NOR-banding studies of Acipenser baeri karyotype

Arefjev VA.

Traditional method of Ag-staining of somatic karyotype and interphase nuclei of the Siberian sturgeon Acipenser baeri Brandt was used. On the average, there are four nucleolar-organizing regions (NOR) on the somatic chromosomes, i.e. on one small acrocentric and one microchromosome pairs. The interphase nuclei also include four (from two to six, but with a low level of variation) nucleoli. Thus, the patterns of NOR-banding are similar in thc karyotypes of the Siberian sturgeon and the sterlet, Acipenser ruthenus L. (P. Rab, personal communication). According to some authors (Vasil’ev, 1985, etc.) the Siberian sturgeon is a member of the so-called “high-chromosome” group of sturgeons: its karyotype consists of 250 chromosomes (Vasil’ev, 1985, our unpublished data); the group includes such species as A. gueldenstaedti, A. naccarii and A. sinensis. But the karyotype morphology of A. baeri differs dramatically from those of typical “high-chromosome” species and is closer to that of ‘‘low chromosome species, such as sterlet (60 macrochromosomes in the karyotype, etc.). The similarity of NOR and nucleoli patterns provides further evidence for a discrete position of the Siberian sturgeon in the group of the “high-chromosome” acipenserids, thc phylogenetic pathways of which need further analysis.