Laboulbeniales hyperparasites (Fungi, Ascomycota) of bat flies: Independent origins and host associations

Hyperparasitism in bat flies (Diptera: Streblidae): new records and interaction networks in the Neotropics

Hyperparasitism is defined as the interaction where one parasite is infected by another parasite. In bat flies (Streblidae and Nycteribiidae), both hyperparasites and microparasites (bacteria, viruses, fungi, and arthropods such as mites) have been documented. Fungi belonging to the order Laboulbeniales are microscopic parasites of a wide diversity of arthropod hosts. Three genera exclusively target bat flies: Arthrorhynchus, which parasitizes species within Nycteribiidae in the Eastern Hemisphere, while genus Gloeandromyces and Nycteromyces parasitize Streblidae in the Western Hemisphere. Among the hyperparasitic arthropods, mites of family Neothrombidiidae, particularly the monospecific genus Monunguis, are known to parasitize bat flies. Here we present the first records of the hyperparasites Monunguis streblida and Gloeandromyces pageanus f. polymorphus parasitizing Streblidae bat flies in Colombia and a summary of these hyperparasitic interactions in the Neotropics. We detected fungi and mites parasitizing bat flies that were collected in the Magdalena River Basin, Colombia, in field expeditions in 2018, 2022, and 2023. We identified 17 bat flies and two species of hyperparasites, specifically M. streblida and the fungi Gloeandromyces. Our search for reports of these interactions in the Neotropics revealed that seven species of Trichobius (Streblidae) are parasitized by M. streblida, whereas Paratrichobius longicrus (Streblidae) is parasitized by Gloeandromyces pageanus f. polymorphus. These interactions have been reported in 11 countries, but our records are the first of M. streblida and Laboulbeniales fungi parasitizing bat flies in Colombia. So far, a total of 14 species of fungi and one species of mite have been associated with 19 species of bat flies, which in turn, are linked to 15 species of Neotropical bats.

New insights into the DNA extraction and PCR amplification of minute ascomycetes in the genus Laboulbenia (Pezizomycotina, Laboulbeniales)

Molecular studies of fungi within the order Laboulbeniales (Ascomycota, Pezizomycotina) have been hampered for years because of their minute size, inability to grow in axenic culture, and lack of reliable and cost-efficient DNA extraction protocols. In particular, the genus Laboulbenia is notorious for low success with DNA extraction and polymerase chain reaction (PCR) amplification. This is attributed to the presence of melanin, a molecule known to inhibit PCR, in the cells. We evaluated the efficacy of a standard single cell-based DNA extraction protocol by halving the recommended amount of reagents to reduce the cost per extraction and adding bovine serum albumin (BSA) during the multiple displacement amplification step to reverse the effect of melanin. A total of 196 extractions were made, 111 of which were successful. We found that halving the reagents used in the single cell-based extraction kit did not significantly affect the probability of successful DNA extraction. Using the halved protocol reduces cost and resource consumption. Moreover, there was no significant difference in the probability of successfully extracting DNA based on whether BSA was added or not, suggesting that the amount of melanin present in cells of the thallus has no major inhibitory effect on PCR. We generated 277 sequences from five loci, but amplification of the internal transcribed spacer region, the mitochondrial small subunit rDNA, and protein-coding genes remains challenging. The probability of successfully extracting DNA from Laboulbeniales was also impacted by specimen storage methods, with material preserved in > 95% ethanol yielding higher success rates compared to material stored in 70% ethanol and dried material. We emphasize the importance of proper preservation of material and propose the design of Laboulbeniales-specific primers to overcome the problems of primer mismatches and contaminants. Our new insights apply not only to the genus Laboulbenia; Laboulbeniales generally are understudied, and the vast majority of species remain unsequenced. New and approachable molecular developments will benefit the study of Laboulbeniales, helping to elucidate the true diversity and evolutionary relationships of these peculiar microfungi.

Five new species of Gloeandromyces (Fungi, Laboulbeniales) from tropical American bat flies (Diptera, Streblidae), revealed by morphology and phylogenetic reconstruction

This paper describes and illustrates five new species of Gloeandromyces (Ascomycota, Laboulbeniales) associated with tropical American bat flies (Diptera, Streblidae). These are Gloeandromyces cusucoensis sp. nov. from Trichobius uniformis in Costa Rica and Honduras, G. diversiformis sp. nov. from Strebla wiedemanni in Costa Rica, G. plesiosaurus sp. nov. from Trichobius yunkeri in Panama, G. pseudodickii sp. nov. from Trichobius longipes in Ecuador and Panama, and G. verbekeniae sp. nov. from Strebla galindoi in Ecuador and Panama. The description of these five species doubles the number of known species in the genus. Morphological characteristics, host association, and a three-locus (18S nuc rDNA, 28S nuc rDNA, TEF1) phylogenetic reconstruction support placement of these taxa in the genus Gloeandromyces. Three of the new species are polymorphic; they have multiple morphotypes that grow in specific positions on the host integument: G. diversiformis f. diversiformis, f. musiformis, and f. vanillicarpiformis; G. plesiosaurus f. asymmetricus and f. plesiosaurus; and G. verbekeniae f. verbekeniae and f. inflexus. Finally, a dichotomous key to all species and morphotypes is presented.

