Comparison of Gonadal Development in Diploid and Triploid Hybrid Groupers, Epinephelus coioides♀ × Epinephelus lanceolatus♂

Abstract

In this study, the gonadal development of 10‐ to 43‐mo‐old diploid and triploid orange‐giant grouper hybrids, Epinephelus coioides♀ × Epinephelus lanceolatus♂, was investigated. The diploid hybrid groupers exhibited normal gonadal development and experienced vitellogenesis at 43 mo of age. In contrast, the triploid gonad was masculinized and gradually filled with spermatogenic cysts. Radioimmunoassays revealed that the diploid hybrids showed high serum E2 levels at 10 and 43 mo and high T levels at 43 mo, while the triploid hybrids showed high E2 levels at 18 and 30 mo and high T levels at 18 mo. Furthermore, the messenger RNA (mRNA) expression of genes related to reproductive regulation was examined in these hybrids. The mRNA levels of fshb, fshr, lhb, lhr, dmrt1, and sox9 varied significantly during gonadal development. Interestingly, the expression levels of fshr, lhr, dmrt1, and sox9 were higher in triploid hybrids than in diploid hybrids. The hyperactive expression of these genes may be associated with the gonadal masculinization of triploid hybrids.

Karyotypic changes and diversification time in Epinephelidae groupers (Perciformes). Implications on reproductive isolation

“…The previous description of the karyotypes of E. coioides, which classified the Ag-NOR pair as submetacentric chromosomes (2sm+46a; Wang et al 2010), and E. lanceolatus (8sm+40a;Jiun & Mei 2009) were considered in the estimates of karyotypic divergences of the species involved in interspecific crossings. Hybrids of E. coioides ♀ (48a/2sm+46a; FN=48/50) X E. lanceolatus ♂ (2n=6sm+42a/8sm+40a; FN=54/56), with at least four detectable pericentric inversions (ΔFN=4-8), reach maturity and normal gonadal development (Li et al 2018). Hybrids from phylogenetically close lineages may even show a greater growth and adaptability than their parental species (Senoo 2006, Liufu et al 2007, Huang et al 2016.…”

Progress in Aquaculture Genetics and Breeding in China

“…Li et al () also explored mechanisms of gonadal masculinization of triploid, but in hybrid groupers Epinephelus coioides ♀ × Epinephelus lanceolatus ♂. They found that the diploid hybrids showed high serum E2 levels at 10 and 43 mo and high T levels at 43 mo, while the triploid hybrids showed high E2 levels at 18 and 30 mo and high T levels at 18 mo.…”