Cytogenetics as a tool for an exploration of A. sturio status within sturgeons. In Biology and Conservation of the European Sturgeon Acipenser sturio L. 1758

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A karyotype analysis carried out on the European sturgeon, Acipenser sturio, revealed a chromosome number of 2n = 122 ± 3. A representative karyotype of 122 chromosomes was composed of 66 meta- and submetacentrics, 56 acrocentrics and microchromosomes. The telomeric sequence repeat (TTAGGG)n detected by fluorescent in situ hybridization (FISH) was localized at the telomeres of all chromosomes. The ribosomal DNA (rDNA) genes were detected by FISH with a digoxigenin-labelled probe for 28S rDNA in the telomeric regions of six chromosomes. The 5S rDNA was found in the interstitial region of a small metacentric pair. The close association between the two rDNA families detected by simultaneous two-colour in situ hybridization (sim-FISH) supports the hypothesis that the A. sturio karyotype is primitive. The results are discussed in relation to morphophysiological affinities between A. sturio and A. oxyrinchus.