Karyological characterization and identification of four repetitive element groups (the 18S - 28S rRNA gene, telomeric sequences, microsatellite repeat motifs, retroelements) of the Asian swamp eel ().

Among teleost fishes, Asian swamp eel ( Zuiew, 1793) possesses the lowest chromosome number, 2n = 24. To characterize the chromosome constitution and investigate the genome organization of repetitive sequences in , karyotyping and chromosome mapping were performed with the 18S - 28S rRNA gene, telomeric repeats, microsatellite repeat motifs, and retroelements. The 18S - 28S rRNA genes were observed to the pericentromeric region of chromosome 4 at the same position with large propidium iodide and C-positive bands, suggesting that the molecular structure of the pericentromeric regions of chromosome 4 has evolved in a concerted manner with amplification of the 18S - 28S rRNA genes. (TTAGGG)n sequences were found at the telomeric ends of all chromosomes. Eight of 19 microsatellite repeat motifs were dispersedly mapped on different chromosomes suggesting the independent amplification of microsatellite repeat motifs in . () was observed at interstitial sites of all chromosomes and in the pericentromeric regions of most chromosomes whereas was scattered and localized to all chromosomes and to several chromosomes. This suggests that these retroelements were independently amplified or lost in . Among (, , and ), showed higher interspecific sequence divergences from other teleost species in comparison. This suggests that the divergence of sequences of might have occurred a relatively long time ago.