''Crithidia'' is a genus of
trypanosomatid
Trypanosomatida is a group of kinetoplastid unicellular organisms 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 trypanosoma ...
Euglenozoa
Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by four major groups, ''i.e.,'' Kinetoplastea, ...
. They are
parasites
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...
that exclusively parasitise
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s, mainly insects. They pass from host to host as cysts in infective
faeces
Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) 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 ...
and typically, the parasites develop in the digestive tracts of insects and interact with the intestinal
epithelium
Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...
using their
flagellum
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 ...
. They display very low host-specificity and a single parasite can infect a large range of invertebrate hosts. At different points in its life-cycle, it passes through
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 ...
,
promastigote, and epimastigote phases; the last is particularly characteristic, and similar stages in other trypanosomes are often called crithidial.
The
etymology
Etymology ( ) is the study of the origin and evolution of words—including their constituent units of sound and meaning—across time. In the 21st century a subfield within linguistics, etymology has become a more rigorously scientific study. ...
of the genus name ''Crithidia'' derives from the
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
word (), meaning "small grain of barley".
Species
* ''
Crithidia bombi
''Crithidia bombi'' is a parasitic protist from the order Trypanosomatida. It is the most prevalent parasite of bumblebees.
Ecology
''Crithidia bombi'' is an important parasite of various bumblebee species, including common species like '' Bomb ...
'' is a well documented species, notable for being a parasite of various
bumblebee
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only Extant taxon, extant group in the tribe Bombini, though a few extinct r ...
species, including common species like ''
Bombus terrestris
''Bombus terrestris'', the buff-tailed bumblebee or large earth bumblebee, is one of the most numerous bumblebee species in Europe. It is one of the main species used in greenhouse pollination, and so can be found in many countries and areas wher ...
'', ''
Bombus muscorum
''Bombus muscorum'', commonly known as the large carder bee or moss carder bee, is a species of bumblebee in the family Apidae. The species is found throughout Eurasia in fragmented populations, but is most commonly found in the British Isles. '' ...
'', and ''
Bombus hortorum
''Bombus hortorum'', the garden bumblebee or small garden bumblebee, is a species of bumblebee found in most of Europe north to 70°N, as well as parts of Asia and New Zealand. It is distinguished from most other bumblebees by its long tongue ...
''.
* ''
Crithidia mellificae'' is a parasite of the
western honeybee
The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for 'bee', and ''mellifera'' is the Latin for 'honey-bearing' or 'honey-carrying', ...
, ''Apis mellifera''.
* ''
Crithidia brevicula'' might incorporate species of the genus ''
Wallaceina'' (''Wallaceina brevicula'', ''W. inconstans'', ''W. vicina'', and ''W. podlipaevi'') as suggested by molecular phylogenies based on
18S ribosomal RNA
18S ribosomal RNA (abbreviated 18S rRNA) is a part of the ribosomal RNA in eukaryotes. It is a component of the Eukaryotic small ribosomal subunit (40S) and the cytosolic homologue of both the 12S ribosomal RNA, 12S rRNA in mitochondria and the 1 ...
and
glycosomal glyceraldehyde-3-phosphatedehydrogenase sequences.
* Other species include ''
C. fasciculata'', ''
C. guilhermei'' and ''
C. luciliae''.
* ''C. luciliae'' is the substrate for the
antinuclear antibody
Antinuclear antibodies (ANAs, also known as antinuclear factor or ANF) are autoantibodies that bind to contents of the cell nucleus. In normal individuals, the immune system produces antibodies to foreign proteins (antigens) but not to human pro ...
test used to diagnose lupus and other autoimmune disorders
Impact on bumble bees
These parasites may be at least partially responsible for declining wild bumble bee populations. They cause the bumble bees to lose their ability to distinguish between flowers that contain
nectar
Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
and those that don't. They make many mistakes by visiting nectar scarce flowers and in so doing, slowly starve to death. Commercially bred bumble bees are used in greenhouses to pollinate plants, for example tomatoes, and these bumble bees typically harbor the parasite, while wild bumble bees do not. It is believed that the commercial bumble bees transmitted the parasite to wild populations in some cases. They escape from the greenhouses through vents; a simple mesh could help prevent this.
Bibliography
Further reading
External links
{{Authority control
Trypanosomatida
Parasitic excavates
Euglenozoa genera
Taxa described in 1902