Submetacentric Pair Research Articles

The Giemsa C-banded Karyotype of Crithopsis Delileana (Poaceae; Triticeae)

Three populations of Crithopsis delileunu had similar karyotypes. They included 14 large chromosomes; five pairs of metacentrics, one pair of submetacentrics, and one pair of metacentric SAT-chromosomes with rather small satellites. The karyotypes of two populations were investigated in detail through application of Giemsa C-banding, Giemsa N-banding and AgN0,-staining to meta- and interphases. The C-banding patterns included a few small to very small, mainly centromeric or telomeric bands. The chromosomes of the two populations were differentiated by banding pattern polymorphism. Banding patterns identified homologous and discriminated among non-homologous chromosomes within the same population. The scarcity of diagnostic bands prevented identification of homologous chromosomes between populations beyond the level obtained from morphology, i.e., of submetdcentrics and SAT chromosomes. N-banding produced no or few weak bands. Silver nitrate staining produced two NORs and two nucleoli corresponding to the number of SAT-chromosomes. The data give some support to a hypothesis of a closer relationship between the genera Critlzopsis and Tueniutherum, than between either of these and the genera Psuthyrostuchys and Hordeum.

Karyotypes of Elymus scabrifolius (Poaceae: Triticeae) from South America studied by banding techniques and in situ hybridization.

Karyotypes of 4 accessions of Elymus scabrifolius (2n = 4x = 28) were investigated by Giemsa C- and N-banding, GAA-banding (one accession), AgNO3-staining and in situ hybridization with the rDNA probe pTa71. Two additional accessions were studied in less detail. The chromosomes were large (9-14 microns). The complements included 11 pairs of metacentrics, one with conspicuous satellites on the short arms, and 3 pairs of submetacentrics. Two of 4 accessions from Eastern Argentina and Uruguay had minute or small satellites on a submetacentric pair. No such satellites were observed in the other two accessions. In two accessions from the Cordoba province, a non-homologous submetacentric pair had very long satellites. AgNO3-staining established the presence of 4 nucleoli, two larger and two small ones, in 5 accessions. The C-banding patterns comprised from one to 12 conspicuous bands per chromosome at no preferential positions. The amount of constitutive heterochromatin (19-21%) was the highest hitherto established in the Triticeae. Similarities in banding patterns and chromosome morphology identified homologous and discriminated between non-homologous chromosomes within and, except for two chromosomes, between plants. Heteromorphic chromosome pairs were identified in satellite-carrying chromosomes only. N-banding produced conspicuous bands overall at the same positions as C-banding. GAA-banding patterns were similar to N-banding patterns. The rDNA probe hybridized to chromosome segments at nucleolar constrictions only. The production of C- and N-banding patterns in both genomes of E. scabrifolius suggests the presence of two H genomes and the absence of the pivotal St genome of Elymus. On account of the uncertain identity of one genome, and the overall similar gross morphology of E. scabrifolius and other tetraploid South American species referred to Elymus, E. scabrifolius is retained in Elymus.

Chromosome numbers, karyotypes and 4C DNA contents ofAchillea sipikorensisHausskn. and Bornm. andAchillea sintenisiiHub.-Mor. (Asteraceae)

Abstract The cytological features including chromosome numbers, detailed chromosome measurements and 4C DNA values were reported in Achillea sipikorensis and A. sintenisii from Turkey. Total chromosome lengths, relative lengths, long/short arm ratios and centromeric index of mitotic chromosomes were calculated. Somatic chromosome numbers were found to be 2n=2x=18 in A. sipikorensis and 2n=4x=36 in A. sintenisii for the first time. The mean of chromosome length ranged from 6.92±0.08 to 9.23±0.58 μm in A. sipikorensis and from 6.54±0.91 to 9.62±0.79 μm in A. sintenisii. The karyotype consists of six pairs metacentric chromosomes, two submetacentric pairs and a subte-locentric pairs in A. sipikorensis and of fifteen pairs metacentric chromosomes, a submetacentric pairs and two sub-telocentric pairs in A. sintenisii. The nuclear DNA C-value was estimated to be 4C= 24.63±0.01 pg of A. sipikorensis and 4C= 35.73±0.05 pg of A. sintenisii.

