Cytogenetic Comparison and Chromosome Localization of the Nucleolar Organizer Region of Four Grouper Genera (Pisces, Epinephelinae) from Thailand

Abstract

We report the first cytogenetic comparison of four grouper genera from Thailand. Kidney cell samples were taken from the blueline hind (Cephalopholis formosa), humpback grouper (Cromileptes altivelis), orange-spotted grouper (Epinephelus coioides), and leopard coralgrouper (Plectropomus leopardus). The mitotic chromosome samples were prepared directly from the kidney cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that diploid chromosome numbers of Ce. formosa, Cr. altivelis, E. coioides, and P. leopardus were 2n=48 for all species, and the fundamental numbers (NF) were 52, 52, 50, and 48, respectively. The presence of metacentric, submetacentric, acrocentric, and telocentric chromosomes were 2-0-2-44, 0-2-2-44, 0-0-2-46, and 0-0-0-48, respectively. After the Ag-NOR banding technique, one pair of nucleolar organizer regions (NORs) was observed on the short arm telomeric region of chromosome pair No. 2 in Ce. formosa, on the short arm telomeric region of chromosome pair No. 18 in Cr. altivelis, on the short arm telomeric region of chromosome pair No. 20 in E. coioides, and on the long arm subcentromeric region of chromosome pair No. 20 in P. leopardus. The karyotype formula could be deduced as Ce. formosa (2n=48): L^a₂+L^t₂₈+M^t₁₆+S₂^m; Cr. altivelis (2n=48): L^a₂+L^t₂₄+M₂^sm+M^t₈+S^t₂; E. coioides (2n=48): L^t₂₈+M^a₂+M^t₁₆+S^t₂; and P. leopardus (2n=48): L^t₂₄+M^t₂₄.