Sumalee Phimphan

Chromosomes of Asian cyprinid fishes: cytogenetic analysis of two representatives of small paleotetraploid tribe Probarbini

BackgroundPolyploidy, although still poorly explored, represents an important evolutionary event in several cyprinid clades. Herein, Catlocarpio siamensis and Probarbus jullieni - representatives of the paleotetraploid tribe Probarbini, were characterized both by conventional and molecular cytogenetic methods.ResultsAlike most other paleotetraploid cyprinids (with 2nu2009=u2009100), both species studied here shared 2nu2009=u200998 but differed in karyotypes: C. siamensis displayed 18mu2009+u200934smu2009+u200946st/a; NFu2009=u2009150, while P. jullieni exhibited 26mu2009+u200914smu2009+u200958st/a; NFu2009=u2009138. Fluorescence in situ hybridization (FISH) with rDNA probes revealed two (5S) and eight (18S) signals in C. siamensis, respectively, and six signals for both probes in P. jullieni. FISH with microsatellite motifs evidenced substantial genomic divergence between both species. The almost doubled size of the chromosome pairs #1 in C. siamensis and #14 in P. jullieni compared to the rest of corresponding karyotypes indicated chromosomal fusions.ConclusionBased on our findings, together with likely the same reduced 2nu2009=u200998 karyotypes in the remainder Probarbini species, we hypothesize that the karyotype 2nu2009=u200998 might represent a derived character, shared by all members of the Probarbini clade. Besides, we also witnessed considerable changes in the amount and distribution of certain repetitive DNA classes, suggesting complex post-polyploidization processes in this small paleotetraploid tribe.

Chromosomal analysis and meiosis studies of Oxya chinensis (Orthoptera: Acrididae) from Thailand

The standard karyotype and meiotic cell divisions of Oxya chinensis Thunberg, 1815 (Orthotera: Acrididae) from Khon Kaen, Thailand were studied by conventional and silver staining techniques. Chromosomal preparations were made from grasshopper testes. The results showed that the male O. chinensis had diploid chromosome number 2nxa0=xa023 (XO). Karyotype was presented with eight long (1–4 pairs), eight medium (5–8 pairs) and six short (9–11 pairs) acrocentric chromosomes with minute short arms in all autosomes. The acrocentric X chromosome was approximately same in size as found for medium autosomes. The nucleolar organizer regions (NORs) were found on telomeric regions of all minute short arm acrocentric chromosomes in metaphase, including X chromosome. In zygotene stage of meiotic cell division, NORs were detected in three regions per cell by silver staining while only one region was found by conventional staining. Meiotic cell divisions were also studied to confirm the diploid chromosome number and normal meiotic behaviour. The karyotype formula was found in O. chinensis: 2nxa0=xa023 (XO); La 4xa0+xa0Ma 4xa0+xa0Sa 3xa0+xa0X-chromosome.

Karyotypic study of five Lutjanid species using conventional and Ag-NORs banding techniques

The first cytogenetic comparisons of five snapper species from Thailand were presented here. Renal cell samples were taken from blacktail snapper (Lutjanus fulvus), five lined snapper (L. quinquelineatus), dory snapper (L. fulviflamma), brownstripe red snapper (L. vitta), and mangrove red snapper (L. argentimaculatus). The mitotic chromosome preparation was prepared directly from kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results exhibited that all five snapper species have the diploid chromosome numbers of 2n = 48 and the fundamental numbers (NF) of 48. The presences of large, medium, and small telocentric chromosomes were 22-24-2, 24-20-4, 36-10-2, 28-16-4 and 36-10-2, respectively. The Ag- NORs banding technique provides the pair of nucleolar organizer regions (NORs) at subcentromeric region of the long arm of the respective telocentric chromosome pairs 9, 1, 3, 4 and 9. Their karyotype formulas is as follows: L. fulvus (2n = 48): L22t + M24t + S2t, L. quinquelineatus (2n = 48): L24t + M20t + S4t, L. fulviflamma (2n = 48): Lt36 + Mt10 + St2, L. vitta (2n = 48): L28t + M16t + S4t, and L. argentimaculatus (2n = 48): L36t + M10t + S2t.

