The Mesomycetozoea (or DRIP

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 ter ...

, or Ichthyosporea) are a small group of

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 ...

a in

Eukaryota 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. Bacter ...

(formerly

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 e ...

s), mostly

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson h ...

s of fish and other animals.

Significance

They are not particularly distinctive morphologically, appearing in host tissues as enlarged spheres or ovals containing

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

s, and most were originally classified in various groups as fungi, protozoa, or colorless algae. However, they form a coherent group on molecular trees, closely related to both

animal 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 ...

s and

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 fr ...

and so of interest to biologists studying their origins. In a 2008 study they emerge robustly as the sibling-group of the

Filozoa The Filozoa are a monophyletic grouping within the Opisthokonta. They include animals and their nearest unicellular relatives (those organisms which are more closely related to animals than to fungi or Mesomycetozoa). Three groups are current ...

, which includes the animals. Huldtgren et al., following x-ray tomography of

microfossil 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, ...

s of the

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and t ...

Doushantuo Formation The Doushantuo Formation (formerly transcribed as Toushantuo or Toushantou, from ) is a geological formation in western Hubei, eastern Guizhou, southern Shaanxi, central Jiangxi, and other localities in China. It is known for the fossil Lagerst ...

, has interpreted them as mesomycetozoan spore capsules.

Terminology

The name DRIP is an acronym for the first protozoa identified as members of the group,

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 ...

later treated them as the class Ichthyosporea, since they were all parasites of fish. * order

Dermocystida Dermocystida is an order of parasitic eukaryotes. Taxonomy * Family Rhinosporidiaceae Mendoza et al. 2001 ** Genus '' Amphibiocystidium'' Pascolini et al. 2003 ** Genus '' Chromosphaera'' Grau-Bové et al. 2017 ** Genus ''Dermocystidium ''De ...

** "D": ''

Dermocystidium ''Dermocystidium'' is a genus of cyst-forming, parasitic eukaryotes of fish, which are the causative agents of dermocystidiosis. Taxonomic History The genus ''Dermocystidium'' was described in 1907. It was previously thought to be a genus of fu ...

''. One species, ''

Rhinosporidium seeberi ''Rhinosporidium seeberi'' is a eukaryotic pathogen responsible for rhinosporidiosis, a disease which affects humans, horses, dogs, and to a lesser extent cattle, cats, foxes, and birds. It is most commonly found in tropical areas, especially I ...

'', infects birds and mammals, including humans. ** "R": the "rosette agent", now known as '' Sphaerothecum destruens'' * order

Ichthyophonida Ichthyophonida is an order of parasitic eukaryotes. Taxonomy Members of Ichthyophonida include: * Amoebidiaceae **''Amoebidium'' ***'' Amoebidium appalachense'' ***''Amoebidium parasiticum'' * Paramoebidiidae **''Paramoebidium'' ***'' Param ...

** "I": ''

Ichthyophonus ''Ichthyophonus'' is a genus of unicellular eukaryotic parasites of fish. They were once considered to be fungi, but phylogenetic evidence suggests they are protists related to both fungi and animal Animals are multicellular, eukary ...

'' ** "P": ''

Psorospermium ''Psorospermium haeckeli'' (or ''Psorospermium haeckelii'') is a parasitic species. References Parasitic opisthokonts Mesomycetozoea {{Holozoa-stub ...

'' Since other new members have been added (e.g. the former fungal orders Eccrinales and

Amoebidiales Amoebidiidae is a family of single-celled eukaryotes, previously thought to be zygomycete fungi belonging to the clasTrichomycetes but molecular phylogenetic analysesBenny, G. L., and O'Donnell, K. 2000. ''Amoebidium parasiticum'' is a protozoan ...

