Chromosomal polymorphism has been studied in 31 natural populations of . For 11 out of 31 populations quantitative analysis of chromosomal polymorphism has been performed. Data from previous publications (10 populations) have also been used to perform an overview of the chromosomal polymorphism of and to establish the species range. Most studied populations show a high level of chromosomal polymorphism: on average 66.1 ± 2.6% of specimens were heterozygotes with 1.1 ± 0.6 heterozygotic inversions per larvae. The number of banding sequences found in populations varied from 7 to 18 per population with an average of 12 ± 3. Inversions were found in all chromosomal arms. Besides inversions, B-chromosome was present in 13 populations, and 5 translocations were found. The total number of banding sequences found in banding sequence pool of is 40. Twenty six banding sequences are described for the first time for the species.

The barbels of the subfamilies ´Poropuntinae´ and Smiliogastrinae within the family Cyprinidae play a significant role as a food source for fish in artisanal fisheries and are highly valued as ornamental fish in Thailand. In this study, we employed both conventional and molecular cytogenetics to analyze the karyotype of 15 fish species from two cyprinid lineages. All analyzed species had a diploid chromosome number of 2n = 50. Despite sharing the same 2n, our analyses revealed species-specific distribution patterns of the mapped microsatellite motifs [(CA)₁₅, (TA)₁₅, (CAC)₁₀, and (CGG)₁₀]. They were predominantly found at telomeric sites of all-to-few chromosomes. Additionally, some species exhibited a widespread distribution of the mapped microsatellites across the chromosomes while others showed no signal. These variations reflect the evolutionary divergence and chromosomal diversity within the cyprinids. Thus, our findings support the 2n stability in cyprinoid lineages while emphasizing the intrachromosomal evolutionary diversity accompanied by species-specific microsatellite distribution.

We analyzed chromosomes of four species of East Asian dobsonflies (Megaloptera: Corydalidae): (Thunberg, 1781), Kuwayama, 1964, Liu, Hayashi et Yang, 2007 and (Walker, 1853). The chromosome number in all species was 2n = 24, consisting of 11 pairs of autosomes plus the XX chromosomes in females and the Xy in males. The karyotype of which occurs in near the central part of the Ryukyu Islands, and is a vicarious species of , was similar to the karyotype of . On the other hand, the karyotype of , which is from the Sakishima Islands, and is a vicarious species of , resembled that of . The X chromosomes are submetacentric, while the Y is the smallest, dot-like chromosome of the set. The sex chromosomes of the first meiotic metaphase (MI) spermatocytes in all species invariably appear as a bivalent-like structure known as parachut bivalents Xy, suggesting that the species in this genus share a common sex-bivalent mechanism.

We analyzed chromosomes of four species of fishflies (Megaloptera: Chauliodinae). Three species were from western North America ( (Walker, 1866), Chandler, 1954, and (Chandler, 1954)), and another one from eastern North America ( (Say, 1824)). The chromosome number of the three western species was 2n = 22, with the karyotype consisting of 10 pairs of autosomes plus XY in males. The X chromosomes of these three species are subtelocentric, while the Y chromosomes are small and dot-like. Of the ten pairs of autosomes, the last pair is substantially smaller than the others. The chromosome number in the first meiotic metaphase in spermatocytes of from Michigan was n = 10 (9 autosomal bivalents + Xy in the male). The sex chromosomes of formed parachute-type bivalents synchronously with the autosomes. The parachute-type bivalent Xy has also been found in four fishflies and four dobsonflies (Megaloptera: Corydalinae) from East Asia, as well as in a fishfly and a dobsonfly from North America. These data suggest that the two subfamilies of Corydalidae share a common sex-bivalent mechanism, along with many beetles (Coleoptera).

To identify nucleolus organizing regions (NORs), fluorescence hybridization (FISH) with 18S rDNA probe was performed on chromosomes of Linnaeus, 1758 (Tenthredinidae), (Linnaeus, 1767) (Argidae) (n = 10 in both) and (Bouché, 1834) (Cynipidae) (2n = 20). In all these species, a single pericentromeric rDNA cluster per haploid karyotype was detected. This number of NORs is confirmed as ancestral for the order Hymenoptera.

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 Pocock, 1893 and nine populations of 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 , a diploid number of 2n = 30 was recorded in geographically distant populations, whereas 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 . When comparing heterochromatin patterns between the two species, larger blocks of constitutive heterochromatin were observed in than in . Variation in the amount of heterochromatin among populations of 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 , and it significantly expands the karyotypic information available for scorpions with monocentric chromosomes.

Triploid female 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 are given and chromosomal variation in is discussed.

The fish species has an interesting B chromosome system, with three morphological types as acrocentric, metacentric, and submetacentric. However, most cytogenetic studies on this species are restricted to the natural population of the Mogi Guaçu River. Given this, the present work aimed to study the structure karyotypic profile as well as the occurrence of supernumeraries in in several localities in the Paraná River basin, where this species is abundant. The results obtained showed a predominantly conserved karyotypic macrostructure and the presence of B chromosomes in all the seven localities studied, with the exception of the Apa River. Additionally, new variants of morphological characteristics were found in the population of the Batalha River (Reginópolis). These results allow us to infer that there is a large occurrence of B chromosomes in this species, with important differences in B chromosome frequency between the populations, especially in acrocentric and submetacentric B variants. Considering the possible origin and evolution of B chromosomes in , our results allow us to describe the dispersion of metacentric B variants, in contrast with the elimination observed in acrocentric and submetacentric variants.