Karyotype description of Pomacea patula catemacensis (Caenogastropoda, Ampullariidae), with an assessment of the taxonomic status of Pomacea patula

Mitotic chromosomes of the freshwater snail Pomacea patula catemacensis (Baker 1922) were analyzed on gill tissue of specimens from the type locality (Lake Catemaco, Mexico). The diploid number of chromosomes is 2n = 26, including nine metacentric and four submetacentric pairs; therefore, the fundamental number is FN = 52, No sex chromosomes could be identified. The same chromosome number and morphology were already reported for P. flagellata, i.e., the other species of the genus living in Mexico. The basic haploid number for family Ampullariidae was reported to be n = 14 in the literature; so, its reduction to n = 13 is probably an apomorphy of the Mexican Pomacea snails. Lanistes bolteni, from Egypt, also shows n = 13, but its karyotype is much more asymmetrical, and seems to have evolved independently from P. flagellata and P. patula catemacensis. The nominotypical subspecies, P. patula patula (Reeve 1856), is a poorly known taxon, whose original locality is unknown. A taxonomical account is presented here, and a Mexican origin postulated as the most parsimonious hypothesis.

Chromosome Localization of the Ribosomal Genes 18S and 5S in Four Stocks of Rainbow Trout (Oncorhynchus mykiss) from Cultivated and Naturalized Stocks in Brazil

In the present study, fluorescence in situ hybridization (FISH) was employed to determine the chromosomal location of genes 18S rDNA and 5S rDNA in four rainbow trout stocks. In specimens from the stocks of Nucleo Experimental de Salmonicultura de Campos do Jordao and Gaviao river, 18S genes were located at a subterminal position in the long arms of two submetacentric chromosomes, whereas in specimens from stocks of Mount Shasta and Teresopolis they were found in the short arms. In all analyzed stocks, 5S genes were located in two chromosome pairs. In a subtelocentric pair, 5S genes were present in the short arms and, in the other submetacentric pair, 5S genes were at an interstitial position. In the latter, 18S and 5S genes were contiguous. Taking into account that both 18S and 5S rDNA genes have been localized in the short arm of a submetacentric chromosome in almost all rainbow trout samples so far studied, the presence of such genes in the long arm, as seen in the samples from Nucleo Experimental de Salmonicultura de Campos do Jordao and Gaviao river, supports the hypothesis of a pericentric inversion involving this chromosome segment in the ancestor line of these stocks. The observed polymorphism allowed the identification of a very useful genomic marker, and may therefore constitute an important tool in the genetic management of rainbow trout stocks.

Multiple pericentric inversions and chromosomal divergence in the reef fishes Stegastes (Perciformes, Pomacentridae)

Damselfishes (Pomacentridae, Perciformes) occur in all major oceans of the world and, with approximately 320 species, represent one of the most diverse families of marine Teleostei. The taxonomy of these reef fishes is problematic because of the large number of complex species and the range of color patterns they display, which vary among individuals and populations of the same species. In this study, we examined the cytogenetic composition of four species of Stegastes (S. pictus, S. fuscus, S. variabilis and S. leucostictus) found along the coast of Brazil. Stegastes pictus had a chromosomal number of 2n = 48 (14m+28sm+2st+4a, fundamental number (FN) = 92), S. fuscus had 2n = 48 (20m+22sm+6a, FN = 90), S. variabilis had 2n = 48 (18m+22sm+8a, FN = 88), and S. leucostictus had 2n = 48, (18m+22sm+8a, FN = 88). The nucleolar organizing regions were single and homologous in all of the species, and were located in the interstitial region on the short arm of the first submetacentric pair. The heterochromatin segments were reduced in size and were distributed conservatively over the centromeric and pericentromeric regions of most of the chromosomes. The marked divergence in the number of chromosomal arms, compared to other perciformes (2n = 48, FN = 48), indicated that varying degrees of multiple pericentric inversions had occurred during the karyotypic evolution of the Pomacentridae. Subtle karyotypic differences between S. variabilis and S. leucostictus suggested a recent divergence or that their karyotypes were less susceptible to changes. These results indicate that cytogenetic analyses could provide important complementary data for the characterization of populations and species of Stegastes and damselfishes in general.

