''Crithidia fasciculata'' is a species of

parasitic 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 ha ...

excavates Excavation may refer to: * Excavation (archaeology) * Excavation (medicine) * ''Excavation'' (The Haxan Cloak album), 2013 * ''Excavation'' (Ben Monder album), 2000 * ''Excavation'' (novel), a 2000 novel by James Rollins * '' Excavation: A Memo ...

. ''C. fasciculata'', like other species of ''

Crithidia ''Crithidia'' is a genus of trypanosomatid Euglenozoa. They are parasites that exclusively parasitise arthropods, mainly insects. They pass from host to host as cysts in infective faeces and typically, the parasites develop in the digestive ...

'' have a single host life cycle with

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

host, in the case of ''C. fasciculata'' this is the

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "lit ...

. ''C. fasciculata'' have low host species specificity and can infect many species of mosquito.

Life cycle

''C. fasciculata'' is found in two morphologically different life cycle stages - the free swimming choanomastigote form, which has a long external

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

for motility, and the attached, immotile,

amastigote An amastigote is a protist cell that does not have visible external flagella or cilia. The term is used mainly to describe an intracellular phase in the life-cycle of trypanosomes that replicates. It is also called the leishmanial stage, since in ...

form in the mosquito gut. Amastigotes excreted in the

faeces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

contaminate the mosquito habitat; contamination of flowers during nectar feeding is common. Transmission of ''C fasciculata'' primarily occurs when amastigotes, washed into standing water, are ingested by mosquito

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...

. The amastigotes are typically found in the rectum of a larva. Each molt of the larva results in loss of infection, but it is generally quickly re-acquired from the environment by ingestion of more amastigotes. When the fourth instar larva

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

tes the amastigote infection is maintained in the gut through metamorphosis giving rise to an infected adult mosquito.

Role in research

''C. fasciculata'' is an example of a non-human infective

trypanosomatid Trypanosomatida is a group of kinetoplastid excavates distinguished by having only a single flagellum. The name is derived from the Greek ''trypano'' (borer) and ''soma'' (body) because of the corkscrew-like motion of some trypanosomatid species. ...

and is related to several human parasites, including ''

Trypanosoma brucei ''Trypanosoma brucei'' is a species of parasitic kinetoplastid belonging to the genus ''Trypanosoma'' that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extracel ...

'' (which causes African trypanosomiasis) and ''

Leishmania ''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus '' ...

'' spp. (which cause

Leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus '' Leishmania''. It is generally spread through the bite of phlebotomine sandflies, '' Phlebotomus'' and ''Lutzomyia'', and occurs most f ...

). ''C. fasciculata'' parasitizes several species of insects and has been widely used to test new therapeutic strategies against parasitic infections. ''C. fasciculata'' is often used as a model organism in research into trypanosomatid biology that may then be applied to understanding the biology of the human infective species. As is typical of the trypanosomatids, but unlike many other protists, ''C. fasciculata'' possess one mitochondrion. The mitochondrial DNA is found in a single structure, the

kinetoplast A kinetoplast is a network of circular DNA (called kDNA) inside a large mitochondrion that contains many copies of the mitochondrial genome. The most common kinetoplast structure is a disk, but they have been observed in other arrangements. Kineto ...

, at the base of the single flagellum. As is common with parasitic species ''C. fasciculata'' requires a high nutrient content broth (including heme and folic acid) in which to grow under laboratory conditions.

Life cycle

Role in research

References

Further reading