Subtelocentric Chromosome Pair Research Articles

Cytogenetic analysis of sympatric Trachelyopterus Valenciennes 1840 (Siluriformes, Auchenipteridae) species reveals highly conserved karyotypes despite the geographic distance

Trachelyopterus Valenciennes 1840 species exhibit striking morphological and cytogenetic similarities, leading to persistent taxonomic challenges. This research focuses on Trachelyopterus galeatus Linnaeus 1766 and Trachelyopterus porosus Eigenmann & Eigenmann 1888, both widely distributed throughout South America and often sympatric, facilitating cytogenetic comparisons. These taxonomic entities are noteworthy for their extensive geographical ranges within the genus. We examined two populations of T. galeatus and T. porosus collected from sympatric sites in the Amazon and Pantanal regions. Both species had the same diploid number and simple Ag-NORs. The 18S rDNA sites were found in only one subtelocentric chromosome pair. Meanwhile, the 5S rDNA sites were found on two distinct chromosomal pairs, with differences in the chromosomal morphology and site position among the species, constituting the most efficient chromosomal marker to distinguish them. The 5S rDNA pattern differed between species but remained consistent between populations of the same species. Minor differences were observed between the T. galeatus populations, probably related to chromosomal rearrangements. In contrast, despite the considerable geographical distance, no cytogenetic differences were detected among the T. porosus populations. Overall, the congruence between cytogenetic and morphological characteristics, combined with our findings from sympatric samples and existing data from geographically separated populations of Trachelyopterus, indicates that the cytogenetic is a promising tool for species differentiation and for delving into the cytotaxonomic and evolutionary aspects of Auchenipteridae.

Cytogenetic Characterization of Three Arabian Gulf Bivalve Species

The diploid number and karyotype of three endemic and highly distributed species from the Qatari shores: Brachidontes variabilis (Krauss, 1848) (Mytilidae), Isognomon nucleus (Lamarck, 1819) (Pteriidae) and Neotrapezium sublaevigatum (Lamarck, 1819) (Trapezidae), are described for the first time. Brachidontes variabilis presented a diploid number of 2n = 30 and the karyotype included 2 metacentric, 6 submetacentric, 3 subtelocentric and 4 telocentric chromosome pairs. Isognomon nucleus had a diploid number 2n = 28 and the karyotype was comprised of 3 metacentric, 4 submetacentric and 7 subtelocentric chromosomal pairs and the karyotype of Neotrapezium sublaevigatum, with 2n = 36, included 5 metacentric, 9 submetacentric, 2 submetacentric/subtelocentric and 2 subtelocentric chromosome pairs. A review of the previously published cytogenetic studies in all three families was also performed, as well as a comparative karyological analysis within those families.

Characterization of the karyotype and accumulation of repetitive sequences in Australian Darling hardyhead Craterocephalus amniculus (Atheriniformes, Teleostei).

Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding, CMA3/DAPI staining), and fluorescence in situ hybridization (FISH) with telomeric DNA and rDNA probes were used to examine the karyotypes and other chromosomal characteristics of Darling hardyhead (Craterocephalus amniculus) from New South Wales, Australia. We identified a diploid chromosome number 2n = 48 (NF = 58) in all studied individuals. FISH with rDNA probes showed a nonsyntenic pattern, with signals on one pair of subtelocentric chromosomes for 5S rDNA and one pair of submetacentric chromosomes for 28S rDNA. C-banding displayed the accumulation of constitutive heterochromatin in the centromeric regions of approximately 40 chromosomes. CMA3/DAPI fluorescence staining revealed extremely GC-rich signals in the pericentromeric region of one submetacentric chromosomal pair with size polymorphism. We detected telomeric signals at the end of all chromosomes and no interstitial signals.

