CHROMOSOME POLYMORPHISM OF ATLANTIC SALMON (SALMO-SALAR) FROM THE RIVER DZWINA, BALTIC SEA BASIN - ARM LENGTH AND NOR LOCATION VARIATION OFTHE 8TH CHROMOSOME

A population of Atlantic salmon from the River Dzwina was karyotyped u sing conventional staining and banding techniques. The chromosome numb er was 2n = 58, and the chromosome arm number (NF) was 74. Variation i n the size of the long arm of the eighth chromosome pair was observed. The presence of constitutive heterochromatin on this arm was confirme d by C-banding. Silver banding revealed variability in the location of nucleolus organizer regions (NORs) on this arm. Four cytotypes and th ree phenotypes of the NOR-bearing chromosome were found. The polymorph ism of the eighth metacentric pair of chromosomes observed in Atlantic salmon was probably due to deletion and paracentric inversion of the arm involved.