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a cell that arises from the asexual division of a parent sporozoan during its life cycle

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/01/09 15:15:27」(JST)

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Cellular structure of a typical, generalised Apicomplexan: 1-polar ring, 2-conoid, 3-micronemes, 4-rhoptries, 5-nucleus, 6-nucleolus, 7-mitochondria, 8-posterior ring, 9-alveoli, 10-golgi apparatus, 11-micropore.

Apicomplexans, a group of intracellular parasites, have life cycle stages evolved to allow them to survive the wide variety of environments they are exposed to during their complex life cycle.^[1] Each stage in the life cycle of an apicomplexan organism is typified by a cellular variety with a distinct morphology and biochemistry.

Not all apicomplexa develop all the following cellular varieties and division methods. This presentation is intended as an outline of a hypothetical generalised apicomplexan organism.

Methods of asexual replication[edit]

Glossary of cell types[edit]

An ookinete (motile), a sporozoite (motile) and a merozoite (non-motile) of Plasmodium falciparum.

Infectious stages[edit]

A sporozoite (G. sporos, seed + zōon, animal) is the cell form that infects new hosts. In Plasmodium, for instance, the sporozoites are cells that develop in the mosquito's salivary glands, leave the mosquito during a blood meal, and enter liver cells (hepatocytes) where they multiply. Cells infected with sporozoites eventually burst, releasing merozoites into the bloodstream.^[7] Sporozoites are motile and they move by gliding.

A merozoite (G. meros, part [of a series], +zōon, animal) is the result of merogony that takes place within a host cell. In coccidiosis, merozoites form the first phase of the internal life cycle of coccidian. In the case of Plasmodium, merozoites infect red blood cells and then rapidly reproduce asexually. The red blood cell host is destroyed by this process, which releases many new merozoites that go on to find new blood-borne hosts. Merozoites are non-motile.

A gametocyte (G. gametēs, partner + kytos, hollow) is a name given to a parasite's gamete-forming cells. A male gametocyte divides to give many flagellated microgametes, whereas the female gametocyte differentiates to a macrogamete.^[8]

An ookinete (G. ōon, egg + kinētos, motile) is a fertilised zygote capable of moving spontaneously. It penetrates epithelial cells lining the midgut of mosquitos to form a thick-walled structure known as an oocyst under the mosquito's outer gut lining.^[9] Ookinetes are motile and they move by gliding.

A trophozoite (G. trophē, nourishment + zōon, animal) is the activated, intracellular feeding stage in the apicomplexan life cycle. After gorging itself on its host, the trophozoite undergoes schizogony and develops into a schizont, later releasing merozoites.

A bradyzoite (G. bradys, slow + zōon, animal) is a sessile, slow-growing form of zoonotic microorganisms such as Toxoplasma gondii, among others responsible for parasitic infections. In chronic (latent) toxoplasmosis, bradyzoite microscopically presents as clusters enclosed by an irregular crescent-shaped wall (a pseudocyst), in infected muscle and brain tissues.

A tachyzoite (G. tachys, fast + zōon, animal), contrasting with a bradyzoite, is a form typified by rapid growth and replication. Tachyzoites are motile forms of coccidians that form tissue cysts, such as Toxoplasma and Sarcocystis. Typically infecting cellular vacuoles, tachyzoites divide by endodyogeny and endopolygeny.

An oocyst (G. ōon, egg + kystis, bladder) is a hardy, thick-walled spore able to survive for lengthy periods outside a host. The zygote develops within the spore, which acts to protect it during transfer to new hosts. Organisms that create oocysts include Plasmodium, Cryptosporidium and Toxoplasma.

