Revisiting the Karyotype Evolution of Neotropical Boid Snakes: A Puzzle Mediated by Chromosomal Fissions

The Boidae family is an ancient group of snakes widely distributed across the Neotropical region, where several biogeographic events contributed towards shaping their evolution and diversification. Most species of this family have a diploid number composed of 2n = 36; however, among Booidea families, the Boidae stands out by presenting the greatest chromosomal diversity, with 2n ranging between 36 and 44 chromosomes and an undifferentiated XY sex chromosome system. Here, we applied a comparative chromosome analysis using cross-species chromosome paintings in five species representing four Boidae genera, to decipher the evolutionary dynamics of some chromosomes in these Neotropical snakes. Our study included all diploid numbers (2n = 36, 40, and 44) known for this family and our comparative chromosomal mappings point to a strong evolutionary relationship among the genera Boa, Corallus, Eunectes, and Epicrates. The results also allowed us to propose the cytogenomic diversification that had occurred in this family: a process mediated by centric fissions, including fission events of the putative and undifferentiated XY sex chromosome system in the 2n = 44 karyotype, which is critical in solving the puzzle of the karyotype evolution of boid snakes.

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A new sympatric region for distinct karyotypic forms of Hoplias malabaricus (Pisces, Erythrinidae)

Brazilian Journal of Biology ◽

10.1590/s1519-69842006000200004 ◽

2006 ◽

Vol 66 (1b) ◽

pp. 205-210 ◽

Cited By ~ 13

Author(s):

G. G. Born ◽

L. A. C. Bertollo

Keyword(s):

Sex Difference ◽

Sex Chromosomes ◽

Diploid Number ◽

Sex Chromosome ◽

Minas Gerais ◽

Female Specimen ◽

Male Specimen ◽

Hoplias Malabaricus ◽

Sex Chromosome System ◽

Sympatric Cytotypes

Specimens of Hoplias malabaricus from Lagoa Carioca, an isolated lake of the Rio Doce State Park (state of Minas Gerais, Brazil), were cytogenetically studied. The diploid number was found to be constant, i.e., 2n = 42 chromosomes, although two karyotypic forms were found: karyotype A, characterized by 22M + 20SM chromosomes, observed only in a male specimen, and karyotype B, characterized by 24M + 16SM + 2ST and 24M + 17SM + 1ST chromosomes in female and male specimens, respectively. This sex difference found in karyotype B is related to an XX/XY sex chromosome system. Another female specimen of H. malabaricus, also carrying karyotype A, had previously been found in the same lake. The available data indicate that two sympatric cytotypes of H. malabaricus exist in the Lagoa Carioca, with cytotype A occurring at a lower frequency and differing from cytotype B by undifferentiated sex chromosomes.

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Comparative cytogenetics of two species of Dermanura (Chiroptera, Phyllostomidae) in Midwestern Brazil

Comparative Cytogenetics ◽

10.3897/compcytogen.v15i2.60577 ◽

2021 ◽

Vol 15 (2) ◽

pp. 89-99

Author(s):

Ricardo Firmino de Sousa ◽

Paulo Cesar Venere ◽

Karina de Cassia Faria

Keyword(s):

