Submetacentric Chromosomes Research Articles

Novel cytogenetic data in two gudgeons from the genera Gobio and Romanogobio (Teleostei: Cypriniformes: Gobionidae): chromosomal mapping of rDNAs and telomeric repeats

The taxonomic status of gudgeons (Gobionidae) and the genetic relationships among them are still unclear. The current knowledge on the molecular cytogenetics of gudgeons is quite limited and concerns the basic parameters of their karyotype. Therefore, the main aim of this study was to obtain new data on the chromo- somes of two gudgeons – Gobio gobio and Romanogobio belingi – which would allow for characterising these species in a more precise way. Chromosomes of the examined species were analysed by conventional Giemsa staining and, for the first time, by fluorescence in situ hybridisation (FISH) with 28S rDNA, 5S rDNA and telomeric probes. The diploid chromosome numbers in both species were the same and equalled 2n=50, while the chromosome arm number (NF) was 96 and 98 in G. gobio and R. belingi, respectively. Moreover, small interspecific differences concerning the chromosomal morphology were observed. Major 28S rDNA sites were mapped to the short (p) arms of two submetacentric chromosomes with a similar size in G. gobio, whereas in R. belingi, FISH signals were observed from the short and the long (q) arms of two different-sized submetacentric chromosomes. Minor 5S rDNA sites were found on the p arms of eight submetacentric chromosomes of different sizes in G. gobio and on five submetacentric chromosomes in R. belingi. Unique chromosomal co-locations of major and minor rDNA sites were observed in the karyotypes of both species. In the chromosomes of both species, telomeric DNA sequences were typically located at the ends of all chromosomes. The number of chromosome arms, as well as the number and lo- cation of 45S and 5S rDNAs, and the number of unexpected co-located major and minor ribosomal genes may be useful cytotaxonomic species-specific markers.

Karyotype analysis and chromosomal characterization of hibiscus cannabinus l.

Seven germplasm of Hibiscus cannabinus L. (Acc. No. 95, 4652, 4654, 4655, 4656, 4657, and 4810) were investigated for their karyotype analysis and chromosomal characterization. These germplasm of H. cannabinus were found to possess 2n = 36 chromosomes. Symmetric nature of karyotype was observed in Acc. No. 4654. In contrast, metacentric and submetacentric chromosomes were present in other six accessions revealing the asymmetric nature of karyotype. Based on karyotypic features Acc. No. 4654 was considered relatively primitive and Acc. No. 4652 was relatively advanced among the seven germplasm. Moreover, karyomorphological study proved their divergence in relation to different morphological feature of the chromosomes. Bangladesh J. Bot. 53(4): 967-971, 2024 (December)

A Detailed Karyological Investigation of three Endemic Cobitis Linnaeus, 1758 Species (Teleostei, Cobitidae) in Anatolia, Türkiye

Introduction: Comparative cytogenetics is a vital approach for diagnosing chromosome abnormalities and identifying species-specific patterns. In this study, chromosomal analysis of three Anatolian endemic Cobitis species was performed: Cobitis bilseli, C. fahireae, and C. turcica. Methods: Conventional cytogenetic techniques such as Giemsa staining, C-banding, and Ag-NOR staining were applied, followed by measurements of chromosome arm lengths including analysis of the measured data. Results: The diploid chromosome number, 2n = 50, was determined for all three species. The karyotype formulas were as follows: four pairs of metacentric, 5 pairs of submetacentric, and 16 pairs of subtelo-telocentric chromosomes in C. bilseli; 11 pairs of metacentric, 7 pairs of submetacentric, and 7 pairs of subtelo-telocentric chromosomes in C. fahireae; and 4 pairs of metacentric, 4 pairs of submetacentric, and 17 pairs of subtelo-telocentric chromosomes in C. turcica. Dark C-bands were observed on the pericentromeres of nearly all chromosomes in C. bilseli and C. turcica, whereas light C-bands appeared on the pericentromeres of some chromosomes in C. fahireae. Silver-stained metaphases revealed signals on the short arm of a submetacentric chromosome pair in C. fahireae (each homologous chromosome carries one signal), while in C. bilseli and C. turcica, Ag-NOR signals were detected on the long arm of a single metacentric chromosome (only one homologous chromosome carries the signal, and the signal-carrying chromosome is the largest chromosome in the karyotype). Conclusion: This study provides new cytogenetic data consistent with the phylogenetic distances between the studied species, indicating that pericentric inversions and/or translocations govern the formation of Cobitis karyotypes.