Cytogenetic Characterization of Two Metynnis Species (Characiformes, Serrasalmidae) Reveals B Chromosomes Restricted to the Females

Karyotypes and chromosomal characteristics with focus on B chromosomes of 2 species of the serrasalmid genus Metynnis, namely M. lippincottianus and M. maculatus, were examined using conventional (C-banding) and molecular (FISH mapping of minor and major rDNAs and Rex1, Rex3, and Rex6 retrotransposable elements) protocols. Both species possessed a diploid chromosome number of 2n = 62 and karyotypes composed of 32 metacentric + 28 submetacentric + 2 subtelocentric and 32 metacentric + 26 submetacentric + 4 subtelocentric, respectively; one small B element was found in the female genome of M. lippincottianus. C-banding revealed heterochromatin in the pericentromeric and terminal portions of all chromosomes of both species; the B chromosome was entirely heterochromatic. FISH showed 18S rDNA sites in 2 chromosome pairs in both species (pairs 19 and 22), and a large block in the B chromosome, while 5S rDNA signals were detected in the first pair of subtelocentric chromosomes in both species, moreover in M. maculatus an additional labeled pair 4 was observed. Mapping of the Rex1, Rex3, and Rex6 retrotransposable elements in the genomes of M. lippincottianus and M. maculatus indicated that they were dispersed throughout nearly all the chromosomes of the complement, except for the B chromosome of M. lippincottianus.

Cytogenetics characterization of Crenuchus spilurus (Günther, 1863): a remarkable low diploid value within family Crenuchidae (Characiformes)

Conventional and molecular cytogenetic analyses were performed in specimens of the Neotropical Crenuchus spilurus freshwater fish species from a single location (Caete River, Brazil). All specimens presented diploid values of 2n = 38 chromosomes (12 m + 4sm + 2st + 20a), the lowest reported for family Crenuchidae up to now. A single pair of nucleolar organizing regions (NORs) was detected in the subtelocentric chromosome pair no. 9 by silver-staining and fluorescence in situ hybridization (FISH) with 18S rDNA sequence-specific probe. Two pairs of 5S rRNA gene clusters were found either interstitial or terminally located in the long arms of the acrocentric chromosome pairs nos. 10 and 13. Heterochromatic regions were clearly observed in the short arms of the NOR-bearing chromosome pair and weakly-positive to the pericentromeric regions of most acrocentric chromosomes. Additionally, no sex chromosomes were identified in the surveyed specimens. Crenuchidae have signals of several mechanisms involved in karyotype diversification within this family: differential location of heterochromatin-rich regions, multiplication, and translocation of rDNA clusters, presence/absence of sex chromosomes, macrostructural changes in morphology and number of chromosomes. This variety of karyotype patterns reveals the importance of widening cytogenetic studies to more taxa for better know the chromosomal evolution occurred in this group.

Fluorescence in situ Hybridization Karyotype Analysis of Seven Platycodon grandiflorum (Jacq.) A. DC. Cultivars

Platycodon grandiflorum has long been cultivated for its medicinal properties and economic value, prompting crop improvement programs that have spurred the development of new cultivars. However, limited cytogenetic information is available for this species, especially for different P. grandiflorum cultivars. Karyotype analysis via fluorescence in situ hybridization (FISH) provides essential information about chromosome count and the localization of DNA sequences, thus providing a chromosome-level understanding of genome structure. Here, we carried out triple-color FISH karyotype analysis of various P. grandiflorum (Jacq.) A. DC. cultivars using 5S and 45S ribosomal DNA (rDNA) and telomeric repeat probes. The karyotype is composed of 2n = 18 chromosomes consisting of seven pairs of metacentric chromosomes, one pair of submetacentric chromosomes, and one pair of subtelocentric chromosomes. The chromosome length ranges from 1.92 to 4.98 μm. One pair of 5S rDNA loci was observed on either the intercalary or pericentromeric regions of chromosome 3. All cultivars showed 45S rDNA signals on chromosome 9, and in two closely related cultivars, one additional pair of 5S rDNAs co-localized with these 45S rDNAs. Arabidopsis -type telomeric repeats were observed in most telomeric regions of the chromosomes in all seven cultivars. Our data lay the foundation for future cytogenetic studies of P. grandiflorum focusing on breeding and the elucidation of its genome structure.

