The small-sized Crocidura horsfieldii (Tomes, 1856) species complex, comprising C. watasei (Kuroda, 1924), C. tadae (Tokuda et Kano, 1936), C. kurodai (Jameson et Jones, 1977), C. wuchihensis (Wang, 1966), and C. indochinensis (Robinson et Kloss, 1922), has long been the subject of taxonomic confusion in the literature. Here, we report for the first time the karyotype of female C. indochinensis from Yongde Snow Mountain, based on conventional Giemsa staining and the GTG-banding technique. C. indochinensis has 2n = 38 and FN = 56. The autosomes consist of four metacentric or submetacentric pairs, four subtelocentric pairs, and ten acrocentric pairs, whereas the X chromosome is a medium-sized submetacentric. Our results demonstrate that the karyotype of C. indochinensis differs markedly in 2n and FN from those of C. horsfieldii, C. watasei, C. tadae and C. kurodai, providing further evidence for the distinct species status of C. indochinensis within this complex. Furthermore, comparative analysis of the G-banded chromosomes of C. indochinensis and C. dsinezumi revealed a high degree of karyotypic homology, with their karyotypes differing primarily by a single fusion/fission event and a centromeric shift or a pericentric inversion, thereby enhancing our understanding of karyotype evolution within the genus Crocidura Wagler, 1832.
Gobies (family Gobiidae) rank among the most diverse of all marine fish families. Although the cytogenetics of these small, ubiquitous fish is still a young field, studies on Atlantic species, despite their limited number, have already revealed a remarkable level of karyotypic variation. This karyotype diversity has provided critical evidence for discovering new species, uncovering population structures, identifying sex chromosomes, and pinpointing major shifts in repetitive DNA. This study presents the first chromosomal characterization of two Atlantic goby species, Coryphopterus glaucofraenum (Gill, 1863) and Evorthodus lyricus (Girard, 1858), using classical cytogenetics and base-specific fluorochrome staining. Our analyses revealed a striking divergence in their karyotypes. Evorthodus lyricus exhibited a karyotype of 2n = 46 (FN = 92), whereas C. glaucofraenum presented 2n = 40 (FN = 42), indicating significant differences in both chromosome and fundamental number (FN). These cytogenetic patterns, combined with existing data for the family, reinforce the high karyotypic diversity within Gobiidae and suggest a relationship between speciation processes and chromosomal modifications in the diversification of this family.
Telomeric sequences in the insect infraorder Nepomorpha (Hemiptera: Heteroptera) have previously been characterized only in the basal superfamily Nepoidea, where the canonical arthropod motif (TTAGG)n was confirmed by fluorescence in situ hybridization (FISH). The telomeric repeat composition of the remaining Nepomorpha superfamilies remained unknown. Using TREW, a tool for de novo identification of candidate telomeric sequences from short-read whole-genome sequencing data, we screened 32 publicly available NCBI datasets representing 24 genera and all 13 Nepomorpha families. The method was validated against species with known (TTAGG)n telomeres in Nepoidea, successfully recovering the expected motif. In Corixoidea, (TTAGG)n was uniformly identified as the best candidate for telomeric sequence across all eight species of three families – Corixidae, Diaprepocoridae and Micronectidae. In contrast, derived 10-bp motifs were recovered from the remaining four superfamilies: (TGGTTAGTGA)n and (TGGTTAGTGT)n in Ochteroidea, (TGGATAGGTG)n and (TGGATAGGAG)n in Naucoroidea (including Aphelocheiridae and Potamocoridae), and (TGGATAGGGT)n uniformly across Notonectoidea and Pleoidea. All derived decamers except those from Ochteroidea share the core octamer TGGATAGG. The retention of (TTAGG)n in the two basal superfamilies and the occurrence of derived decamers in more derived clades are congruent with most current phylogenetic hypotheses for Nepomorpha and support independent evolution of 10-bp motifs within the infraorder. The presence of an identical candidate for telomeric sequence – (TGGATAGGGT)n in Notonectoidea and Pleoidea provides additional support for their close phylogenetic relationship and might be a synapomorphy for this clade. These findings extend the known pattern of telomeric diversification within Heteroptera to Nepomorpha and demonstrate the utility of short-read archival data for taxonomic surveys of telomeric composition.