Viral Hyperparasitism in Bat Ectoparasites: Implications for Pathogen Maintenance and Transmission

Humans continue to encroach on the habitats of wild animals, potentially bringing different species into contact that would not typically encounter each other under natural circumstances, and forcing them into stressful, suboptimal conditions. Stressors from unsustainable human land use changes are suspected to dramatically exacerbate the probability of zoonotic spillover of pathogens from their natural reservoir hosts to humans, both by increasing viral load (and shedding) and the interface between wildlife with livestock, pets and humans. Given their known role as reservoir hosts, bats continue to be investigated for their possible role as the origins of many viral outbreaks. However, the participation of bat-associated ectoparasites in the spread of potential pathogens requires further work to establish. Here, we conducted a comprehensive review of viruses, viral genes and other viral sequences obtained from bat ectoparasites from studies over the last four decades. This review summarizes research findings of the seven virus families in which these studies have been performed, including Paramyxoviridae, Reoviridae, Flaviviridae, Peribunyaviridae, Nairoviridae, Rhabdoviridae and Filoviridae. We highlight that bat ectoparasites, including dipterans and ticks, are often found to have medically important viruses and may have a role in the maintenance of these pathogens within bat populations.

Hyperparasitic Fungi on Black Mildews (Meliolales, Ascomycota): Hidden Fungal Diversity in the Tropics

Hyperparasitism on plant-parasitic fungi is a widespread but rarely studied phenomenon. Here, for the first time, we compile in a checklist information provided by peer-reviewed literature for fungi growing on colonies of black mildews (Meliolales, Ascomycota), a species-rich group of tropical and subtropical plant-parasitic microfungi. The checklist contains information on 189 species of contact-biotrophic microfungi in 82 genera. They belong to seven morphological groups: dematiaceous hyphomycetes, moniliaceous hyphomycetes, pycnidioid, perithecioid, catathecioid, and apothecioid fungi. By the fact that species accumulation curves do not reach saturation for any tropical country, it is evident that the knowledge of the diversity of hyperparasitic fungi on Meliolales is incomplete. A network analysis of records of hyperparasitic fungi, their host fungi and host plants shows that genera of hyperparasitic fungi are generalists concerning genera of Meliolales. However, most species of hyperparasitic fungi are restricted to meliolalean hosts. In addition to hyperparasitic fungi, diverse further microorganisms use meliolalean colonies as ecological niche. Systematic positions of most species are unknown because DNA sequence data are lacking for species of fungi hyperparasitic on Meliolales. We discuss the specific challenges of obtaining DNA sequence data from hyperparasitic fungi. In order to better understand the diversity, evolution and biology of hyperparasitic fungi, it is necessary to increase sampling efforts and to undertake further morphological, molecular, and ecological studies.

Focus on Hyperparasites: Biotic and Abiotic Traits Affecting the Prevalence of Parasitic Microfungi on Bat Ectoparasites

The tritrophic association of bats, bat flies, and Laboulbeniales microfungi is a remarkably understudied system that may reveal patterns applicable to community ecology theory of (hyper)parasites. Laboulbeniales are biotrophic microfungi, exclusively associated with arthropods, with several species that are specialized on bat flies, which themselves are permanent ectoparasites of bats. Several hypotheses were tested on biotic and abiotic traits that may influence the presence and prevalence of hyperparasitic Laboulbeniales fungi on bat flies, based on southeastern European data. We found a wide distribution of fungal infection on bat flies, with underground-dwelling bats hosting more Laboulbeniales-infected flies compared to crevice-dwelling species. Bat host behavior, sociality, roost selection (underground versus crevice), bat fly sex, and season all have significant effects on the prevalence of fungal infection. Laboulbeniales infections are more common on bat flies that are infecting bat species with dense and long-lasting colonies (Miniopterus schreibersii, Myotis myotis, Myotis blythii), which roost primarily in underground sites. Inside these sites, elevated temperature and humidity may enhance the development and transmission of Laboulbeniales fungi. Sexual differences in bat hosts’ behavior also have an effect on fungal infection risk, with densely roosting female bat hosts harboring more Laboulbeniales-infected bat flies.

