Molecular cytogenetic analysis of the karyotype of the European Atlantic sturgeon, Acipenser sturio

A karyotype analysis was carried out on the European Atlantic sturgeon, Aci penser sturio (2n = 121 +/- 3). The telomeric sequence repeat (TTAGGG)(n) d etected by fluorescent in situ hybridization (FISH) was mostly localized at the telomeres of ail chromosomes. Ribosomal DNA (rDNA) genes were detected by silver staining techniques and by FISH with digoxigenin-labelled probe for 28S rDNA. Silver staining detected active NORs in the telomeric regions of six chromosomes, and by FISH one or two additional minor sites were det ected. The 5S rDNA was found in the interstitial region of a small metacent ric pair. The 5S rRNA gene was completely sequenced for the first time in a sturgeon species. The A. sturio karyotype organization is discussed in rel ation to phylogenesis of the species within the Acipenseridae and to polypl oidization events characterizing sturgeon evolution.