Rapid chromosomal evolution in the bush-cricket Gonatoxia helleri Hemp, 2016 (Orthoptera, Phaneropterinae)

Gonatoxia helleri Hemp, 2016 is one of the most widespread bush-crickets of the genus Gonatoxia Karsch, 1889 in East Africa. This species with seven large chromosomes (2n♂ = 7) differs from other representatives of the genus Gonatoxia drastically by its reduced chromosome number, the asymmetrical karyotype including karyomorphs rarely found in tettigoniids, as well as in irregularities in the course of meiosis. To better understand the origin of such an exceptional karyotype, chromosomes of 29 specimens from four populations/localities were studied using classical techniques, such as C-banding, silver impregnation, fluorochrome double staining and fluorescence in situ hybridization (FISH) technique with 18S rDNA and (TTAGG)n telomeric probes. FISH showed many 18S rDNA loci as well as interstitial telomeric sequences, where chromosome morphology varied in these components in terms of quantity and distribution. The 18S rDNA loci coincided with active NORs and C-banding patterns. We suggest that a combination of Robertsonian rearrangements and/or multiple common tandem fusions involving the same chromosomes contributed to the formation of this karyotype/karyomorphs. The results are the first step towards a better understanding of chromosomal reorganization and evolution within the genus Gonatoxia. Low chromosome number, together with the incidence of chromosomal polymorphism that is higher in G. helleri than previously reported in bush-crickets, implies that this species can be a valuable new model for cytogenetic and speciation studies. Our findings suggest that chromosomal translocations lead to diversification and speciation in this species and could be the driving force of adaptive radiation.

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Cytogenetically Elusive Sex Chromosomes in Scincoidean Lizards

International Journal of Molecular Sciences ◽

10.3390/ijms22168670 ◽

2021 ◽

Vol 22 (16) ◽

pp. 8670

Author(s):

Alexander Kostmann ◽

Barbora Augstenová ◽

Daniel Frynta ◽

Lukáš Kratochvíl ◽

Michail Rovatsos

Keyword(s):

Sex Chromosomes ◽

Chromosome Morphology ◽

Comparative Genomic ◽

Morphological Divergence ◽

Telomeric Sequences ◽

Molecular Cytogenetic ◽

Interstitial Telomeric Sequences ◽

Rdna Loci ◽

Cytogenetic Methods

The lizards of the species-rich clade Scincoidea including cordylids, gerrhosaurids, skinks, and xantusiids, show an almost cosmopolitan geographical distribution and a remarkable ecological and morphological divergence. However, previous studies revealed limited variability in cytogenetic traits. The sex determination mode was revealed only in a handful of gerrhosaurid, skink, and xantusiid species, which demonstrated either ZZ/ZW or XX/XY sex chromosomes. In this study, we explored the karyotypes of six species of skinks, two species of cordylids, and one gerrhosaurid. We applied conventional and molecular cytogenetic methods, including C-banding, fluorescence in situ hybridization with probes specific for telomeric motifs and rDNA loci, and comparative genomic hybridization. The diploid chromosome numbers are rather conserved among these species, but the chromosome morphology, the presence of interstitial telomeric sequences, and the topology of rDNA loci vary significantly. Notably, XX/XY sex chromosomes were identified only in Tiliqua scincoides, where, in contrast to the X chromosome, the Y chromosome lacks accumulations of rDNA loci. We confirm that within the lizards of the scincoidean clade, sex chromosomes remained in a generally poor stage of differentiation.

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Extraordinary and extensive karyotypic variation: A 48-fold range in chromosome number in the gall-inducing scale insect Apiomorpha (Hemiptera: Coccoidea: Eriococcidae)

Genome ◽

10.1139/g99-121 ◽

2000 ◽

Vol 43 (2) ◽

pp. 255-263 ◽

Cited By ~ 14

Author(s):

Lyn G Cook

Keyword(s):