Diploid Number ◽

Constitutive Heterochromatin ◽

Sex Chromosome ◽

Type System ◽

Pericentromeric Region ◽

Morphological Characters ◽

Comparative Cytogenetics ◽

Taxonomic Implications ◽

Sex Chromosome System ◽

First Time

Dermanura Gervais, 1856 is represented by small frugivorous bats of the Stenodermatinae subfamily. The taxonomy of this group presents controversies and has been subject to changes, especially since the morphological characters evaluated have left gaps that are difficult to fill regarding good species characterization. Previous studies performed in Dermanura cinerea Gervais, 1856 found that the karyotype of this species has a diploid number of chromosomes equal to 30 and 56 autosomal arms. The objective of the present study was to describe, for the first time, the karyotypes of the species Dermanura anderseni (Osgood, 1916) and Dermanura gnoma (Handley, 1987) based on classical cytogenetic markers. For both species, the diploid number found was 2n = 30 and NFa = 56. Two pairs of chromosomes showed markings of the nucleolus organizing regions (AgNORs) in the species D. anderseni and only one pair in D. gnoma, differing from what has already been described for D. cinerea. The two species analyzed here also showed differences in the sex chromosome system, with D. gnoma showing a neo-XY type system while in D. anderseni the classic XY sexual system was observed. In both species, visualization of the constitutive heterochromatin occurred in the pericentromeric region of all chromosomes, as well as in the short arms of the subtelocentric chromosomes. The present work represents an important expansion of karyotypic information for the subfamily Stenodermatinae, bringing chromosomal features that are possible to use in the taxonomic implications of the group.

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Karyotypes of three species of Hyperophora Brunner von Wattenwyl, 1878 (Tettigoniidae, Phaneropterinae) enable morphologically similar species to be distinguished

Comparative Cytogenetics ◽

10.3897/compcytogen.v13i1.31803 ◽

2019 ◽

Vol 13 (1) ◽

pp. 87-93 ◽

Cited By ~ 1

Author(s):

Bruno Cansanção Silva ◽

Lucas Henrique Bonfim Souza ◽

Juliana Chamorro-Rengifo ◽

Douglas Araujo

Keyword(s):

Chromosome Number ◽

Diploid Number ◽

Sex Chromosome ◽

Acrocentric Chromosome ◽

Chromosome Morphology ◽

Similar Species ◽

Cerrado Biome ◽

Cytogenetic Studies ◽

Sex Chromosome System ◽

The Difference

Phaneropterinae is the largest subfamily of Tettigoniidae, distributed across the globe. There are few cytogenetic studies regarding this group, as in the case of the genus group Aniarae, which represents only two karyotyped species. The current study aims to analyze cytogenetically three species of Hyperophora Brunner von Wattenwyl, 1878 from Brazil. The male diploid number of Hyperophoraminor Brunner von Wattenwyl, 1891 and Hyperophoramajor Brunner von Wattenwyl, 1878 is 2n♂= 31, whereas Hyperophorabrasiliensis Brunner von Wattenwyl, 1878 has shown 2n♂= 29. These three species possess an X0 sex chromosome system and telo/acrocentric chromosome morphology. The only species found in the Pantanal biome, H.brasiliensis, can be chromosomally distinguished from the Cerrado biome species H.major and H.minor, due to the difference in chromosome number (2n♂= 29 and 2n♂= 31, respectively).

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A new Roncus species (Pseudoscorpiones: Neobisiidae) from Montseny Natural Park (Catalonia, Spain), with remarks on karyology

Zootaxa ◽

10.11646/zootaxa.1693.1.2 ◽

2008 ◽

Vol 1693 (1) ◽

pp. 27 ◽

Cited By ~ 6

Author(s):

JUAN A. ZARAGOZA ◽

FRANTI“EK ŠÿÁHLAVSKÝ

Keyword(s):

New Species ◽

Diploid Number ◽

Sex Chromosome ◽

Natural Park ◽

Y Chromosomes ◽

Sex Chromosome System ◽

Acrocentric Chromosomes

Roncus montsenyensis sp. nov. is described from Montseny Natural Park (Catalonia, Spain). The new species is geographically and morphologically close to Roncus cadinensis Zaragoza, 2007, but can be separated from it by palpal morphometrics, the chelal microsetae pattern and karyology. The diploid number was found to be 2n=16 in R. montsenyensis, with only biarmed chromosomes. The diploid number was found to be 2n=38 in R. cadinensis, with a predominance of acrocentric chromosomes. Both species possess the XY sex chromosome system and the X and Y chromosomes are only weakly differentiated.

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Snake W Sex Chromosome: The Shadow of Ancestral Amniote Super-Sex Chromosome

Cells ◽

10.3390/cells9112386 ◽

2020 ◽

Vol 9 (11) ◽

pp. 2386

Author(s):

Worapong Singchat ◽

Syed Farhan Ahmad ◽

Nararat Laopichienpong ◽

Aorarat Suntronpong ◽

Thitipong Panthum ◽

...