Two species of Polycelis (Platyhelminthes, Tricladida, Planariidae) newly recorded for the Qinling Mountains and the Loess Plateau in China, with a comparative discussion on their karyotypes.

The paper details new geographic records of two species of the genus Polycelis Ehrenberg,1831 (Platyhelminthes, Tricladida, Planariidae) for the Qinling Mountains and the Loess Plateau in China and provides redescriptions of these species based on an integrative taxonomic study involving morphology, karyology, and histology. This new information considerably expands our knowledge on these species, for which until now only limited data was available. The species Polycelis asiatica Selinova, 1985 is characterized by the following features: 63-80 eyes; sperm ducts that exhibit an intrabulbar knee-shaped bend towards the ventral surface before opening separately and symmetrically into the antero-dorsal portion of a large seminal vesicle; the latter is ventrally displaced, thus creating a narrow ventral lip on the penis papilla; dorsal wall of the seminal vesicle is provided with several well-developed folds; more or less bulbous penis papilla protrudes from the dorsal wall of the male atrium and is provided with a slender and flexible tip; chromosome complement diploid with 30 metacentric chromosomes, 8 submetacentric chromosomes, and 2 subtelocentric chromosomes. The species Polycelis eudendrocoeloides (Zabusova, 1929) is characterized by: 49-80 eyes; highly reduced and blunt penis, provided with a kind of flagellum that projects into the seminal vesicle; a relatively thick coat of circular and longitudinal muscles around the entire male atrium; generally, a very large intrabulbar seminal vesicle, extending from near the ventral body surface to occupy the major part of both the penis bulb and the dorso-ventral space of the body; diploid chromosome complement consisting of 36 metacentric chromosomes.

What is the True Karyotype of <i>Bufotes latastii</i> (Amphibia, Anura, Bufonidae)?

The karyotype is one of the most important characteristics of an animal species and can be very useful for identifying taxa. The chromosome sets of the West Himalayan endemic Ladakh toad, Bufotes latastii, were previously described in several papers, but differed greatly from each other. To deal with these contradictions, we re-examined the karyotype of B. latastii from India and compared it with the sets of chromosomes of the most morphologically similar toad species inhabiting East Asia. It turned out that the diploid set of B. latastii consists of 22 chromosomes (2n = 22; NF = 44), of which six pairs are large and five are small. As a rule, the 4th, 5th, and 7th pairs of chromosomes are submetacentric and all the others are metacentric. The chromosomal formula is 2n = 16 m + + 6 sm = 22. The nucleolar organizers (NOR) in B. latastii are located on the long arms of submetacentric chromosomes of the 5th pair, which greatly distinguishes this species from most diploid species of the genus Bufotes. Karyotypes of two other studied species (Duttaphrynus stomaticus and Strauchbufo raddei), which can be morphologically similar to B. latastii, also consist of 22 chromosomes (2n = 22; NF = 44) of which six pairs are large and five are small, but there is only a pair of submetacentric chromosomes (2n = 20 m + 2 sm = 22). The most notable differences between these three species were in the position of NORs. In B. latastii they were located in the telomeric region of the long arm of the 5th pair, in D. stomaticus in the submedial region of the short arm of the 7th pair, and in S. raddei in the telomeric region of the short arm of the 4th pair. Discriminant analyses of the relative length of chromosomes and centromeric indices also revealed significant differences between the karyotypes of these three species. Our study made it possible to clearly distinguish B. latastii from D. stomaticus and S. raddei by karyotype characteristics. This may be important if it is necessary to identify East Asian morphologically similar toad species.

The Detailed Karyotype Analysis, Karyotype Asymmetry and Polyploidy in Hemp (Cannabis sativa L.)