Lifecycle of the Babesia parasite
Lifecycle of the Eimeria parasite
Erythrocytic lifecycle of the Plasmodium parasite
Lifecycle of the Toxoplasma parasite

References[edit]

^ Jadwiga Grabda (1991). Marine fish parasitology: an outline. VCH. p. 8. ISBN 0-89573-823-6.
^ Yoshinori Tanada, Harry K. Kaya (1993). Insect pathology. Gulf Professional Publishing. ISBN 978-0-12-683255-6.
^ "Schizogony definition". MSN Encarta. Retrieved 2009-12-11.
^ Herwaldt et al.; Persing, DH; Précigout, EA; Goff, WL; Mathiesen, DA; Taylor, PW; Eberhard, ML; Gorenflot, AF (1 April 1996). "A Fatal Case of Babesiosis in Missouri: Identification of Another Piroplasm That Infects Humans". Annals of Internal Medicine 124 (7): 643–650. doi:10.1059/0003-4819-124-7-199604010-00004. PMID 8607592. Retrieved 2009-12-11.
^ Zhou et al.; Liu, Q.; Wongsrichanalai, C.; Suwonkerd, W.; Panart, K.; Prajakwong, S.; Pensiri, A.; Kimura, M. et al. (6 January 2002). "High prevalence of Plasmodium malariae and Plasmodium ovale in malaria patients along the Thai-Myanmar border, as revealed by acridine orange staining and PCR-based diagnoses". Tropical Medicine & International Health 3 (4): 304–312. doi:10.1046/j.1365-3156.1998.00223.x. Retrieved 2009-12-11. |displayauthors= suggested (help)
^ ^a ^b James Desmond Smyth, Derek Wakelin (1994). Introduction to animal parasitology (3 ed.). Cambridge University Press. pp. 101–102. ISBN 0-521-42811-4.
^ "Malaria - Life Cycle Of Plasmodium.swf". esnips. Archived from the original on 21 November 2009. Retrieved 2009-12-11.
^ Sinden, R. E.; Talman, A.; Marques, S. R.; Wass, M. N.; Sternberg, M. J. E. (2010). "The flagellum in malarial parasites". Current Opinion in Microbiology 13 (4): 491–500. doi:10.1016/j.mib.2010.05.016. PMID 20566299. edit
^ "Ookinete (Medical Dictionary)". Dictionary.com. Retrieved 2009-12-11.

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Expression and localization of rhoptry neck protein 5 in merozoites and sporozoites of Plasmodium yoelii.

Mutungi JK1, Yahata K2, Sakaguchi M3, Kaneko O4.
Parasitology international.Parasitol Int.2014 Dec;63(6):794-801. doi: 10.1016/j.parint.2014.07.013. Epub 2014 Aug 4.
Host cell invasion by Apicomplexan parasites marks a crucial step in disease establishment and pathogenesis. The moving junction (MJ) is a conserved and essential feature among parasites of this phylum during host cell invasion, thus proteins that associate at this MJ are potential targets of drug a
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An epidemiological survey of bovine Babesia and Theileria parasites in cattle, buffaloes, and sheep in Egypt.

Elsify A1, Sivakumar T2, Nayel M3, Salama A3, Elkhtam A4, Rizk M5, Mosaab O6, Sultan K7, Elsayed S8, Igarashi I2, Yokoyama N9.
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Cattle, buffaloes, and sheep are the main sources of meat and milk in Egypt, but their productivity is thought be greatly reduced by hemoprotozoan parasitic diseases. In this study, we analyzed the infection rates of Babesia bovis, B. bigemina, Theileria annulata, and T. orientalis, using parasite-s
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Calcium ions are involved in egress of Babesia bovis merozoites from bovine erythrocytes.

Mossaad E1, Asada M, Nakatani D, Inoue N, Yokoyama N, Kaneko O, Kawazu SI.
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Bovine babesiosis is a livestock disease known to cause economic losses in endemic areas. The apicomplexan parasite Babesia bovis is able to invade and destroy the host's erythrocytes leading to the serious pathologies of the disease, such as anemia and hemoglobinuria. Understanding the egress mecha
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