Tiny Colonizers of Frog Skin: Composition and Diversity of Diatoms in the Pelophylax esculentus complex

Abstract

Diatoms, microscopic algae found in various aquatic environments, have recently been recognised as epibionts on the skin of amphibians, although their diversity and ecological role remain underexplored. In this study, the diatom communities on the skin of frogs of the Pelophylax esculentus complex are investigated at three freshwater sites in southern Banat (Serbia), which differ in the degree of eutrophication and anthropogenic pressure. A total of 59 frogs representing all three taxa of the complex were collected and sampled using standard algological methods: adhesive tape and brush scraping. A total of 203 diatom taxa from 54 genera were identified. Statistical analyses showed that the environmental conditions significantly influenced the structure of the diatom community. A two-way ANOSIM revealed significant differences between localities (R = 0.23, p = 0.03), but not between frog taxa (R = 0.08, p = 0.24). PERMANOVA confirmed a significant effect of locality (F = 1.39, p = 0.03), with no significant effect of frog taxa (F = 12.35, p = 0.11) or their interaction (F = 10.64, p = 0.32). Principal coordinate analysis revealed two environmental gradients: The first separated sites according to trophic state (mesotrophic, eutrophic, hypertrophic), with diatom diversity higher in eutrophic conditions; the second reflected saprobial levels and distinguished oligosaprobic/β- mesosaprobic from α-mesosaprobic/polysaprobic habitats. The weak differences in the diatom communities between the frog taxa indicate that the environmental conditions and not the host taxa characterise these communities. This emphasises the ecological role of amphibian skin as a suitable microhabitat for periphytic algae and highlights the need for further research to determine whether it serves as a transient or stable habitat for diatom colonisation.