Hemp (Cannabis sativa L.) is an economical plant with a diploid chromosome number of 2n = 20 and used in many areas, especially in industry. The aim of this study is to perform detailed karyotype analysis and detailed chromosomal measurements using five different genotypes of the plant known as diploid chromosome number 2n = 20, to determine the karyotype asymmetry for the first time, and to investigate the polyploidy variations. The diploid chromosome number and karyotype formula were 2n = 2x = 20 = 18m + 2sm. The karyotype had small metacentric and submetacentric chromosomes. The smallest chromosome length, largest chromosome length, total haploid chromosome length, and average haploid chromosome length were 2.41, 3.55, 29.87, and 2.99 μm, respectively. Intrachromosomal and interchromosomal karyotype asymmetries were calculated using many different parameters, mainly MCA (mean centromeric asymmetry) and CVCL (variation coefficient of chromosome length). According to the asymmetry values, the species had quite symmetrical karyotype. Although the diploid chromosome number was known as 2n = 20, detailed karyotype analysis and karyotype asymmetry data were presented for the first time by this study. In addition, in the study carried out on five different genotypes, polyploidy variation was detected in one genotype.

Comparative molecular and conventional cytogenetic analyses of three species of Rhinella (Anura; Bufonidae).

The genus Rhinella corresponds to a group of anurans characterized by numerous taxonomic and systemic challenges, leading to their organization into species complexes. Cytogenetic data for this genus thus far are limited to the diploid number and chromosome morphology, which remain highly conserved among the species. In this study, we analyse the karyotypes of three species of the genus Rhinella (Rhinella granulosa, Rhinella margaritifera, and Rhinella marina) using both classical (conventional staining and C-banding) and molecular (FISH-fluorescence in situ hybridization with 18S rDNA, telomeric sequences, and microsatellite probes) cytogenetic approaches. The aim of this study is to provide data that can reveal variations in the distribution of repetitive sequences that can contribute to understanding karyotypic diversification in these species. The results revealed a conserved karyotype across the species, with 2n = 22 and FN = 44, with metacentric and submetacentric chromosomes. C-banding revealed heterochromatic blocks in the pericentromeric region for all species, with a proximal block on the long arms of pairs 3 and 6 in R. marina and on the short arms of pairs 4 and 6 in R. margaritifera. Additionally, 18S rDNA probes hybridized to pair 5 in R. granulosa, to pair 7 in R. marina, and to pair 10 in R. margaritifera. Telomeric sequence probes displayed signals exclusively in the distal region of the chromosomes, while microsatellite DNA probes showed species-specific patterns. These findings indicate that despite a conserved karyotypical macrostructure, chromosomal differences exist among the species due to the accumulation of repetitive sequences. This variation may be attributed to chromosome rearrangements or differential accumulation of these sequences, highlighting the dynamic role of repetitive sequences in the chromosomal evolution of Rhinella species. Ultimately, this study emphasizes the importance of the role of repetitive DNAs in chromosomal rearrangements to elucidate the evolutionary mechanisms leading to independent diversification in the distinct phylogenetic groups of Rhinella.

Karyotype diversity and genome size in the Cyphomandra clade of Solanum L. (Solanaceae)

Abstract The Cyphomandra clade, a distinct group within the Solanum L. genus, is characterized by remarkable traits, including large chromosomes and big genome sizes. We aimed to investigate whether these features are conserved within the Cyphomandra clade and how they differentiate this group from other Solanum species. We elaborated karyotypes based on CMA/DAPI banding and rDNA fluorescence in situ hybridization (FISH) and estimated the genome size from 12 species, eight belonging to Cyphomandra and four from related clades. All species showed metacentric or submetacentric chromosomes and symmetrical karyotypes, with 2n = 24, except S. mammosum L. (2n = 22). CMA/DAPI banding in combination with rDNA FISH revealed three distinct patterns of heterochromatin distribution (number and position of bands, all CMA+). Most species showed one pair of 35S and 5S rDNA on different chromosomes, except S. mammosum (one of the two pairs was observed in the same chromosome). Notable, the Cyphomandra clade species showed larger chromosomes and genome sizes than other species of Solanum, corroborating that these karyotype attributes are valuable to characterize the clade. The number of CMA/DAPI bands and rDNA sites does not justify the differences in the genome size. Therefore, the accumulation and dispersion of other repetitive sequences, like transposable elements, may be associated with the karyotype changes.

