Characterization of triploid hybrid groupers from interspecies hybridization (Epinephelus coioides ♀ × Epinephelus lanceolatus ♂)

Interspecies hybridization is widely used in aquaculture as a beneficial strategy. Diploid and triploid hybrids have been detected from the interspecies hybridization of Epinephelus coioides ♀ × Epinephelus lanceolatus ♂. This is the first report of triploidization through hybridization in grouper. Confirmation has been obtained through flow cytometry, karyotyping and erythrocyte nuclei measurement. The chromosome numbers of E. coioides, E. lanceolatus, diploid hybrid grouper are 48 and triploid hybrid grouper are 72. Measurements of erythrocyte nuclei indicate that triploid fish have a larger nuclear surface than the diploid groupers, and the average ratio of triploid to diploid surface area is 1.59. During the first 1.5 years, triploid hybrid groupers grow faster than diploid hybrid groupers or either parent species. The average growth rate of triploid hybrids is 1.61 times greater than that of diploid hybrids at 6 months of age and 1.43 times greater at 18 months of age. The triploid hybrid groupers are inferior in gonadal development, with no primary-growth-stage oocytes appearing in the gonads at 18 months of age. Morphological studies indicate that triploid hybrid groupers have distinctive differences in snout length, eye diameter, body trunk shape, and tail shape development compared with diploid hybrid groupers. Triploid hybrid groupers have an advantage in growth ability, and artificial breeding of triploid groupers might be of great potential use in the grouper aquaculture industry.