To improve the yield of hybrid mandarin fish, RNA-seq technology is used to further investigate the growth and disease resistance advantages of hybrid mandarin fish and the associated molecular mechanisms. Cluster analysis of the transcriptomes of the three fish groups Siniperca schezeri (S), Siniperca chuatsi (C) and hybrid mandarin fish (H) shows that the gene expression pattern of H is closer to C. We also found that the metabolic pathways in the body of C are the most active. The glycolysis/gluconeogenesis pathway (ko00010) is most typical. This phenomenon is also observed in H, suggesting that both H and C have the advantage of rapid metabolism. When comparing the different genes, we also found that the immune system of S is more active, as evidenced mainly by the significant activation of the ECM- receptor interaction (ko04512) and the phagosome signalling pathway (ko04145). This suggests that S induces the immune system to respond more rapidly by increasing the sensitivity of molecules related to the processing of environmental information in the body. To better understand the mechanism of disease resistance of H, we analysed the target genes of differentially expressed miRNAs and found that the Toll receptor signalling pathway (ko04620) and related immune pathways were significantly enriched. This suggests that H enhances the defence capability of the immune system by improving the ability to sensing the environment. This study revealed the growth and disease resistance mechanism of Hyb through mRNA and miRNA and provided a theoretical basis for crossbreeding.

Live prey is characterized by balanced rich nutrients and high palatability and is widely used for the seedling cultivation of freshwater dark sleeper (Odontobutis potamophila) larvae. In this study, we evaluated the effects of four groups of paired feeding regimens (group C (Daphnia magna), group L (Limnodrilus hoffmeisteri), group H (Hypophthalmichthys molitrix fry), and group M (mixed groups C, L, and H)) on glycolipid and energy metabolism in O. potamophila larvae. We observed that fatty acid synthase (FAS) and sterol-regulatory-element-binding protein-1 (SREBP-1) mRNA levels were significantly lower in group H when compared to mRNA levels in the other three groups (p < 0.05) and that carnitine palmitoyltransferase 1α (CPT1-α) mRNA levels were significantly lower in group L when compared to group M (p < 0.05). Relative glucokinase (GK) expression levels were significantly lower in group M when compared to the other three groups (p < 0.05). Using proteomics, we analyzed and compared groups H and L and identified 457 differentially expressed proteins (DEPs), of which 151 were significantly up-regulated and 306 were significantly down-regulated. In the comparison of group M with groups C, L, and H, we found significant enrichment in glycolytic processes, the endoplasmic reticulum lumen, NAD binding, intermediate filaments, and nutrient reservoir activity. Our results provide a theoretical guidance for bait selection during larvae cultivation stages in carnivorous fish.