Keyword(s):

Sex Chromosomes ◽

Evolutionary Dynamics ◽

Sex Chromosome ◽

Chromosomal Rearrangements ◽

Chromosome Analysis ◽

Chromosome Conformation ◽

Principal Mechanism ◽

Squamate Reptiles ◽

Genomic Landscape ◽

Heteromorphic Sex Chromosomes

Heteromorphic sex chromosomes, particularly the ZZ/ZW sex chromosome system of birds and some reptiles, undergo evolutionary dynamics distinct from those of autosomes. The W sex chromosome is a unique karyological member of this heteromorphic pair, which has been extensively studied in snakes to explore the origin, evolution, and genetic diversity of amniote sex chromosomes. The snake W sex chromosome offers a fascinating model system to elucidate ancestral trajectories that have resulted in genetic divergence of amniote sex chromosomes. Although the principal mechanism driving evolution of the amniote sex chromosome remains obscure, an emerging hypothesis, supported by studies of W sex chromosomes of squamate reptiles and snakes, suggests that sex chromosomes share varied genomic blocks across several amniote lineages. This implies the possible split of an ancestral super-sex chromosome via chromosomal rearrangements. We review the major findings pertaining to sex chromosomal profiles in amniotes and discuss the evolution of an ancestral super-sex chromosome by collating recent evidence sourced mainly from the snake W sex chromosome analysis. We highlight the role of repeat-mediated sex chromosome conformation and present a genomic landscape of snake Z and W chromosomes, which reveals the relative abundance of major repeats, and identifies the expansion of certain transposable elements. The latest revolution in chromosomics, i.e., complete telomere-to-telomere assembly, offers mechanistic insights into the evolutionary origin of sex chromosomes.

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Chromosomal analysis of Centromochlus heckelii (Siluriformes: Auchenipteridae), with a contribution to Centromochlus definition

Neotropical Ichthyology ◽

10.1590/1982-0224-2020-0009 ◽

2020 ◽

Vol 18 (3) ◽

Author(s):

Samantha Kowalski ◽

Leonardo Marcel Paiz ◽

Maelin da Silva ◽

Amanda de Souza Machado ◽

Eliana Feldberg ◽

...

Keyword(s):

River Basin ◽

Chromosome Pair ◽

Diploid Number ◽

Sex Chromosome ◽

Chromosomal Analysis ◽

Amazon River Basin ◽

Terminal Position ◽

Chromosomal Markers ◽

Sex Chromosome System ◽

Acrocentric Chromosomes

ABSTRACT Historically, there are divergences in the species allocation between Centromochlus and Tatia. This study aimed to generate the first cytogenetic data about Centromochlus and, by analyzing a population of Centromochlus heckelii from the Amazon River basin, to contribute as evidence to a historical taxonomic dilemma. Diploid number of 46 chromosomes and a heteromorphic pair was found in the female karyotypes, thus characterizing a ZZ/ZW sex chromosome system. Pale blocks of heterochromatin were located in centromeric regions of some chromosomes; however, the exclusive female chromosome (W) is almost entirely heterochromatic. AgNORs were detected in terminal position on the short arms of one acrocentric pair in males and two chromosome pairs in females, the acrocentric plus the sex chromosome pair. Notable differences between Centromochlus heckelii and previous data about species of Tatia are: lower diploid number, presence of a sex chromosome system and multiple AgNORs in Centromochlus, while species of Tatia have simple AgNORs and the absence of acrocentric chromosomes. Results in this study show that chromosomal markers could contribute as evidence to taxonomic delimitation studies.