Karyotype description of five species of Trichomycterus (Teleostei: Siluriformes: Trichomycteridae)

Trichomycteridae is a family of small catfish which are widely distributed throughout Southern Central America and South America. The present study showed that the cis-Andean species Trichomycterus florensis, Trichomycterus sp. aff. Trichomycterus itatiyae, Trichomycterus reinhardti, Trichomycterus davisi and Trichomycterus auroguttatus had 2n = 54 chromosomes (42 metacentric, 10 submetacentric and 2 subtelocentric), with T. reinhardti, T. auroguttatus and T. sp. aff. T. itatiyae exhibiting only one chromosome pair with silver-stained nucleolus organizer regions (NORs). The cytogenetic data suggest the existence of at least two groups of species in the cis-Andean representatives of the genus Trichomycterus. In the first group the first metacentric pair is considerably larger than the second metacentric pair and the NORs occur in the pericentromeric position of the short arm of a large submetacentric pair while in the second group the first and second metacentric pairs are about the same size and larger than the other metacentric pairs and the NORs are located in the pericentromeric position of the long arm of a large metacentric pair. The relative conservatism of the karyotype of the cis-Andean Trichomycterus species contrasts with the wide diversification observed in the trans-Andean species, reinforcing the hypothesis that the genus is not monophyletic.

Conventional karyotype and nucleolar organizer regions of the toadfish <i>Halobatrachus didactylus</i> (Schneider, 1801) (Pisces: Batrachoididae)

For this report, we studied the conventional karyotype and the NOR-bearing chromosomes in the toadfish Halobatrachus didactylus . We found a karyotype of 46 chromosomes made up of 8 metacentric, 12 submetacentric, and 26 acrocentric elements (FN = 66). No heteromorphic sex chromosomes were observed in the species. Metacentric chromosomes were easily classified as homologous pairs according to their morphology and L/S ratio. The rest of the chromosomes could not be accurately classified as homologous pairs because differences in chromosome size and L/S ratio were too slight between adjacent pairs within a size-ranged series. A single pair of NOR-bearing chromosomes was found. Active NORs were terminally located in a submetacentric pair of chromosomes.

Multicolor FISH와 Feulgen 염색법을 이용한 Angelica속 식물의 세포유전학적 분석

Karyotype analysis and chromosomal localization of 5S and 45S rDNAs using multi-color fluorescence in situ hybridization (McFISH) technique were carried out in two Angelica species. The numbers of diploid chromosomes were the same in two same in two species as 2n=22, however the lengths of chromosomes were varied from 4.25 to 6.50 <TEX>${\mu}{\textrm}{m}$</TEX> in A gigas and 4.95 to 8.50 <TEX>${\mu}{\textrm}{m}$</TEX> in A acutiloba. The chromosomes of A. gigas were composed of five metacentric and six submetacentric pairs, while those of A. acutiloba were six metacentic, one submetacentric and four subtelocentric paris. In FISH experiments, the numbers and size of 45S rDNA signals were varied between two species, however dach signal of the 5S rDNA was observed in two species.

Replication banding patterns in the spined loach, Cobitis taenia L. (Pisces, Cobitidae).

The chromosomal complement of Cobitis taenia was analysed by replication banding techniques to determine whether there were specific patterns that could allow distinction of the different chromosomes. The diploid chromosome number of 2n = 48 is diagnostic of this species. In vivo 5-bromodeoxyuridine (5-BrdU) incorporation induced highly reproducible replication bands. Most of the chromosome pairs were distinguishable on the base of their banding patterns. The karyotype, consisting of five pairs of metacentrics, nine pairs of submetacentrics and 10 pairs of subtelocentrics and acrocentrics, was confirmed. C-banding and replication banding patterns were compared, and heterochromatin was both early and later replicating. C-positive heterochromatin in centromeric regions was mainly early replicating, but that located in pericentromeric regions was late replicating. Most of the late-replicating regions found interstitially were C-band negative. The results obtained so far for combined chromosomal staining methods of C. taenia and other Cobitis fish species are discussed.

A preliminary note on banded karyotypes of the Perny's long-nosed squirrel Dremomys pernyi (Mammalia, Rodentia) from Taiwan

Abstract The chromosomes of the Perny's long-nosed squirrel Dremomys pernyi owstoni that is endemic subspecies to Taiwan were examined with conventional and Ag-NOR staining and G- and C-banding technique. The diploid chromosome number (2.) and fundamental autosomal arm number (FN) of this squirrel were 38 and 68, respectively. The karyotype consisted of 7 pairs of metacentrics (nos. 1–7), 9 pairs of submetacentrics or subtelocentrics (nos. 8–16), 2 pairs of acrocentrics (nos. 17 and 18), a medium-sized submetacentric X chromosome, and an acrocentric Y chromosome. On the terminal region of short arm of no. 17 chromosomes, the prominent satellite the stalk potion of which essentially corresponded to Ag-NOR was recognized. The no. 18 chromosome was markedly minute acrocentric. In the C-banded karyotype, the all autosomes and X chromosome carried centromeric constitutive heterochromatin (C-heterochromatin), and the Y chromosome appeared to be entirely heterochromatic. Based on the cytogenetical characteristic...

