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The Apicomplexa are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of plastid called an apicoplast, and an apical complex structure. The organelle is an adaptation that the apicomplexan applies in penetration of a host cell.
Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within an animal cell. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa.
Eimeria is a genus of apicomplexan parasites that includes various species capable of causing the disease coccidiosis in animals such as cattle, poultry, dogs, cats, and smaller ruminants including sheep and goats. Eimeria species are considered to be monoxenous because the life cycle is completed within a single host, and stenoxenous because they tend to be host specific, although a number of exceptions have been identified. Species of this genus infect a wide variety of hosts. Thirty-one species are known to occur in bats (Chiroptera), two in turtles, and 130 named species infect fish. Two species infect seals. Five species infect llamas and alpacas: E. alpacae, E. ivitaensis, E. lamae, E. macusaniensis, and E. punonensis. A number of species infect rodents, including E. couesii, E. kinsellai, E. palustris, E. ojastii and E. oryzomysi. Others infect poultry, rabbits and cattle. For full species list, see below.
The gregarines are a group of Apicomplexan alveolates, classified as the Gregarinasina or Gregarinia. The large parasites inhabit the intestines of many invertebrates. They are not found in any vertebrates. However, gregarines are closely related to both Toxoplasma and Plasmodium, which cause toxoplasmosis and malaria, respectively. Both protists use protein complexes similar to those that are formed by the gregarines for gliding motility and invading target cells. This makes them excellent models for studying gliding motility with the goal of developing treatment options for toxoplasmosis and malaria. Thousands of different species of gregarines are expected to be found in insects, and 99% of these gregarines still need to be described. Each insect can be the host of multiple species. One of the most studied gregarines is Gregarina garnhami. In general, gregarines are regarded as very successful parasites, as their hosts are spread over the entire planet.
Conoidasida is a class of parasitic alveolates in the phylum Apicomplexa. The class was defined in 1988 by Levine and contains two subclasses – the coccidia and the gregarines. All members of this class have a complete, hollow, truncated conoid. Gregarines tend to parasitize invertebrates with the mature gamonts being extracellular, the coccidia mostly infect vertebrates and have intracellular gamonts.
The genus Polychromophilus consists of obligate intracellular eukaryotic parasites that infect bats from every continent except Antarctica. They are transmitted by bat flies, which act as an insect vector as well as the parasite’s site of sporogeny. Polychromophilus follows a fairly typical Haemospororidian lifecycle, with gametocytes and gametes restricted to the bloodstream of the host and meronts infecting organs – most notably the lungs and the liver. The type species is Polychromophilus melanipherus, and was described by Dionisi in 1898.
The genus Schellackia comprises obligate unicellular eukaryotic parasites within the phylum Apicomplexa, and infects numerous species of lizards and amphibians worldwide. Schellackia is transmitted via insect vectors, primarily mites and mosquitoes, which take up the parasite in blood meals. These vectors then subsequently infect reptilian and amphibian which consume the infected insects. The parasites deform erythrocytes of the host into crescents, and can be visualised using a blood smear.
The Archigregarinorida are an order of parasitic alveolates in the phylum Apicomplexa. Species in this order infect marine invertebrates — usually annelids, ascidians, hemichordates and sipunculids.
The Exoschizonidae are a family in the phylum Apicomplexa.
The Eugregarinorida are the most large and diverse order of gregarines — parasitic protists belonging to the phylum Apicomplexa. Eugregarines are found in marine, freshwater and terrestrial habitats. These species possess large trophozoites that are significantly different in morphology and behavior from the sporozoites. This taxon contains most of the known gregarine species.
The Lipotrophidae are a family of parasitic alveolates in the phylum Apicomplexa. Species in this family infect insects.
The Syncystidae are a family of parasitic alveolates in the phylum Apicomplexa. Species in this family infect insects (Aeshnidae).
Farinocystis is a genus of parasitic alveolates of the phylum Apicomplexa. Species in this genus infect insects (Coleoptera).
The Platyproteum are a genus of parasitic alveolates in the phylum Apicomplexa. Species in this genus infect marine invertebrates.
Exoschizon is a genus in the phylum Apicomplexa.
Cystoisospora canis, previously known as Isospora canis, is a microscopic, coccidian parasite that causes an intestinal tract infection in dogs. The intestinal tract infection is coccidiosis caused by a protozoa called coccidia.
Stylocephaloidea is a superfamily of parasites of the phylum Apicomplexia.
Syncystis is a genus of parasitic alveolates in the phylum Apicomplexa.
Lipocystis is a genus of parasitic alveolates of the phylum Apicomplexa.
Nematopsis (Nee-mah-top-cis) is a genus gregarine Apicomplexan of the family Porosporidae. It is an aquatic parasite of crustaceans with a molluscan intermediate host. Nematopsis has been distinguished from the similar genus Porospora by its resistant and encapsulated oocyst. Little molecular biology has been performed on the members of the Nemaptosis and species are described based on molluscan and crustacean hosts as well as oocyst structure. A total of 38 species have been described and are found all over the world.
References
- ↑ Cavalier-Smith, Thomas (2014). "Gregarine site-heterogeneous 18S rDNA trees, revision of gregarine higher classification, and the evolutionary diversification of Sporozoa". European Journal of Protistology. 50 (5): 472–495. doi:10.1016/j.ejop.2014.07.002. PMID 25238406.
- ↑ Hukui (1939). "On the gregarines from Siphonosoma kumanense (Kefer-stein), Spengel". J Sci Hiroshima Uni Zool. 7: 1–23.
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