Chromosome Number ◽

Chromosomal Rearrangements ◽

Chromosomal Polymorphism ◽

Chromosomal Evolution ◽

Scale Insect ◽

Closely Related Species ◽

Host Genus ◽

Species Complexes ◽

Species Groups ◽

Karyotypic Variation

Chromosome number reflects strong constraints on karyotype evolution, unescaped by the majority of animal taxa. Although there is commonly chromosomal polymorphism among closely related taxa, very large differences in chromosome number are rare. This study reports one of the most extensive chromosomal ranges yet reported for an animal genus. Apiomorpha Rübsaamen (Hemiptera: Coccoidea: Eriococcidae), an endemic Australian gall-inducing scale insect genus, exhibits an extraordinary 48-fold variation in chromosome number with diploid numbers ranging from 4 to about 192. Diploid complements of all other eriococcids examined to date range only from 6 to 28. Closely related species of Apiomorpha usually have very different karyotypes, to the extent that the variation within some species- groups is as great as that across the entire genus. There is extensive chromosomal variation among populations within 17 of the morphologically defined species of Apiomorpha indicating the existence of cryptic species-complexes. The extent and pattern of karyotypic variation suggests rapid chromosomal evolution via fissions and (or) fusions. It is hypothesized that chromosomal rearrangements in Apiomorpha species may be associated with these insects' tracking the radiation of their speciose host genus, Eucalyptus. Key words: Apiomorpha, cytogenetics, chromosomal evolution, holocentric.

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Cytogenetics of Four Species of the Green Clade Aplastodiscus Lutz, 1950 (Anura: Cophomantinae): New Insights into the Chromosomal Evolution of the Genus

Cytogenetic and Genome Research ◽

10.1159/000512816 ◽

2021 ◽

pp. 1-7

Author(s):

Késsia L. Souza ◽

Marco A. Peixoto ◽

Cynthia A.V. Barreto ◽

Renato N. Feio ◽

Jorge A. Dergam

Keyword(s):

18S Rdna ◽

Chromosome Pair ◽

Chromosomal Evolution ◽

Chromosome Morphology ◽

Small Chromosome ◽

Tree Frog ◽

Chromosome Fusion ◽

Clade B ◽

Number Variation ◽

Molecular Cytogenetic Techniques

The tree frog Aplastodiscus is a Neotropical taxon that encompasses 15 species in the Atlantic forest biome, with one isolated species in the Central Brazilian Cerrado. To date, only 8 species have been karyotyped, showing high levels of diploid number variation, which allowed clustering species in chromosome number groups: 2n = 24 (Aplastodiscus perviridis group), 2n = 22 (Aplastodiscus albofrenatus group), 2n = 20, and 2n = 18 (both within Aplastodiscus albosignatus group). This study aims to report karyotypic information on 4 species from the last 2 groups using classical and molecular cytogenetic techniques and hypothesize chromosomal evolutionary trends within the species groups. Aplastodiscus weygoldti showed 2n = 22; Ag-NOR and FISH 18S rDNA signals were located in the interstitial region of the short arms of chromosome pair 6. Aplastodiscus cavicola, Aplastodiscus sp. 4, and Aplastodiscus sp. 6 showed 2n = 18; Ag-NOR and FISH 18S rDNA bands were located in the terminal region of the long arm of chromosome pair 9. Our results support multiple and independent chromosome fusion events within Aplastodiscus, including a new chromosome fission event. Ag-NOR and FISH 18S rDNA patterns were restricted to the small chromosome pairs, similar to the other species within this genus, and confirm overall chromosome morphology conservation among the genera of Cophomantinae.

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Distribution of Telomeric Sequences (TTAGGG)n in Rearranged Chromosomes of Phyllotine Rodents (Cricetidae, Sigmodontinae)

Cytogenetic and Genome Research ◽

10.1159/000444602 ◽

2015 ◽

Vol 147 (4) ◽

pp. 247-252 ◽

Cited By ~ 5

Author(s):

Cecilia Lanzone ◽

Carolina Labaroni ◽

Natalia Suárez ◽

Daniela Rodríguez ◽

Macarena L. Herrera ◽

...

Keyword(s):

