''Ascosphaera callicarpa'' is a

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

common on the larval feces of the solitary bee ''

Chelostoma florisomne ''Chelostoma florisomne'', the large scissor-bee, is a species of hymenopteran in the family Megachilidae. Etymology The Latin species name ''florisomne'' refers to the habit of some males to sleep inside the buttercup flowers. Distribution and ...

'', which nests in the Phragmites reeds of

thatched roof Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge (''Cladium mariscus''), rushes, heather, or palm branches, layering the vegetation so as to shed water away from the inner roof. Since the bulk of ...

s in Europe. Pathogenic ''

Ascosphaera ''Ascosphaera'' is a genus of fungi in the family Ascosphaeraceae. It was described in 1955 by mycologists Charles F. Spiltoir and Lindsay S. Olive. Members of the genus are insect pathogens. The type species, '' A. apis'', causes chalkbro ...

'' species afflict only the

larva 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. The ...

l stage of bees. Typically, diseased larvae die in the larval stage; in rare occurrences, however, larvae have been observed to enter

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 ...

tion before being overcome by the fungus.

Description

The

mating system A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mating, mate under which circumstances. Reco ...

heterothallic Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of ...

. Infected larvae appear shrunken, pale

buff Buff or BUFF may refer to: People * Buff (surname), a list of people * Buff (nickname), a list of people * Johnny Buff, ring name of American world champion boxer John Lisky (1888–1955) * Buff Bagwell, a ring name of American professional wr ...

, covered by a weft of

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e, with or without the production of

ascomata An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are mo ...

. The ascomata are greenish (immature) to black (mature) spore cysts produced on aerial hyphae above the larval cuticle, measuring 40–119

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

in diameter. The spore wall is pale greenish to yellowish-brown, nearly smooth with minute punctae at high magnification. Spore balls are

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

to pale yellowish, without granules, 7–20 µm in diameter, and mostly persistent. The

ascospore An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...

s are

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

to somewhat sausage shaped, and measure 2.1–3.9 by 1.1–1.7 µm. Cultures grown on

Sabouraud dextrose agar Sabouraud agar or Sabouraud dextrose agar (SDA) is a type of agar growth medium containing peptones. It is used to cultivate dermatophytes and other types of fungi, and can also grow filamentous bacteria such as '' Nocardia''. It has utility ...

show rapid growth after 2–6 days; they are white with abundant production of spore cysts when both mating strains are present.

Ecology and distribution

''Ascosphaera aggregate'' is an obligate pathogen with a preference for bees belonging to the family

Megachilidae Megachilidae is a cosmopolitan family of mostly solitary bees. Both that their pollen-carrying structure (called a ''scopa'') is restricted to the ventral surface of the abdomen (rather than mostly or exclusively on the hind legs as in other b ...

. This species has a broad distribution, with reports from both North America and Europe. This fast-growing

saprotroph Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...

is associated primarily with solitary bees. This species is typically found growing on pollen provisions. Less common substrates from which ''A. agra'' has been isolated include the surface of a diseased ''M. rotundata'' larva with chalkbrood caused by ''A. aggregate'', from pollen within the gut of an otherwise healthy ''M. rotundata'' larva and from the honey of ''A. mellifera''. ''Ascosphaera agra'' is the only species of the genus that has been found growing on plant material (grass silage) outside of the bee habitat. Pathogenicity studies demonstrated that ''A. agra'' is not a pathogen of solitary bees; however it has been concluded that it is a weak pathogen of honeybees.

References

{{Taxonbar, from=Q16748692 Onygenales Fungi described in 2013 Fungi of Europe