Characterization of yellow grouper Epinephelus awoara (Serranidae) karyotype by chromosome bandings and fluorescence in situ hybridization.

The cytogenetics of yellow grouper Epinephelus awoara was studied using multiple cytogenetic markers [Giemsa staining, C-banding, Ag-NORs and fluorescence in situ hybridization (FISH)]. Giemsa staining results showed that the karyotypic formula of E. awoara was 2n = 48a, FN (fundamental number) = 48. Faint C-bandings were only detected at the centromeric regions of chromosome pair number 24, being almost indiscernible on the other chromosome pairs. After Ag-NOR staining, one pair of nucleolar organizer regions (NOR) was observed in the subcentromeric region of pair number 24. FISH results showed that 5S rDNA was located at a pair of medium-sized chromosomes, while 18S rDNA appeared at the same location in the subcentromeric region of pair number 24 where Ag-NORs were detected. The telomeric sequence (TTAGGG)(n) detected by FISH was located at both ends of each chromosome. The results suggested that E. awoara has retained general karyotypic structure stability during the evolutionary diversification process.