The Ichthyosporea (or DRIP

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

, or Mesomycetozoea) are a small group of Opisthokonta in

Eukaryota The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

(formerly

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s), mostly

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

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 reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

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 Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

s and

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

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

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

Ediacaran The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...

Doushantuo Formation, 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 later treated them as the class Ichthyosporea, since they were all parasites of fish. * order Dermocystida ** "D": '' Dermocystidium''. One species, '' Rhinosporidium seeberi'', infects birds and mammals, including humans. ** "R": the "rosette agent", now known as '' Sphaerothecum destruens'' * order Ichthyophonida ** "I": '' Ichthyophonus'' ** "P": '' Psorospermium'' Since other new members have been added (e.g. the former fungal orders Eccrinales and Amoebidiales), Mendoza ''et al.'' suggested changing the name to Mesomycetozoea, which refers to their evolutionary position. On Eukaryota tree, in Opisthokont clade, Mesomycetozoea is in the middle ("Meso-") of the fungi ("-myceto-") and the animals ("-zoea"). 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 Dermocystida Cavalier-Smith 1998 *** Family Rhinosporidiaceae Mendoza et al. 2001 ** Order Ichthyophonida Cavalier-Smith 1998 *** Suborder Sphaeroformina Cavalier-Smith 2012 **** Family Creolimacidae Cavalier-Smith 2012 **** Family Psorospermidae Cavalier-Smith 2012 **** Family Piridae Cavalier-Smith 2012 *** Suborder Trichomycina Cavalier-Smith 2012 **** Genus †'' Paleocadus'' Poinar 2016 **** Family Amoebidiidae Lichtenstein 1917 ex Kirk et al. 2001 **** Family Ichthyophonidae Cavalier-Smith 2012 **** Family Paramoebidiidae Reynolds et al. 2017 **** Family Parataeniellaceae Manier & Lichtward 1968 **** Family Eccrinaceae Leger & Duboscq 1929 alavasciaceae Manier & Lichtward 1968

References

* {{Taxonbar, from=Q129081, from2=Q29405749 Parasites of fish Parasitic opisthokonts Opisthokont classes