Faecal pellets of lichenivorous mites contain viable cells of the lichen-forming ascomycete Xanthoria parietina and its green algal photobiont, Trebouxia arboricola

Abstract

The bright yellow wall lichen, Xarzthoria parietina, is usually inhabited by oribatid mites (Acari) which do not only find shelter, but also graze on selected areas of the thallus. As X. parietina does not produce symbiotic vegetative propagules and its compatible photobiont, unicellular green algae of the genus Debouxia, are rare outside lichen thalli, we tested the hypothesis of dispersal of viable Trebouxia cells via acarine faeces. The lichenivorous mites, Trhypochtonius tectorum and Trichoribates trimaculatus, were isolated from thalli of X. parietina and cultured in the laboratory on a lichen diet. Light microscopic investigations of faecal pellets from mites that had been feeding on X . parietina indicated gut passage of intact ascospores and photobiont cells. In a series of experiments, viable algal and fungal cells contained in such faecal pellets were cultured. The taxonomic affiliation of these isolates was identified using molecular techniques, i.e. comparative investigations of nuclear ribosomal gene data (ITS 1 and 2, 5.8s rDNA) in the algal and fungal partners, and of the species-specific hydrophobin gene sequence in the fungal partner. Our culturing experiments demonstrated that the faecal pellets of both lichenivorous mites, upon feeding on X. parietina, contain viable ascospores and photobiont cells (Trebouxia arboricola) and thus might be a common and successful mode of vegetative short-and long-distance dispersal of this and numerous other lichen-forming ascomycetes and their photobionts. Future studies will have to elucidate the evolutionary significance of invertebrate interactions with lichens. 0 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76, 259-268.ADDITIONAL KEYWORDS: Acari -comparative rDNA sequence analysis culturing experiments -hydrophobin gene sequence -lichen-arthropod interactions -oribatid mites -Trhypochtonius tectorum -Trichoribates trimaculatus -vegetative dispersal of lichens.

Estimating the dispersal capacity of the rare lichen Cliostomum corrugatum

“…Perhaps dispersal in C. corrugatum is facilitated by winged insects carrying ascospores, conidia, or pieces of lichen thallus. Ascospores and algal cells have been shown to be viable after having passed through the gut of mites (Meier et al 2002). Mites, in turn, could be carried over large distances with the help of mammals or birds.…”

Isotopic labeling and antifungal resistance as tracers of gut passage of the sea fan pathogen Aspergillus sydowii

“…If sufficient fecal matter had accumulated during the course of the experiment, the isotopically enriched fungi could also be used to determine viability. These methods are useful alternatives to microscopic or molecular techniques to detect the successful gut passage of specific species or strains of fungi (Dromph 2001, Colgan & Claridge 2002, Meier et al 2002, Malaquias et al 2004, Prom & Lopez 2004, Lilleskov & Bruns 2005.…”

“…Previous studies tracing the gut passage of pathogens often relied on direct culturing or molecular identification (Dromph 2001, Colgan & Claridge 2002, Meier et al 2002, Lilleskov & Bruns 2005, both of which are ineffective for cosmopolitan species such as Aspergillus sydowii, which is a common indoor air contaminant (Klich 2002). Here we investigated 2 methods for tracing pathogen propagules through the environment: the use of isotopically labeled or hygromycin-resistant A. sydowii.…”

Die Hard: Lichens

“…On the other hand, some lichen symbionts can survive the enteric passage of invertebrates, which then even contributes to their dispersal (Meier et al, 2002;Fröberg et al, 2001). …”