The Percolozoa are a group of colourless, non-photosynthetic

Excavata Excavata is a major supergroup of unicellular organisms belonging to the domain Eukaryota. It was first suggested by Simpson and Patterson in 1999 and introduced by Thomas Cavalier-Smith in 2002 as a formal taxon. It contains a variety of free- ...

, including many that can transform between

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 ...

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 thei ...

, and

cyst 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) ...

stages.

Characteristics

Most Percolozoa are found as bacterivores in soil, fresh water and occasionally in the ocean. The only member of this group that is infectious to humans is '' Naegleria fowleri'', the causative agent of the often fatal disease amoebic meningitis. The group is closely related to the

Euglenozoa Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by three major clades, i.e., Kinetoplastea, D ...

, and share with them the unusual characteristic of having

mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

with discoid

crista 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 fo ...

e. The presence of a ventral feeding groove in the flagellate stage, as well as other features, suggests that they are part of the

group. The amoeboid stage is roughly cylindrical, typically around 20-40 μm in length. They are traditionally considered lobose amoebae, but are not related to the others, and unlike them, do not form true lobose

pseudopods 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 filame ...

. Instead, they advance by eruptive waves, where hemispherical bulges appear from the front margin of the cell, which is clear. The flagellate stage is slightly smaller, with two or four anterior flagella anterior to the feeding groove. Usually, the amoeboid form is taken when food is plentiful, and the flagellate form is used for rapid locomotion. However, not all members are able to assume both forms. The genera '' Percolomonas'', ''

Lyromonas Lyromonas is a genus of Excavata unicellular organism A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fal ...

'', and ''

Psalteriomonas ''Psalteriomonas'' is a genus of excavates in the group of Heterolobosea The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages. Characteristics Mos ...

'' are known only as flagellates, while '' Vahlkampfia'', ''

Pseudovahlkampfia ''Pseudovahlkampfia'' is a genus of Excavates It includes the species ''Pseudovahlkampfia emersoni''. References Percolozoa Excavata genera {{Excavata-stub ...

'', and most

acrasid The family Acrasidae (International Code of Zoological Nomenclature, ICZN, or Acrasiomycota, ICBN) is a family of slime molds which belongs to the Excavata, excavate group Percolozoa. The name element - comes from the Greek ''akrasia'', meaning ...

s do not have flagellate stages. As mentioned above, under unfavourable conditions, the acrasids aggregate to form sporangia. These are superficially similar to the sporangia of the dictyostelids, but the amoebae only aggregate as individuals or in small groups and do not die to form the stalk.

Terminology and classification

These are collectively referred to as schizopyrenids, amoeboflagellates, or vahlkampfids. They also include the acrasids, a group of social amoebae that aggregate to form

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 entire group is usually called the Heterolobosea, but this may be restricted to members with amoeboid stages. One Heterolobosea classification system is: * Order Schizopyrenida ** Family Vahlkampfiidae ** Family

Gruberellidae Gruberellidae is a family of Heterolobosea 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 bact ...

* Order

Acrasida The family Acrasidae (ICZN, or Acrasiomycota, ICBN) is a family of slime molds which belongs to the excavate group Percolozoa. The name element - comes from the Greek ''akrasia'', meaning "acting against one's judgement". This group consists ...

** Family Acrasidae ''Pleurostomum flabellatum'' has recently been added to Heterolobosea.

Phylogeny

Based on the cladogram from Tolweb and updated with new data from Pánek & Čepička 2012 and Pánek, Ptackova & Čepička 2014.

