Latest Articles from Comparative Cytogenetics Latest 7 Articles from Comparative Cytogenetics https://compcytogen.pensoft.net/ Fri, 29 Mar 2024 07:07:10 +0200 Pensoft FeedCreator https://compcytogen.pensoft.net/i/logo.jpg Latest Articles from Comparative Cytogenetics https://compcytogen.pensoft.net/ Detection of cryptic diversity in lizards (Squamata) from two Biosphere Reserves in Mesoamerica https://compcytogen.pensoft.net/article/57765/ Comparative Cytogenetics 14(4): 613-638

DOI: 10.3897/CompCytogen.v14.i4.57765

Authors: Riccardo Castiglia, Oscar Alberto Flores-Villela, Alexandra M. R. Bezerra, Ekaterina Gornung, Flavia Annesi, Luis Antonio Muñoz-Alonso, Emanuela Solano

Abstract: A combined approach based on karyology and DNA taxonomy allowed us to characterize the taxonomic peculiarities in 10 Mesoamerican lizard species, belonging to six genera and five families, inhabiting two Biosphere Reserve in Chiapas, Mexico: La Sepultura Biosphere Reserve, and Montes Azules Biosphere. The karyotypes of four species, Phyllodactylus sp. 3 (P. tuberculosus species group) (2n = 38), Holcosus festivus (Lichtenstein et von Martens, 1856) (2n = 50), Anolis lemurinus Cope, 1861 (2n = 40), and A. uniformis Cope, 1885 (2n = 29–30) are described for the first time, the last one showing a particular X1X1X2X2/X1X2Y condition. In Aspidoscelis deppii (Wiegmann, 1834) (2n = 50) and Anolis capito Peters, 1863 (2n = 42), we found a different karyotype from the ones previously reported for these species. Moreover, in A. capito, the cytogenetic observation is concurrent with a considerable genetic divergence (9%) at the studied mtDNA marker (MT-ND2), which is indicative of a putative new cryptic species. The skink Scincella cherriei (Cope, 1893), showed high values of genetic divergence (5.2% at 16S gene) between the specimens from Montes Azules and those from Costa Rica and Nicaragua, comparable to the values typical of sister species in skinks. A lower level of genetic divergence, compatible with an intraspecific phylogeographic structure, has been identified in Lepidophyma flavimaculatum Duméril, 1851. These new data identify taxa that urgently require more in-depth taxonomic studies especially in these areas where habitat alteration is proceeding at an alarming rate.

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Research Article Tue, 22 Dec 2020 07:21:27 +0200
Identification of sex chromosomes in Eremias velox (Lacertidae, Reptilia) using lampbrush chromosome analysis https://compcytogen.pensoft.net/article/34116/ Comparative Cytogenetics 13(2): 121-132

DOI: 10.3897/CompCytogen.v13i2.34116

Authors: Artem P. Lisachov, Svetlana A. Galkina, Alsu F. Saifitdinova, Svetlana A. Romanenko, Daria A. Andreyushkova, Vladimir A. Trifonov, Pavel M. Borodin

Abstract: Reptiles are good objects for studying the evolution of sex determination, since they have different sex determination systems in different lineages. Lacertid lizards have been long-known for possessing ZZ/ZW type sex chromosomes. However, due to morphological uniformity of lacertid chromosomes, the Z chromosome has been only putatively cytologically identified. We used lampbrush chromosome (LBC) analysis and FISH with a W-specific probe in Eremias velox (Pallas, 1771) to unequivocally identify the ZW bivalent and investigate its meiotic behavior. The heterochromatic W chromosome is decondensed at the lampbrush stage, indicating active transcription, contrast with the highly condensed condition of the lampbrush W chromosomes in birds. We identified the Z chromosome by its chiasmatic association with the W chromosome as chromosome XIII of the 19 chromosomes in the LBC karyotype. Our findings agree with previous genetic and genomic studies, which suggested that the lacertid Z chromosome should be one of the smaller macrochromosomes.

