Persistence of a core microbiome through the ontogeny of Coitocaecum parvum

We investigated the persistence of microbial communities throughout the life of a parasite with a complex life cycle. Using 16S amplicon sequencing, we characterise the microbiome of the trematode Coitocaecum parvum across four of its life stages: sporocysts, metacercariae and adults inhabiting (respectively) snails, crustaceans and fish, as well as free-living cercariae. Our study is the first demonstration of the persistence of a core microbiome in a parasite despite major transitions among life stages that change morphologically from host to host, supporting the idea that parasitic worms and their bacteria may function as an integrated holobiont. Our study uses molecular genetic techniques to explore hidden microbial diversity that can shape coevolutionary interactions.