percolozoa 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 clade: diphoda clade: discoba superphylum: discicristata phylum: percolozoacavalier-smith 1991 classes, orders and families class heterolobosea page & blanton 1985 order schizopyrenida family vahlkampfiidae family gruberellidae order acrasida family acrasidae incertae sedis family lyromonadidae class percolatea 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: order schizopyrenida family vahlkampfiidae family gruberellidae order acrasida family acrasidae pleurostomum flabellatum has recently been added to heterolobosea. phylogeny based on the cladogram from tolweb and updated by pánek and čepička 2014. 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 barbellidae barbelia nonamonas lulaidae lula percolomonadidae percolomonas nakurumonas stephanopogonidae stephanopogon taxonomy phylum percolozoa cavalier-smith 1991 subphylum pharyngomonada class pharyngomonadea order pharyngomonadida family pharyngomonadidae cavalier-smith 2008 genus pharyngomonas cavalier-smith 2008 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 genus euhyperamoeba goodkov & seravin 1984 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 cavalier-smith 1993 genus lyromonas 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 gruberellidae 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 psalteriomonas broers et al. 1990 genus pseudomastigamoeba genus harpagon panek et al. 2012 genus monopylocystis o'kelly et al. 2003 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 genus guttulina cienkowski 1873 non d’orbigny 1839 genus guttulinopsis olive 1901 genus rosculus hawes 1963 order schizopyrenida singh 1952 s.s. family naegleriidae 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 family vahlkampfiidae jollos 1917 s.s. genus tetramitus perty 1852 genus vahlkampfia chatton & lalung-bonnaire 1912 family percolomonadidae cavalier-smith 1993 genus percolomonas fenchel & patterson 1986 family barbeliidae arndt 2023 genus barbelia arndt 2021 genus nonamonas hohlfeld, meyer & arndt 2023 family lulidae hohlfeld & arndt 2023 genus lula arndt, nitsche & carduck 2021 family stephanopogonidae corliss 1961 genus stephanopogon entz 1884 history the heterolobosea were first defined by page and blanton in 1985 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. cavalier-smith maintained the heterolobosea as a class for amoeboid forms. he has defined percolozoa as "heterolobosea plus percolatea classis nov."