''Apicystis bombi'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of parasitic alveolates in the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

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. T ...

. It infects bees, especially

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 group in the tribe Bombini, though a few extinct related gener ...

s. It is believed to have a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

in bumblebees and a sporadic occurrence in

honey bees A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...

, and causes disease symptoms in nonresistant bee species.

Taxonomy

This protozoan was first described by Liu in 1974 as ''Mattesia bombi''. In 1996, Lipa and Triggiani transferred it to the new genus ''Apicystis'' on the basis of

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

and

life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring * Life-cycle hypothesis ...

Distribution

This protozoan was found in Canada in overwintering queens and in males of various species of ''Bombus'', with the half-black bumblebee (''

Bombus vagans The half-black bumblebee (''Bombus vagans'') is a small bumblebee with a wide distribution in North America, its range extending from Ontario to Nova Scotia and southward to Georgia. Description ''Bombus vagans'' is a common species of bumblebee ...

'') at 8% being the most heavily infected species. It was later identified in ''Bombus'' species in France, and also in Switzerland, where infection rates varied between 4 and 7%. The

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 i ...

s were found in Italy in the garden bumblebee ('' B. hortorum'') and the buff-tailed bumblebee ('' B. terrestris'') and in 1990, in Finland, were found in a single specimen of the honey bee ('' Apis mellifera''). Further finds were made in Italy over the next few years with the level of infection in ''Bombus'' species being considered low and that in ''A. mellifera'' sporadic. With specimens being found in Canada, France, Italy, Finland and Switzerland, it is likely that the parasite is

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

in distribution and will be identified in other countries. In 2009 the parasite was identified in

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...

in ''A. mellifera,'' ''B. terrestris'', and '' B. ruderatus'', only the second occasion on which it had been found in a honeybee. However extensive sampling in the

Pampas The Pampas (from the qu, pampa, meaning "plain") are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all of Uruguay; and Brazi ...

, the most productive honey-producing region of Argentina, failed to detect it there. Because there was only one detection in one specimen of ''Apis'' before, this (Plischuk et al 2011) is considered the first real detection. ''A. bombi''s host range spanning ''Apis'' and ''Bombus'' may indicate that they are sharing

gregarine The gregarines are a group of Apicomplexan alveolates, classified as the Gregarinasina or Gregarinia. The large (roughly half a millimeter) parasites inhabit the intestines of many invertebrates. They are not found in any vertebrates. However, gr ...

s at the shared pollen source. It is thought that the parasite was introduced in 1998 with commercially reared ''B. terrestris'' being imported into Chile for their use as

pollinator A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains. Insects are the maj ...

s. ''Apicystis bombi'' appears to have no adverse effects on ''B. terrestris''. The introduction of ''B.terrestris'' into certain regions of Patagonia and southern South America (starting around the 1980s) have led to the rapid decline of ''

Bombus dahlbomii ''Bombus dahlbomii'', also known as the moscardón, is a species of bumblebee endemic to southern South American temperate forests. ''B. dahlbomii'' is one of the largest bee species in the world, with matured queens growing up to long.King, A. ...

'' populations in the area. A large part of this decline can be attributed to ''Apicystis bombi'' pathogen spillover. Unlike ''B. terretstris'', ''B.dahlbomii'' does not have a natural resistance of ''A.bombi''. ''A.bombi'' infection prevents ''B.dahlbomii'' from completing proper foraging behaviors by inducing a plethora of behavioral and physiological impairments. Although transmission is not well understood, ''

Bombus affinis ''Bombus affinis'', commonly known as the rusty patched bumble bee, is a species of bumblebee endemic to North America. Its historical range in North America has been throughout the east and upper Midwest of the United States, north to Ontario, ...

'' has also been adversely affected by the ''A. bombi''. Incidence of infection has been observed in about 3% of all ''B. affinis'', and has become particularly prevalent in northern Ontario. This parasite causes increased worker death and prevention of new colony formation. In 2013 the parasite was identified, along with several others, to be infecting bumblebees imported into the UK and potentially in bumblebees imported around Europe. In 2014 the parasite was identified to be present in a large numbers of bumblebees in England. This prevalence was greatest in bumblebees which foraged close to farms using commercial (imported) bumblebees. Whilst it's not clear if this pattern is a result of parasite spillover, it is clear that the prevalence in England is far greater than previously detected.

Life cycle

Oocysts are ingested by the bee and

sporozoite 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 is ...

s develop from these in the intestine. They migrate through the wall of the gut before taking up residence in the

fat body 300px, Stained cells of an insect fat body Fat body is a highly dynamic insect tissue composed primarily of storage cells. It is distributed throughout the insect's internal body cavity; the haemocoel, in close proximity to the epidermis, dig ...

cells, where they develop and multiply. The presence of the pathogen gives the fat tissue a white appearance but microscopic examination of the tissue is required to confirm the presence of oocysts.

Effects

The effects of ''Apicystis bombi'' differ between host species. Heavily infected bees are rare, but this may be due to high pathogenicity of the neogregarine. Infected workers have increased mortality, reduced fatbody and increased sensitivity to sucrose. Infected queen bumblebees are unlikely to survive hibernation which is thought to be due to the reduced fatbody of infected queens. There is also some evidence that

Deformed wing virus ''Deformed wing virus'' (DWV) is an RNA virus, one of 22 known viruses affecting honey bees. While most commonly infecting the honey bee, '' Apis mellifera'', it has also been documented in other bee species, like ''Bombus terrestris'', thus, i ...

may reduce some of the negative effects of ''Apicystis bombi''.

References

{{Taxonbar, from=Q20685929 Conoidasida Parasites of bees