Karyotype analysis of Piptanthus concolor based on FISH with a oligonucleotides for rDNA 5S

Abstract The karyotype of Piptanthus concolor was analysed via fluorescence in situ hybridization (FISH) using oligonucleotide probe for ribosomal DNA (rDNA) (5S rDNA, 41 bp). P. concolor had 2n = 18 chromosomes. The karyotype was composed of 3 pairs of metacentric chromosomes (including one pair of satellites), 3 pairs of submetacentric chromosomes, and 3 pairs of subtelocentric chromosomes. 5S rDNA loci were detected in 8 chromosome pairs. The density and location of signals for both 5S rDNA varied among individual chromosomes. High-intensity 5S signals were detected in the short arms of chromosomes 7 and 8, and weak signals were also detected in the long arms of the same chromosomes. For the satellite chromosomes, 17 and 18, the 5S rDNA signal was located at the end of the long arm. The third pair of chromosomes, 9 and 10, also significantly differed from other chromosomes with respect to the 5S rDNA signals observed in the subterminal region. The fourth pair of chromosomes, 11 and 12, had no 5S rDNA signal. The other pairs of chromosomes also exhibited individual signals. Our results provide information that may be beneficial for future cytogenetic studies and could contribute to the physical assembly of the Piptanthus genome.

Chromosomal organization of four classes of repetitive DNA sequences in killifish Orestias ascotanensis Parenti, 1984 (Cyprinodontiformes, Cyprinodontidae).

Orestias Valenciennes, 1839 is a genus of freshwater fish endemic to the South American Altiplano. Cytogenetic studies of these species have focused on conventional karyotyping. The aim of this study was to use classical and molecular cytogenetic methods to identify the constitutive heterochromatin distribution and chromosome organization of four classes of repetitive DNA sequences (histone H3 DNA, U2 snRNA, 18S rDNA and 5S rDNA) in the chromosomes of O. ascotanensis Parenti, 1984, an endemic species restricted to the Salar de Ascotán in the Chilean Altiplano. All individuals analyzed had a diploid number of 48 chromosomes. C-banding identified constitutive heterochromatin mainly in the pericentromeric region of most chromosomes, especially a GC-rich heterochromatic block of the short arm of pair 3. FISH assay with an 18S probe confirmed the location of the NOR in pair 3 and revealed that the minor rDNA cluster occurs interstitially on the long arm of pair 2. Dual FISH identified a single block of U2 snDNA sequences in the pericentromeric regions of a subtelocentric chromosome pair, while histone H3 sites were observed as small signals scattered in throughout the all chromosomes. This work represents the first effort to document the physical organization of the repetitive fraction of the Orestias genome. These data will improve our understanding of the chromosomal evolution of a genus facing serious conservation problems.

Preliminary karyotype analysis of Amolops panhai and Sylvirana nigrovittata (Anura, Ranidae) from southern Thailand

Karyotype and ideogram analyses of Somsak’s cascade frog (Amolops panhai) and dark-sided frog (Sylvirana nigrovittata), collected from Nakhon Si Thammarat Province, southern Thailand, were performed. Chromosomes were prepared from the intestinal epithelium and stained by conventional Giemsa staining. From this study, we found that A. panhai possesses the diploid chromosome number of 26 (2n = 26), while the chromosome number of S. nigrovittata is 24 (2n = 24). This is the first report on karyotype of A. panhai, containing 10 pairs of metacentric (m), 2 pairs of submetacentric (sm) and 1 pair of subtelocentric (st) chromosomes with the arm number of 52. The S. nigrovittata’s karyotype contains 12 pairs of chromosomes with the arm number of 48 in only the metacentric form. The karyotype formulae could be represented as 2n (26) = 10m + 2sm + 1st and 2n (24) = 12m for A. panhai and S. nigrovittata, respectively.

Phytochemical and Cytogenetic Characterization of Centaurea solstitialis L. (Asteraceae) from Croatia.

The cytogenetic characterization of Centaurea solstitialis L. (Asteraceae) showed a chromosome number of 2n=16. Karyotype is composed by four pairs of metacentric, two pairs of submetacentric and two pairs of subtelocentric chromosomes. Physical mapping of two rDNA probes revealed two loci of 35S and one locus of 5S rRNA genes. Chromomycin fluorochrome banding revealed that all rDNA loci were GC rich. The genome size (2C-value) of 1.95pg classes this species in the group of very small genomes. Chemical composition of C.solstitialis volatile oil (VO) from Croatia, studied with gas chromatography-mass spectrometry showed dominant components as it follows: hexadecanoic acid, α-linolenic acid, germacrene D and heptacosane. Antioxidant capacity, measured by ferric reducing power assay and 2,2-diphenyl-1-picrylhydrazyl methods, as well as inhibition of acetyl- and butyrylcholinesterase of VO was lower comparing to a standard solutions. Volatile oil tested with disc diffusion method showed good inhibitory potential against Pseudomonas aeruginosa, Escherichia coli and all tested fungi: Candida albicans, Penicillium funiculosum and Aspergillus fumigatus. The microdilution method showed best activity against Chronobacter sakazakii and A.fumigatus.

