Green frogs skin harbours microbiota treasure

Abstract

Cutaneous microbiota of amphibians is considered to be an indicator of the health status of examined individuals, as well as of environmental factors. In that sense the skin of the captured individuals belonging to Pelophylax esculenta complex on the locality Stevanove ravnice within the Special Nature Reserve “Deliblato Sand” (Serbia) was screened for the presence of biofilm-forming cyanobacteria, algae and fungi dwelling directly on frogs’ stratum corneum. Biofilm was sampled using non-aggressive “adhesive tape method” and their constituents were analyzed and characterized microscopically (Carl Zeiss AxioImager.M1 with AxioVision 4.9 software). We detected high diversity and abundance of diatom taxa overall, particularly belonging to genera Navicula, Gomphonema, Geissleria, Placoneis and Nitzschia. Cyanobacteria were less present and with low abundance. Among them chroococcal genera Gloeocapsopsis, Pseudocapsa and Aphanocapsa were recorded. Outside of diatoms and cyanobacteria, genus Chlorella was the only present photoautotrophic biofilm constituent. We consider highly mucous green frogs skin as a favorable environment for the survival of diatoms and cyanobacteria. Light microscopy analyses of biofilm fragments revealed the presence of variety of fungal structures. Documented coenocytic mycelium with zoosporangium, originated presumably from oomycetes, as well as septate melanized hyphae of dematiaceous fungi, suggested colonization of frog skin from both types of environments present, water and surrounding vegetation. A variety of fungal spores (fragmospores, amerospores, dictyospores, didymospores), and in few cases spore germination were recorded on frog skin. Detected biofilm composition was not determinate by species and gender-specific.