Cytogenetic analysis of Citrus Linnaeus, 1753 species is complicated by the small size and morphological similarity of their chromosomes. In this study, we applied the fluorescence in situ hybridization (FISH) method using rDNA probes, as well as newly developed oligonucleotide probes based on previously uncharacterized tandem repeats identified in citrus genomes. Four tandem repeats (CL1, CL14, CL262, and CL122) were mapped to the chromosomes of five Citrus species: Citrus medica Linnaeus, 1753, Citrus × aurantiifolia (Christmann, 1777) Swingle, 1913, Citrus × limon (Linnaeus, 1753) Osbeck, 1765, Citrus myrtifolia Rafinesque, 1838, and Citrus × latifolia Tanaka, 1951. The repeats exhibited distinct and partially species-specific distribution patterns: CL1 was detected in all species, whereas CL262, CL122, and CL14 exhibited more restricted localization. A comparative analysis of their chromosomal distribution in relation to 45S- and 5S-rDNA loci revealed differences between the conserved regions of ribosomal DNA and the more dynamic tandem repeats. The identified repeats represent useful cytogenetic markers for chromosome identification, karyotyping, and comparative analysis within the genus Citrus.
Flying fishes (Exocoetidae) constitute a group of fish with adaptations for life in the epipelagic zone, notably featuring one or two pairs of expanded fins that enable gliding flight. Most of their 80 species have an interoceanic distribution, where they stand out as economic resources, as well as a key component of the trophic base of large pelagic predators. However, despite being a charismatic evolutionary model with considerable knowledge about its biology, that group remains neglected regarding its cytogenetic characterization. Here, we performed cytogenetic analyses for the first time in Hirundichthys affinis (Günther, 1866) (two Atlantic populations) and in Cheilopogon exsiliens (Linnaeus, 1771) and C. furcatus (Mitchill, 1815) (Saint Peter and Saint Paul Archipelago, mid-Atlantic region). These analyses included C-banding, silver nitrate staining (Ag-NOR), and fluorescent in situ hybridization (FISH) with 18S rDNA, 5S rDNA, and (CA)15 microsatellite probes. The three species share 2n = 48 but exhibit discernible intergeneric karyotypic divergences. Thus, while the karyotype of H. affinis displays exclusively acrocentric chromosomes (48a, FN = 48), C. exsiliens (2st+46a, FN = 50) and C. furcatus (2m+46a, FN = 50) both differ due to one pair of bi-armed chromosomes. Heterochromatin shows an occasional accumulation of (CA)15 clusters predominantly in pericentromeric regions of the chromosomes. The rDNA sites display variations in number and location, proving to be effective cytotaxonomic and population markers for the group. Our data indicate that the distribution of the flying fishes was accompanied by their chromosomal reorganizations. Thus, cytogenetic data stand out as promising tools for unraveling environmental adaptations, reproductive isolation, and speciation in the vast epipelagic areas they occupy.
Polygala fallax Hemsley, 1886 is a perennial herb of the family Polygalaceae. Because of its antioxidant, anti-aging, anti-inflammatory, and antibacterial properties, it is regarded as a traditional medicinal plant in China with high economic value. Although this species has significant medicinal and health benefits, cytological research on it remains very limited. In the present study, the genome size and chromosome number of P. fallax were determined through k-mer analysis, flow cytometry, and cytogenetics. Firstly, a genome survey was conducted using Illumina NovaSeq 6000 DNA sequencing. K-mer analysis revealed that the genome size of P. fallax was approximately 2199.64 Mb (ca. 2.20 Gb), the heterozygosity rate was about 1.11%, and the proportion of repeated sequences was about 73.61%. As for flow cytometry analysis, Solanum lycopersicum Linnaeus, 1753 was used as internal standard species, and the 2C-DNA value of P. fallax is 2.49 Gb. We counted the chromosome number of P. fallax using a common cytogenetic method, and the result showed a chromosome number of 2n = 40. This comprehensive study offers a foundation for subsequent whole-genome sequencing of P. fallax, contributing valuable insights into its genetic characteristics and providing genomic information for further research on the synthesis mechanisms of its medicinal secondary metabolites, species conservation, and sustainable utilization.
