Triploid production and performance in hybrid grouper (Epinephelus fuscoguttatus ♀ x Epinephelus lanceolatus ♂)

The hybrid grouper Epinephelus fuscoguttatus female x Epinephelus lanceolatus male has high economic value due to its rapid growth and delicious flesh. However, this hybrid is reproductively capable, implying a certain risk of genetic contamination to wild populations. Therefore, this study aimed to produce sterile triploid hybrids using cold shock and examine gonads of triploid individuals. The highest triploid production efficiency (80.00 +/- 34.64%) occurred under a 4-6 degrees C cold-shock, initiated at 6 min after fertilization, and maintained for 17.5 min. The efficiency was confirmed by counting the chromosome number and examining DNA content. The chromosome count of induced triploids was 3n = 72, while diploid fish had 2n = 48. Flow cytometry showed that DNA content in the triploid group was 1.5 times the diploid group. The growth performance of the triploid hybrid was equivalent to that of the diploid hybrid. Histological analysis of the gonadal tissues confirmed that all 18-month-old triploids were sterile, unlike the diploids. Gonad transcriptome analysis showed that the abnormal ovarian development of triploid hybrid groupers may due to the disorders of gamete generation during meiosis. In conclusion, this study explored the optimal conditions for triploid induction in hybrid grouper using cold shock and analyzed the potential for reproduction. These results not only represent a theoretical foundation for the large-scale preparation of triploid hybrid grouper, but also provide a reference case for future studies of grouper breeding.