Localization of 5S rRNA loci in three coregonid species (Salmonidae).

In the present study the chromosome distribution of the 5S rDNA loci and its relation to the major rDNA genes were investigated in three Coregonid species (Salmonidae): Coregonus lavaretus, Coregonus peled and Coregonus albula, a family which has experienced large karyotype rearrangements along its evolution starting from a tetraploid ancestor. 5S PRINS/CMA3 sequential staining together with previous data enabled us to locate 5S rRNA genes and nucleolar organizer regions (NORs) in the three species analyzed. PRINS revealed the 5S rDNA cluster at the distal part of the long arm of a similar submetacentric chromosome pair in the three species. Our data indicate that 5S rDNA clusters have probably conserved chromosomal location in the genus Coregonus, whereas 45S rDNA (NOR) sites are clearly differentiated, from a single locus in C. peled, to multiple loci in C. lavaretus and highly polymorphic multichromosomal location in C. albula.

The chromosomal complement of the artedidraconid fish Histiodraco velifer (Perciformes: Notothenioidei) from Terra Nova Bay, Ross Sea

The karyotype of Histiodraco velifer from the Antartic Ocean was analyzed using various banding methods and in situ hybridization with a telomeric probe. A male and a female had a diploid set of 46 chromosomes (6 submetacentric + 40 acrocentric, FN = 52); the nucleolar organizer was CMA₃-positive and was located on the short arm of a medium-sized submetacentric pair. All chromosomes stained uniformly with DAPI, whereas C-banding revealed heterochromatic blocks that were mostly located centromerically and telomerically and were resistant to AluI digestion. The substantial identity of the karyotype of H. velifer with that of the other artedidraconids investigated so far suggests that chromosome changes must have played a less than significant role in the speciation among the lineages of this fish family endemic to Antarctica.

First Cytogenetic Description of the Species Rhamdella microcephala (Pisces, Hepapteridae).

Summary Cytogenetic studies were carried out on Rhamdella microcephala collected from the headwaters of the Machado river, a tributary of the Sapucai river, Minas Gerais, Brazil. Sixteen specimens exhibited 2n556 chromosomes, with 18 metacentrics, 30 submetacentrics and 8 subtelocentric-acrocentrics (FN584). The nucleolar organizing regions (NORs) were identified in the interstitial position on the long arm of a submetacentric pair (pair 12). Chromomycin A3 staining evidenced only the NOR-bearing segments. Positive C-band segments were identified in a pericentromeric position in most of the chromosomes and the NOR-bearing segments were also C-band positive. Some aspects related to the chromosomal characteristics of Rhamdella microcephala are discussed.

NORs inheritance analysis in crossings including individuals from two stocks of rainbow trout (Oncorhynchus mykiss).

Silver nitrate staining of rainbow trouts (Oncorhynchus mykiss) chromosomes, for the identification of the nucleolar organizing regions (NORs), revealed that in individuals from Núcleo Experimental de Salmonicultura de Campos do Jordão (Brazil) NORs were located in the long arms of submetacentric pair while in specimens from Mount Shasta (USA) NORs were located in the short arms of a submetacentric pair. Cytogenetic analysis of the offspring, obtained through artificial crosses including individuals from both stocks, allowed the identification of NORs in two submetacentric chromosomes, one in the short arms and the other in the long arms, confirming the effectiveness of the hybridization process. Complementary results obtained using the FISH technique with 18S and 5S rDNA probes showed that NOR-bearing chromosomes exhibited a cluster of 5S genes located in tandem with the 18S gene cluster in both stocks. The results allow us to suggest that the difference in NOR-bearing chromosomes found between the two stocks is likely to be due to pericentric inversion involving the chromosome segment where 18S and 5S rDNA genes are located. The presence of ribosomal genes in the long arms of a submetacentric chromosome is apparently a particular characteristic of the rainbow trout stock of Campos do Jordão and might be used as a chromosome marker in studies of controlled crosses in this species.

Comparative cytogenetics and supernumerary chromosomes in the Brazilian lizard genus Enyalius (Squamata, Polychrotidae).

