Summary A discovery of nucleolar organizer regions (NORs) polymorphism and karyological analysis in the Smith s barb, Puntioplites proctozysron (Bleeker, 1865) from Nong Khai province, in the northeast of Thailand, were studied. Blood samples were taken from 4 male and 4 female fish. After standard whole blood lymphocytes had been cultured at 27 C for 96 hours in the presence of colchicine, metaphase spreads were performed on microscopic slides and air-dried. Conventional and Ag-NOR staining techniques were applied to stain the chromosome. The results showed that the diploid chromosomes number of P. proctozysron was 2n=50 and the fundamental numbers (NF) of both sexes were 82. The types of autosomes were 4 large metacentric, 8 large submetacentric, 2 large acrocentric, 2 large telocentric, 2 medium metacentric, 6 medium submetacentric, 10 medium acrocentric, 14 medium telocentric and 2 small telocentric chromosomes. No strange size chromosomes related to sex were observed. In addition, the short arm near telomere of chromosome pair 4 showed clearly observable nucleolar organizer regions (NORs). This is the first report on polymorphism of NORs in P. proctozysron. The result showed that a heteromorphism in 1 female had a different size of NORs of chromosome pair 4 (4a4b), while 3 females and 4 males had an equal size of both chromosome pair 4 with a homomorphism (4a4a). The karyotype formula for P. proctozysron is as follows: 2n (diploid) 50=L

The first chromosomal characteristics of nucleolar organizer regions (NORs) and karyological analysis of triangle butterflyfish (Chaetodon triangulum) and yellow butterflyfish (C. andamanensis) from Andaman Sea, Phuket and Phang Nga Province, Thailand, were studied. Kidney cell samples were taken from five male and five female fish. Mitotic chromosome preparations were conducted using standard squash technique as well as taken directly from kidney cells. Metaphase spreads were performed on microscopic slides and then airdried. Conventional and Ag-NOR banding techniques were applied to stain the chromosome. The results showed that the diploid chromosome number of C. triangulum and C. andamanensis was 2n=48, and the fundamental numbers (NFs) were 48 and 52, respectively. Karyotpes were present as 46 large telocentric and two medium telocentric chromosomes in C. triangulum; and 2 large metacentric, 8 large telocentric, 34 medium telocentric, 2 medium acrocentric, and 2 small telocentric chromosomes in C. andamanensis. No strange sized chromosomes related to sex were observed. After the Ag-NOR banding technique, one pair of NORs was observed on the long arm centromeric region of large telocentric chromosome pair 21 in C. triangulum and on the long arm subcentromeric region of the largest metacentric chromosome pair 1 in C. andamanensis. The karyotype formulas are as follows:

The snakeheads, freshwater perciform fish are the member of the family Channidae. The karyotype diversification was observed in this species. In this study, we investigate the karyotype and chromosomal characteristic of nucleolar organizing regions (NORs) in Channa marulius (Hamilton, 1822) and C. marulioides (Bleeker, 1851) from Thailand. The metaphase chromosomes were prepared from kidney cells of five male and five female fishes. Conventional and Ag-NOR staining techniques were applied to the chromosomes. The results revealed that: the diploid chromosome number (2n) of C. marulius was 44, fundamental number (NF) was 56, the karyotype formula should be deduced as 2n=L m 4 +L a 6 +L t 10 +M a 2 +M t 22 , the NORs are located at the telomeric position of the short arm of chromosome pairs 3 and 4; the 2n of C. marulioides was 38, NF was 68, the karyotype formula should be deduced as 2n=L m 8 +L a 2 +M m 2 +M a 18 +M t 8 , the NORs are located at the telomeric position of the short arm of chromosome pairs 10 and 11. The difference of 2n and NF in males and females fish was not observed. The number of Ag-NORs in metaphase cell varies between two and four among the cells in the same sample both in C. marulius and C. marulioides.

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.

This study analyzed the karyological features of two bird species – Spilopelia chinensis and Tachybaptus ruficollis – from Northeastern Thailand. Mitotic chromosomes were indirectly prepared by fibroblast cell culture. The chromosomes were stained by conventional Giemsa staining and microsatellite repeat of fluorescence in situ hybridization techniques. Giemsa staining showed that the diploid chromosome number of S. chinensis was 2n=70 and T. ruficollis was 60. The types of chromosomes observed in S. chinensis were 4 large metacentric, 2 medium acrocentric, 2 small metacentric, 2 small submetacentric, 2 sex chromosomes and 58 microchromosomes; the karyotype of T. ruficollis comprised 2 large metacentric, 2 large submetacentric, 2 large acrocentric, 8 small metacentric, 4 small submetacentric, ZW sex chromosomes and 40 microchromosomes. The molecular cytogenetical features that were exhibited only on the male T. ruficollis chromosome included two microsatellites and telomeric sequences: two signals of d(CA)15 on two microchromosomes, one signal of d(GC)15 on one of the first pair, and signals of AGGGTTn sequences on each telomeric region of all macro- and microchromosomes. The karyotype formula was deduced as: 2n (70) = Lm4 + Ma2 + Sm2 + Ssm2 + 2 sex chromosomes (Sm1/Ssm1) + 58 microchromosomes for S. chinensis and 2n (60) = Lm2 +Lsm2 + La2 + Sm8 + Ssm4 + Z (Msm1) W (Ssm1) + 40 microchromosomes for T. ruficollis.