Comparative Cytogenetics最新文献

We first studied several rare cases of over-diploid spermatocyte emergence using advanced immunocytochemical methods and a cross-species approach in subterranean rodents Ellobius tancrei (Blasius, 1884), E. alaicus Vorontsov et al., 1969, E. talpinus (Pallas, 1770), and Nannospalax leucodon (Nordmann, 1840) (all belong to the order Rodentia). The tetraploid spermatocytes exhibited specific features during meiotic prophase I, including symmetric and asymmetric chromosome quadrivalents with partner-switching, extended asynapsis, altered recombination patterns, and variable chromatin inactivation. These anomalies suggest that meiotic checkpoints, which are potentially triggered by failed synapsis or incomplete sex chromosome silencing, may act to prevent progression of polyploid spermatocytes. However, the quadrivalents assembled shelterin complexes at chromosome ends, as observed in E. talpinus, and these ends were connected to the nuclear envelope through the linker of nucleoskeleton and cytoskeleton (LINC) complex, as observed in E. alaicus, similarly to normal spermatocytes.

The article is dedicated to the anniversary of Professor, Dr. Sci. Valentina G. Kuznetsova, Editor-in-Chief and co-founder of the journal "Comparative Cytogenetics". V. Kuznetsova is the principal researcher at the Zoological Institute of the Russian Academy of Sciences, Head of the Department of Karyosystematics. Under her leadership, many Russian and foreign cytogeneticists have successfully defended their dissertations. Today, Valentina Kuznetsova is one of the world's leading experts in the field of comparative cytogenetics and karyosystematics of insects. The list of her publications includes 200 scientific articles, chapters in books and collective monographs.

Gymnophthalmidae is a monophyletic family of currently 297 Neotropical lizard species. Over the past 25 years, molecular studies have redefined previous morphology-based classifications, confirming the family's monophyly and revealing three major clades plus Rachisaurinae: ((Riolaminae(Rachisaurinae(Gymnophthalminae)))(Cercosaurinae)). Despite increased taxonomic efforts, especially in the tribes Bachiini and Cercosaurini, of Cercosaurinae, cytogenetic data remain limited. Of over 200 species in these tribes, only three had published karyotypes. Here, we provide new karyotypic data for seven species of Cercosaurini using standard cytogenetic techniques (Ag-NOR, C- and RBG-banding). Diploid numbers ranged from 2n = 32 in Bachia dorbignyi (Duméril et Bibron, 1839) to 2n = 58 in Placosoma glabellum (Peters, 1870). Almost all species displayed karyotypes composed of macro- and microchromosomes, that varied in morphology. Ag-NORs were observed on macro- or microchromosomes in several species, with notable variability in Bachia bresslaui (Amaral, 1935). Constitutive heterochromatin was mostly restricted to centromeric or telomeric regions. In Bachia dorbignyi, we found a putative XX:XY system due to the presence of a dot-like microchromosome exclusively in male specimens. These results comprise the threefold amount of cytogenetic data available for Bachiini and Cercosaurini and help fill a major gap into our understanding of diversity and chromosome evolution within Gymnophthalmidae.

Ribosomal DNA (rDNA) clusters are important cytogenetic markers that can inform both taxonomic delimitation and chromosomal evolution in ants. In this study, we molecularly characterize and validate the widely used 18S rDNA probe applied in cytogenetic studies of Hymenoptera and provide new FISH-based chromosomal data for two previously unstudied leaf-cutting ant species (Acromyrmex ambiguus (Emery, 1888) and Ac. crassispinus (Forel, 1909)). While the general distribution of 45S rDNA loci in leafcutting is relatively well documented (copy number and site), we expand the comparative framework by testing the phylogenetic structure of rDNA positioning across genera. Our results confirm the conserved number of rDNA loci per species but reveal lineage-specific variation in chromosomal location, including both subterminal and pericentromeric arrangements. Phylogenetic signal analyses suggest non-random patterns consistent with evolutionary constraints in locus positioning. Together, our findings refine current cytogenetic models for leafcutting ants and demonstrate the utility of rDNA as a cytotaxonomic character and evolutionary marker for assessing chromosomal diversification.

Data on chromosomal polymorphism in two natural populations from the Inya River in Western Siberia (Novosibirsk province) of Chironomus sp. J (Kiknadze, 1991) -one of the sibling species from the Chironomus plumosus group - are presented for the first time. The species belongs to the "thummi" cytocomplex with 2n = 8 and the arm's combination AB CD EF G and is closely related to Ch. nudiventris Ryser, Scholl et Wülker, 1983, which has 2n = 6 with the arm's combination AB CD GEF (a modified "thummi" cytocomplex). The main difference between these two species is the number of chromosomes, apart from that they only differ by the frequencies of banding sequences in arm A, and the presence or absence of some polymorphic inversions. The banding sequence pool of Chironomus sp. J consists of 15 banding sequences. Inversions were found in five chromosomal arms - A, B, D, E, F. The most polymorphic arms were B and D. Two studied populations differed by the level of chromosomal polymorphism with one population being completely monomorphic and the other showing high level of polymorphism with 62-65% of heterozygotes and 0.83-0.88 heterozygotic inversion per larva (depending on the year of collection). Comparison of banding sequences to other species from the group showed that Chironomus sp. J is indeed closest to Ch. nudiventris, with the cytogenetic distance of 0.058 or 0.471 depending on the method of calculation, which indicates that these two species are very closely related. The relationship between Chironomus sp. J and other species from the Ch. plumosus group was discussed.

