Heterochromatin and NOR location in northern pike (Esox lucius)

Heterochromatin and the location of nucleolar organizer regions (NOR) were analyzed in northern pike (Esox lucius). The degree to which heterochromatin is present and its location are indicators of reorganization in karyotypes. Karyotypic analysis along with the use of conventional banding techniques and fluorochromes showed that the standard karyotypes was 2n = 50 chromosomes, with 50 chromosome arms (NF). NOR showed C- and CMA(3)-positive staining and were localized near the centromere of chromosome pair No. 11. Sequential staining using C-banding and DAPI techniques showed bright dots in the same region where NOR were localized. No sex heterochromosomes were recognizable on the basis of the staining techniques applied.