Chromosomal mapping of tandem repeats in the Yesso Scallop, Patinopecten yessoensis (Jay, 1857), utilizing fluorescence in situ hybridization.

Construction of cytogenetic maps can provide important information for chromosome identification, chromosome evolution and genomic research. However, it hasn’t been conducted in many scallop species yet. In the present study, we attempted to map 12 fosmid clones containing tandem repeats by fluorescence in situ hybridization (FISH) in the Yesso scallop Patinopecten yessoensis (Jay, 1857). The results showed 6 fosmid clones were successfully mapped and distributed in 6 different pairs of chromosomes. Three clones were respectively assigned to a pair of metacentric chromosomes, a pair of submetacentric chromosomes and a pair of telocentric chromosomes and the remaining 3 clones showed their loci on three different pairs of subtelocentric chromosomes by co-hybridization. In summary, totally 8 pairs of chromosomes of the Yesso scallop were identified by 6 fosmid clones and two rDNA probes. Furthermore, 6 tandem repeats of 5 clones were sequenced and could be developed as chromosome specific markers for the Yesso scallop. The successful localization of fosmid clones will undoubtedly facilitate the integration of linkage groups with cytogenetic map and genomic research for the Yesso scallop.

Karyotype analysis and chromosome banding ofUpeneus moluccensis(Bleeker, 1855) from the north-eastern Mediterranean

Chromosome number, morphology and location of the nucleolus organizer region (NOR) are useful cytological characters for taxonomic and evolutionary studies. The karyotype of Upeneus moluccensis from the north-eastern Mediterranean was investigated through conventional Giemsa staining, Ag-NOR staining, C-banding and GTG-banding techniques. The results showed 2n = 44 (FN = 46), 2m + 2st + 40a chromosomes and four NORs. Two telomeric C-band regions were observed on a metacentric and subtelocentric chromosome pair. On the basis of the chromosome morphology, the GTG and C-banding pattern, it is hypothesized that Upeneus moluccensis is more primitive than the Mediterranean native fish species, Mullus barbatus and Mullus surmuletus. In this study, the cytogenetic characterization of U. moluccensis has been carried out for the first time.

Karyotype analysis and ribosomal gene localization of spotted knifejaw Oplegnathus punctatus.

The spotted knifejaw, Oplegnathus punctatus, is an important aquaculture fish species in China. To better understand the chromosomal microstructure and the karyotypic origin of this species, cytogenetic analysis was performed using Giemsa staining to identify metaphase chromosomes, C-banding to detect C-positive heterochromatin, silver staining to identify the nucleolus organizer regions (Ag-NORs), and fluorescence in situ hybridization (FISH) for physical mapping of the major (18S rDNA) and minor (5S rDNA) ribosomal genes. The species showed a karyotype of 2n = 48 for females, composed of 2 submetacentric and 46 telocentric chromosomes, with a fundamental number (FN) = 50, while the karyotype of males was 2n = 47, composed of 1 exclusive large metacentric, 2 submetacentric, and 44 telocentric chromosomes, with FN = 50. These karyotype results suggest that O. punctatus might have an X1X1X2X2/X1X2Y multiple sex chromosome system. C-positive heterochromatin was distributed in the centromeres of all chromosomal pairs and in the terminal portions of some chromosomes. A single pair of Ag-positive NORs was found to be localized at the terminal regions of the short arms of the subtelocentric chromosome pair, which was supported by FISH of 18S rDNA. After FISH, 5S rDNA were located on the interstitial regions of the smallest telocentric chromosome pair. This study was the first to identify the karyotype of this species and will facilitate further research on karyotype evolution in the order Perciformes.

