Growth Performance, Digestive Capacity, and Transcriptomic Analysis of the Hybrid Offspring of <i>Mastacembelus armatus</i> × <i>Mastacembelus favus</i>

Hybrid breeding is a crucial approach in aquaculture for improving stock performance. This study systematically evaluated heterosis in hybrid offspring from a cross between the zig-zag eel (<i>Mastacembelus armatus</i>) and the tire track eel (<i>Mastacembelus favus</i>). The hybrids exhibited significantly superior growth performance and a higher survival rate than both parental populations. Physiological analyses revealed distinct advantages in digestive enzyme activity and intestinal tissue structure. Liver transcriptome sequencing revealed that most of the differentially expressed genes (DEGs) in the hybrids displayed non-additive expression patterns and were significantly enriched in pathways associated with growth hormone synthesis, insulin secretion and lipid metabolism. The upregulation of <i>igf2</i> and the downregulation of <i>socs1</i> were identified as key molecular drivers of enhanced growth. This multi-level analysis, spanning from phenotype to molecular mechanisms, sheds light on the heterogeneous basis of these hybrids and provides theoretical insights and practical guidance for breeding work with zig-zag eels and related species.