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Research Article Tue, 14 May 2019 13:07:10 +0300
Immunocytological analysis of meiotic recombination in two anole lizards (Squamata, Dactyloidae) https://compcytogen.pensoft.net/article/10916/ Comparative Cytogenetics 11(1): 129-141

DOI: 10.3897/CompCytogen.v11i1.10916

Authors: Artem P. Lisachov, Vladimir A. Trifonov, Massimo Giovannotti, Malcolm A. Ferguson-Smith, Pavel M. Borodin

Abstract: Although the evolutionary importance of meiotic recombination is not disputed, the significance of interspecies differences in the recombination rates and recombination landscapes remains under-appreciated. Recombination rates and distribution of chiasmata have been examined cytologically in many mammalian species, whereas data on other vertebrates are scarce. Immunolocalization of the protein of the synaptonemal complex (SYCP3), centromere proteins and the mismatch-repair protein MLH1 was used, which is associated with the most common type of recombination nodules, to analyze the pattern of meiotic recombination in the male of two species of iguanian lizards, Anolis carolinensis Voigt, 1832 and Deiroptyx coelestinus (Cope, 1862). These species are separated by a relatively long evolutionary history although they retain the ancestral iguanian karyotype. In both species similar and extremely uneven distributions of MLH1 foci along the macrochromosome bivalents were detected: approximately 90% of crossovers were located at the distal 20% of the chromosome arm length. Almost total suppression of recombination in the intermediate and proximal regions of the chromosome arms contradicts the hypothesis that “homogenous recombination” is responsible for the low variation in GC content across the anole genome. It also leads to strong linkage disequilibrium between the genes located in these regions, which may benefit conservation of co-adaptive gene arrays responsible for the ecological adaptations of the anoles.

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Research Article Mon, 6 Mar 2017 12:39:51 +0200
Microchromosome polymorphism in the sand lizard, Lacerta agilis Linnaeus, 1758 (Reptilia, Squamata) https://compcytogen.pensoft.net/article/7655/ Comparative Cytogenetics 10(3): 387-399

DOI: 10.3897/CompCytogen.v10i3.7655

Authors: Artem P. Lisachov, Pavel M. Borodin

Abstract: Most true lizards (Lacertidae) share a conservative karyotype, consisting of 18 pairs of macrochromosomes and one microchromosome pair. Homeologues of the microchromosome are present in other squamates and even in chickens. No structural autosomal microchromosome polymorphisms have been described previously in lizards. We found homozygous and heterozygous carriers of a microchromosome variant in a Siberian population of the sand lizard, Lacerta agilis Linnaeus, 1758. The variant microchromosome was almost twice as long as the standard one. In heterozygotes at pachytene, the microchromosomes firstly pair in proximal regions and the central part of the longer axial element undergoes foldback synapsis, then its distal region pairs with the distal region of the standard partner. At metaphase-I, the heteromorphic microchromosome bivalents have a proximal chiasma. The content of the additional segment was Ag-NOR, C-like DAPI, CMA3 negative. FISH with telomere PNA probe did not detect interstitial (TTAGGG)n sequences in the heteromorphic and any other bivalents. Both homo- and heterozygous carriers were phenotypically normal. The presence of homozygotes shows that heterozygotes are fertile. Reduction in the number of microchromosomes is a clear trend in squamate evolution, as a result of microchromosomes fusing together or with macrochromosomes. Our findings indicate that gaining additional DNA may lead to a transformation of microchromosomes into small macrochromosomes without fusion.

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Research Article Thu, 8 Sep 2016 11:46:51 +0300
Differential repetitive DNA composition in the centromeric region of chromosomes of Amazonian lizard species in the family Teiidae https://compcytogen.pensoft.net/article/7081/ Comparative Cytogenetics 10(2): 203-217

DOI: 10.3897/CompCytogen.v10i2.7081

Authors: Natalia D. M. Carvalho, Edson Carmo, Rogerio O. Neves, Carlos Henrique Schneider, Maria Claudia Gross

