The representatives of cyprinid lineage ‘Poropuntiinae’ with 16 recognized genera and around 100 species form a significant part of Southeast Asian ichthyofauna. Cytogenetics are valuable when studying fish evolution, especially the dynamics of repetitive DNAs, such as ribosomal DNAs (5S and 18S) and microsatellites, that can vary between species. Here, karyotypes of seven ‘poropuntiin’ species, namely Cosmochilus harmandi, Cyclocheilichthys apogon, Hypsibarbus malcomi, H. wetmorei, Mystacoleucus chilopterus, M. ectypus, and Puntioplties proctozysron occurring in Thailand were examined using conventional and molecular cytogenetic protocols. Variable numbers of uni- and bi-armed chromosomes indicated widespread chromosome rearrangements with a stable diploid chromosome number (2n) of 50. Examination with fluorescence in situ hybridization using major and minor ribosomal probes showed that Cosmochilus harmandi, Cyclocheilichthys apogon, and Puntioplites proctozystron all had one chromosomal pair with 5S rDNA sites. However, more than two sites were found in Hypsibarbus malcolmi, H. wetmorei, Mystacoleucus chilopterus, and M. ectypus. The number of chromosomes with 18S rDNA sites varied amongst their karyotypes from one to three; additionally, comparative genomic hybridization and microsatellite patterns varied among species. Our results reinforce the trend of chromosomal evolution in cyprinifom fishes, with major chromosomal rearrangements, while conserving their 2n.

The cyprinids, freshwater perciform fish belong to the subfamily Cyprininae. Among them, the genus Osteochilus contains 11 recognized valid species. Here, karyotype and chromosomal characteristics of Hypsibarbus malcolmi and H.wetmorei were examined applying conventional and nucleolar organizing region (NORs) staining with molecular cytogenetics.The diploid chromosome number (2n) of H.malcolmi was 50, fundamental number (NF) 62, and the karyotype displayed 8m +4sm +38 a with NORs being located at a centromeric and telomeric position of the short arms of chromosome pairs 1 and 2 ,respectively. 2n of H.wetmoreiwas 50, NF 67, karyotype 14m +14sm +22 a with the NORs at the telomeric position of the short arm of chromosome pairs 2. 2n and NF in males and females fish were identical. Fluorescence in situ hybridization using different microsatellite motifs as probes also showed substantial genomic divergence between both studied species. In H. wetmorei (CAG)n and (CAC)n microsatellites accumulated in the telomeric regions of all chromosomes, while in H. malcolmi they had scattered signals on all chromosome. Besides, the (GAA)n microsatellites were distributed along all chromosomes of H. malcolmi, but a strong hybridization pattern in the centromeric region of a single pair in H. malcolmi, but gave a strong hybridization pattern in the centromeric region of a single pair in H. wetmorei. These cytogenomic different patterns across the genomes of these Hypsibarbus species are markers for specific evolutionary differentiation inside these two species.