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 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
multinucleated. 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]
Taxonomy
Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009[3][4][5]