Penetrative and non-penetrative interaction between Laboulbeniales fungi and their arthropod hosts

Laboulbeniales are a highly specialized group of fungi living only on arthropods. They have high host specificity and spend their entire life-cycle on an arthropod host. Taxonomic characters of Laboulbeniales are based on the architecture of the cells of the parenchymal thallus, i.e. the visible part of the fungus outside the host. The extent of the fungus spreading inside the host-the haustorium-remains largely unknown. The attachment to the arthropod host is fundamental to understand the fungus-animal interaction, but how this truly occurs is unclear. Recent evidences question the strictly parasitic life-style of Laboulbeniales. We used micro-computed tomography (µCT) and 3D reconstructions to visualize, for the first time, the complete structure of Laboulbeniales species in situ on their hosts. We compared the haustoriate species, Arthrorhynchus nycteribiae on an insect host to the non-haustoriate species, Rickia gigas on a millipede host. Our results confirm that some Laboulbeniales species are ectoparasitic and have a haustorial structure that penetrates the host's cuticle, while others are ectobionts and are only firmly attached to the host's cuticle without penetrating it. The presence and the morphology of the haustorium are important traits for Laboulbeniales evolution, and key factors for future understanding of host dependence and specificity.

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

Parasitism is one of the most diverse and abundant modes of life, and of great ecological and evolutionary importance. Notwithstanding, large groups of parasites remain relatively understudied. One particularly unique form of parasitism is hyperparasitism, where a parasite is parasitized itself. Bats (Chiroptera) may be parasitized by bat flies (Diptera: Hippoboscoidea), obligate blood-sucking parasites, which in turn may be parasitized by hyperparasitic fungi, Laboulbeniales (Ascomycota: Laboulbeniomycetes). In this study, we present the global tritrophic associations among species within these groups and analyze their host specificity patterns. Bats, bat flies, and Laboulbeniales fungi are shown to form complex networks, and sixteen new associations are revealed. Bat flies are highly host-specific compared to Laboulbeniales. We discuss possible future avenues of study with regard to the dispersal of the fungi, abiotic factors influencing the parasite prevalence, and ecomorphology of the bat fly parasites.

The paradoxical rarity of a fruit fly fungus attacking a broad range of hosts

Understanding the factors that determine the realized and potential distribution of a species requires knowledge of abiotic, physiological, limitations as well as ecological interactions. Fungi of the order Laboulbeniales specialize on arthropods and are typically thought to be highly specialized on a single species or closely related group of species. Because infections are almost exclusively transmitted through direct contact between the hosts, the host ecology, to a large extent, determines the distribution and occurrence of the fungus. We examined ~20,000 fruit flies (Diptera: Dacinae) collected in Malaysia, Sulawesi, Australia, and the Solomon Islands between 2017 and 2019 for fungal infections and found 197 infected flies across eight different Bactrocera species. Morphology and 1,363 bps of small subunit (18S) DNA sequences both support that the infections are from a single polyphagous fungal species Stigmatomyces dacinus-a known ectoparasite of these fruit flies. This leads to the question: why is S. dacinus rare, when its hosts are widespread and abundant? In addition, the hosts are all Bactrocera, a genus with ~480 species, but 37 Bactrocera species found sympatric with the hosts were never infected. Host-selection does not appear to be phylogenetically correlated. These results suggest a hidden complexity in how different, but closely related, host species vary in their susceptibility, which somehow limits the abundance and dispersal capability of the fungus.

A new species of Herpomyces (Laboulbeniomycetes: Herpomycetales) on Periplaneta fuliginosa (Blattodea: Blattidae) from Argentina

We are becoming increasingly aware of the dazzling diversity of fungi-new taxa are being discovered from poorly sampled habitats and integrative approaches point at (near-)cryptic species in many groups. The class Laboulbeniomycetes, which is composed of three orders (Herpomycetales, Laboulbeniales, Pyxidiophorales), is no exception. However, still, in the orders Herpomycetales and Laboulbeniales, species are predominantly described based on morphology alone. Here, we present a new species of Herpomyces from Argentina parasitic on Periplaneta fuliginosa, the smokybrown cockroach. Herpomyces spegazzinii, sp. nov., is characterized based on morphology and molecular data. Phylogenetic inference based on internal transcribed spacer (ITS, consisting of ITS1-5.8S-ITS2) barcode region supports the status of this fungus as a separate species, sister to the recently described H. shelfordellae.

