Hybrids with heterosis possess a more diverse intestinal microbiome than that of carnivorous and herbivorous parental fishes in controlled conditions

The intestinal microbiome plays critical, interactive roles in host nutrition and metabolism and may be involved in the known growth advantage of hybrids. In a previous study, we obtained healthy F1 hybrids (PS) by crossing carnivorous Percocypris pingi (PP, male) and herbivorous Schizothorax wangchiachii (SW, female) and found that the PS hybrids exhibited a growth advantage and that their feeding traits were similar to those of omnivorous S. davidi (SD). In this study, we compared the intestinal histology and anatomy of four fish lines (PP, PS, SW, SD) and, using 16S rRNA gene sequencing, constructed a map of their intestinal microbiome to explore host-influenced intestinal microbiome community composition among them under the same diet. We found that the intestinal anatomical and histological traits of PS and SD were similar, and intermediate between PP and SW, but closer to SW. Although PS and SD have similar feeding traits, their intestinal microbiome composition varied remarkably and, notably, the SD microbiome was closer to that of SW, indicating that phylogenetic effects may play a stronger role in gut microbiome development than the effects of feeding traits. Cetobacterium and Aeromonas were the predominant components of the intestinal microbiome in the four fishes, the former was more abundant in PP, and the latter was more abundant in SW and SD. The relative abundances of Cetobacterium and Aeromonas were lower in PS than in the other three fish lines, but the relative abundances of other microorganisms were generally higher in the PS microbiome, which led to more OTUs and higher alpha diversity. In addition, trypsin activity and amylase activity were strongly positively correlated with the relative abundance of Cetobacterium and Aeromonas, respectively. Although the digestive enzyme activities of PS showed hybrid weakness, its intestinal microbial diversity was higher, which may be related to its growth advantage. •Hybrids with heterosis possess a more diverse intestinal microbiome than their parents.•Cetobacterium and Aeromonas were the predominant components of the intestinal microbiome in the four experimental fishes.