Parasites of parasites: blood-sucking bat flies infected with enigmatic Laboulbeniales fungi

Bats (Chiroptera) sustain highly diverse communities of invertebrate parasites. Two families of flies (Diptera: Nycteribiidae and Streblidae) and one family of bugs (Heteroptera: Polyctenidae) are exclusively ectoparasitic on bats, among with a plethora of other insect and mite species. Some of these parasites – several genera of bat flies – are themselves parasitized by ectoparasitic fungi in the order Laboulbeniales (Ascomycota). They were initially described as acanthocephalan worms in Kolenati’s article “Epizoa der Nycteribien” in 1857, which illustrated how atypical Laboulbeniales fungi are in their morphology and lifestyle.

Roland Thaxter’s pioneering and extensive efforts on Laboulbeniales diversity included description of three genera of bat fly-specific species: Arthrorhynchus (3 species), Gloeandromyces (2), and Nycteromyces (1). Only a handful of distribution records are known regarding bat-fly associated Laboulbeniales. These hyperparasitic fungi are ecological and evolutionary enigmas that are rarely encountered by entomologists or mycologists. However, chiropterologists and parasitologists working with bats and bat flies occasionally encounter and easily recognize fly specimens infected with these fungi. The authors of this report were independently approached by enthusiastic and alert zoologists who observed these fungi on Eastern Hemisphere and Neotropical bat flies. This led to the collaboration of our research groups at Harvard University and the University of Debrecen, dealing with evolutionary and ecological aspects of these fungi. Over the past year and a half, in two collecting trips to Panama by Haelewaters and one research visit of Pfliegler to the Farlow Herbarium, more than 12,000 previously collected bat flies were screened for fungi. This has broadened our knowledge of bat fly-infecting Laboulbeniales.

This screening process involved determining the presence of the fungi on the fly specimens, recording the level of infection (number of fruiting bodies or thalli), the position(s) of infection (several members of the order are known to display position specificity regarding their infection, although this phenomenon has not been suggested for bat fly-associated species), and making slide preparations of thalli for species identification. Thalli of highly infected flies were used for DNA isolation and amplification of nuclear ribosomal gene regions using molecular methods developed by our groups.

The host flies included more than a dozen genera collected from several host bat species in Hungary, Romania, Ecuador, Honduras, Mexico, and Trinidad. We found all three genera that infect bat flies. Nycteromyces was described by Roland Thaxter and was only known from the holotype specimens. We managed to significantly extend the geographic range and known host species of this genus, and to generate ribosomal DNA sequences suitable for phylogenetic studies. The genus Gloeandromyces was also described by Thaxter over a hundred years ago, with two species that also had not been recorded after their first description. We sampled these two species from several genera of flies both from Central and South America, and discovered three new species. To properly characterize the new fungi and to prepare species descriptions, we compared our specimens to the original holotype slides of the two known species at the Farlow Herbarium. We made updated morphological descriptions of these, as well as the new material, using differential interference contrast (DIC) optics and microphotography. Additionally, we managed to generate sequences from three species for phylogenetic studies. Arthrorhynchus, was finally found on bat flies collected in Hungary and Romania.

Using our previously generated database of Laboulbeniales sequences, we determined the phylogenetic positions of bat fly-infecting genera on the phylogenetic tree of the order. Surprisingly, we identified the three genera as independent lineages. One of these lineages, Gloeandromyces, falls within the species-rich genus Stigmatomyces, which is specific to flies. The other two lineages (Nycteromyces and Arthrorhynchus) each have a sister group relationship to genera that are associated with bugs (Heteroptera). We hypothesized that a host shift from bugs to bat flies has occurred at least twice which may or may not have been associated with bat-associated bugs.

Although many of these fungi have been described in the early 20th century, much about their biology is still unknown. In this project, we seek to unravel evolutionary patterns and ecological traits that may be related to parasitism by Laboulbeniales. These are exciting times; we are only at the cusp of new insights on the ecology, evolutionary driving forces, and phylogeny of this diverse order of fungi.

Walter P. Pfliegler & Danny Haelewaters, Friends of the Farlow Newsletter 67