''Apicystis bombi'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of parasitic alveolates in the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

Apicomplexa The Apicomplexa (also called Apicomplexia; single: apicomplexan) are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of non-photosynthetic plastid called an ap ...

. 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 taxon, extant group in the tribe Bombini, though a few extinct r ...

s. It is believed to have a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

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 mainland Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the ...

, 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.

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'') 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 ...

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 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', ...

''). 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: Internationalism * World citizen, one who eschews traditional geopolitical divisions derived from national citizenship * Cosmopolitanism, the idea that all of humanity belongs to a single moral community * Cosmopolitan ...

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

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

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 Quechua 'plain'), also known as the Pampas 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 o ...

, 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. Gregarines ...

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 carpel, 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 ...

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 endemism, 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 ...

'' 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 Spillover may refer to: * Adsorption spillover, a chemical phenomenon involving the movement of atoms adsorbed onto a metal surface * Catalyst support#Spillover * Behavioral spillover, the effect that one behavior has on other behaviors with a s ...

, 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 organis ...

s develop from these in the intestine. They migrate through the wall of the gut before taking up residence in the fat body 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 may reduce some of the negative effects of ''Apicystis bombi''.

References

{{Taxonbar, from=Q20685929 Conoidasida Parasites of bees Protists described in 1974