Successional Changes of Microbial Communities and Host-Microbiota Interactions Contribute to Dietary Adaptation in Allodiploid Hybrid Fish.

Host-microbiota interactions play critical roles in host development, immunity, metabolism, and behavior. However, information regarding host-microbiota interactions is limited in fishes due to their complex living environment. In the present study, an allodiploid hybrid fish derived from herbivorous Megalobrama amblycephala (♀) × carnivorous Culter alburnus (♂) was used to investigate the successional changes of the microbial communities and host-microbiota interactions during herbivorous and carnivorous dietary adaptations. The growth level was not significantly different in any developmental stage between the two diet groups of fish. The diversity and composition of the dominant microbial communities showed similar successional patterns in the early developmental stages, but significantly changed during the two dietary adaptations. A large number of bacterial communities coexisted in all developmental stages, whereas the abundance of some genera associated with metabolism, including Acinetobacter, Gemmobacter, Microbacterium, Vibrio, and Aeromonas, was higher in either diet groups of fish. Moreover, the abundance of phylum Firmicutes, Actinobacteria, and Chloroflexi was positively correlated with the host growth level. In addition, Spearman's correlation analysis revealed that the differentially expressed homologous genes in the intestine associated with cell growth, immunity, and metabolism were related to the dominant gut microbiota. Our results present evidence that host genetics-gut microbiota interactions contribute to dietary adaptation in hybrid fish, which also provides basic data for understanding the diversity of dietary adaptations and evolution in fish.