Achromatorida is an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

of non-pigmented intraerythrocytic parasitic alveolates belonging to the subclass Haemosporidiasina. The order was created by

Jacques Euzéby Jacques Achille Marie Euzéby (11 August 1920 – 16 April 2010) was a French parasitologist, born in Bagnols-sur-Cèze. Euzéby specialized in the study of parasites (including the Apicomplexa and fungi) and parasitic diseases. Euzéby was gran ...

in 1988. The taxonomy of these organisms has been one of some controversy. Weylon in 1926 grouped many of these genera into the genus ''Babesia'' - given what is now known about these genera this was probably an error. Agreement on the organisation of these genera probably cannot be regarded as being settled.

Description

These are minute rounded or pyriform parasites found within

erythrocytes Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

, or other circulating or

endothelial cell The endothelium (: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and th ...

s of

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

s. The parasites 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 ...

without

oocyst 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 ...

s or

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s. The apical complex has a polar ring and

rhoptries A rhoptry is a specialized secretory organelle. They are club-shaped organelles connected by thin necks to the extreme apical pole of the parasite. These organelles, like micronemes, are characteristic of the motile stages of Apicomplexa p ...

. 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 rig ...

is lacking and most species lack the associated pellicular

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nanometer, nm and have an inner diameter bet ...

Flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

e are lacking. 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 complementary form of the t ...

stage is separated from erythrocyte by single membrane (in the other groups there usually 2 or more). Vectors include

tick Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. Ticks a ...

s and

leech Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

es.

Evolution

A Bayesian analysis based on the nuclear genes suggests a date of divergence between ''

Babesia ''Babesia'', also called ''Nuttallia'', is an apicomplexan parasite that infects red blood cells and is transmitted by ticks. Originally discovered by 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 ...

'' of ( 95% credible interval –)

Taxonomy

This order is divided into two suborders:

Suborder Babesiina

These are agents of

piroplasmosis Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or ''Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via t ...

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

''. The species have been placed into two families. Family Babesiidae Poche 1913 This family excludes species that undergo

schizogony Fission, in biology, is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. The object experiencing fission is usually a cell, but the term may also refer to ho ...

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), an ...

s before parasitizing

erythrocyte Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood ce ...

s. these species have been placed in the genus ''

''. Species in this family have

, a polar ring and subpellicular tubules in its apical complex. With the exception of the genus ''Tunetella'' which infects tortoises, species in this family infect in warm-blooded vertebrates and are transmitted by ticks. *Genus ''

'' Starcovici 1893 *Genus '' Echinozoon'' Garnham 1951 *Genus '' Entopolypoides'' Mayer 1933 *Genus '' Microbabesia'' Sohns 1918 *Genus '' Rangelia'' *Genus '' Tunetella'' Brumpt & Lavier 1935 Family '' Haemohormidiidae'' Levine 1984 This family includes species that infect marine animals. A notable exception is the genus ''Serpentoplasma'' which infects reptiles. Very little is known about most of these genera. *Genus '' Cardiosporidium'' Gaver & Stephan 1907 *Genus '' Cristalloidophora'' Dehorne 1934, Porchet 1978 *Genus '' Dobellia'' Brumpt 1913 *Genus '' Echinococcidium'' Porchet 1978 *Genus '' Globidiellum'' Neumann 1909 *Genus '' Haemohormidium'' Léger & Duboscq 1910 *Genus '' Haematractidium'' Henry 1910 *Genus '' Joyeuxella'' Le Calvez 1939 *Genus '' Rhabdospora'' Landau, Boulard & Houin 1969 *Genus ''

Serpentoplasma ''Serpentoplasma'' is a genus of parasitic alveolates belonging the phylum Apicomplexa. The genus was described in 1962 by Pienaar. The species in this genus infect snakes. Morphology The trophozoite A trophozoite (G. ''trope'', nourishment + ...

'' Pienaar 1962 *Genus '' Spermatobium'' Eisen 1895 *Genus '' Toxocystis'' Henry 1910 *Genus '' Trophosphaera'' du Toit 1938 The genus ''

Nephromyces ''Nephromyces'' is a genus of apicomplexans that are symbionts of the ascidian genus '' Molgula'' (sea grapes). Systematics ''Nephromyces'' was first described in 1888 by Alfred Mathieu Giard as a chytrid fungus, because of its filamentous ...

