TheAscetosporea are a group ofeukaryotes that areparasites of animals, especially marineinvertebrates. 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 theCercozoa.[1] Both producespores without the complex structures found in similar groups (such as polar filaments or tubules).
Haplosporid spores have a singlenucleus 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 marinemollusc orannelid, although some infect other groups or freshwater species. The trophic cell is generallymultinucleated. Paramyxids develop within the digestive system of marine invertebrates, and undergo internal budding to produce multicellular spores.
A 2009 study concluded thatHaplosporidium species form aparaphyletic group and that the taxonomy of the haplosporidians needs a thorough revision.[2]
