Project description:Understanding natural defence mechanisms against parasites can be a valuable tool for the development of innovative therapies. In this study, we investigated the interplay between the gill mucus metabolome and microbiome of Chaetodon lunulatus, a butterflyfish known to avoid gill monogeneans whilst living amongst closely related parasitized species. In an attempt to identify metabolites and OTUs potentially involved in parasite defence mechanisms, we studied the metabolome (LC-MS/MS) and microbiome of several sympatric butterflyfish species, including the only non-parasitized species C. lunulatus. After observing significant differences between the metabolome and microbiome of parasitized versus non-parasitized fish (PCoA, ANOSIM), we obtained the discriminant metabolites and OTUs using a supervised analysis. Some of the most important discriminant metabolites were identified as peptides, and three new β-subunit haemoblogin-derived peptides from C. lunulatus (CLHbβ-1, CLHbβ-2 and CLHbβ-3) were purified, characterised and synthesised. We also identified specific bacterial families and OTUs typical from low-oxygen habitats in C. lunulatus gill mucus. By using a correlation network between the two datasets, we found a Fusobacteriaceae strain exclusively present in C. lunulatus highly correlated to the peptides. Finally, we discuss the possible involvement of these peptides and Fusobacteriaceae in monogenean avoidance by this fish species.
