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Cytogenetic Analyses In Eight Species Of Teleostean Fishes (Pisces): Karyotypes, Multiple Ag-NORs, Sex Chromosomes

Anisur Rahman Khuda-Bukhsh, Jayanta Kumar Das

Cytogenetic analyses of karyotypes and Ag-NORs have been made in eight species of teleostean fishes, namely, Thunnus orientalis (Scombridae), Valamugil speigleri ( Mugilidae), Balantiocheilos melanopterus, Amblypharyngodon microlepis (Cyprinidae), Lepidocephalichthys guntea (Cobitidae), Pangasius hypophthalmus (Pangasiidae), Nandus nandus (Nandidae) and Ompok bimaculatus (Siluridae). Of these, L.guntea (male ZZ: female ZO) and O. bimaculatus (male X1X1X2: female X1X1X2X2) have morphologically identifiable sex chromosomes. The nucleolar organizing regions (NORs) were located terminally at centromeric regions of one pair of acrocentric chromosomes (Tc, No.1) in T.orientalis and V.speigleri (2n=48), at shorter arm (Tp) of one pair of submetacentric chromosomes in B.melanopterus (2n=50; No.6), in A.microlepis (2n=50; No.1) and in P.hypophthalmus (2n=60; No. 1), at whole shorter arm (p) of one pair of submetacentric chromosomes in L.guntea (No.1; male, 2n=52, female 2n=51), at the longer arms of one pair of interstitial sub-terminal (Ist –q, No.1) and at terminal regions of one pair of submetacentric chromosomes (Tq, No.10) in N.nandus (2n=48) and at shorter arm of one pair of submetacentric chromosomes (Tp, No.4) in O.bimaculatus (male 2n=41, female 2n=42). The significance of the study has been discussed in the light of other previous studies and their karyotypic evolution.