Molecular Cytogenetic Analysis of the European Hake Merluccius merluccius (Merlucciidae, Gadiformes): U1 and U2 snRNA Gene Clusters Map to the Same Location.

The European hake (Merluccius merluccius) is a highly valuable and intensely fished species in which a long-term alive stock has been established in captivity for aquaculture purposes. Due to their huge economic importance, genetic studies on hakes were mostly focused on phylogenetic and phylogeographic aspects; however chromosome numbers are still not described for any of the fifteen species in the genus Merluccius. In this work we report a chromosome number of 2n = 42 and a karyotype composed of three meta/submetacentric and 18 subtelo/telocentric chromosome pairs. Telomeric sequences appear exclusively at both ends of every single chromosome. Concerning rRNA genes, this species show a single 45S rDNA cluster at an intercalary location on the long arm of subtelocentric chromosome pair 12; the single 5S rDNA cluster is also intercalary to the long arm of chromosome pair 4. While U2 snRNA gene clusters map to a single subcentromeric position on chromosome pair 13, U1 snRNA gene clusters seem to appear on almost all chromosome pairs, but showing bigger clusters on pairs 5, 13, 16, 17 and 19. The brightest signals on pair 13 are coincident with the single U2 snRNA gene cluster signals. Therefore, the use of these probes allows the unequivocal identification of at least 7 of the chromosome pairs that compose the karyotype of Merluccius merluccius thus opening the way to integrate molecular genetics and cytological data on the study of the genome of this important species.

Cytogenetic and Molecular Data Demonstrate that the Bryconinae (Ostariophysi, Bryconidae) Species from Southeastern Brazil Form a Phylogenetic and Phylogeographic Unit.

Brycon spp. occur in Neotropical watersheds to the west and east of the Andes, and as they are sensitive to anthropogenic changes, many these species are endangered in southeastern Brazil. Coastal rivers in southeastern Brazil are characterized by the presence of relatively few freshwater fish species and high endemism of this fauna. The objective of this study was to examine whether Brycon spp. occurring in the coastal basins of southeastern Brazil are monophyletic, using cytogenetic data, mitochondrial, and nuclear molecular markers. All the species showed a diploid number of 50 chromosomes, a conserved number within the subfamily Bryconinae. However, the karyotypic formulas were unique to most species, including Brycon devillei (26m+22sm+2st), Brycon ferox (26m+12sm+12st), Brycon insignis (22m+20sm+8st), Brycon opalinus, and Brycon vermelha (24m+20sm+6st), indicating the prevalence of pericentric and paracentric inversions in the chromosomal evolution of these species. All of them had nucleolar organizer regions in the first pair of subtelocentric chromosomes and no equilocal distribution of heterochromatin in the first pair of chromosomes of the karyotype. These two features, not seen in any other Brycon spp. examined to date, indicate that Bryconinae species from the Brazilian southeastern coastal basins, including the monotypic genus Henochilus, are monophyletic. Also, this is the first study that reports NOR location and C-banding patterns as synapomorphies for a Neotropical fish species group. The monophyly was also supported by a phylogenetic analysis of 16S rDNA (16S), cytochrome oxidase subunit I (COI), alpha-myosin (MYH6) genes and S72 intron molecular data. Our results partially corroborate the “Brycon acuminatus” group proposed by Howes in 1982: our proposed clade keeps B. devillei, B. ferox, and B. insignis; but it also includes B. opalinus, B. vermelha, and H. weatlandii whereas it excludes B. nattereri. The phylogeographic unit formed by Bryconinae species in southeastern Brazil reflects the long and isolated paleohydrological history of these coastal basins relative to the continental watersheds.

First description of the karyotype and localization of major and minor ribosomal genes in Rhoadsiaaltipinna Fowler, 1911 (Characiformes, Characidae) from Ecuador.

