Early development of hybrids of Epinephelus lanceolatus(♀) × Epinephelus moara(♂) and growth characteristics of reciprocal crosses

Hybridization is the most widely used and an effective way of artificial breeding in aquaculture. This study using Epinephelus lanceolatus as female parent, E. moara as male parent by artificial insemination technology has conducted the interspecific cross experiment, and developmental sequence of fertilized egg, and growth of larvae, juveniles and young fish were observed and studied, and then with the phenotypic of traits, the parent and the hybrid F₁ generation “Yunlong grouper” (E. moara ♀× E. lanceolatus ♂) were compared. Results showed that the embryo was oval, transparent, floating, the fertilized eggs size (0.787±0.013) mm, each egg has one oil globule in the center. At sea-water temperature of 24 °C, salinity 30, pH 7.8, embryos can develop normally, according to the data, six periods including 25 stages of embryos were recorded,which were fertilized egg, cleavage, blastula, gastrula, organogenesis and hatching period. The length of newly hatched larvae (1.595±0.015) mm shows the feasibility of the cross;3 days after hatching, the yolk membranes disappeared and became the late larva, with a total length of (2.530±0.023) mm. 52 days after hatching, entering the juvenile stage, the total length (17.500±1.915) mm, the length of the second dorsal fin spine (5.795±0.049) mm, and the length of the first pelvic fin (2.992±0.911) mm. When the dorsal fin spine contracted to the minimum value (4.460±0.600) mm, scales began to appear and body color began to darken. The second dorsal fin spine and the first pelvic fin spine completely degenerated. The body shape was similar to that of the adult fish. The whole body was covered with scales. The growth comparison results showed that the growth rate of the direct and reciprocal cross F₁ generation was between those of the parents, which was faster than that of E. moara, and slower than that of E. lanceolatus, and the growth rate of the reciprocal cross F₁ generation was slower than that of the direct F₁ generation. The results provide a basis for the formation of hybrid heterosis traits and genetic analysis of grouper.