Percolozoa

The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages.

Percolozoa
The three different stages of N. fowleri
Scientific classification
Domain: Eukaryota
(unranked): Excavata
(unranked): Discoba
Superphylum: Discicristata
Phylum: Percolozoa
Cavalier-Smith 1991
Classes, Orders and Families

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, and share with them the unusual characteristic of having mitochondria with discoid cristae. The presence of a ventral feeding groove in the flagellate stage, as well as other features, suggests that they are part of the Excavata 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. 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, and Psalteriomonas are known only as flagellates, while Vahlkampfia, Pseudovahlkampfia, and most acrasids 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. The entire group is usually called the Heterolobosea, but this may be restricted to members with amoeboid stages.

One Heterolobosea classification system is:[1]

Pleurostomum flabellatum has recently been added to Heterolobosea.[2]

Phylogeny

Based on the cladogram from Tolweb and updated with new data from Pánek & Čepička 2012 and Pánek, Ptackova & Čepička 2014.[3]

 
Pharyngomonadea
 

Pharyngomonas

 
 
Tetramitia
Selenaionida
 

Selenaionidae

 
 
 
Neovahlkampfiida

Neovahlkampfia

 
 
Lyromonadea
Paravahlkampfiidae
 

Fumarolamoeba

 
 

Paravahlkampfia

 
 
Lyromonadida
Plaesiobystridae
 

Euplaesiobystra

 
 

Heteramoeba

 
 
 
Gruberellidae
 

Vrihiamoeba

 
 
 

Oramoeba

 
 

Stachyamoeba

 
 
 
Psalteriomonadidae
 

Pseudoharpagon

 
 
 
 

Sawyeria

 
 

Psalteriomonas

 
 
 
 

Pseudomastigamoeba

 
 
 

Harpagon

 
 

Monopylocystis

 
 
 
 
 
 
 
 
Heterolobosea
Acrasida
 
 

Allovahlkampfia

 
 

Solumitrus

 
 
 
 

Pocheina

 
 

Acrasis

 
 
 
Schizopyrenida s.s.
Naegleriidae
 
 

Pleurostomum

 
 

Tulamoeba

 
 
 
 

Marinamoeba

 
 
 

Naegleria

 
 

Willaertia

 
 
 
 
 
Vahlkampfiidae s.s.
 

Tetramitus

 
 

Vahlkampfia

 
 
Percolatea
 

Percolomonas

 
 

Stephanopogon

 
 
 
 
 
 
 
 
 

Taxonomy

Phylum Percolozoa Cavalier-Smith 1991[4]

  • Subphylum Pharyngomonada
    • Class Pharyngomonadea [Macropharyngomonadidea]
      • Order Pharyngomonadida [Macropharyngomonadida]
        • Family Pharyngomonadidae Cavalier-Smith 2008 [Macropharyngomonadidae Cavalier-Smith 2008]
          • Genus Pharyngomonas Cavalier-Smith 2008 [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 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 [Hyperamoebidae Goodkov, Seravin & Railkin 1982]
        • Genus Euhyperamoeba Goodkov & Seravin 1984 [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
    • 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
    • Class Heterolobosidea
      • Order Acrasida 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 [Guttulinidae 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 [Tulamoebidae 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 Singh 1952]
        • Family Vahlkampfiidae Jollos 1917 s.s. [Tetramitaceae]
          • Genus Tetramitus Perty 1852 [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 [Choanogasteraceae]
          • Genus Percolomonas Fenchel & Patterson 1986 [Choanogaster Pochmann 1959]
        • Family Stephanopogonidae Corliss 1961

History

The Heterolobosea were first defined by Page and Blanton in 1985[5] as a class of amoebae, and so only included those forms with amoeboid stages. Cavalier-Smith created the phylum Percolozoa for the extended group, together with the enigmatic flagellate Stephanopogon.[6]

Cavalier-Smith maintained the Heterolobosea as a class for amoeboid forms. He has defined Percolozoa as "Heterolobosea plus Percolatea classis nov."[7]

References
  1. "Heterolobosea". Retrieved 2009-03-25.
  2. Park JS, Simpson AG, Lee WJ, Cho BC (July 2007). "Ultrastructure and phylogenetic placement within Heterolobosea of the previously unclassified, extremely halophilic heterotrophic flagellate Pleurostomum flabellatum (Ruinen 1938)". Protist. 158 (3): 397–413. doi:10.1016/j.protis.2007.03.004. PMID 17576098.
  3. Pánek, Ptackova & Čepička (2014). "Survey on diversity of marine/saline anaerobic Heterolobosea (Excavata: Discoba) with description of seven new species". International Journal of Systematic and Evolutionary Microbiology. 64 (Pt 7): 2280–2304. doi:10.1099/ijs.0.063487-0. PMID 24729392.CS1 maint: uses authors parameter (link)
  4. "Part 1- Virae, Prokarya, Protists, Fungi". Collection of genus-group names in a systematic arrangement. Retrieved 30 June 2016.
  5. Page, F.C.; R.L. Blanton (1985). "The Heterolobosea (Sarcodina: Rhizopoda), a new class uniting the Schizopyrenida and Acrasidae (Acrasida)". Protistologica. 21: 121–132.
  6. Cavalier-Smith, T. (1991). "Cell diversification in heterotrophic flagellates". In D.J. Patterson & J. Larsen (ed.). The Biology of Free-living Heterotrophic Flagellates. Oxford University Press. pp. 113–131.
  7. Cavalier-Smith T (November 2003). "The excavate protozoan phyla Metamonada Grassé emend. (Anaeromonadea, Parabasalia, Carpediemonas, Eopharyngia) and Loukozoa emend. (Jakobea, Malawimonas): their evolutionary affinities and new higher taxa". Int. J. Syst. Evol. Microbiol. 53 (Pt 6): 1741–58. doi:10.1099/ijs.0.02548-0. PMID 14657102.
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