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A New Diploid Number and Sex Chromosome System for the Family Hersiliidae from the Mediterranean Region of Turkey

Pakistan Journal of Zoology ◽

10.17582/journal.pjz/2018.50.1.131.134 ◽

2018 ◽

Vol 50 (1) ◽

Cited By ~ 1

Author(s):

Ümit Kumbıçak ◽

Zübeyde Kumbıçak ◽

Gülnare Huseynli

Keyword(s):

Mediterranean Region ◽

Diploid Number ◽

Sex Chromosome ◽

The Family ◽

Sex Chromosome System ◽

The Mediterranean

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Interspecific chromosomal divergences in the genus Characidium (Teleostei: Characiformes: Crenuchidae)

Neotropical Ichthyology ◽

10.1590/s1679-62252010000100010 ◽

2010 ◽

Vol 8 (1) ◽

pp. 77-86 ◽

Cited By ~ 15

Author(s):

José Carlos Pansonato Alves ◽

Luiz Ricardo de Souza Paiva ◽

Claudio Oliveira ◽

Fausto Foresti

Keyword(s):

Chromosome Pair ◽

Diploid Number ◽

Constitutive Heterochromatin ◽

Sex Chromosome ◽

Way Of Life ◽

Geographical Isolation ◽

Relevant Role ◽

Sex Chromosome System ◽

Morphological Differences ◽

First Time

Karyotypes of seven fish species of the genus Characidium, three of them studied for the first time, were characterized using conventional cytogenetic techniques (Giemsa staining, Ag-NOR, and C-banding). All species presented a diploid number of 2n=50, with only metacentric and submetacentric chromosomes, as observed in all Characidium species studied. In two species cells with one to three B chromosomes were observed. All species analyzed have a single NOR-bearing chromosome pair with morphological differences among them. Characidium cf. zebra shows heterochromatic blocks restricted to the pericentromeric regions of all chromosomes denoting the absence of a sex chromosome system. On the other hand, the species Characidium lanei, C. pterostictum, C. lauroi, C. oiticicai, C. schubarti, and Characidium sp., besides presenting pericentromeric heterochromatic blocks, exhibited large interstitial and/or terminal heterochromatic blocks, and a ZZ/ZW sex chromosome system. The constitutive heterochromatin seems to play a relevant role in the chromosome differentiation process of the studied species, mainly in relation to the sex chromosomes. The geographical isolation of the rivers in which the species were sampled, associated with their way of life restricted to headwaters environments, may have favored the process of fixation of different karyotypes found in each of the analyzed species.

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Highly Rearranged Karyotypes and Multiple Sex Chromosome Systems in Armored Catfishes from the Genus Harttia (Teleostei, Siluriformes)

Genes ◽

10.3390/genes11111366 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1366

Author(s):

Geize Aparecida Deon ◽

Larissa Glugoski ◽

Marcelo Ricardo Vicari ◽

Viviane Nogaroto ◽

Francisco de Menezes Cavalcante Sassi ◽

...

Keyword(s):

Sex Chromosome ◽

Neotropical Region ◽

Valid Species ◽

Comparative Genomic ◽

Isolated Populations ◽

Shared Content ◽

Rdna Sites ◽

Number Variation ◽

Fish Group ◽

Sex Chromosome System

Harttia comprises an armored catfish genus endemic to the Neotropical region, including 27 valid species with low dispersion rates that are restricted to small distribution areas. Cytogenetics data point to a wide chromosomal diversity in this genus due to changes that occurred in isolated populations, with chromosomal fusions and fissions explaining the 2n number variation. In addition, different multiple sex chromosome systems and rDNA loci location are also found in some species. However, several Harttia species and populations remain to be investigated. In this study, Harttia intermontana and two still undescribed species, morphologically identified as Harttia sp. 1 and Harttia sp. 2, were cytogenetically analyzed. Harttia intermontana has 2n = 52 and 2n = 53 chromosomes, while Harttia sp. 1 has 2n = 56 and 2n = 57 chromosomes in females and males, respectively, thus highlighting the occurrence of an XX/XY1Y2 multiple sex chromosome system in both species. Harttia sp. 2 presents 2n = 62 chromosomes for both females and males, with fission events explaining its karyotype diversification. Chromosomal locations of the rDNA sites were also quite different among species, reinforcing that extensive rearrangements had occurred in their karyotype evolution. Comparative genomic hybridization (CGH) experiments among some Harttia species evidenced a shared content of the XY1Y2 sex chromosomes in three of them, thus pointing towards their common origin. Therefore, the comparative analysis among all Harttia species cytogenetically studied thus far allowed us to provide an evolutionary scenario related to the speciation process of this fish group.

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