Molecular cytogenetic characterization of 9 populations of four species in the genus Polygonatum (Asparagaceae).

To characterize the chromosomes of the four species of Polygonatum Miller, 1754, used in traditional Chinese medicine, P.cyrtonema Hua, 1892, P.kingianum Collett et Hemsley, 1890, P.odoratum (Miller, 1768) Druce, 1906, and P.sibiricum Redouté, 1811, and have an insight into the karyotype variation of the genus Polygonatum, fluorescence in situ hybridization (FISH) with 5S and 45S rDNA oligonucleotide probes was applied to analyze the karyotypes of 9 populations of the four species. Detailed molecular cytogenetic karyotypes of the 9 populations were established for the first time using the dataset of chromosome measurements and FISH signals of 5S and 45S rDNA. Four karyotype asymmetry indices, CVCI, CVCL, MCA and Stebbins' category, were measured to elucidate the asymmetry of the karyotypes and karyological relationships among species. Comparison of their karyotypes revealed distinct variations in the karyotypic parameters and rDNA patterns among and within species. The basic chromosome numbers detected were x = 9, 11 and 13 for P.cyrtonema, x = 15 for P.kingianum, x = 10 and 11 for P.odoratum, and x = 12 for P.sibiricum. The original basic chromosome numbers of the four species were inferred on the basis of the data of this study and previous reports. All the 9 karyotypes were of moderate asymmetry and composed of metacentric, submetacentric and subtelocentric chromosomes or consisted of two of these types of chromosomes. Seven populations have one locus of 5S rDNA and two loci of 45S rDNA, and two populations added one 5S or 45S locus. The karyological relationships among the four species revealed by comparison of rDNA patterns and PCoA based on x, 2n, TCL, CVCI, MCA and CVCL were basically accordant with the phylogenetic relationships revealed by molecular phylogenetic studies. The mechanisms of both intra- and inter-specific dysploidy in Polygonatum were discussed based on the data of this study and literature.

Karyotypes and Physical Mapping of Ribosomal DNA with Oligo-Probes in Eranthis sect. Eranthis (Ranunculaceae).

A comparative karyotype analysis of four species of yellow-flowered Eranthis sect. Eranthis, i.e., E. bulgarica, E. cilicica, E. hyemalis, and E. longistipitata from different areas, has been carried out for the first time. All the studied specimens had somatic chromosome number 2n = 16 with basic chromosome number x = 8. Karyotypes of the investigated plants included five pairs of metacentric chromosomes and three pairs of submetacentric/subtelocentric chromosomes. The chromosome sets of the investigated species differ mainly in the ratio of submetacentric/subtelocentric chromosomes, their relative lengths, and arm ratios. A new oligonucleotide probe was developed and tested to detect 45S rDNA clusters. Using this probe and an oligonucleotide probe to 5S rDNA, 45S and 5S rDNA clusters were localized for the first time on chromosomes of E. cilicica, E. hyemalis, and E. longistipitata. Major 45S rDNA clusters were identified on satellite chromosomes in all the species; in E. cilicica, minor clusters were also identified in the terminal regions of one metacentric chromosome pair. The number and distribution of 5S rDNA clusters is more specific. In E. cilicica, two major clusters were identified in the pericentromeric region of a pair of metacentric chromosomes. Two major clusters in the pericentromeric region of a pair of submetacentric chromosomes and two major clusters in the interstitial region of a pair of metacentric chromosomes were observed in E. longistipitata. E. hyemalis has many clusters of different sizes, localized mainly in the pericentromeric regions. Summarizing new data on the karyotype structure of E. sect. Eranthis and previously obtained data on E. sect. Shibateranthis allowed conclusions to be formed about the clear interspecific karyological differences of the genus Eranthis.

