Comparative chromosomal studies on two minnow fish, Phoxinus phoxinus (Linnaeus, 1758) and Eupallasella perenurus (Pallas, 1814); an associated cytogenetic-taxonomic considerations.

The present work provides new data on the banding pattern of two cyprinid fish species Phoxinus phoxinus and Eupallasella perenurus from Poland. C-banding, silver-staining (Ag), and fluorescent staining with chromomycin A3 techniques were used to describe the karyotypes. Both of the species karyotypes of 2n = 50 were characterised by one pair of acrocentric chromosomes, the largest in the set, and by two pairs of NOR-bearing chromosomes. In the chromosome set of Ph. phoxinus Ag-stained NORs were located on telomeres of two metacentric and two submetacentric chromosomes, but in most metaphases only one of the two homologous was observed. The karyotype of E. perenurus was characterised by Ag-NOR regions at a telomeric position on the shorter arm of two submetacentric chromosome pairs. In most metaphases only three NOR-bearing chromosomes were observed. In both investigated species the location of the A3 positive signals corresponded with the location of Ag-stained NORs and these sites were associated with heterochromatin shown as C-bands. The results of cytogenetical studies on other related, mainly the North American phoxinins, species are compared and discussed.