Karyotypic features of Rhoadsia altipinna Fowler, 1911 from Ecuador were investigated by examining metaphase chromosomes through Giemsa staining, C-banding, Ag-NOR, and two-color-fluorescence in situ hybridization (FISH) for mapping of 18S and 5S ribosomal genes. The species exhibit a karyotype with 2n = 50, composed of 10 metacentric, 26 submetacentric and 14 subtelocentric elements, with a fundamental number FN=86 and is characterized by the presence of a larger metacentric pair (number 1), which is about 2/3 longer than the average length of the rest of the metacentric series. Sex chromosomes were not observed. Heterochromatin is identifiable on 44 chromosomes, distributed in paracentromeric position near the centromere. The first metacentric pair presents two well-defined heterochromatic blocks in paracentromeric position, near the centromere. Impregnation with silver nitrate showed a single pair of Ag-positive NORs localized at terminal regions of the short arms of the subtelocentric chromosome pair number 12. FISH assay confirmed these localization of NORs and revealed that minor rDNA clusters occur interstitially on the larger metacentric pair number 1. Comparison of results here reported with those available on other Characidae permit to hypothesize that the presence of a very large metacentric pair might represent a unique and derived condition that characterize one of four major lineages molecularly identified in this family.

A biosystematic study of new records of the marsh frog Pelophylax ridibundus (Pallas, 1771) (Amphibia: Ranidae) from the southeast of Iran

The marsh frog, Pelophylax ridibundus, is reported from all over Iran except from the southeast and central deserts. This study provides records of 12 specimens of Pelophylax ridibundus from the easternmost extent of its range in Iran, Zabol, Sistan, and Baluchestan Province. Morphological, morphometric, and karyological characteristics of the specimens were investigated and compared with populations from other parts of Iran. Zabol specimens demonstrated 2n = 26, comprising one pair of metacentric, six pairs of submetacentric, and six pairs of subtelocentric chromosomes. Karyological results indicated Zabol specimens are the same as specimens from the central north of Iran. In addition, specimens from the southeast of Iran demonstrated a lower than average size except for tympanum and inter naris length compared with that of specimens from the north, and the northeast of Iran which may be the result of implications of Bergmann's rule due to the higher temperatures of the region.

Chromosomes of Two Species of Acanthocephalans Collected from the Fishes of Kashmir Valley, India

In the present study, karyotypes and chromosomes of two species of the families Pomphorhynchidae (Pomphorhynchus kashmirensis, Kaw 1941) and Neoechinorhynchidae (Neoechinorhynchus manasbalensis, kaw 1951) from intestinal tissues of Schizothorax and Cyprinus spps, were studied. Karyotypes of both the species is 2n=8 in which P. kashmirensis possess 4 submetacentric and 4 subtelocentric chromosome pairs whereas in case of N. manasbalensis first two pairs are metacentric, next two pairs are submetacentric and last 4 pairs are telocentric. The karyotype of N. manasbalensis seems to be more ancient, because its chromosomes are nearly telocentric. Such uniformity could be regarded as a plesiomorphic character of an ancestral karyotype.

Karyotypes of some species of the genusLessingianthus(Vernonieae, Asteraceae) and taxonomic implications

We determined the karyotypes of nine species of Lessingianthus, eight of which are here analyzed for the first time. The results include the first chromosome count for L. plantaginoides, which is tetraploid with 2n = 64. All species showed a high proportion of metacentric chromosomes combined with a lower proportion of submetacentric pairs. Only L. coriaceus had a subtelocentric chromosome pair. B chromosomes were observed in L. coriaceus and L. varroniifolius, which were subtelocentric. Differences among the karyotypes of the studied species were small, suggesting that karyotype diversity in the genus evolved by small changes in the structure of chromosomes. Karyotype features appear useful to distinguish Lessingianthus from the closely related genera Chrysolaena and Lepidaploa.

Tulipa albanica (Liliaceae), a new species from northeastern Albania

Tulipa albanica (Liliaceae) is illustrated and described as a new species from a serpentine area in Kukesi district, northeastern Albania. It is compared with T. scardica from the western Balkans (Macedonia and Kosovo) and with T. schrenkii from the Ukraine, Caucasus, Central and Southwest Asia. The chromosome number, karyotype features and nuclear DNA content (2C-value) were assessed by karyological and flow cytometry techniques and provided for the first time for this species. The chromosome formula is 2n = 2x = 24 (2 metacentric, 3 submetacentric and 7 subtelocentric chromosome pairs) and the genome size 54.15 (+/- 0.23) pg. Two different morphotypes of T. australis were noted as occurring on limestone or serpentine in Albania.