), Mendoza ''et al.'' suggested changing the name to Mesomycetozoea, which refers to their evolutionary position. On Eukaryota tree, in

clade, Mesomycetozoea is in the middle ("Meso-") of the fungi ("-myceto-") and the animals ("-zoea"). Note the name Mesomycetozoa (without a third e) is also used to refer to this group, but Mendoza ''et al.'' use it as an alternate name for basal Opisthokonts.

Phylogeny

Taxonomy

* Class Ichthyosporea Cavalier-Smith 1998 ** Order

Cavalier-Smith 1998 *** Family Rhinosporidiaceae Mendoza et al. 2001 **** Genus '' Amphibiocystidium'' Pascolini et al. 2003 **** Genus '' Chromosphaera'' Grau-Bové et al. 2017 **** Genus ''

'' Pérez 1908 'Amphibiothecum''_Feldman,_Wimsatt_&_Green,_2005;_''Dermocystis.html" ;"title="Amphibiothecum.html" ;"title="'Amphibiothecum">'Amphibiothecum'' Feldman, Wimsatt & Green, 2005; ''Dermocystis">Amphibiothecum.html" ;"title="'Amphibiothecum">'Amphibiothecum'' Feldman, Wimsatt & Green, 2005; ''Dermocystis'' Pérez 1907 non] **** Genus ''Dermosporidium'' Carini 1940 **** Genus ''Dermotheca'' **** Genus ''Rhinosporidium'' Minchin & Fantham 1905 **** Genus ''Sphaerothecum'' Arkush et al. 2003 (Rosette agent) **** Genus '' Valentines (genus), Valentines'' Borteiro et al. 2018 ** Order

Cavalier-Smith 1998 chthyophonae Mendoza et al. 2001; Amoebidiales; Eccrinales Léger & Dubosq 1929*** Suborder Sphaeroformina Cavalier-Smith 2012 **** Family Creolimacidae Cavalier-Smith 2012 ***** Genus '' Anurofeca'' Baker, Beebee & Ragan 1999 ***** Genus '' Creolimax'' Marschall et al. 2008 ***** Genus ''

Sphaeroforma ''Sphaeroforma arctica'', is a unicellular eukaryote with a pivotal position in the tree of life. It was first isolated from the arctic marine amphipod '' Gammarus setosus''. Like other Ichthyosporeans such as ''Creolimax'' and ''Abeoforma'', ''S ...

'' Jostensen et al. 2002 'Pseudoperkinsus'' Figueras et al. 2000**** Family Psorospermidae Cavalier-Smith 2012 ***** Genus '' Psorospermis'' Cavalier-Smith 2012 [''

Psorospermium ''Psorospermium haeckeli'' (or ''Psorospermium haeckelii'') is a parasitic species. References Parasitic opisthokonts Mesomycetozoea {{Holozoa-stub ...

'' Hilgendorf 1883 non Eimer 1870] **** Family Piridae Cavalier-Smith 2012 ***** Genus ''Caullerya'' Chatton 1907 ***** Genus ''Abeoforma'' Marshall & Berbee 2011 ***** Genus '' Pirum'' Marshall & Berbee 2011 *** Suborder Trichomycina Cavalier-Smith 2012 **** Genus †'' Paleocadus'' Poinar 2016 **** Family

Amoebidiidae Amoebidiidae is a family of single-celled eukaryotes, previously thought to be zygomycete fungi belonging to the clasTrichomycetes but molecular phylogenetic analysesBenny, G. L., and O'Donnell, K. 2000. ''Amoebidium parasiticum'' is a protozoan ...

Lichtenstein 1917 ex Kirk et al. 2001 ***** Genus ''

Amoebidium ''Amoebidium'' is a genus of unicellular, symbiotic eukaryotes in the Opisthokont group Mesomycetozoea, family Amoebidiidae.Reynolds, N.K., M.E. Smith, E.D. Tretter, J. Gause, D. Heeney, M.J. Cafaro, J.F. Smith, S.J. Novak, W.A. Bourland, M.M. ...