Sex Chromosomes ◽

Chromosomal Evolution ◽

Robertsonian Translocations ◽

Telomeric Sequences ◽

Molecular Cytogenetic ◽

Interstitial Telomeric Sequences ◽

Robertsonian Rearrangements ◽

Recent Origin ◽

Chromosome Fusions ◽

Molecular Cytogenetic Techniques

Phyllotines are sigmodontine rodents endemic to South America with broad genetic variability, Robertsonian polymorphisms being the most frequent. Moreover, this taxon includes a species with multiple sex chromosomes, which is infrequent in mammals. However, molecular cytogenetic techniques have never been applied to phyllotines to elucidate their karyotypic evolution. We studied the chromosomes of 4 phyllotine species using FISH with a pantelomeric probe (TTAGGG)n. Graomys griseoflavus, Eligmodontia puerulus, and E. morgani are polymorphic for Robertsonian translocations, whereas Salinomys delicatus possesses XX/ XY1Y2 sex chromosomes. Telomeric signals were detected at both ends of all chromosomes of the studied species. In S. delicatus interstitial telomeric sequences (ITS) were observed in the 3 major chromosome pairs, which are equidistant from one of the telomeres in these chromosomes. These results suggest that ITS are important in the reshuffling of the highly derived karyotype of S. delicatus. Considering the phylogeny of phyllotines, the Robertsonian rearrangements of G. griseoflavus, E. puerulus, and E. morgani possibly represent chromosome fusions which have occurred independently. The pericentromeric regions of the biarmed chromosomes of these species do not contain telomeric sequences characteristic for strict fusions of recent origin, suggesting a common pattern of telomeric repeat loss during chromosomal evolution of these rodents.

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Chromosome spreading of the (TTAGGG)n repeats in the Pipa carvalhoi Miranda-Ribeiro, 1937 (Pipidae, Anura) karyotype

Comparative Cytogenetics ◽

10.3897/compcytogen.v13i3.35524 ◽

2019 ◽

Vol 13 (3) ◽

pp. 297-309 ◽

Cited By ~ 4

Author(s):

Michelle Louise Zattera ◽

Luana Lima ◽

Iraine Duarte ◽

Deborah Yasmin de Sousa ◽

Olívia Gabriela dos Santos Araújo ◽

...

Keyword(s):

Chromosome Pair ◽

Diploid Number ◽

Centromeric Region ◽

Chromosomal Evolution ◽

Unique Combination ◽

Significant Component ◽

Aquatic Life ◽

Telomeric Sequences ◽

Interstitial Telomeric Sequences ◽

Chromosome Spreading

Pipidae is a clade of Anura that diverged relatively early from other frogs in the phylogeny of the group. Pipids have a unique combination of morphological features, some of which appear to represent a mix of adaptations to aquatic life and plesiomorphic characters of Anura. The present study describes the karyotype of Pipa carvalhoi Miranda-Ribeiro, 1937, including morphology, heterochromatin distribution, and location of the NOR site. The diploid number of P. carvalhoi is 2n=20, including three metacentric pairs (1, 4, 8), two submetacentric (2 and 7), three subtelocentric (3, 5, 6), and two telocentric pairs (9 and 10). C-banding detected centromeric blocks of heterochromatin in all chromosome pairs and the NOR detected in chromosome pair 9, as confirmed by FISH using the rDNA 28S probe. The telomeric probes indicated the presence of interstitial telomeric sequences (ITSs), primarily in the centromeric region of the chromosomes, frequently associated with heterochromatin, suggesting that these repeats are a significant component of this region. The findings of the present study provide important insights for the understanding of the mechanisms of chromosomal evolution in the genus Pipa, and the diversification of the Pipidae as a whole.

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Extensive Amplification of Telomeric Repeats in the Karyotypically Highly Diverse African Pygmy Mice

Cytogenetic and Genome Research ◽

10.1159/000478297 ◽

2017 ◽

Vol 152 (2) ◽

pp. 55-64 ◽

Cited By ~ 4

Author(s):

Victor Colomina ◽

Josette Catalan ◽

Janice Britton-Davidian ◽

Frédéric Veyrunes

Keyword(s):

