All multicellular organisms harbour a microbiota that plays a role that is still sometimes poorly known but crucial for many functions of their hosts, especially in relation to their pathogens. We have recently shown that the bacterial community of the external mucus of teleost fish is involved in the relationship with their monogenean ectoparasites. With the MONAMI project, we will better understand through a laboratory approach whether the modification of the microbiota is a cause or a consequence of the presence of monogeneans, and whether the molecules that attract these ectoparasites are of bacterial origin. We will also monitor the response of the microbiota and the holobiont to parasitic infection through a multi-omics approach. Using teleost fish of commercial interest, the red porgy (Pagrus pagrus) and the golden sea bream (Sparus aurata), we will conduct experimental approaches to study for the first time how parasite attraction is modulated by hosts with characterised microflora, as well as the transcripts and metabolites they produce. The MONAMI project will provide an understanding of how the microbiota influences the relationship between ectoparasites and their hosts, paving the way for the development of new antiparasitic treatments.