Distant hybridization induces genomic instability in offspring, driving the occurrence of gene recombination and mutation. Analysis of the genomic genetic composition can be used to infer the genetic evolutionary relationships between species. Based on the improved diploid carp (IDC) and the improved diploid scattered mirror carp (IDMC) lineages derived from distant hybridization between female common carp and male blunt snout bream, this study analyzed the genetic variation in their mitochondrial genomes to investigate the impact of distant hybridization on mitochondrial DNA (mtDNA) structural variation. Analysis of complete mitochondrial genome sequence structure and composition revealed subtle structural divergence across generations in both the IDC and IDMC lineages. Analysis of the protein-coding gene sequence structure demonstrated mitochondrial genome structure instability in nascent hybrid diploid lineages. Yet, subsequent self-crossing significantly narrowed the range of structural variation within each lineage. Furthermore, analysis of the genetic variation in the mitochondrial genome sequence structure revealed that paternal base insertions occurred in both F₁ lineages, accompanied by mutations predominantly consistent with those in crucian carp. The results of this study also indicated that the strictness of the paternal mtDNA elimination mechanism varied significantly among polymorphic individuals across different generations of the hybrid lineages, reflecting the randomness of paternal leakage.

This study investigated the effects of dietary hydrolyzed collagen supplementation on muscle quality and its underlying molecular mechanisms in large yellow croaker ( Larimichthys crocea ) (initial weight: 332.27 ± 3.79 g) over a 128‐day feeding trial. The results demonstrated that dietary supplementation with 6% hydrolyzed collagen significantly increased muscle collagen content and collagen volume fraction (CVF) in both female and male fish ( p < 0.05). Furthermore, hydrolyzed collagen significantly enhanced muscle springiness in females, as well as springiness and chewiness in males ( p < 0.05). Multiomics analysis revealed substantial alterations in gene expression and DNA methylation: 1146 differentially expressed genes (DEGs) and 4655 differentially methylated regions (DMRs) were identified in females, while 2460 DEGs and 5846 DMRs were detected in males. Functional enrichment analysis indicated that differentially methylated genes (DMGs) in females were predominantly associated with pathways related to muscle cell morphology and differentiation, such as “regulation of actin cytoskeleton.” In contrast, DMGs in males were significantly enriched in pathways governing cell proliferation, adhesion, and migration, such as “MAPK signaling pathway” and “focal adhesion.” Integrative analysis of RNA sequencing (RNA‐seq) and whole‐genome bisulfite sequencing (WGBS) confirmed a negative correlation between DNA methylation and gene expression, identifying key collagen synthesis‐related genes regulated by methylation, including col6a2 , col4a5 , and hat1 in females, and col6a2 , col27a1b , col12a1 , p4ha1 , loxl2 , tgfβr2 , and bmp1 in males. This study reveals that hydrolyzed collagen enhances collagen deposition and textural properties by modulating collagen synthesis networks via DNA methylation, providing a molecular basis for its application in aquafeed.