Mammalian Species ◽

Chromosomal Rearrangements ◽

Replication Timing ◽

Pericentromeric Region ◽

Chromosomal Evolution ◽

Telomeric Repeats ◽

Telomeric Sequences ◽

Interstitial Telomeric Sequences ◽

Karyotypic Diversity ◽

The One

Telomeres are ribonucleoprotein structures protecting the physical ends of eukaryotic chromosomes. However, telomeric sequences can also occur at non-terminal regions of chromosomes, forming the so-called interstitial telomeric sequences (ITSs). Some ITSs are considered as relics of past chromosomal rearrangements and as such provide important insights into karyotype evolution. By FISH, we explored the distribution of telomeric motifs in the genome of a complex of mammalian species that has long been recognized for its extraordinary karyotypic diversity: the African pygmy mice. This survey involved 5 species, representing 10 highly diverse karyotypes with or without autosomal and sex-autosome robertsonian (Rb) fusions. The study revealed that in species with an ancestral-like karyotype (i.e., no fusions; Mus mattheyi and M. indutus), only terminal telomeres were observed, whereas in species experiencing intense chromosomal evolution (e.g., M. minutoides, M. musculoides), a large amplification of telomeric repeats was also identified in the pericentromeric region of acrocentrics and most metacentrics. We concluded that (i) the mechanism of Rb fusion in the African pygmy mice is different than the one highlighted in the house mouse; (ii) the intensity of the ITS hybridization signal could be a signature of the age of formation of the Rb fusion; (iii) the large amplification of pericentromeric telomeric sequences in acrocentrics may mediate the formation of Rb fusions, and (iv) the ITSs on the sex-autosome fusion Rb(X.1) may participate to the insulation buffer between the sexual and autosomal arms to prevent X inactivation from spreading and silencing autosomal genes and allow the independent regulation of replication timing of both segments.

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Chromosomal Analysis of Ctenolucius hujeta Valenciennes, 1850 (Characiformes): A New Piece in the Chromosomal Evolution of the Ctenoluciidae

Cytogenetic and Genome Research ◽

10.1159/000515456 ◽

2021 ◽

pp. 1-8

Author(s):

José Souza ◽

Erika Guimarães ◽

Vanessa Pinheiro-Figliuolo ◽

Marcelo B. Cioffi ◽

Luiz A.C. Bertollo ◽

...

Keyword(s):

Chromosome Number ◽

5S Rdna ◽

Chromosomal Evolution ◽

Freshwater Fishes ◽

Rdna Genes ◽

Telomeric Sequences ◽

Generic Status ◽

Cytogenetic Studies ◽

Chromosomal Markers ◽

Unusual Phenomenon

Ctenoluciidae (Characiformes), a family of freshwater fishes, comprises 2 genera, Ctenolucius and Boulengerella, with 7 recognized species. Up to now, only species of the genus Boulengerella have been subjected to cytogenetic studies. Here, we investigated the karyotype and other cytogenetic features of pike characin, Ctenolucius hujeta, using conventional (Giemsa staining, C-banding, Ag-NOR staining) and molecular (rDNA, telomeric sequences, and fiber-FISH mapping) procedures. This species has a diploid chromosome number of 2n = 36, and a karyotype composed of 12m + 20sm + 4a and FN = 68, similar to that found in Boulengerella species. However, differences regarding the number and distribution of several chromosomal markers support a distinct generic status. Colocalization of the 18S and 5S rDNA genes is an exclusive characteristic of the C. hujeta genome, with an interspersed distribution in the chromosomal fiber, an unusual phenomenon among eukaryotes. Additionally, our results support the view that Ctenoluciidae and Lebiasinidae families are closely related.

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Detection of interstitial telomeric sequences in the Arctic charr (Salvelinus alpinus) (Teleostei: Salmonidae)

Genome ◽

10.1139/g11-073 ◽

2012 ◽

Vol 55 (1) ◽

pp. 26-32 ◽

Cited By ~ 6

Author(s):

K. Pomianowski ◽

M. Jankun ◽

K. Ocalewicz

Keyword(s):

Chromosome Number ◽

Brook Trout ◽

Lake Trout ◽

Salvelinus Alpinus ◽

Arctic Charr ◽

Interindividual Variation ◽

The Arctic ◽

Telomeric Sequences ◽

Interstitial Telomeric Sequences

Highly polymorphic Arctic charr ( Salvelinus alpinus Linnaeus, 1758) chromosomes were studied using conventional and molecular methods. The diploid chromosome number in the studied individuals was 2n = 81 or 2n = 82, with a fundamental arm number (NF) = 100. These differences are due to Robertsonian fusions. Interindividual variation in the number and size of DAPI and CMA3 positively stained chromatin sites was observed in studied specimens. In the case of two individuals, the subtelomeric region of the long arm (q) of the largest acrocentric chromosome (chromosome number 10) was positively stained by CMA3 fluorochrome. Both primed in situ labelling (PRINS) and fluorescence in situ hybridization (FISH) revealed that this CMA3-positive region was flanked by telomeric sequences. Previously, the subterminal position of interstitial telomeric sequences located in the vicinity of the CMA3-positive guanine-rich chromatin have been described in two other Salvelinus species, brook trout ( Salvelinus fontinalis ) and lake trout ( Salvelinus namaycush ). Moreover, multichromosomal location and variation in size of CMA3 bands have been observed in various Salvelinus taxa, including fishes with internally located telomeric sequences. These results suggest that relocation of CMA3-positive chromatin segments in these species may be facilitated by flanking interstitial telomeric sequences (ITSs).

