Comparative Analysis of Embryonic Development and Mitochondrial Genome of a New Intergeneric Hybrid Grouper (Epinephelus fasciatus ♀ × Plectropomus leopardus ♂)

To investigate the early developmental characteristics and mitochondrial inheritance patterns of the hybrid offspring of a paternal Plectropomus leopardus and maternal Epinephelus fasciatus, the study systematically mapped the embryonic developmental trajectory and mitochondrial genome of the new germplasm. Results revealed that the fertilized hybrid eggs completed embryonic development within 28h55min, with the newly hatched larvae measuring 2.05 ± 0.37 mm in total length. The mitochondrial genome length of the hybrid was 16,570 bp, preserving 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and 22 transfer RNA (tRNA) genes. The hybrid's mitochondrial gene composition and arrangement showed high consistency with that of the maternal E. fasciatus. Concurrently, the co-linearity, Ka/Ks, and phylogenetic tree analyses collectively indicate that the hybrid progeny has a closer genetic relationship with the maternal parent, supporting the mitochondrial maternal inheritance of this species. This study details the embryonic development and mitochondrial inheritance of an intergeneric hybrid grouper germplasm, providing significant molecular biological evidence for grouper hybrid breeding, germplasm resource identification, and genetic diversity conservation.