| Summary: | The epidermal microbiome is a critical element of marine organismal immunity, but the epidermal virome of marine organisms remains largely unexplored. The epidermis of sharks represents a unique viromic ecosystem. Sharks secrete a thin layer of mucus which harbors a diverse microbiome, while their hydrodynamic dermal denticles simultaneously repel environmental microbes. Here, we sampled the virome from the epidermis of three shark species in the family <i>Carcharhinidae</i>: the genetically and morphologically similar <i>Carcharhinus obscurus</i> (<i>n</i> = 6) and <i>Carcharhinus galapagensis</i> (<i>n</i> = 10) and the outgroup <i>Galeocerdo cuvier</i> (<i>n</i> = 15). Virome taxonomy was characterized using shotgun metagenomics and compared with a suite of multivariate analyses. All three sharks retain species-specific but highly similar epidermal viromes dominated by uncharacterized bacteriophages which vary slightly in proportional abundance within and among shark species. Intraspecific variation was lower among <i>C. galapagensis</i> than among <i>C. obscurus</i> and <i>G. cuvier.</i> Using both the annotated and unannotated reads, we were able to determine that the <i>Carcharhinus galapagensis</i> viromes were more similar to that of <i>G. cuvier</i> than they were to that of <i>C. obscurus</i>, suggesting that behavioral niche may be a more prominent driver of virome than host phylogeny.
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