'' Cienkowski 1861 **** Family Ichthyophonidae Cavalier-Smith 2012 ***** Genus ''

'' Plehn & Mulsow 1911 **** Family

Paramoebidiidae ParamoebidiidaeReynolds, N.K., M.E. Smith, E.D. Tretter, J. Gause, D. Heeney, M.J. Cafaro, J.F. Smith, S.J. Novak, W.A. Bourland, M.M. White. 2017. Resolving relationships at the animal-fungal divergence: A molecular phylogenetic study of the prot ...

Reynolds et al. 2017 ***** Genus ''

Paramoebidium ''Paramoebidium'' is a genus of unicellular, symbiotic eukaryotes that inhabit the digestive tract of immature freshwater arthropod hosts (e.g. black fly larvae, mayfly and stonefly nymphs).Lichtwardt, R.W., M.J. Cafaro, M.M. White. 2001. The Tric ...

'' Léger & Duboscq 1929 **** Family Parataeniellaceae Manier & Lichtward 1968 ***** Genus '' Lajassiella'' Tuzet & Manier 1951 ex Manier 1968 ***** Genus '' Nodocrinella'' Scheer 1977 ***** Genus '' Parataeniella'' Poiss. 1929 **** Family Eccrinaceae Leger & Duboscq 1929 alavasciaceae Manier & Lichtward 1968***** Genus '' Alacrinella'' Manier & Ormières ex Manier 1968 ***** Genus '' Arundinula'' Léger & Duboscq 1906 'Arundinella''_Léger_&_Duboscq_1905_non_Raddi_1823.html" ;"title="Arundinella.html" ;"title="'Arundinella">'Arundinella'' Léger & Duboscq 1905 non Raddi 1823">Arundinella.html" ;"title="'Arundinella">'Arundinella'' Léger & Duboscq 1905 non Raddi 1823***** Genus ''Astreptonema'' Hauptfleisch 1895 [''Eccrinella'' Léger & Duboscq 1933] ***** Genus ''Eccrinidus'' Manier 1970 ***** Genus ''Eccrinoides'' Léger & Duboscq 1929 'Eccrinopsis''_Léger_&_Duboscq_1916.html" ;"title="Eccrinopsis.html" ;"title="'Eccrinopsis">'Eccrinopsis'' Léger & Duboscq 1916">Eccrinopsis.html" ;"title="'Eccrinopsis">'Eccrinopsis'' Léger & Duboscq 1916***** Genus ''Enterobryus'' [''Andohaheloa'' Manier 1955; ''Capillus (genus), Capillus'' Granata 1908; ''Cestodella'' Tuzet, Manier & Jolivet 1957; ''Daloala'' Tuzet, Manier & Vog.-Zuber 1952; '' Eccrina'' Leidy 1852; '' Lactella'' Maessen 1955; '' Paratrichella'' Manier 1947; '' Pistillaria'' Jeekel et al. 1959 non Fries 1821; '' Recticoma'' Scheer 1935; '' Trichella'' Léger & Duboscq 1929; '' Trichellopsis'' Maessen 1955] ***** Genus '' Enteromyces'' Lichtwardt 1961 ***** Genus ''

Enteropogon ''Enteropogon'' is a genus of tropical and subtropical plants in the grass family. It is widespread across many parts of Asia, Africa, Australia, the Americas, and various islands.Leidyomyces'' Lichtwardt et al. 1999 ***** Genus '' Palavascia'' Tuzet & Manier 1947 ex Lichtwardt 1964 ***** Genus '' Paramacrinella'' Manier & Grizel 1971 ***** Genus '' Passalomyces'' Lichtwardt et al. 1999 ***** Genus '' Ramacrinella'' Manier & Ormiéres 1962 ex Manier 1968 ***** Genus '' Taeniella'' Léger & Duboscq 1911 ***** Genus '' Taeniellopsis'' Poisson 1927

References

* {{Taxonbar, from=Q129081 Parasites of fish Parasitic opisthokonts Opisthokont classes