Dynamic changes of gut microbiota of discus fish (Symphysodon haraldi) at different feeding stages

Abstract

Discus fish (Symphysodon haraldi) is an important ornamental fish. Owing to its unique parental care behavior, there are generally four feeding stages from fry to adult. Gut microbiota plays an important role in fish nutrition metabolism. Different food resources may potentially affect the structure and function of host intestinal microbiota. However, studies on the response of discus intestinal microbiota during feeding changes are scarce at present. Here, we determined the succession of gut microbiota of discus that were subjected to abrupt and extreme diet changes, from parental skin-mucus, Artemia nauplii, Chironomidae larvae to beef-heart hamburger, a total of four feeding stages. As diets changed, the community diversity and richness of discus intestinal microbiota first decreased, then increased, and finally decreased. Content of Firmicutes in the gut of discus gradually increased, while the level of Chloroflexi gradually decreased. The levels of Fusobacteria and Verrucomicrobia increased and then decreased, while the contents of Proteobacteria and Actinobacteria decreased and then increased. Gut bacterial community of discus feeding parental skin-mucus was significantly different from other three feeding stages. Moreover, at the stage of feeding parental skin-mucus, the predicted pathways of RNA processing and modification and extracellular structures were more enriched than those at other feeding stages. However, at the stage of feeding beef-heart hamburger, the pathways related to nutrients transport and metabolism and energy production and conversion were more enriched than those at other stages. Changes in discus intestinal microbiota might suggest their potential in adapting to different food resources.