Taxonomy

Phylum Percolozoa Cavalier-Smith 1991 * Subphylum Pharyngomonada ** Class Pharyngomonadea acropharyngomonadidea*** Order Pharyngomonadida acropharyngomonadida**** Family Pharyngomonadidae Cavalier-Smith 2008 acropharyngomonadidae Cavalier-Smith 2008***** Genus '' Pharyngomonas'' Cavalier-Smith 2008 'Macropharyngomonas''_nomen_nudum.html" ;"title="Macropharyngomonas.html" ;"title="'Macropharyngomonas">'Macropharyngomonas'' nomen nudum">Macropharyngomonas.html" ;"title="'Macropharyngomonas">'Macropharyngomonas'' nomen nudum* Subphylum Tetramitia Cavalier-Smith 1993 emend. Cavalier-Smith 2008 ** Genus ?''Costiopsis'' Senn 1900 ** Genus ?''Hoehnmastix'' Skvortzov 1974 ** Genus ?''Planiosculum'' Szabados 1948 ** Genus ?'' Protomyxomyces'' Cunningham 1881 ** Genus ?'' Protonaegleria'' Michel & Raether 1985 ** Genus ?''

Pseudovahlkampfia ''Pseudovahlkampfia'' is a genus of Excavates It includes the species ''Pseudovahlkampfia emersoni''. References Percolozoa Excavata genera {{Excavata-stub ...

'' Sawyer 1980 ** Genus ?'' Schizamoeba'' Davis 1926 ** Genus ?'' Tetramastigamoeba'' Singh & Hanumaiah 1977 ** Genus ?'' Trimastigamoeba'' Whitmore 1911 ** Genus ?'' Wasielewskia'' Hartmann & Schuessler 1913 ** Order ? Euhyperamoebida *** Family Euhyperamoebidae Goodkov & Seravin 1984 yperamoebidae Goodkov, Seravin & Railkin 1982**** Genus '' Euhyperamoeba'' Goodkov & Seravin 1984 'Hyperamoeba''_Goodkov,_Seravin_&_Railkin_1982_non_Alexeieff_1923.html" ;"title="Hyperamoeba.html" ;"title="'Hyperamoeba">'Hyperamoeba'' Goodkov, Seravin & Railkin 1982 non Alexeieff 1923">Hyperamoeba.html" ;"title="'Hyperamoeba">'Hyperamoeba'' Goodkov, Seravin & Railkin 1982 non Alexeieff 1923** Order Selenaionida Hanousková, Táborský & Čepička 2018 *** Family Selenaionidae Hanousková, Táborský & Čepička 2018 **** Genus ''Selenaion koniopes'' Park, De Jonckheere & Simpson 2012 **** Genus '' Dactylomonas'' Hanousková, Táborský & Čepička 2018 ** Order Neovahlkampfiida *** Family Neovahlkampfiidae **** Genus '' Neovahlkampfia'' Brown & de Jonckheere 1999 ** Class Lyromonadea Cavalier-Smith 1993 *** Order Paravahlkampfiida **** Family Paravahlkampfiidae ***** Genus '' Fumarolamoeba'' De Jonckheere, Murase & Opperdoes 2011 ***** Genus '' Paravahlkampfia'' Brown & de Jonckheere 1999 *** Order Lyromonadida Cavalier-Smith 1993 **** Family

Lyromonadidae Lyromonas is a genus of Excavata unicellular organism A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fal ...

Cavalier-Smith 1993 ***** Genus ''

'' Cavalier-Smith 1993 **** Family Plaesiobystridae ***** Genus '' Pernina'' El Kadiri, Joyon & Pussard 1992 ***** Genus '' Euplaesiobystra'' Park et al. 2009 ***** Genus '' Plaesiobystra'' ***** Genus '' Heteramoeba'' Droop 1962 **** Family

Page & Blanton 1985 ***** Genus '' Gruberella'' Page 1984 non Gruber 1889 non Corliss 1960 ***** Genus '' Vrihiamoeba'' Murase, Kawasak & Jonckheere 2010 ***** Genus '' Oramoeba'' ***** Genus '' Stachyamoeba'' Page 1975 **** Family Psalteriomonadidae Cavalier-Smith 1993 ***** Genus '' Pseudoharpagon'' Panek et al. 2012 ***** Genus '' Sawyeria'' O'Kelly et al. 2003 ***** Genus ''

'' Broers et al. 1990 ***** Genus '' Pseudomastigamoeba'' ***** Genus '' Harpagon'' Panek et al. 2012 ***** Genus '' Monopylocystis'' O'Kelly et al. 2003 ** Class Heterolobosidea *** Order

