Comparison of karyotypes of Acipenser oxyrinchus and A. sturio by chromosome banding and fluorescent in situ hybridization
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A highly debated problem in Acipenseridae taxonomy is whether Acipenser oxyrinchus (North American Atlantic sturgeon) and A. sturio (European Atlantic sturgeon) are true species: a detailed comparison of their karyotypes could provide relevant information. Here we describe for the first time the karyotype of A. oxyrinchus (2n = 121 ± 3), and its features, among which the constitutive heterochromatin, revealed by C-banding technique, the distribution of telomeric regions, and the 5S rRNA genes, detected by FISH. The results reveal that A. oxyrinchus and A. sturio karyotypes and features are quite similar. Moreover, comparing the results obtained through hybridization by FISH with HindIII and PstI satellite DNA in these and in other sturgeon species, no hybridization signals are detected in A. sturio and A. oxyrinchus, while A. stellatus and A. gueldenstaedtii show hybridization. Thus A. sturio and A. oxyrinchus appear very similar from a cytogenetic point of view: these and molecular data repeatedly point out that A. sturio and A. oxyrinchus represent a sister clade in comparison to all other sturgeon species up to now studied.
KeywordsAtlantic sturgeon Karyotype C-banding Telomeric sequence Satellite DNA 5S rDNA
The authors wish to thank Dipl.-Biol. Jörn Geßner and Dr Sven Würtz, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, for their help in the collection of the tissues. They also wish to thank Dr James Tagliavini, Department of Evolutionary and Functional Biology, University of Parma, and Dr Milvia Chicca, Department of Biology, University of Ferrara, for critically reviewing the manuscript. This research was supported by Italian Ministry of Instruction, University and Research (MIUR) grant n. DM219-22-12-05, National Relevant Interest Research Projects (PRIN), 2005, and from the Spanish Ministerio de Educaciòn y Ciencia (Ref. n. AGL2003-04716).
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