that in humans is encoded by the ''SPO11'' gene. Spo11, in a complex with mTopVIB, creates double strand breaks to initiate meiotic recombination. Its active site contains a tyrosine which ligates and dissociates with DNA to pr ...
,
Mre11
Double-strand break repair protein MRE11 is an enzyme that in humans is encoded by the ''MRE11'' gene. The gene has been designated ''MRE11A'' to distinguish it from the pseudogene ''MRE11B'' that is nowadays named ''MRE11P1''.
Function
This ge ...
,
Rad50
DNA repair protein RAD50, also known as RAD50, is a protein that in humans is encoded by the ''RAD50'' gene.
Function
The protein encoded by this gene is highly similar to ''Saccharomyces cerevisiae'' Rad50, a protein involved in DNA double- ...
,
Rad51
DNA repair protein RAD51 homolog 1 is a protein encoded by the gene ''RAD51''. The enzyme encoded by this gene is a member of the RAD51 protein family which assists in repair of DNA double strand breaks. RAD51 family members are homologous to th ...
,
Rad52
RAD52 homolog (S. cerevisiae), also known as RAD52, is a protein which in humans is encoded by the ''RAD52'' gene.
Function
The protein encoded by this gene shares similarity with ''Saccharomyces cerevisiae'' Rad52, a protein important for DNA ...
, Mnd1,
Dmc1
Meiotic recombination protein DMC1/LIM15 homolog is a protein that in humans is encoded by the ''DMC1'' gene.
Meiotic recombination protein Dmc1 is a homolog of the bacterial strand exchange protein RecA. Dmc1 plays the central role in homologous ...
, Msh'' and '' Mlh''. This finding suggests that ''Acanthamoeba'' is capable of some form of meiosis and may be able to undergo sexual reproduction.
In sexually reproducing eukaryotes,
homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
(HR) ordinarily occurs during meiosis. The meiosis-specific
recombinase
Recombinases are genetic recombination enzymes.
Site specific recombinases
DNA recombinases are widely used in multicellular organisms to manipulate the structure of genomes, and to control gene expression. These enzymes, derived from bacteria (b ...
,
Dmc1
Meiotic recombination protein DMC1/LIM15 homolog is a protein that in humans is encoded by the ''DMC1'' gene.
Meiotic recombination protein Dmc1 is a homolog of the bacterial strand exchange protein RecA. Dmc1 plays the central role in homologous ...
, is required for efficient meiotic HR, and Dmc1 is expressed in ''
Entamoeba histolytica
''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...
''. The purified Dmc1 from ''E. histolytica'' forms
presynaptic
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from ...
filaments and catalyzes ATP-dependent homologous DNA pairing and DNA strand exchange over at least several thousand
base pairs
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
. The DNA pairing and strand exchange reactions are enhanced by the eukaryotic meiosis-specific recombination accessory factor (heterodimer) Hop2-Mnd1. These processes are central to meiotic recombination, suggesting that ''E. histolytica'' undergoes meiosis.
Studies of '' Entamoeba invadens'' found that, during the conversion from the
tetraploid
Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
uninucleate
{{Short pages monitor The reason these species haven't been differentiated until recently is because of the reliance on appearance.
Gallery
File:Amoeba proteus.jpg, ''
Amoeba proteus
''Amoeba proteus'' is a large species of amoeba closely related to another genus of giant amoebae, ''Chaos''. As such, the species is sometimes given the alternative scientific name ''Chaos diffluens''.
This protozoan uses extensions called pseu ...
'' (
Lobosa
Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered ''Sapocribrum,'' has slender and threadlike (filose) pseudopodia. ...
:
Tubulinea
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like ''Amoeba'', ''Arcella'', ''Difflugia'' and ''Hartmannella''.
Characteristics
During locomotion most Tubulinea have a roughly cylindrical for ...
)
File:Arcella sp.jpg, ''
Arcella
''Arcella'' is a genus of testate amoebae in the order Arcellinida, usually found in freshwaters and mosses, and rarely in soils. A key characteristic of ''Arcella'' is the circular test with a hole on its center from where finger-like pseudopod ...
Acanthamoeba
''Acanthamoeba'' is a genus of amoeboid, amoebae that are commonly recovered from soil, fresh water, and other habitat (ecology), habitats.
''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resi ...
'' sp. (Lobosa:
Discosea
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a ...
)
File:Thecamoeba striata001.JPG, ''
Thecamoeba
''Thecamoeba ''is a genus 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 tradition ...
Entamoeba histolytica
''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwid ...
''
trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the '' Giardia'' group. (The complement of the trophozo ...
(
Conosa
Conosa is a grouping of Amoebozoa. It is subdivided into three groups – Archamoebae, Variosea (paraphyletic) and Mycetozoa (polyphyletic).
In some classifications, the mycetozoan Myxogastria and Dictyostelia are united in Macromycetozoa. ...
:
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 sp ...
)
Pelomyxa palustris.jpg, ''
Pelomyxa palustris
''Pelomyxa'' is a genus of giant flagellar amoebae, usually 500-800 μm but occasionally up to 5 mm in length, found in anaerobic or microaerobic bottom sediments of stagnant freshwater ponds or slow-moving streams.Chistyakova, L. V., and A ...
Stemonitis
''Stemonitis'' is a distinctive genus of slime moulds found throughout the world (except Antarctica). They are characterised by the tall brown sporangia, supported on slender stalks, which grow in clusters on rotting wood. The genus was first des ...
'' sp. (Conosa:
Myxogastria
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 ...
)
File:Dictyostelium discoideum 02.jpg, ''
Dictyostelium discoideum
''Dictyostelium discoideum'' is a species of soil-dwelling 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 unicellular ...