Abstract. Chaiyasan P, Mingkwan B, Jantarat S, Suwannapoom C, Cioffi MDB, Liehr T, Talumphai S, Tanomtong A, Supiwong W. 2021. Classical and molecular cytogenetics of Belontia hasselti (Perciformes: Osphronemidae): Insights into the ZZ/ZW sex chromosome system. Biodiversitas 22: 546-554. Karyotype of Java combtail fish, Belontia hasselti, from To Daeng peat swamp forest, Narathiwat Province, southern Thailand, was studied for the first time. Mitotic chromosome preparations were prepared directly from kidney cells from ten male and ten female fish. Conventional staining, NOR banding, and molecular cytogenetics with fluorescence in situ hybridization (FISH) using 5S and 18S rDNAs, as well as microsatellites d(CA)15 and d(CAC)10 as probes were applied. The diploid chromosome number (2n) was 48 and a female heterogametic sex chromosome system (ZZ/ZW) is suggested. The fundamental numbers (NF) were 48 and 49 in males and females, respectively. The karyotype of males comprised 48 telocentric chromosomes while the female ones were composed of one metacentric and 47 telocentric chromosomes. A single Ag-NOR-bearing chromosomal pair was identified. The NOR positions were characterized at the interstitial sub-centromeric region of pair 13, which coincided with signals of 18S rDNA and d(CAC)10 probes. The 5S rDNA signals were located at interstitial sites of the largest telocentric pair. Microsatellite d(CA)15 repeats were highly distributed throughout almost all entire chromosomes except for centromeric regions on some chromosome pairs, including sex chromosomes. The present study is a novel report for a ZZ/ZW sex chromosome system of this fish family in Thailand.

Abstract. Supiwong W, Wongchantra P, Thongnetr W, Mingkwan B, Chaiyasan P, Pinmongkhonkul S, Pinthong K, Tanomtong A. 2021. Comparative cytogenetic analysis of fishes in the genus Trichopodus (Osphronemidae) in Thailand. Biodiversitas 22: 3029-3036. Comparative cytogenetic study of four species of the genus Trichopodus including T. leerii, T. microlepis, T. pectoralis, and T. trichopterus from Thailand, was carried out. The specimens were collected from the Basins throughout Thailand. Chromosome preparation was directly performed from the kidney tissues. Conventional staining by Giemsa solution, Ag–NOR banding by silver nitrate solution and C-banding by NaOH solution were conducted to stain the chromosomes. Results showed that four species studied have the same diploid number and fundamental number as 46 composing of all telocentric chromosomes. Karyotypes consisting of large-medium-small sizes in T. leerii, T. microlepis, T. pectoralis and T. trichopterus were 16–28–2, 14–32–0, 20–26–0 and 10–30–6 chromosomes, respectively. The marker chromosomes which present the NOR positions are the single pair in all species but there are differences in the locations and pairs such as pairs no. 1, 7, 2 and 1, respectively. Most species except T. trichopterus, NOR sites locate at interstitial region adjacent to the centromere. T. trichopterus had the telomeric NORs. Constitutive heterochromatin blocks displayed at the centromeric/pericentromeric regions of all chromosomes in T. leerii and T. microlepis whereas in T. pectoralis and T. trichopterus, those presented at not only centromeres of several chromosome pairs, but they also were found at interstitial sites. The obtained finding, cytogenetic data has species-specific. Thus, it can be used for further study on taxonomy. Moreover, this data shows the close relationship of genetics among these species so that the application for breeding may be used in the future.