The Ascetosporea are a group of

eukaryote 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 ...

s that are

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 animals, especially marine

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecular trees, which place them near the base of the

Cercozoa Cercozoa (now synonymised with Filosa) is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by phylogeny, molecular phylogenies of rRNA and actin or Ubiqu ...

. Both produce

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 without the complex structures found in similar groups (such as polar filaments or tubules). Haplosporid spores have a single

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

and an opening at one end, covered with an internal diaphragm or a distinctive hinged lid. After emerging, it develops within the cells of its host, usually a marine

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

annelid The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to vario ...

, although some infect other groups or freshwater species. The trophic cell is generally

multinucleate Multinucleate cells (also known as multinucleated cells or polynuclear cells) are eukaryotic cells that have more than one nucleus, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinate ...

d. Paramyxids develop within the digestive system of marine invertebrates, and undergo internal budding to produce multicellular spores. A 2009 study concluded that ''Haplosporidium'' species form a

paraphyletic group Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In con ...

and that the taxonomy of the haplosporidians needs a thorough revision.

Taxonomy

Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009 * Genus ?'' Marteilioides'' Comps, Park & Desportes 1986 * Genus ?'' Oryctospora'' Purrini & Weiser 1991 * Order

Claustrosporida The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecula ...

Cavalier-Smith 2003 ** Family Claustrosporidiidae Larsson 1987 *** Genus '' Claustrosporidium'' Larsson 1987 * Order

Paradiniida The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecula ...

Cavalier-Smith 2009 ** Family Paradiniidae Schiller 1935 *** Genus '' Paradinium'' Chatton, 1910 * Order

Mikrocytida The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecula ...

Hartikainen et al. 2014 ** Family Mikrocytidae Hartikainen et al. 2014 *** Genus '' Paramikrocytos'' Hartikainen et al. 2014 *** Genus '' Microcytos'' Farley, Wolf & Elston 1988 * Order

Paramyxida The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecula ...

Chatton 1911 aramyxea Chatton 1911; Paramyxidea Chatton 1911; Paramyxa** Family Marteiliidae Grizel et al. 1974 cclusosporida; Marteiliida Desportes & Ginsburger-Vogel, 1977; Marteiliidea Desportes & Ginsburger-Vogel, 1977*** Genus '' Paramarteilia'' Ginsburger-Vogel & Desportes 1979 *** Genus ''

Marteilia ''Marteilia'' is a protozoan genus of organisms that are parasites of bivalves. It causes QX disease in Sydney rock oysters and Aber disease in European flat oysters. After being infected by ''Marteilia'', bivalves lose pigmentation in their vi ...

'' Grizel et al. 1974 ** Family Paramyxidae Chatton 1911 *** Genus '' Paramyxa'' Chatton 1911 * Order

Haplosporida The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecula ...

Caullery & Mesnil 1899 [Balanosporida Sprague, 1979; Haplosporidia Hall, 1953; Haplosporea Caullery 1953; Haplospora Margulis & Schwartz, 1998; Haplosporidiidea Poche, 1913; Haplosporidies Caullery and Mesnil, 1905] ** Genus ?''Bertramia'' Mesnil & Caullery 1897 non Weiser & McCauley 1974 ** Genus ?''Coleospora'' Gibbs 1959 ** Family Nephridiophagidae Sprague 1970 ephridiophagea*** Genus '' Nephridiophaga'' Woolever 1966 'Coelosporidium'' Mesnil & Marchoux 1897">Coelosporidium.html" ;"title="'Coelosporidium">'Coelosporidium'' Mesnil & Marchoux 1897** Family Urosporidiidae Sprague 1979 [Anurosporidiidae] *** Genus ''Urosporidium'' Caullery & Mesnil 1905 [''Anurosporidium'' Caullery & Chappelier 1906] (8 species) ** Family Haplosporidiidae Sprague 1979 *** Genus ''

Bonamia ''Bonamia'' is a genus of the flowering plant family Convolvulaceae, commonly known as the bindweed family and named after the French physician and botanist François Bonamy François Bonamy (10 May 1710 in Nantes – 5 January 1786 in Nan ...

'' Pichot et al. 1980 *** Genus ''

Haplosporidium ''Haplosporidium'' is a genus in the order Haplosporida.WoRMS (2021). Haplosporidium Lühe, 1900. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=391857 on 2021-12-28 They are a group of eukaryotes that are Parasitism, paras ...

'' Caullery & Mesnil 1899 (23 species) *** Genus '' Minchinia'' (Lankester 1895) Labbe 1896 (5 species)

References

Endomyxa Parasitic rhizaria Rhizaria classes {{Parasitic SAR-stub