Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Rhizaria
Phylum: Cercozoa
Class: Ascetosporea
Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009
  • Claustrosporida
  • Mikrocytida
  • Paradiniida
  • Paramyxida
  • Haplosporida
  • Ascetospora Sprague 1979
  • Stellatosporea
  • Aplosporidies Caullery & Mesnil, 1899

The Ascetosporea are a group of protists that are parasites of animals, especially marine invertebrates. There are two groups, the haplosporids and paramyxids, which are not particularly similar morphologically but consistently group together on molecular trees, which place them near the base of the Cercozoa.[1] Both produce spores without the complex structures found in similar groups (such as polar filaments or tubules).

Haplosporid spores have a single nucleus 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 or annelid, although some infect other groups or freshwater species. The trophic cell is generally multinucleate. 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 and that the taxonomy of the haplosporidians needs a thorough revision.[2]


Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009[3][4]

See also


  1. Thomas Cavalier-Smith & Ema E.-Y. Chao (2003). "Phylogeny of Choanozoa, Apusozoa, and other Protozoa and early eukaryote megaevolution". Journal of Molecular Evolution. 56 (5): 540–563. doi:10.1007/s00239-002-2424-z. PMID 12698292.
  2. P. M. Hine; R. B. Carnegie; E. M. Burreson; M. Y. Engelsma (2009). "Inter-relationships of haplosporidians deduced from ultrastructural studies" (PDF). Diseases of Aquatic Organisms. 83 (3): 247–256. doi:10.3354/dao02016. PMID 19402456.
  3. Brands, S.J. (ed.). "Class Ascetosporea Sprague 1979". The Taxonomicon. Zwaag, The Netherlands: Universal Taxonomic Services. Retrieved August 14, 2016.
  4. "Part 1- Virae, Prokarya, Protists, Fungi". Collection of genus-group names in a systematic arrangement. Retrieved 30 June 2016.
  5. Hartikainen; et al. (2014). "Mikrocytids Are a Broadly Distributed and Divergent Radiation of Parasites in Aquatic Invertebrates" (PDF). Current Biology. 24 (7): 807–812. doi:10.1016/j.cub.2014.02.033. Retrieved 30 June 2016.
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