Photoautotrophic and fungal biofilm constituents of European pond turtle (Emys orbicularis L.) carapace from Deliblato sand (Serbia)

Abstract

The composition of biofilm formed on the carapace of European Pond turtle (Emys orbicularis L.) was investigated during two years (2017-2018) at the locality Stevanove ravnice within Special Nature Reserve “Deliblato Sand“. The aim of this study was to determine the qualitative composition of cyanobacteria, algae and fungi which settled the turtle carapaces. Biofilm was removed by non-aggressive adhesive tape method and scraping with a rough brush. Cyanobacteria, algae and fungi were identified using optical microscopy (Carl Zeiss AxioImager.M1 with AxioVision 4.9 software). For diatom identification, the samples were treated with standard laboratory methods to prepare permanent slides. Sixteen cyanobacterial and 85 algal taxa were recorded. The photosynthetic organisms of the biofilm were comprised of 16 cyanobacteria, 76 diatoms, 5 taxa of green algae, 3 taxa of euglenoid algae and only 1 taxon from chrysophytes. Cyanobacteria and diatoms were dominant and occur with a great abundance on the carapaces. The most abundant cyanobacteria-forming biofilm was the members of genera: Phormidium, Oscillatoria and Gloeocapsopsis. The dominant diatom genera were Gomphonema and Cymbella. Somatic and reproductive fungal structures embedded in the analyzed biofilm were also documented. Melanized hyphae forming branched septate mycelium found in few samples suggested optimal conditions for fungal growth and proliferation. In all investigated biofilm samples the high diversity of fungal spores were recorded. Based solely on micromorphology criteria presented fungal identification was precise only to “genus-like” level. The most abundant spore types were fragmospores (Sporidesmiella, Drechslera, Fusarella, Torula, Spiropes, Corynespora, Taeniollela, Curvularia and Dendrophyon), amerospores (Acremoniella, Wardomyces, Scytalidium, Acrogenospora, Beltrania and Cladosporium), didymospores (Pseudobotrytis, Trichocladium, Veronaea and Scolecobasidium) and dictyospores (Alternaria, Berkleasmium, Monodyctys and Pythomyces). Cheirospores (Zalerion), scoleciospores (Pleiochaeta), and staurospores (Diplocladiella) were less abundant. In one sample pycnidium resembling fruiting body (Phoma) was documented. All documented fungal structures belong to genera frequently cited as transients in fresh-water habitats.