Abstract: Differences in heterochromatin distribution patterns and its composition were observed in Amazonian teiid species. Studies have shown repetitive DNA harbors heterochromatic blocks which are located in centromeric and telomeric regions in Ameiva ameiva (Linnaeus, 1758), Kentropyx calcarata (Spix, 1825), Kentropyx pelviceps (Cope, 1868), and Tupinambis teguixin (Linnaeus, 1758). In Cnemidophorus sp.1, repetitive DNA has multiple signals along all chromosomes. The aim of this study was to characterize moderately and highly repetitive DNA sequences by Cot1-DNA from Ameiva ameiva and Cnemidophorus sp.1 genomes through cloning and DNA sequencing, as well as mapping them chromosomally to better understand its organization and genome dynamics. The results of sequencing of DNA libraries obtained by Cot1-DNA showed that different microsatellites, transposons, retrotransposons, and some gene families also comprise the fraction of repetitive DNA in the teiid species. FISH using Cot1-DNA probes isolated from both Ameiva ameiva and Cnemidophorus sp.1 showed these sequences mainly located in heterochromatic centromeric, and telomeric regions in Ameiva ameiva, Kentropyx calcarata, Kentropyx pelviceps, and Tupinambis teguixin chromosomes, indicating they play structural and functional roles in the genome of these species. In Cnemidophorus sp.1, Cot1-DNA probe isolated from Ameiva ameiva had multiple interstitial signals on chromosomes, whereas mapping of Cot1-DNA isolated from the Ameiva ameiva and Cnemidophorus sp.1 highlighted centromeric regions of some chromosomes. Thus, the data obtained showed that many repetitive DNA classes are part of the genome of Ameiva ameiva, Cnemidophorus sp.1, Kentroyx calcarata, Kentropyx pelviceps, and Tupinambis teguixin, and these sequences are shared among the analyzed teiid species, but they were not always allocated at the same chromosome position.

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Research Article Wed, 6 Apr 2016 10:12:08 +0300
Karyological evidence for diversification of Italian slow worm populations (Squamata, Anguidae) https://compcytogen.pensoft.net/article/1796/ Comparative Cytogenetics 7(3): 217-227

DOI: 10.3897/compcytogen.v7i3.5398

Authors: Marcello Mezzasalma, Fabio Maria Guarino, Gennaro Aprea, Agnese Petraccioli, Angelica Crottini, Gaetano Odierna

Abstract: A karyological analysis on six Italian populations the slow worm (Anguis veronensis Pollini, 1818) was performed and their genetic differentiation at the mitochondrial 16S rRNA gene fragment from a Spanish sample has been assessed. The Italian populations were karyologically uniform, all showing 2n= 44 elements, of which 20 were macrochromosomes and 24 microchromosomes. Comparison with literature data on Central European populations showed a difference on the morphology of the 10th chromosome pair: submetacentric in Italian populations and telocentric in the Central European ones. Our analysis showed the presence of a fragile site on chromosomes of this pair, suggesting its propensity for structural rearrangements. Analysis of the 16S rRNA gene fragment showed uniformity among Italian populations (uncorrected genetic distance of 0.4%), and their genetic distinctness from the Spanish individual (uncorrected genetic distance of 4.2%). Our results confirm the existence of two different Anguis fragilis Linnaeus, 1758 lineages, each one characterized by a different cytotype.

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Research Article Mon, 23 Sep 2013 00:00:00 +0300
The first cytogenetic description of Euleptes europaea (Gené, 1839) from Northern Sardinia reveals the highest diploid chromosome number among sphaerodactylid geckos (Sphaerodactylidae, Squamata) https://compcytogen.pensoft.net/article/1789/ Comparative Cytogenetics 7(2): 153-161

DOI: 10.3897/compcytogen.v7i2.4881

Authors: Ekaterina Gornung, Fabio Mosconi, Flavia Annesi, Riccardo Castiglia

Abstract: The karyotype of a sphaerodactylid gecko Euleptes europaea (Gené, 1839) was assembled for the first time in this species. It is made of 2n = 42 gradually decreasing in size chromosomes, the highest chromosome number so far acknowledged in the family Sphaerodactylidae. The second chromosome pair of the karyotype appears slightly heteromorphic in the male individual. Accordingly, FISH with a telomeric probe revealed an uneven distribution of telomeric repeats on the two homologues of this pair, which may be indicative of an XY sex-determination system in the species, to be further investigated.

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Research Article Mon, 10 Jun 2013 00:00:00 +0300