Morphological species of Gloeandromyces (Ascomycota, Laboulbeniales) evaluated using single-locus species delimitation methods

In this paper, new species and formae of the genus Gloeandromyces (Ascomycota, Laboulbeniales) are described and illustrated. These are: Gloeandromyces dickii sp. nov. on Trichobius joblingi from Nicaragua and Panama; G. pageanus f. alarum f. nov. on Tri. joblingi from Panama; G. pageanus f. polymorphus f. nov. on Tri. dugesioides and Tri. joblingi from Panama and Trinidad; and G. streblae f. sigmomorphus f. nov. on Tri. joblingi from Panama. Gloeandromyces pageanus on Tri. dugesioides from Panama as described in Nova Hedwigia 105 (2017) is referred to as G. pageanus f. pageanus. Support for these descriptions of species and formae comes from phylogenetic reconstruction of the large subunit ribosomal DNA and from the application of species delimitation methods (ABGD, bPTP, GMYC). Host specialization results in phylogenetic segregation by host species in both G. pageanus and G. streblae and this may represent a case of incipient speciation. A second mechanism driving diversity involves position-induced morphological adaptations, leading to the peculiar morphotypes that are associated to growing on a particular position of the integument (G. pageanus f. alarum, G. streblae f. sigmomorphus).

Hyperparasitism in caves: Bats, bat flies and ectoparasitic fungus interaction

Bat flies (Diptera: Nycteribiinae) are highly specialized bloodsucking bat ectoparasites. Some of the ectoparasitic bat flies are themselves parasitized with an ectoparasitic fungus of the genus Arthrorhynchus (Laboulbeniales). Ascospores of the fungus attach to the cuticle of a bat fly and develop a haustorium that penetrates the host cuticle. This interaction defines the fungus as a hyperparasite. Both the fly and the fungus are obligate parasites and this peculiar case of hyperparasitism has remained largely unstudied. We studied the prevalence of Laboulbeniales, genus Arthrorhynchus, in natural populations of bat flies infesting the bat species Miniopterus schreibersii, Myotis bechsteinii, My. blythii, My. daubentonii, My. escalerai and My. myotis in Portuguese caves. Laboulbeniales were found infecting 10 of the 428 screened bat flies (2.3%) in natural populations, with fewer infections in winter. Images obtained with transmission electron microscopy show the fungal haustorium within the bat fly host tissue, from where it extracts nutrition.

Studies of Laboulbeniales on Myrmica ants (IV): host-related diversity and thallus distribution patterns of Rickia wasmannii

Fungal species identities are often based on morphological features, but current molecular phylogenetic and other approaches almost always lead to the discovery of multiple species in single morpho-species. According to the morphological species concept, the ant-parasitic fungus Rickia wasmannii (Ascomycota, Laboulbeniales) is a single species with pan-European distribution and a wide host range. Since its description, it has been reported from ten species of Myrmica (Hymenoptera, Formicidae), of which two belong to the rubra-group and the other eight to the phylogenetically distinct scabrinodis-group. We found evidence for R. wasmannii being a single phylogenetic species using sequence data from two loci. Apparently, the original morphological description (dating back to 1899) represents a single phylogenetic species. Furthermore, the biology and host-parasite interactions of R. wasmannii are not likely to be affected by genetic divergence among different populations of the fungus, implying comparability among studies conducted on members of different ant populations. We found no differences in total thallus number on workers between Myrmica species, but we did observe differences in the pattern of thallus distribution over the body. The locus of infection is the frontal side of the head in Myrmica rubra and M. sabuleti whereas in M. scabrinodis the locus of infection differs between worker ants from Hungary (gaster tergites) and the Netherlands (frontal head). Possible explanations for these observations are differences among host species and among populations of the same species in (i) how ant workers come into contact with the fungus, (ii) grooming efficacy, and (iii) cuticle surface characteristics.

Studies on Dimorphomyceteae: I. New species of Nycteromyces and Dimeromyces (Laboulbeniales) on bat flies (Streblidae)

Three new species, Nycteromyces orientalis, Dimeromyces capensis, and D. streblidarum, belonging to the Laboulbeniales (Fungi, Ascomycota) and collected on bat flies (Diptera, Streblidae), are described and illustrated. The new species of Nycteromyces is the second described in this rarely collected genus, with the type species, N. streblidinus, previously collected only three times from Venezuela, Panama, and Honduras. The material for our new species comes from Australia, India, Philippines, and Tanzania, and morphological characters of these new collections require emendation of the original generic diagnosis. The distribution of N. streblidinus is also extended with additional collections from Costa Rica and Peru. We describe two new species of Dimeromyces from streblid hosts, the first report of any members of this large, diverse genus on this host family. Newly described taxa are compared with known species and the genera Nycteromyces and Dimeromyces discussed in relation to other known Laboulbeniales taxa.