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Comparative Cytogenetics of Omophoita abbreviata and O. aequinoctialis (Coleoptera, Chrysomelidae, Alticini) from the Adolpho Ducke Forest Reserve in Brazilian Amazonia: Intrapopulation Variation in Karyotypes

Cytogenetic and Genome Research ◽

10.1159/000490835 ◽

2018 ◽

Vol 156 (1) ◽

pp. 56-64 ◽

Cited By ~ 1

Author(s):

Leonardo G. Goll ◽

Roberto F. Artoni ◽

Maria C. Gross ◽

Lucas R.A. Mello ◽

Maria P.B. Coelho ◽

...

Keyword(s):

Flea Beetle ◽

Chromosomal Evolution ◽

Typical Feature ◽

Chromosome Morphology ◽

Comparative Cytogenetics ◽

Forest Reserve ◽

Telomeric Sequences ◽

Intrapopulation Variation ◽

Central Amazonia ◽

Intrapopulational Variation

The chromosomes of 2 flea beetle species from central Amazonia, Omophoita abbreviata and O. aequinoctialis (Alticini), were investigated through analysis of meiotic and mitotic cells. These species belong to the subtribe Oedionychina, a taxon that has unique cytogenetic features, such as giant sex chromosomes which are aligned at a distance during meiosis I (asynaptic). O. abbreviata and O. aequinoctialis have a meiotic formula of 10II + X + y, which is predominant in this subtribe. While the species of the genus Omophoita possess a relatively stable karyotype, a typical feature for Oedionychina, the present study identified inter- and intrapopulational variation in chromosome morphology, constitutive heterochromatin, and the presence and number of B chromosomes in O. aequinoctialis. In addition, FISH mapping of telomeric sequences revealed signals in the collochores, raising several questions on the chromosomal evolution in this group.

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Chromosome Painting in Tyrant Flycatchers Confirms a Set of Inversions Shared by Oscines and Suboscines (Aves, Passeriformes)

Cytogenetic and Genome Research ◽

10.1159/000486975 ◽

2017 ◽

Vol 153 (4) ◽

pp. 205-212 ◽

Cited By ~ 3

Author(s):

Benilson S. Rodrigues ◽

Rafael Kretschmer ◽

Ricardo J. Gunski ◽

Analia D.V. Garnero ◽

Patricia C.M. O'Brien ◽

...

Keyword(s):

18S Rdna ◽

Chromosome Painting ◽

Constitutive Heterochromatin ◽

Neotropical Region ◽

Telomeric Sequences ◽

General Terms ◽

Interstitial Telomeric Sequences ◽

Cytogenetic Studies ◽

Pericentric Inversions ◽

Conventional Cytogenetics

Tyrannidae is the largest family of Passeriformes in the Neotropical region. However, despite an interesting chromosomal diversity, there are only few cytogenetic studies of this family, and most of these are based on conventional cytogenetics. Hence, we analyzed here the chromosomal diversity and karyotypical evolution of this group by chromosome painting in 3 different species - Pitangus sulphuratus, Serpophaga subcristata, and Satrapa icterophrys - and make comparisons with previous data. In addition to chromosome painting with Gallus gallus (GGA) and Leucopternis albicollis (LAL) probes, karyotypes were analyzed by conventional staining, C-banding, and FISH with 18S rDNA and telomeric probes. Although this family is characterized by extensive chromosomal variation, we found similar karyotypes and diploid numbers ranging from 2n = 80 in P. sulphuratus to 2n = 82 in S. subcristata and S. icterophrys. Constitutive heterochromatin was located centromerically in all 3 species. Clusters of 18S rDNA were present in 1 pair of microchromosomes, except in S. subcristata, where 2 pairs of microchromosomes were labeled. No interstitial telomeric sequences were detected. GGA and LAL whole-chromosome probes revealed the occurrence of fissions and both paracentric and pericentric inversions commonly seen in other Passeriformes. In general terms, tyrants show the typical karyotype found in Passeriformes, suggesting that the observed rearrangements occurred before the division of the suborders Oscines and Suboscines.

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