Cutaneous microbiota of the Japanese giant salamander (Andrias japonicus), a representative of an ancient amphibian clade

Andrias japonicus, the Japanese giant salamander, is the second largest amphibian species in the world. The biology of this long-lived, fully aquatic salamander is still incompletely known, and studying the threats it experiences is important for conservation management. We used 16S amplicon sequencing to provide the first data on the composition and diversity of the cutaneous microbiome of this species. Skin bacterial communities of adult and larval giant salamanders were composed primarily of taxa belonging to the phyla Proteobacteria and Bacteroidetes, and, their community structure differed significantly from that of two other syntopic amphibians (Cynops pyrrhogaster and Glandirana rugosa). We also found differences between wild A. japonicus and captive individuals, with the latter having an increased bacterial diversity. The fungal pathogen Batrachochytrium dendrobatidis (Bd) was detected only in captive individuals (40% prevalence), and did not correlate with a particular bacterial community structure. We identified eight bacteria that were significantly more abundant on A. japonicus compared to syntopic amphibians, one of which was Janthinobacterium lividum, a bacterial species known to exert Bd-inhibiting effects. Our study provides baseline data for future in-depth studies on the microbial ecology of cutaneous bacteria and the contribution of cutaneous bacteria to Bd resistance in giant salamanders.