Cytogenetical analyses based on conventional and differential staining were performed for the first time on five species of the Brazilian lizard genus Enyalius: E. bibronii, E. bilineatus, E. iheringii, E. leechii, and E. perditus. The species share a similar 2n = 36 (12M + 24m) karyotype, comprised of 12 metacentric or submetacentric macrochromosomes, except for an acrocentric pair 6 that characterizes E. bibronii. The 24 microchromosomes were acrocentrics, but in E. perditus two meta/submetacentric microchromosome pairs were unambiguously identified. Karyotypes with 2n = 37 and 2n = 37/38 chromosomes were also observed in some specimens of E. bilineatus as a result of the presence of supernumerary chromosomes (Bs). Ag-NORs were always located at the distal region of the long arm of the submetacentric pair 2. The constitutive heterochromatin was mostly restricted to the pericentromeric regions of some macrochromosomes and microchromosomes. A XX:XY mechanism of sex determination with a dot-like Y microchromosome occurs in E. bilineatus, E. leechii, and E. perditus.

Chromosomal characterization of the Formosan striped squirrel Tamiops maritimus formosanus (Mammalia, Rodentia)

Abstract Chromosomes of the Formosan striped squirrel Tamiops maritimus formosanus were analyzed with conventional and silver staining and G- and Cbanding technique. The diploid chromosome number (2n) and fundamental autosomal arm number (FN) were 38 and 68, respectively. Karyotype consisted of seven pairs of metacentrics (nos. 1–7), nine pairs of submetacentrics or subtelocentrics (nos. 8–16), two pairs of acrocentrics (nos. 17 and 18), a medium-sized submetacentric X chromosome, and a small acrocentric Y chromosome. All autosomes and the X chromosome carried centromeric constitutive heterochromatin, but the Y chromosome was entirely euchromatic. In the short arm of no. 17 chromosomes, the prominent satellite structure with its long stalk, which corresponded to the nucleolus organizer region (NOR), was observed, suggesting that it could have been shared with other squirrel species through the evolutionary process.

Karyotype, C- and G-band patterns and DNA content of Callimenus (=Bradyporus) macrogaster macrogaster.

Chromosomes and detailed karyotype information (the number, shape, relative length, arm ratio, centromeric index) of Callimenus (=Bradyporus) macrogaster macrogaster Lef. (Orthoptera: Tettigonioidea, Bradyporini) of Turkey belonging to the subfamily Bradyporinae are described. The diploid number of chromosomes was found to be 2n male symbol = 23, with 2 metacentric pairs, 2 submetacentric pairs, 6 acrocentric pairs. The X chromosome is metacentric. This species has a XX female symbol / X0 male symbol sex determining mechanism. The basic karyotype is complemented by a description of C- and G-banding patterns. The C-banding pattern in spermatogonial metaphase was characterized by the presence of paracentromeric C-bands in all chromosomes, and a distal C-band in chromosome 5. The G-banding pattern was complex. The 2C nuclear DNA content was found to be 10.26 +/- 0.16 picograms by microspectrophotometry.

Banded karyotypes of the hairy-footed flying squirrel Belomys (Trogopterus) pearsonii (Mammalia, Rodentia) from Taiwan

Abstract The chromosomes of the hairy-footed flying squirrel Belomys pearsonii from Taiwan were analyzed with conventional and Ag-NOR staining and G- and C-banding technique. The diploid chromosome number (2n) and fundamental autosomal arm number (FN) were 38 and 72, respectively. The karyotype consisted of six pairs of metacentrics (nos. 1–6), twelve pairs of submetacentrics or subtelocentrics (nos. 7–18), an unusually large-sized metacentric X chromosome, and an acrocentric Y chromosome. The satellite structure, which corresponded to the NOR detected by silver-staining, was observed on the long arm of no. 1 chromosomes. All autosomes and the X chromosome had centromeric constitutive heterochromatin (C-heterochromatin), and the long arms of nos. 17 and 18 chromosomes were entirely heterochromaic. By the C-banding technique, the Y chromosome was entirely stained somewhat darkly than euchromatic region, but did not seem to be genuinely heterochromatic. On the basis of the cytogenetical characteristics of s...

The Karyotype of Chukotka Chars from the Estikhed Lake (Eastern Chukotka)

The karyotype of chars from the Estikhed Lake (Eastern Chukotka) was examined. This karyotype comprises 78 chromosomes, NF = 98. Marker chromosomes include one pair of submetacentrics, one pair of large acrocentrics, and one pair of large subtelocentrics with very short second arms. Nucleolus organizer regions are located in telomeric regions of short arms of marker submetacentric chromosomes. Small heterochromatin blocks are observed in centromeric regions of most chromosomes. The Chukotka char karyotype is very similar to that of Taranetz charSalvelinus taranetzi from the Achchen Lake: these karyotypes differ only in stability of the chromosome number.