Karyotype analysis in white bream (Blicca bjoerkna transcaucasica) from north coast of Iran

Abstract

Preparation of chromosome spreads and karyotype analysis in Blicca bjoerkna transcaucasica were carried out using 0.01% solution of colchicines and Phytohaemagglutinin (PHA) (20 µg g-1 body weight). The gill and kidney tissues were collected and let to stand in a hypotonic solution of 0.075 M KCl and then treated with a fixative (Carnoy's solution) in three steps. The chromosomes spreads were then stained with 5% Giemsa solution for 20 min and examined under a light microscope. Appropriate metaphase plates were photographed in order to prepare karyotype. The size of the chromosomes (short and long arms), relative length of chromosomes and centromere index were calculated. Chromosome spreads from gill tissue cultures which were colchicine treated with PHA, had a well defined size, shape and number of chromosomes for karyotype analysis. Based on the 76 metaphase plates studied, chromosome count in 59 metaphase plates was 2n=49.74±0.25. By arranging homologous chromosomes beside each other the chromosome formula was calculated as 6 pairs of Metacentric, 10 pairs of Sub-Metacentric and 9 pairs of Sub-Telocentric (2n=6M+10+Sm+9St) and the chromosome arm number (NF) was 100. The largest chromosome in this species was a pair of metacentric chromosomes. On the basis of the number and type of chromosomes, the karyotype obtained for this species conformed to the findings of other researchers, but the chromosome formula was different, which could be attributed to the existence of different populations for this species.