Comparative Cytogenetic Analysis of Diploid and Triploid Pacific Abalone, Haliotis discus hannai

Introduction: The Pacific abalone, Haliotis discus hannai, is one of the most commercially important marine shellfish in China. Cell engineering breeding is an important tool in abalone genetic breeding, and the triploids obtained through this method have high commercial value. However, current research mainly focuses on establishing induction methods and evaluating the growth traits of triploids, while there is a lack of basic research on triploid cytogenetics. Method: In this study, Cytogenetic analysis of triploid Haliotis discus hannai larvae (produced by chemical treatment) and diploid larvae was performed. Result: The results showed that triploid H. discus hannai had a chromosome number of 3n = 54, consisting of 30 metacentric (m) and 24 submetacentric (sm) chromosomes, while the diploids had a chromosome number of 2n = 36, consisting of 20 metacentric (m) and 16 submetacentric (sm) chromosomes. Notably, both triploids and diploids displayed variation in the number of NORs and/or their diameter. The average number of NORs in triploid was significantly higher than that in diploids (p < 0.05), but the average diameter of NORs of triploid was no significant different from that of diploid (p > 0.05). Additionally, 5S rDNA localization to 3 submetacentric chromosomes was observed in triploids, compared to 2 submetacentric chromosomes in diploids. The number of 18S rDNA sites displayed positional conservancy and quantitative variability in both diploids and triploids. Specifically, 18S rDNA was found at the end of the chromosome in both groups, with triploids exhibiting a significantly higher number of loci than diploids (p < 0.01). Conclusion: This study provides valuable insights into the cytogenetic characteristics of triploid H. discus hannai, which could facilitate further research on the stability of the chromosome set in this species.

Cytogenetic characteristics of invasive Corbicula fluminalis (Bivalvia: Cyrenidae) of the Northern Dvina River basin

The ploidy between invasive Corbicula lineages can be di-, tri-, and tetraploid. Currently, some invasive populations of this genus remain unaffected by cytogenetic studies. In this study, we determined the chromosome set of invasive C. fluminalis (O. F. Muller, 1774) from Northern European Russia. According to our results, the chromosome set C. fluminalis consists of 54 chromosomes, which can be divided into 18 groups of 3 phenotypically identical chromosomes. Among them we can distinguish 3 metacentric chromosomes, 15 submetacentric chromosomes and 36 subtelo-acrocentric chromosomes.

Karyotype and genome size variation in Delphinium subg. Anthriscifolium (Ranunculaceae).

Five taxa of Delphiniumsubg.Anthriscifolium have been karyologically studied through chromosome counting, chromosomal measurement, and karyotype symmetry. Each taxon that we investigated has a basic chromosome number of x = 8, D.anthriscifoliumvar.savatieri, D.anthriscifoliumvar.majus, D.ecalcaratum, and D.callichromum were diploid with 2n = 16, while D.anthriscifoliumvar.anthriscifolium was tetraploid with 2n = 32. Monoploid chromosome sets of the investigated diploid taxa contained 1 metacentric chromosome, 3 submetacentric chromosomes, and 4 subtelocentric chromosomes. Higher interchromosomal asymmetry (CVCL) was present in D.ecalcaratum and D.callichromum than in other taxa. The highest levels of intrachromosomal asymmetry (MCA) and heterogeneity in centromere position (CVCI) were found in D.anthriscifoliumvar.majus. Diploid and tetraploid genome sizes varied by 3.02-3.92 pg and 6.04-6.60 pg, respectively. Karyotype and genome size of D.anthriscifoliumvar.savatieri, D.anthriscifoliumvar.majus, D.callichromum, and D.ecalcaratum were reported for the first time. Finally, based on cytological and morphological data, the classification of Delphiniumanthriscifolium was revised.

