The barbels of the subfamilies ´Poropuntinae´ and Smiliogastrinae within the family Cyprinidae play a significant role as a food source for fish in artisanal fisheries and are highly valued as ornamental fish in Thailand. In this study, we employed both conventional and molecular cytogenetics to analyze the karyotype of 15 fish species from two cyprinid lineages. All analyzed species had a diploid chromosome number of 2n = 50. Despite sharing the same 2n, our analyses revealed species-specific distribution patterns of the mapped microsatellite motifs [(CA)₁₅, (TA)₁₅, (CAC)₁₀, and (CGG)₁₀]. They were predominantly found at telomeric sites of all-to-few chromosomes. Additionally, some species exhibited a widespread distribution of the mapped microsatellites across the chromosomes while others showed no signal. These variations reflect the evolutionary divergence and chromosomal diversity within the cyprinids. Thus, our findings support the 2n stability in cyprinoid lineages while emphasizing the intrachromosomal evolutionary diversity accompanied by species-specific microsatellite distribution.

• Keywords
• Chromosomal rearrangements, Family Cyprinidae, Fluorescence in situ hybridization (FISH), Microsatellites, comparative cytogenetics,
• Publication type
• Journal Article MeSH

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.

• Keywords
• Ag-NOR, comparative genomic hybridization, repetitive DNAs, ribosomal DNA,
• Publication type
• Journal Article MeSH