The Laboulbeniales is an order of ascomycete fungi, sharing that phylum with its more famous cousins -- yeast, morels, and cup fungi. There are over 2000 species in the order, and they are all ectoparasites of insects, spiders, and crustaceans (2, 3, 4). Commonly called "labdouls," these tiny fungi gather nutrients by digesting chitin from their hosts' shells, and beetles are a favorite (1, 2). An individual labdoul thallus looks like a short, flattened, yellowish hair sticking up off the surface of the insect's shell. Though infested insects often display many such structures, the fungs doesn't seem to do them much harm. Mating can transfer spores of the fungus from one insect to another. Ladybugs (or ladybirds) are commnly infected, and this is often where amateur naturalists first notice this interesting (if a little icky) fungus (3).
The Laboulbeniales is an order of Fungi within the class Laboulbeniomycetes. They are also known by the colloquial name beetle hangers[1] or labouls. The order includes around 2,325 species[2] of obligate insect ectoparasites that produce cellular thalli from two-celled ascospores. 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.[3] Recently, the genus Herpomyces, traditionally considered a basal member of Laboulbeniales, was transferred to the order Herpomycetales based on molecular phylogenetic data.[4][5] Laboulbeniales typically do not kill their hosts, although they may impair host fitness if the parasite density is high.
Laboulbeniales form individual thalli, and lack vegetative hyphae. A thallus is attached to its host by a simple dark-colored foot cell, or a rhizoidal haustorium through which the fungus penetrates the exoskeleton of its host to draw nutrients from the hemolymph.[6] The external part of the thallus may form male structures (antheridia) or female structures (trichogynes and perithecia), 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 (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.[7] The classification of the order Laboulbeniales follows Isabelle Tavares (1985) but several taxa in that system are polyphyletic.[8][9]
The Laboulbeniales is an order of Fungi 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 that produce cellular thalli from two-celled ascospores. 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, and lack vegetative hyphae. A thallus is attached to its host by a simple dark-colored foot cell, or a rhizoidal haustorium through which the fungus penetrates the exoskeleton of its host to draw nutrients from the hemolymph. The external part of the thallus may form male structures (antheridia) or female structures (trichogynes and perithecia), 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 (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.
