Filling gaps in the microsporidian tree: rDNA phylogeny of Chytridiopsis typographi (Microsporidia: Chytridiopsida).

Microsporidia are intracellular eukaryotic parasites of animals, characterized by unusual morphological and genetic features. They can be divided in three main groups, the classical microsporidians presenting all the features of the phylum and two putative primitive groups, the chytridiopsids and metchnikovellids. Microsporidia originated from microsporidia-like organisms belonging to a lineage of chytrid-like endoparasites basal or sister to the Fungi. Genetic and genomic data are available for all members, except chytridiopsids. Herein, we filled this gap by obtaining the rDNA sequence (SSU-ITS-partial LSU) of Chytridiopsis typographi (Chytridiopsida), a parasite of bark beetles. Our rDNA molecular phylogenies indicate that Chytridiopsis branches earlier than metchnikovellids, commonly thought ancestral, forming the more basal lineage of the Microsporidia. Furthermore, our structural analyses showed that only classical microsporidians present 16S-like SSU rRNA and 5.8S/LSU rRNA gene fusion, whereas the standard eukaryote rRNA gene structure, although slightly reduced, is still preserved in the primitive microsporidians, including 18S-like SSU rRNA with conserved core helices, and ITS2-like separating 5.8S from LSU. Overall, our results are consistent with the scenario of an evolution from microsporidia-like rozellids to microsporidians, however suggesting for metchnikovellids a derived position, probably related to marine transition and adaptation to hyperparasitism. The genetic and genomic data of additional members of Chytridiopsida and Rozellomycota will be of great value, not only to resolve phylogenetic relationships but also to improve our understanding of the evolution of these fascinating organisms.

Metschnikowia cf. typographi and other pathogens from the bark beetle Ips sexdentatus - Prevalence, histological and ultrastructural evidence, and molecular characterization.

Ips sexdentatus (six-spined engraver beetle) from Austria and Poland were dissected and examined for the presence of pathogens. Specimens collected in Austria were found to contain the ascomycetous fungus Metschnikowia cf. typographi. Infection rates ranged from 3.6% to 26.8% at different collection sites. M. cf. typographi infected midguts were investigated by histological, ultrastructural and molecular techniques. Extraordinary ultrastructural details are shown, such as ascospores with bilateral flattened flanks resembling alar rims at both sides of their attenuating tube-like ends. These have not yet been described in other yeast species. Molecular investigations showed a close phylogenetic relationship to the fungi Metschnikowia agaves and Candida wancherniae. Presence of the entomopathogenic fungus Beauveria bassiana found in Austria was confirmed both morphologically and molecularly. The eugregarine Gregarina typographi was diagnosed most frequently. Infection rates of all I. sexdentatus specimens ranged from 21.4% to 71.9% in Austria and 54.1% to 68.8% in Poland. Other entomopathogenic protists, bacteria, or viruses were not detected.

Occurrence of Microsporidium sp. and other pathogens in Ips amitinus (Coleoptera: Curculionidae).

A new microsporidium is reported from the small spruce bark beetle, Ips amitinus: Microsporidium sp. with uninucleate oval spores measuring 3.5 × 2.5 µm; infecting cells of the midgut epithelium, midgut muscles, the fat body, the Malpighian tubules, and the gonads of adult beetles collected in Austria. Seven other pathogens were found in beetles collected from Austria, the Czech Republic, and Finland. Six of them were already known from I. amitinus. Nosema cf. typographi is recorded for the first time in the overwintering generation of I. amitinus from the Czech Republic.

Diversity of acaropathogenic fungi in Poland and other European countries.

The occurrence, species diversity and some aspects of taxonomical affinity and host selectivity of acaropathogenic fungi associated with phytophagous, saprotrophic and predacious mites in Poland and other European countries were investigated on wild and cultivated plants, in insect feeding sites under the bark and in decayed wood. From among 33 species of fungi affecting mites only five species of Entomophthorales were separated and the most numerous were Neozygites floridana mostly on Tetranychus urticae, N. abacaridis on a few eriophyid species, and Conidiobolus coronatus attacking gamasid mites most frequently of the genus Dendrolaelaps. The most frequent mite pathogens occurring in mite communities on plants and in wood infested by insects were of the genus Hirsutella. Until now 13 of their form-species have been recognized in these habitats, but only H. kirchneri, H. necatrix and H. thompsonii (including its variety synnematosa) can be treated as exclusive oligophagous pathogens of phytophagous mites, though their potential host range seems to embrace only selected eriophyid or tarsonemid mites. Taxonomical differentiation of fungal strains was based on close morphological observations and molecular analysis of ITS region sequences. Two new species of acaropathogenic fungi were described in these studies. Hirsutella danubiensis sp. nov. was found in the tetranychid T. urticae, whereas H. vandergeesti sp. nov. affected phytoseiid mites of the genera Amblyseius, Neoseiulus, Seiulus and Typhlodromus, and the tarsonemid Tarsonemus lacustris.