Characterising the mycobiome of healthy and wounded reef sharks in the Seychelles archipelago

Abstract Sharks frequently sustain cutaneous injuries throughout their lifetimes, yet subsequent infections are surprisingly rare, and wounds appear to heal rapidly. This has led scientists to explore the potential mechanisms behind shark skin’s putative ‘superior’ capacity for fending off infection. Interestingly, research has turned to the skin-associated microbiome for the answer. Although exploration of the bacterial microbiome has led to its proposal as a potential key factor in wound healing, the role of the fungal microbiome (or mycobiome) remains significantly overlooked. Here, we endeavoured to characterise the fungal communities colonising the skin of 46 blacktip reef sharks ( Carcharhinus melanopterus ) and one sicklefin lemon shark ( Negaprion acutidens ) in order to determine whether the presence of wounds corresponded to shifts within their fungal communities. We found that there were no significant differences between the fungal consortia harboured by insulted and intact skin, mirroring findings related to their bacterial counterparts. Further, we demonstrated fluctuating taxonomic profiles and the lack of a substantial ‘core’ community of fungal members shared across individuals, highlighting the need to disentangle the role of stochastic versus deterministic processes in shaping fungal communities in the shark skin microbiome. Finally, exploring co-occurrence patterns highlighted 21 positive associations between 13 fungal genera. We encourage future research to uncover the role of rare fungal amplicon sequence variants (ASVs) and investigate the ecological consequences of co-occurrence networks in order to elucidate the role of the skin mycobiome in shark health.