Karyological characteristics of the Koh Tao caecilian, Ichthyophis kohtaoensis (Amphibia: Gymnophiona: Ichthyophiidae) by conventional staining and Ag-NOR banding techniques

The karyotypic analysis of the Koh Tao caecilian, Ichthyophis kohtaoensis Taylor, on 1960 from Surin Province, Thailand was obtained from the present study. Mitotic chromosome was prepared directly from the small intestine of specimens after in vivo colchicine treatment. The metaphase spreads were performed on microscopic slides and air-dried. Conventional staining, and Ag-NOR banding techniques were applied to stain the chromosome with Giemsa’s solution. Results showed that the number of diploid chromosome was 2nxa0=xa042, while the fundamental number (NF) was 64 in both males and females. The type of chromosomes included 6 large metacentric, 2 large submetacentric, 12 small metacentric, 2 small submetacentric, and 20 small telocentric chromosomes. We found that nucleolar organizer regions/NORs (the representative of chromosome marker) were located on the small telocentric chromosome pair 19. No cytologically distinguishable sex chromosome was observed. The karyotype formula is as follows: 2n (42)xa0=xa0L6mxa0+xa0L2smxa0+xa0S12mxa0+xa0S2smxa0+xa0S20t.

Karyological study of Lutjanus ehrenbergii and L. carponotatus (perciformes, lutjanidae) by classical and Ag-NOR staining techniques

Standardized karyotype and idiogram of the blackspot snapper (Lutjanus ehrenbergii) and Spanish flag snapper (L. carponotatus) were studied. The renal tissue samples were taken from the male and female fish in each species. The metaphase chromosomes were prepared by the standard protocol. Giemsa’s and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that L. ehrenbergii and L. carponotatus had the same diploid chromosome number of 2nxa0=xa048, besides the fundamental number of these two species (NF) was 48 in both male and female. The types of autosomes were 28 large and 20 medium telocentric in L. ehrenbergii and there were 36 large and 12 medium telocentric chromosomes in L. carponotatus. Interestingly, L. ehrenbergii had the nucleolar organizer regions (NORs) adjacent to the subcentromere of only one of each chromosome pair 10 and 21 (heteromorphic), while for L. carponotatus the NORs were found in chromosome pair 5. The karyotype formula could be deduced as: 2n (diploid) 48xa0=xa0Lt28xa0+xa0Mt20 and Lt36xa0+xa0Mt12 for L. ehrenbergii and L. carponotatus, respectively.

Characterization of chromosomal rearrangements in pileated gibbon (Hylobates pileatus) using multiplex-FISH technique

Here we aimed to characterize evolutionary conserved chromosomal rearrangements of pileated gibbon (H. pileatus, HPI) compared to human using multiplex fluorescence in situ hybridization (M-FISH) technique. Khon Kaen Zoo, Thailand, kindly provided the blood specimen of this gibbon. Lymphoblast cells were cultured from male HPI by standard method; chromosome preparation was done following standard protocols. All 24 human (Homo sapiens, HSA) chromosome probes (M-FISH probe set) were applied on HPI. Results indicated that male HPI had diploid chromosome numbers of 2nxa0=xa044; the karyotype consists of metacentric and submetacentric chromosomes. During evolution chromosomes of HPI underwent certain rearrangements when compared with human chromosomes and showed 55 conserved regions of different sizes. Majority of HPI chromosomes are constituted of regions being homologous to two or more human chromosomes. The remainder appeared to be conserved, such as HPI chromosomes 14, 17, 18, 20, 21, X and Y which were homologous to only one human chromosome, each. To the best of our knowledge, this is the first study using all 24 HSA probes on HPI; the genetic data may be additionally useful for comparison of gibbons, both within and between genera, to elucidate and clarify more regarding evolutionary lineage of animals in the order primates derived from the same common ancestor known so far.