The Laboulbeniales is an
order of
Fungi
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 ...
within the
class Laboulbeniomycetes. They are also known by the colloquial name beetle hangers or labouls. The order includes around 2,325 species of
obligate insect
ectoparasites
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
that produce
cellular thalli from two-celled
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. Of the
described Laboulbeniales, Weir and Hammond 1997 find 80% to be from
Coleoptera and the next largest group to be the 10% from
Diptera.
Recently, the genus ''
Herpomyces'', traditionally considered a basal member of Laboulbeniales, was transferred to the order
Herpomycetales based on
molecular phylogenetic data. Laboulbeniales typically do not kill their hosts, although they may impair host fitness if the parasite density is high.
Laboulbeniales form individual
thalli
Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...
, and lack vegetative
hyphae. A thallus is attached to its host by a simple dark-colored foot cell, or a rhizoidal
haustorium
In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates th ...
through which the fungus penetrates the exoskeleton of its host to draw nutrients from the
hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
. The external part of the thallus may form male structures (antheridia) or female structures (trichogynes and
perithecia
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 mos ...
), or both. New infections are initiated when spores from the perithecia attach to a compatible insect host. Spore transmission can sometimes occur during insect copulation, which may account for the different site specificity sometimes observed in male and female hosts. These fungi do not grow apart from their hosts.
Foundational work on the Laboulbeniales was completed by the American mycologist
Roland Thaxter
Roland Thaxter (August 28, 1858 – April 22, 1932) was an American mycologist, plant pathologist, botanist, and entomologist, renowned for his contribution to the insect parasitic fungi— Laboulbeniales. His college education was completed a ...
(1858–1932), particularly in his five-volume, illustrated ''Monograph of the Laboulbeniaceae'' (Thaxter 1896, 1908, 1924, 1926, 1931).
Recent
molecular phylogenetic work has shown that some taxa are
complexes of multiple species segregated by host, for example ''Hesperomyces virescens''. The classification of the order Laboulbeniales follows Isabelle Tavares (1985) but several taxa in that system are
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
.
References
Further reading
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External links
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Bugguide.net. ''Harmonia axyridis'' with Laboulbeniales fungusArticle about Laboulbeniales on Diptera by Jan MácaLaboulbeniales homepage by Dr. Alex Weir
Ascomycota orders
{{Ascomycota-stub