Ants are present in different environments and regions of the planet, showing little-known biodiversity in the Neotropics, especially among fungus-growing ants (the subtribe Attina). Recent studies seek to combine morphological analysis with other methods, such as cytogenetics, to better define and differentiate species. In this sense, cytogenetic analyses have been important for the study of ants, characterizing chromosome number and morphology, and mapping rDNA genes and microsatellites, which generate important information about the evolution and taxonomy in Attina species. In the Amazon region, there are still few studies that include cytogenetics in their research. In this study, we cytogenetically characterized five fungus-growing ants, belonging to the genera Cyphomyrmex Mayr, 1862 and Apterostigma Mayr, 1865, from the northernmost region of Amapá state within the Guiana Shield region of Brazil. The nests were captured by active search, and the larvae had their brain ganglia extracted to provide metaphase chromosomes. The karyotypes were determined using Giemsa or DAPI staining, and 18S ribosomal DNA (rDNA) and (GA)n microsatellite repetitive sequences were physically mapped with FISH technique with specific probes. Cyphomyrmex transversus Emery, 1894 had 2n = 24 chromosomes (18m+6sm) and Cyphomyrmex laevigatus Weber, 1938 n = 7, all metacentrics. In both species, the rDNA clusters were restricted to a single chromosome pair. In C. transversus the rDNA clusters were mapped to the long arm of the larger submetacentric chromosome pair, while in C. laevigatus they were on the short arm of the fifth chromosome (haploid individuals). These data are aligned to Cyphomyrmex species previously studied from this region. Although the FISH protocol was successfully applied to Cyphomyrmex species, it was unable to localize rDNA sites in the chromosomes of all three Apterostigma species, suggesting that methodological adjustments are required for an effective application to this genus. In Apterostigma, the largest chromosome number of the genus was identified in Apterostigma tropicoxa Lattke, 1997, with 2n = 54 chromosomes, while A. jubatum Wheeler, 1925 and A. andense Lattke, 1997 had 2n = 22 and n = 11 respectively but were strikingly diverse in their karyotype configurations. In C. laevigatus and C. transversus the microsatellite (GA)n clusters were scattered on all chromosomes. While A. jubatum also had a scattered distribution pattern of this microsatellite on all chromosomes, the other Apterostigma species showed more complex patterns. In A. andense these microsatellite sequences were more concentrated at the ends of some chromosomes, while in Apterostigma tropicoxa they were almost absent in the short arms of several submetacentric and subtelocentric chromosomes. The cytogenetic data for Amazonian species in this study highlight the chromosomal diversity among fungus-growing ants, particularly within the genus Apterostigma, providing useful insights into the karyotype evolution of these ants and paving the way for further cytogenetic research in the Amazon region.
In this study, five blind mole rat specimens of the Nannospalax sp. were collected from two different localities in Muş Province, Eastern Anatolia, Türkiye. Cytogenetic analyses of these specimens revealed that the diploid chromosome number, the fundamental chromosome number, and the number of autosomal arms were 2n = 52, NF = 84 and NFa = 80, respectively. The X chromosome was medium-sized and submetacentric, while the Y chromosome was small and acrocentric. Active nucleolus organizer regions (NORs) were observed on the telomeric regions of three bi-armed autosomal pairs in all examined specimens. This study presents new karyological data regarding the blind mole rat with 2n = 52 chromosomes distributed in the Eastern Anatolia region from Türkiye.
The parasitoid wasp Aganaspis daci (Weld, 1951) is a natural enemy of several tephritid fruit flies and was recently detected for the first time in Italy. Despite its biological and applied relevance, no chromosomal data have been available for this species until now. Here we provide the first karyotype description of A. daci, based on specimens from a laboratory stock in Campania (Italy), using chromosome morphometry and acridine orange staining. This species has n = 9 and 2n = 18, with a very large first metacentric chromosome, and acrocentrics prevailing among the remaining ones. The sixth metacentric presumably carries a single nucleolus organizing region (NOR). Staining with acridine orange provides homogeneous staining of all chromosomes. A brief review of the chromosome study of parasitoids of the family Figitidae, which have n = 5 to 11, is given. The haploid karyotype of ten chromosomes apparently represents the ancestral character state at least for the subfamily Eucoilinae, with chromosome sets that include n = 9 and the very large first metacentric, likely result from independent chromosomal fusions.
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.
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.
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.
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.
Triploid female Helophorus brevipalpis Bedel, 1881 are recorded from two localities in Provence, France. Their karyotypes are analysed using both chromosome morphology and C-banding. Their karyotypes appear to be identical with those of Spanish material recorded by Angus (1992) but show minor differences from Italian triploid material described by Angus, Jia (2020). Data on C-banding in English H. brevipalpis are given and chromosomal variation in H. brevipalpis is discussed.
The chromosome number of Hynobius fucus 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.
