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

To develop superior grouper aquaculture varieties, in this study, a intergeneric hybrid breed was constructed by crossing a male <i>Plectropomus leopardus</i>, with a female parent <i>Epinephelus fasciatus</i>. Here, we researched embryonic development and mitochondrial composition of the new hybrid germplasm. Results revealed that the fertilization and hatching rate were 85.87 ± 5.22% and 70.37 ± 0.33%, respectively. Hatching occurred 28 h 55 min after fertilization at 24.8 ± 0.5 °C, and the newly hatched larvae were 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 mitochondrial gene composition and arrangement of the hybrid were very similar to those of the maternal <i>E. fasciatus</i>. Additionally, analyses including co-linearity, Ka/Ks ratio, and phylogenetic tree all demonstrated that the hybrid's mitochondria are inherited from the mother. Furthermore, the genetic distance between the hybrid and species from the maternal genus is shorter than that between the hybrid and the paternal <i>P. leopardus</i>. This study provides detailed insights into the embryonic development and mitochondrial inheritance of an intergeneric hybrid grouper, offering valuable molecular biological evidence to support grouper hybrid breeding, germplasm identification, and the conservation of genetic diversity.