Mapping of five classes of repetitive DNAs and microsatellite repeats in the genome of the Rainbow Shark, Epalzeorhynchos frenatum (Fowler, 1934)

The karyotype and chromosomal characteristics of Epalzeorhynchos frenatum (Fowler, 1934) were examined using different staining techniques (Conventional banding, C-banding and Ag-NORs banding) and the use of fluorescent in situ hybridization (FISH) to detect 18S, 5S rDNA sites and microsatellite sequences ((CA)15, (GA)15 and (CGG)10 as markers). The result revealed karyotypes with 2n = 50 chromosomes (NF=86), consisting of 12 metacentric, 12 submetacentric, 12 acrocentric, and 14 telocentric chromosomes; there were no heteromorphic sex chromosomes. The NORs site was a noticeable proximal heterochromatic block on the short arm of pair No. 13, and C-positive heterochromatin was detected in the centromeric sections of the chromosomes as well as the telomeric regions of other pairs. On the short arm of pairs No. 13 and 15, the telomeric regions contained the 18S and 5S rDNA sites, respectively. Several chromosomes bearing these repetitive DNA sequences were shared, alongside with some exclusive chromosomal markers especially CGG rich segment (No. 13). This means that, as verified by two methods, it involves a syntenic condition for the 18S rDNA, NORs, and (CGG)10 microsatellite probes.