Assemblages of lichen are served as the habitat and food resource for various microinvertebrates. The lichens’ dwelling microfauna is of special interest regarding the maintenance of sustainable balance in terrestrial ecosystems. Little is known about microfauna consisting of protists and micrometazoa. The present study focused on the composition, diversity and distribution of microfauna in lichen Xanthoria parietina in Lithuania. Lichens were investigated beside highways and in unpolluted sites. The microfauna of X. parietina were represented by 24 taxa. Two species of tardigrades, two species of testate amoebae and one species of gymnoamoebae that are new in Lithuania were founded. The study results revealed that dominating protozoa in lichen X. parietina are testate amoebae (genus Arcella) and ciliates (Colpoda, Paramecium). Philodina sp. (Rotifera), Aphelenchoides sp. (Nematoda) and Ramazzottius oberhaueseri (Tardigrada) were found to be dominant micrometazoa in X. parietina. The dominant protozoa (Colpoda cuculus, Paramecium sp. Arcella sp.) and micrometazoa (rotifers Philodina) didn’t reveal the significant difference between polluted and unpolluted sites. Meanwhile the tardigrades were more abundant in unpolluted sites. Further studies on microfauna diversity using increased number of samples, sampling sites and estimating more environmental parameters can result in more distinct conclusions.

Keywords: microfauna, lichen, pollution, protozoa, Tardigrada, rotifera.