Piroplasmida is an order of

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s in the phylum

Apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. Th ...

. They divide by

binary fission Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that ta ...

and as

sporozoan The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. ...

parasites they possess

sex Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones ( ova, of ...

ual and asexual phases (sexual reproduction occurs in the tick gut). They include the

tick Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

parasites ''

Babesia ''Babesia'', also called ''Nuttallia'', is an apicomplexan parasite that infects red blood cells and is transmitted by ticks. Originally discovered by the Romanian bacteriologist Victor Babeș in 1888, over 100 species of ''Babesia'' have since ...

'' and ''

Theileria ''Theileria'' is a genus of parasites that belongs to the phylum Apicomplexa, and is closely related to ''Plasmodium''. Two ''Theileria'' species, ''T. annulata'' and ''T. parva'', are important cattle parasites. ''T. annulata'' causes tropical ...

''.

Description

They are minute rounded or

pyriform Piriform, sometimes ''pyriform'', means pear-shaped (from Latin ''pirum'' "pear" and ''forma'' "shape"). It may also refer to: Going pear-shaped * Going wrong or going pear-shaped Anatomy * Piriform aperture, more commonly known as anterior n ...

parasites found within erythrocytes, or other circulating or endothelial cells of vertebrates, where they reproduce by

merogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

. The

trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the ''Giardia'' group. (The complement of the trophozoi ...

stage is separated from erythrocyte by a single membrane. This distinguishes them from other blood parasites that usually have at least two membranes. An

apical complex The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic Alveolata, alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex stru ...

with a polar ring and rhopteries occurs, but without a

conoid In geometry a conoid () is a ruled surface, whose rulings (lines) fulfill the additional conditions: :(1) All rulings are parallel to a plane, the '' directrix plane''. :(2) All rulings intersect a fixed line, the ''axis''. The conoid is a ri ...

and usually without associated pellicular microtubules. They lack flagella and do not form either

oocysts Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

or spores. The known vectors are

s or

leeches Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bo ...

in which they undergo

sporogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

; sexual reproduction probably occurs in the vector.

References

Apicomplexa orders {{Apicomplexa-stub

Description

See also

References