Fluorescent in situ hybridization with rDNA probes on chromosomes of Acipenser ruthenus and Acipenser naccarii (Osteichthyes Acipenseriformes)

The genes for 28S and 5S rDNA were physically mapped on the chromosomes of two sturgeon species, the sterlet (Acipenser ruthenus, 2n = 118 +/- 4) and the Adriatic sturgeon (Acipenser naccarii, 2n = 248 +/- 4) by fluorescent i n situ hybridization. In the sterlet, the 28S rDNA was located on six chrom osomes, four of which actively transcribed, while in the Adriatic sturgeon the 28S rDNA was located on a chromosome number ranging from 10 to 12, eigh t of which actively transcribed. The 5S rDNA was physically mapped on two c hromosomes in the sterlet and on four in the Adriatic sturgeon. A more deta iled characterization of the latter karyotype was obtained during this stud y. All these data are discussed in connection with the ploidy relationships among sturgeon species.