Bothriurus Peters, 1861 is one of the most diverse genera within the family Bothriuridae. However, to date, only five species have been analyzed using a cytogenetic approach. In this study, for the first time, two populations of Bothriurus asper Pocock, 1893 and nine populations of Bothriurus rochai Mello-Leitão, 1932, two species from northeastern Brazil, were analyzed with respect to diploid number, chromosomal behavior during meiosis, and the localization of heterochromatin and nucleolus organizer regions (NORs). For B. asper, a diploid number of 2n = 30 was recorded in geographically distant populations, whereas B. rochai exhibited intraspecific variation in diploid number (2n = 16 and 2n = 18), representing the lowest diploid numbers ever reported for the family Bothriuridae. Despite the variability in diploid number, the number and localization of NORs remained stable among the populations of B. rochai. When comparing heterochromatin patterns between the two species, larger blocks of constitutive heterochromatin were observed in B. asper than in B. rochai. Variation in the amount of heterochromatin among populations of B. rochai was also observed; in this case, the population with the lowest amount of heterochromatin also exhibited the greatest variation in post-pachytene cell configurations. This is the first study to cytogenetically analyze multiple populations of species within the genus Bothriurus, and it significantly expands the karyotypic information available for scorpions with monocentric chromosomes.

The anuran species group Physalaemus gracilis comprises six species, and variation in the location of nucleolus organizer regions (NORs) was observed across the four species that have been karyotyped to date. The NORs are located interstitially on chromosome 8 of P. carrizorum Cardozo et Pereyra, 2018, and P. lisei Braun et Braun, 1977, terminally on chromosome 8 of P. gracilis (Boulenger, 1883), and terminally on chromosome 10 of P. barrioi Bokermann, 1967. To contribute to the comparative analysis of this group, including the assessment of the hypothesis of homology among these NOR-bearing chromosomes, we described the karyotype of P. evangelistai Bokermann, 1967, and expanded the cytogenetic analyses of P. carrizorum, P. lisei, and P. barrioi. We used classical cytogenetic techniques and mapped, by fluorescent in situ hybridization (FISH), two repetitive sequences: the PcP190 satellite DNA and the U2 snRNA gene. Physalaemus evangelistai exhibited a 2n = 22 karyotype, with meta- and submetacentric chromosomes, which corresponds to the typical karyotypic configuration of the genus. We found an interstitial heterochromatin DAPI-positive band on the short arm of the NOR-bearing chromosomes 8 of P. evangelistai and P. carrizorum from Palmas-PR, and chromosome 10 of P. barrioi, which corroborates the hypothesis that these chromosomes are homologous. In P. evangelistai, an additional NOR was observed on chromosome 9 of females. Moreover, the karyotype of P. carrizorum from Palmas-PR differed from that previously described for P. carrizorum from Misiones, particularly in the number of PcP190 clusters and intrachromosomal position of the NOR on chromosome 8. Specimens from Palmas-PR showed a terminal NOR on chromosome 8 and PcP190 clusters on chromosomes 1 and 3, whereas those from Misiones had an interstitial/pericentromeric NOR on chromosome 8 and a single PcP190 cluster on chromosome 3. Further analyses are still needed to assess whether these cytogenetic differences represent interspecific variation.

Checking old unphotographed slides of chromosome preparations in the possession of R.B.A. revealed one slide labelled "frater ♀7g 6/6/13 ✓". The beetle with these data is a female paratype of H. aquila Angus et al., in the general collection of the Natural History Museum, London. One almost complete dividing nucleus was found, with 32 chromosomes, indicating a triploid nucleus with one chromosome lost in the course of preparation of the slide.

The chromosome number of Hynobiusfucus was found by Lai and Lue (2008) to be 2n = 58, displaying a karyomorph similar to those previously reported in stream-type salamanders from Taiwan. Based not only on cytogenetic features but also on developmental characteristics such as the embryonic stage and the presence of interdigital membranes during limb formation this species can be confidently classified as a lotic stream-type salamander. Morescalchi (1975) proposed that karyotype evolution in families of urodeles tends to proceed from higher to lower chromosome numbers. Our findings from Taiwan suggest karyotype evolution within the genus Hynobius, that is, the chromosome number of this species may have increased from 2n = 56 in the pond-type ancestor to 2n = 58 in this stream-type lineage.

Scleractinian (stony) corals are foundational to reef ecosystems, yet their taxonomy remains unresolved due to morphological plasticity and limited cytogenetic data. This study presents the first molecular cytogenetic characterization of the scleractinian coral Micromussaamakusensis (Veron, 1990), employing fluorescence in situ hybridization (FISH) to isolate and map five DNA markers. Using the conventional Giemsa staining technique, M.amakusensis was found to have a diploid karyotype of 2n = 28, with a prominent homogeneously staining region (HSR) on the long arm of chromosome 12. Subsequently, five FISH markers designated as MA-H3 for histone H3, MA-5S for 5S rRNA, MA-18/28S for 18S-28S rRNA, MA-13C for centromeric region, and MA-TEL for telomeric region were cloned, sequenced, and mapped using FISH. FISH analysis revealed that the MA-H3 localized to the centromeric region of chromosome 1, MA-5S to the telomeric region of chromosome 4, MA-18/28S to the terminal region of chromosome 12 (coinciding with the HSR), MA-13C to the centromere of chromosome 13, and MA-TEL to multiple telomeric regions across several chromosomes. Sequence analysis confirmed marker identities and revealed conserved and novel repetitive elements. Furthermore, Genomic DNA hybridization (GDH) of whole-sperm DNA revealed signals collected at several telomeric regions, suggesting the presence of repetitive sequences. These cytogenetic markers enable the identification of at least 3 out of 14 chromosome pairs, allow for more precise karyotyping, and highlight chromosomal features that may help resolve coral classification and improve understanding of genome evolution. This research demonstrates the utility of molecular cytogenetics in stony coral systematics and provides new FISH markers for future comparative genomic studies.