Laboulbeniomycetes: Intimate Fungal Associates of Arthropods

Abstract

Arthropod–fungus interactions involving the Laboulbeniomycetes have been pondered for several hundred years. Early studies of Laboulbeniomycetes faced several uncertainties. Were they parasitic worms, red algal relatives, or fungi? If they were fungi, to which group did they belong? What was the nature of their interactions with their arthropod hosts? The historical misperceptions resulted from the extraordinary morphological features of these oddly constructed ectoparasitic fungi. More recently, molecular phylogenetic studies, in combination with a better understanding of life histories, have clearly placed these fungi among filamentous Ascomycota (subphylum Pezizomycotina). Species discovery and research on the classification of the group continue today as arthropods, and especially insects, are routinely collected and examined for the presence of Laboulbeniomycetes. Newly armed with molecular methods, mycologists are poised to use Laboulbeniomycetes–insect associations as models for the study of a variety of basic evolutionary and ecological questions involving host–parasite relationships, modes of nutrient intake, population biology, host specificity, biological control, and invasion biology. Collaboration between mycologists and entomologists is essential to successfully advance knowledge of Laboulbeniomycetes and their intimate association with their hosts. Expected final online publication date for the Annual Review of Entomology, Volume 66 is January 11, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

On the Fly: Tritrophic Associations of Bats, Bat Flies, and Fungi

“…Their depositing behavior—especially when distances are large—brings female bat flies in contact with several host bat individuals, increasing potential contacts with conspecific and heterospecific bat flies, and might be an additional reason that female bat flies have a higher frequency of Laboulbeniales infection [ 51 ]. Second, ascospores of Laboulbeniales are usually transmitted directly through interactions among arthropod hosts such as grooming and mating activities [ 46 , 49 ]. Because bats are more likely to be infested, more likely to carry heavier parasite loads, and more likely to harbor more species of bat fly in more permanent roosting structures (caves and tunnels, as opposed to leaf tents) [ 27 ], Laboulbeniales might have more opportunities to disperse to new host species in these roosts where many different bat fly species gather.…”

“…However, on a species-level, ascospores of Laboulbeniales might adhere easier to and develop better on bat fly body parts that are associated with specific bat fly ecomorphology—e.g., on the elongated posterior legs of fur runners. Laboulbeniales infections in other host groups such as beetles (Hexapoda: Coleoptera), corixids (Hexapoda: Hemiptera), and pill-millipedes (Diplopoda: Sphaerotheriida) can be position-specific, and some even exhibit sex-of-host specificity [ 49 ]. This makes it not unimaginable that bat fly ecomorphotype and the associated microhabitat on the bat host may affect the prevalence of Laboulbeniales infection as well, although the exact mechanics of these associations are as yet unstudied.…”

“…Transmission of ascospores largely happens during host activities, such as mating and social grooming; indirect transmission is less often, due in part to the low survivability of ascospores in the environment (<7 days) [ 46 ]. Laboulbeniales exhibit a large morphological and structural diversity, as well as a wide arthropod host range, which place them among the most diverse groups of parasitic fungi with ~2325 described species in 145 genera [ 47 , 48 , 49 ]. Only four genera are found on bat flies: Arthrorhynchus , Dimeromyces , Gloeandromyces , and Nycteromyces [ 33 , 50 ].…”

Peer Review #1 of "Mortality of native and invasive ladybirds co-infected by ectoparasitic and entomopathogenic fungi (v0.1)"

“…Laboulbeniales, including He. virescens, cannot be grown in axenic culture and no asexual stages are known, which makes their study challenging (Haelewaters et al, 2021). Given locally high prevalence of He.…”

Mortality of native and invasive ladybirds co-infected by ectoparasitic and entomopathogenic fungi

“…Laboulbeniales, including He. virescens, cannot be grown in axenic culture and no asexual stages are known, which makes their study challenging (Haelewaters, Blackwell & Pfister, 2021). Given locally high prevalence of He.…”