Schröter 1886 **** ?Genus '' Allovahlkampfia'' Walochnik & Mulec 2009 **** ?Genus '' Solumitrus'' Wang et al. 2011 **** Family Acrasidae Poche 1913 ***** Genus '' Acrasis'' van Tieghem 1880 ***** Genus '' Pocheina'' Loeblich & Tappan 1961 **** Family ? Guttulinopsidae Olive 1970 uttulinidae Berl. 1888; Guttulinopsaceae***** Genus '' Guttulina'' Cienkowski 1873 non D’Orbigny 1839 ***** Genus '' Guttulinopsis'' Olive 1901 ***** Genus '' Rosculus'' Hawes 1963 *** Order Schizopyrenida Singh 1952 s.s. **** Family Naegleriidae ulamoebidae Kirby et al. 2015***** Genus '' Aurem'' Jhin & Park 2018 ***** Genus '' Pleurostomum'' Namyslowski 1913 ***** Genus '' Tulamoeba'' Park et al. 2009 ***** Genus '' Marinamoeba'' De Jonckheere et al. 2009 ***** Genus '' Willaertia'' de Jonckheere et al. 1984 ***** Genus '' Naegleria'' Aléxéieff 1912 Trimastigamoeba''_Whitmore_1911;_''Didascalus.html" ;"title="' Trimastigamoeba'' Whitmore 1911; ''Didascalus">' Trimastigamoeba'' Whitmore 1911; ''Didascalus'' Singh 1952] **** Family Vahlkampfiidae Jollos 1917 s.s. [Tetramitaceae] ***** Genus ''Tetramitus'' Perty 1852 'Copromastix''_Aragao_1916;_''Adelphamoeba.html" ;"title="Copromastix.html" ;"title="'Copromastix">'Copromastix'' Aragao 1916; ''Adelphamoeba">Copromastix.html" ;"title="'Copromastix">'Copromastix'' Aragao 1916; ''Adelphamoeba'' Napolitano, Wall & Ganz 1970, ''Learamoeba'' Sawyer et al. 1998, ''Paratetramitus'' Darbyshire, Page & Goodfellow 1976, ''Singhamoeba'' Sawyer, Nerad & Munson 1992; ''Schizopyrenus'' Singh 1952] ***** Genus '' Vahlkampfia'' Chatton & LaLung-Bonnaire 1912 **** Family Percolomonadidae Cavalier-Smith 1993 hoanogasteraceae***** Genus '' Percolomonas'' Fenchel & Patterson 1986 'Choanogaster''_Pochmann_1959.html" ;"title="Choanogaster.html" ;"title="' 'Choanogaster''_Pochmann_1959">Choanogaster.html"_;"title="'Choanogaster">'Choanogaster''_Pochmann_1959****_Family_Stephanopogonidae.html" ;"title="Choanogaster">'Choanogaster'' Pochmann 1959">Choanogaster.html" ;"title="'Choanogaster">'Choanogaster'' Pochmann 1959**** Family Stephanopogonidae">Choanogaster">'Choanogaster'' Pochmann 1959">Choanogaster.html" ;"title="'Choanogaster">'Choanogaster'' Pochmann 1959**** Family Stephanopogonidae Corliss 1961 ***** Genus '' Stephanopogon'' Entz 1884

History

The Heterolobosea were first defined by F. C. Page, Page and R. L. Blanton, Blanton in 1985 as a class of amoebae, and so only included those forms with amoeboid stages.

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 disc ...

created the phylum Percolozoa for the extended group, together with the enigmatic flagellate '' Stephanopogon''. Cavalier-Smith maintained the Heterolobosea as a class for amoeboid forms. He has defined Percolozoa as "Heterolobosea plus Percolatea classis nov."

References

External links

Tree of Life Heterolobosea
{{Taxonbar, from=Q22094454 Bikont phyla Taxa named by Thomas Cavalier-Smith