The barramundi (Lates calcarifer) mucus glycome is conserved across oral, skin and gill tissues but varies between individuals

Infections cause recurring setbacks in aquaculture and the mucus covering the fish surfaces is the first barrier pathogens encounter. The mucus is made up by highly glycosylated mucin glycoproteins. The glycan part of the mucins confers many of the mucus properties and pathogen regulating activities of the mucins, but these glycans remain largely uncharacterised in a range of aquacultured fish species. Barramundi (Lates calcarifer), also called Asian Sea Bass, is cultured in southeast Asia, Australia, USA, UK, Netherlands and Israel. Here we identified 74 O-glycans and three N-glycans in mucus from the oral cavity, skin, gills and intestine using liquid chromatography mass spectrometry. O-glycans from the oral cavity, skin and gill mucus were highly acidic and similar between these epithelia. The barramundi O-glycome displayed a relatively large inter-individual variation, which lead to that glycan features differing between oral cavity, skin and gills were not clearly distinguishable, although the intestinal glycan profiles clearly differed from the other epithelial sites. Barramundi intestinal glycans contained large glycans consisting of up to 14 monosaccharides, often including core 2 glycans with diHexNAc epitopes. This glycan library can serve as a platform for other studies, for example aiming for characterising host-microbe interactions, diagnostic purposes or disease intervention therapies. Furthermore, identification of novel glycans adds to the total glycan library available, leading to that artificial intelligence driven glycomics will become more accurate, allowing the glycomics field to move from a manual and time-consuming activity performed by specialists to automatic data analysis, more similar to other omics.