New chromosomal data, karyotype asymmetry and polyploid variations of some Gundelia (Asteraceae) species from Turkey

The genus Gundelia is currently represented with 18 species, of which 16 are in Turkey. In genus Gundelia, the chromosomal data were reported from 12 species. In the present study, it is aimed to eliminate the deficiencies in the knowledge about chromosomal data of Gundelia species. In Genus Gundelia, only a single chromosome number had been detected as 2n=18 so far. The chromosome numbers of four species were reported here for the first time: G. armeniaca, G. cappadocica, G. siirtica, and G. tehranica. In addition, the polyploidy in the genus was rare and G. anatolica was identified as the first polyploid species. All karyotypes except G. tehranica were symmetrical, consisting of metacentric and submetacentric chromosomes. Secondary constrictions were observed in the distal regions of the long arms of the longest metacentric and submetacentric chromosomes. Thus, the chromosomal data of all Turkish Gundelia species were completed. In conclusion, the present study presented new data into the karyological records relating the karyotype evolution and interspecific relations of genus Gundelia.

Cytogenetic Study of Five Varieties of Callisia repens (Jacq.) L. (Commelinaceae) from Laos

Cytogenetical studies were carried out on five varieties of Callisia repens, i.e., turtle vine, green, pink lady, gold, and Bianca. The morphological characteristics of all five varieties differed in leaf shape and color of the plant. All five varieties have the same chromosome number, 2n = 12, and the fundamental number (NF) = 24. The number of metacentric (m), submetacentric (sm), and subtelocentric (st) chromosomes was related to the discrepancies between the various karyotypes that were found. The formula for each of the karyotypes was 2m + 2sm + 8st (turtle vine), 2m + 10st (green), 8m + 4st 14 (pink lady), 2m + 4sm + 6st (gold), and 2m + 2sm + 8st (Bianca). Therefore, all five strains had asymmetrical karyotypes. The chromosome number of C. repens has been reported previously, but this is the first report of karyotype variation among the varieties. Furthermore, principal component analysis (PCA) of the karyotype formula was able to distinguish C. repens ‘pink lady’, C. repens ‘green’, and C. repens ‘gold’, but it was unable to differentiate between C. repens ‘Bianca’ and C. repens ‘turtle vine’. Additionally, PCA conducted on the centromeric index (CI) and the leaf colors of the five varieties of C. repens successfully separated all of them. Therefore, the prominent morphological traits and karyotype information of the five varieties of C. repens from Laos can be used to distinguish between them.

Morphological Differentiation and Karyotypic Studies of the African Common Toad Sclerophrys (Bufo) Regularis (Reuss, 1833)

The study analyzed the morphological differentiation and karyotype among populations of the common toad, Sclerophrys (Bufo) regularis from six Local Government Areas in Ondo state. Variations in fifteen morphometric and qualitative characters in one hundred and seventy-one animals from six population samples were analyzed using univariate and multivariate statistics. Descriptives of sexes and correlation between morphological characters was also analyzed. Female toads had larger mean values of most of the morphological characters studied with weight contributing the largest variance. The chromosomes of twenty-four specimens of the toad were also studied using standard bone marrow smear techniques. A chromosome complement of 2n=20 was observed for this species. The chromosomes consists of nine pairs of metacentric and one pair of submetacentric chromosomes. The chromosomes based on centromeric position could be grouped into two - metacentric and submetacentric - and based on size, into three metacentric chromosomes; 1-4 which were large, metacentric chromosomes; 5-6 medium sized metacentric chromosomes, while 7-9 were small sized, and the last pair (10), submetacentric chromosomes were small. The fundamental number of this species is 40 and with no sex chromosomes or satellites reported, while bi-armed chromosomes were observed. Findings also showed that female individuals of the species weighed more than the male.

Chromosomal analysis of Sander lucioperca (L., 1758) (Perciformes: Percidae) from Turkey

Sander lucioperca (pikeperch) is a percid fish species of high commercial value and potential for being aquaculture in Turkey. However, karyological studies are deficient for population of Turkey. So, the aim of this study is to carry out diploid chromosome number, karyotype formula, fundamental arm number and chromosomal banding properties (with C-banding and Ag-NOR staining) of S. lucioperca. Specimens of S. lucioperca were captured from Konya, Turkey and alive specimens carried to the laboratory. Chromosome obtaining was provided by using air-drying technique from the head kidney. Chromosome slides were prepared and banding procedures were applied. Result of the analysis, diploid chromosome number was found as 48 and karyotype of the pikeperch consist of 32 biarmed and 16 uniarmed chromosomes. Constitutive heterochromatin regions were observed on the pericentromeres of some of the chromosomes. Ag-NORs were determined on one pair of submetacentric chromosome. This report is the first that determines chromosomal properties of S. lucioperca from Turkey. This study may contribute the cytogenetic information of this species.

