Gut Microbiota Contribute to Heterosis for Growth Trait and Muscle Nutrient Composition in Hybrid Largemouth Bass (Micropterus salmoides)

Crossbreeding often results in heterosis. In this study, we generated hybrids from largemouth bass from geographically isolated populations. Growth, digestive enzyme activity, and muscle nutrient composition were compared between the hybrid groups (NC and CN) and the purebred groups (NN and CC), and the gut microbiota was investigated. The heterosis rates of body length, body height, and body thickness in hybrid largemouth bass were statistically significant. Digestive enzyme activity was higher in the hybrid groups than in the purebred groups. Compared with the CN and CC groups, the NC group had significantly higher levels of essential amino acids and total amino acids in the muscle. The polyunsaturated fatty acid content was lower in the hybrid groups than in the purebred groups. The gut microbiota in the hybrid groups predominantly exhibited a non-additive inheritance pattern, characterized by a reduced abundance of Proteobacteria and an increased abundance of Fusobacteria. Microbial taxa showing differences in abundance between the hybrid and purebred groups harbored genes enriched in multiple amino acid and fatty acid metabolism pathways. <i>Cetobacterium</i>, <i>Pseudomonas</i>, and <i>Stenotrophomonas</i> were more abundant in the hybrids, and were positively correlated with multiple amino acids and fatty acids. These results highlight the critical role of gut microbiota in heterosis.