Characterization of the intestinal microbiota of two Antarctic notothenioid fish species

The fish fauna of the Southern Ocean is dominated by species of the perciform suborder Notothenioidei, which constitute 46% of fish species and 90% of biomass. Notothenioids have undergone rapid morphological and ecological diversification and developed physiological adaptations to a cold, highly oxygenated environment. Microbes inhabiting animal intestines include those that perform essential nutritional functions, but notothenioid gut microbial communities have not been investigated using cultivation-independent approaches. We analyzed bacterial 16S rRNA gene sequences obtained from the intestinal tract of Notothenia coriiceps and Chaenocephalus aceratus, which differ in their pelagic distribution and feeding strategies. Both samples showed dominance of Gammaproteobacteria (mostly Vibrionaceae), as has been reported for temperate teleost species. Both samples showed low diversity relative to that reported for other fish microbiota studies, with C. aceratus containing fewer OTUs than N. coriiceps. Despite the small sample size of this preliminary study, our findings suggest that Antarctic notothenioids carry a gut microbiota similar in composition to that of temperate fish, but exhibiting lower species-level diversity. The omnivorous N. coriiceps individual exhibited greater diversity than the exclusively carnivorous C. aceratus individual, which may indicate that increasing herbivory in fish leads to gut microbe diversification, as found in mammals. Lastly, we detected members of taxa containing known microbial pathogens, which have not been previously reported in Antarctic notothenioid fish.