Karyotype comparison and characterization of two cauliflower cultivars from Bangladesh

Two cauliflower cultivars were karyotyped for correct characterization after orcein staining. Both cultivars have a simple chromocenter type of interphase nuclei and a gradient type of prophase chromosomes, indicating that they descended from a common ancestor. In addition, both strains were found to have 2n=18 chromosomes with an almost identical range of chromosome lengths. In terms of overall length, the white snow cultivar is almost 7 m shorter than the fresh market cultivar, indicating the presence of chromatin length diversification between specimens. In none of the cases was there a noticeable gradual decrease in chromosome length. The metacentric and submetacentric chromosomes were observed in both samples examined. Apart from other karyotypic features, TF, Syi and AsK % indicate the moderately symmetrical nature of the karyotype. As a result, the two cultivars of cauliflower were moderately primitive in nature. The collection of this karyotypic data will aid in the authentic characterization of the two cauliflower cultivars, which is essential information for the breeding program.&#x0D; Jahangirnagar University J. Biol. Sci. 11(1 &amp; 2): 21-30, 2022 (June &amp; December)

Contributions of species Rineloricaria pentamaculata (Loricariidae:Loricariinae) in a karyoevolutionary context

Species of Rineloricaria demonstrate an interesting evolutionary history from a cytogenetic point of view, due to the occurrence of extensive variation in diploid number (2n=36 -70 chromosomes), with Robertsonian rearrangements mostly responsible for this karyotypic diversity. In this study we present the karyotypic data for a population of Rineloricaria pentamaculata, collected in the Itiz stream, a tributary of the Paraná River Basin (Paraná, Brazil), which exhibited 2n=56 chromosomes distributed in 8m/sm+48st/a (number fundamental equal to 64) and simple NOR system revealed by fluorescent in situ hybridization (FISH) with 18S rDNA probe, silver nitrate and positive C band, located on the first submetacentric chromosome pair (pair 5). In addition, the NOR pair showed a size heteromorphism for this region, rich in GC composition (positive CMA3). Clusters of 5S rDNA were located in 14 chromosomes and the FISH with a telomeric probe was used to map possible evidence of chromosomal fusions, however, it showed only telomeric sites. These results corroborate the data for the species R. pentamaculata and the genus Rineloricaria, showing that they are similar to most of the populations analyzed. About the cytogenetic data of R. pentamaculata, we reaffirm that most populations were conserved, but in those with derived characteristics, Robertsonian chromosomal rearrangements probably contributed to the karyotypic evolution of the group.

Widespread chromosomal rearrangements preceded genetic divergence in a monitor lizard, Varanus acanthurus (Varanidae)

Chromosomal rearrangements are often associated with local adaptation and speciation because they suppress recombination, and as a result, rearrangements have been implicated in disrupting gene flow. Although there is strong evidence to suggest that chromosome rearrangements are a factor in genetic isolation of divergent populations, the underlying mechanism remains elusive. Here, we applied an integrative cytogenetics and genomics approach testing whether chromosomal rearrangements are the initial process, or a consequence, of population divergence in the dwarf goanna, Varanus acanthurus. Specifically, we tested whether chromosome rearrangements are indicators of genetic barriers that can be used to identify divergent populations by looking at gene flow within and between populations with rearrangements. We found that gene flow was present between individuals with chromosome rearrangements within populations, but there was no gene flow between populations that had similar chromosome rearrangements. Moreover, we identified a correlation between reduced genetic variation in populations with a higher frequency of homozygous submetacentric individuals. These findings suggest that chromosomal rearrangements were widespread prior to divergence, and because we found populations with higher frequencies of submetacentric chromosomes were associated with lower genetic diversity, this could indicate that polymorphisms within populations are early indicators of genetic drift.