Crithidia fasciculata
Encyclopedia
Crithidia fasciculata is a species of parasitic protist
. C. fasciculata, like other species of Crithidia
have a single host life cycle with insect
host, in the case of C. fasciculata this is the mosquito
. C. fasciculata have low host species specificity and can infect many species of mosquito.
for motility, and the attached, immotile, amastigote
form in the mosquito gut. Amastigotes excreted in the faeces contaminates 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
. 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
tes the amastigote infection is maintained in the gut through metamorphosis
giving rise to an infected adult mosquito.
(which causes African trypanosomiasis) and Leishmania
spp. (which cause Leishmaniasis
). 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
, 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 to grow under laboratory conditions.
Protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
. C. fasciculata, like other species of Crithidia
Crithidia
Crithidia are members of the trypanosome protozoa. 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 tracts of insects and interact with the intestinal epithelium...
have a single host life cycle with insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
host, in the case of C. fasciculata this is the mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
. 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 flagellumFlagellum
A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...
for motility, and the attached, immotile, amastigote
Amastigote
An amastigote is a cell that does not have a visible external flagella or cilia. The term is used mainly to describe a certain phase in the life-cycle of trypanosome protozoans. It is also called the leishmanial stage, since in Leishmania it is the form the parasite takes in the vertebrate host,...
form in the mosquito gut. Amastigotes excreted in the faeces contaminates 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
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
. 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
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
tes the amastigote infection is maintained in the gut through metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
giving rise to an infected adult mosquito.
Role in research
C. fasciculata is an example of a non-human infective trypanosomatid and is related to several human parasites, including Trypanosoma bruceiTrypanosoma brucei
Trypanosoma brucei is a parasitic protist species that causes African trypanosomiasis in humans and nagana in animals in Africa. There are 3 sub-species of T. brucei: T. b. brucei, T. b. gambiense and T. b. rhodesiense.These obligate parasites have two hosts - an insect vector and mammalian host...
(which causes African trypanosomiasis) and Leishmania
Leishmania
Leishmania is a genus of Trypanosomatid protozoa, and is the parasite responsible for the disease leishmaniasis. It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. Their primary hosts are vertebrates; Leishmania commonly infects...
spp. (which cause Leishmaniasis
Leishmaniasis
Leishmaniasis is a disease caused by protozoan parasites that belong to the genus Leishmania and is transmitted by the bite of certain species of sand fly...
). 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
Kinetoplast
A kinetoplast is a disk-shaped mass of circular DNA inside a large mitochondrion that contains many copies of the mitochondrial genome. Kinetoplasts are only found in protozoa of the class Kinetoplastida...
, 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 to grow under laboratory conditions.