'' may also belong to this family.

Suborder Theileriina

These are parasites of erythrocytes and diverse white blood cells with sexual reproduction by exoerythrocytic or by exo- and endoerythrocytic schizogony. Family Leucocytozoidae *Genus '' Leucocytozoon'' Ziemann 1898 **Subgenus Leucocytozoon **Subgenus Akiba Family Garniidae *Genus '' Fallisia'' Lainson, Landau & Shaw 1974 **Subgenus Fallisia **Subgenus Plasmodioides *Genus '' Garnia'' Lainson ''et al'' 1971 *Genus '' Progarnia'' Lainson 1995 Family '' Theileriidae'' (synonym ''Gonderiidae'') *Genus '' Cytauxzoon'' Neitz & Thomas 1948 *Genus ''

'' Bettencourt, França and Borges 1907 *Genus '' Haematoxenus'' Uilenberg 1964

Notes

There are also a number of genera of uncertain placement that earlier were provisionally included in this taxon: '' Elleipsisoma'' Franca 1912: This genus is currently placed in the ''

Eimeriorina Eimeriorina is a suborder of phylum Apicomplexa. All species in this clade are homoxenous or facultatively homoxenous. Merogony, gamogony and oocyst formation all occur within the same host. The hosts may be vertebrates or invertebrates. Erro ...

''. Its placement there is unusual given that species in this genus infect

s. The families Dactylosomatidae (genera '' Babesiosoma'' Jakowski and Nigrelli 1956 and '' Dactylosoma'' Labbé 1894) were transferred to the suborder ''

Adeleorina ''Adeleorina'' is a suborder of parasites in the phylum Apicomplexa. History Léger proposed this taxon in 1911. The first species identified was '' Dactylosoma ranarum'' by Lankester (1871) in a frog in Europe. It was initially called ''Unduli ...

'' by Boulard ''et al'' in 1982. The position of the Anthemosomatidae (genus '' Anthemosoma'' Landau, Boulard and Houin 1969) remains unclear. The genus ''Nicollia'' Franca 1910 is now regarded as a synonym for ''

''. '' Cytauxzoon'' replicates in

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

s rather than in lymphocytes. For this reason may be moved to a new family at some point. '' Pirhemocyton'' was described as a protozoan infecting lizards but the intraerythrocytic inclusions have since been shown to be due to a viral infection. An additional genus - '' Chelonplasma'' - has been described but its taxonomic status is unclear.

Synonyms

The classification of the species in this group is difficult. Over the passage of time several genera have been described only to re classified as being synonyms of previously described genera. Currently recognised synonyms of the genus ''Babesia'' include: *''Achromaticus'' Dionisi 1899 *''Apiosoma'' *''Babesiella'' Mesnil 1919 *''Francaiella'' Yakimoff 1926 *''Haematococcus'' Babes 1888 *''Luhsia'' Dschunkowsky 1938 *''Microsoma'' Sohns 1918 *''Nicollia'' Franca 1910 *''Patonella'' Ray & Idnani 1943 *''Piroplasma'' Patton 1895 *''Pyrosoma'' Smith 1893 *''Rosiella'' Nuttall 1912 *''Sogdianella'' Schurenkova 1939 Recognised synonyms of the genus ''Nicollia'' - which is now itself regarded as a synonym of ''Babesia'' - include: *''Nuttallia'' Franca 1909 *''Smithia'' Franca 1910 Recognised synonyms of the genus ''Theileria'' include: *''Gonderia''

Notes

'' Apiosoma'' is currently the name of a genus of ciliated protozoa also known as ''Glossatella''. Although this genus is pathogenic to fish it has not related to the parasites in this taxon. ''Nuttallia'' Dall 1898 is a genus of sunset clams (''

Psammobiidae The Psammobiidae, or sunset clams, are a family of medium-sized saltwater clams, marine bivalve molluscs of the order Cardiida. These genera are accepted by the database World Register of Marine Species: *'' Asaphis'' Modeer, 1793 *'' Gari'' S ...

'')

References

{{Taxonbar, from=Q4673905 Apicomplexa orders