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 (Veron, 1990), employing fluorescence in situ hybridization (FISH) to isolate and map five DNA markers. Using the conventional Giemsa staining technique, 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 , MA-5S for , MA-18/28S for , 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.

[This corrects the article DOI: 10.3897/compcytogen.v16.i2.79033.].

The chromosome number of 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 , 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.

Checking old unphotographed slides of chromosome preparations in the possession of R.B.A. revealed one slide labelled " ♀7g 6/6/13 ✓". The beetle with these data is a female paratype of 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 anuran species group 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 Cardozo et Pereyra, 2018, and Braun et Braun, 1977, terminally on chromosome 8 of (Boulenger, 1883), and terminally on chromosome 10 of 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 Bokermann, 1967, and expanded the cytogenetic analyses of , , and . 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. 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 and from Palmas-PR, and chromosome 10 of , which corroborates the hypothesis that these chromosomes are homologous. In , an additional NOR was observed on chromosome 9 of females. Moreover, the karyotype of from Palmas-PR differed from that previously described for 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.

Identifying clades with extensive and conspicuous changes in diploid chromosome number (2n) is an important step in unraveling the evolutionary mechanisms underlying karyotype evolution. Here, we report low 2n in a monophyletic group of teleost fishes within the family Osphronemidae defined by their unique spiral egg structure (the "spiral egg" clade). We sampled seven of the nine known species within the spiral egg clade, reporting novel 2n for five species and confirming two others. We find high variability in both 2n and chromosome arm number (fundamental number, FN), suggesting a 2n reduction during the emergence of the clade and numerous large-scale mutations across evolutionary time. These data provide important information in cataloguing 2n shifts in teleost fishes and highlight this group for further study in chromosomal and genomic evolution due to their karyotypic heterogeneity.

We report on the results of a chromosomal study of the big-eyed true bug Waga, 1839 (Heteroptera: Geocoridae) aimed at obtaining data on its telomeres. Using fluorescence hybridization (FISH), we have shown, that has a non-canonical 10-bp telomeric motif TTAGGGGTGG. This is the first evidence of telomere structure in the family Geocoridae and the first finding of the telomeric sequence (TTAGGGGTGG) in the large superfamily Lygaeoidea (infraorder Pentatomomorpha).

Despite recent advances in telomere research, the telomere DNA organization remains unknown for representatives of several insect orders. In this study, analysis of the chromosome-level genome assembly shows that the telomeric DNA of the earwig (Linnaeus, 1758) (Polyneoptera, Dermaptera, Spongiphoridae) consists of repeats of the 5 bp motif TTCGG/CCGAA. This is the first record describing the structure of telomeric DNA in the order Dermaptera. This record expands the spectrum of the known telomeric sequences, since the TTCGG motif has not been reported for insects previously.

The African non-annual killifish genus Gill, 1862 (family Nothobranchiidae) comprises 36 valid species distributed in West, Central and East Africa. The available cytogenetic information for the genus indicates a wide variability in diploid chromosome number (2n) and number of chromosome arms (FN). Here, we report the karyotype of (Duméril, 1861), one of the two species with the lowest diploid chromosome number (2n = 34) in the genus, from the White Nile basin in Ethiopia. Male and female karyotypes contained 18 metacentric/acrocentric and 16 subtelocentric/acrocentric chromosomes. The number of chromosome arms is, respectively, FN = 52. Analysis of karyotype differentiation in the genus allowed us to suggest that the 2n reduction in and many other members of the genus is mainly due to Robertsonian translocations (reduction of 2n from 48 to 34 with stable NF = 48-52). We provide an up-to-date summary of cytogenetic data and a brief review of chromosome evolution in the genus.

The paper elaborates theoretical basis of the origin of aphid cyclical parthenogenesis in view of the original life of these insects in strobiloid galls on spp. The period of gall opening is greatly extended in time, which prevents normal panmixia and creates a selective advantage for parthenogenetic reproduction. Migration of aphids to secondary host plants, on which closed galls never form, parthenogenetic reproduction on these plants, and the subsequent simultaneous return of "remigrants" to the main host plant make it possible to synchronize the development of the bisexual generation and achieve mass panmixia at the end of the life cycle only; it coincides with the end of summer growth shoots or the autumn end of the vegetation period as a whole. The evolutionary transition of aphids from conifers to angiosperms in the Cretaceous period in parallel meant the possibility of development in more spacious galls accommodating several consecutive parthenogenetic generations, the transition to viviparity and telescopic embryonization, significantly accelerating the propagation.

Supernumerary B chromosomes are significant dispensable genetic elements that follow their own species-specific evolutionary pathways. Despite their widespread occurrence, comprehensive analyses of their meiotic behavior remain limited. In this study, we present the first systematic investigation of B chromosome morphology and meiotic behavior in the hangingfly Tjeder, 1956 using cytogenetic approaches. The male basal chromosome numbers of is 2n = 30 + XO, with 0-5 polymorphic B chromosomes. Intraspecific B chromosome polymorphism manifests as various distinct morphotypes ranging from punctiform, bicentric, and ring-shaped to larger coiled forms, indicating that the B chromosomes may undergo rapid structural changes. During meiosis, B chromosomes display transmission drive through asymmetric segregation, preferentially accumulating in one daughter cell. Most B chromosomes formed univalents, with few forming bivalents or trivalents at meiosis I. Three unconventional retention mechanisms were identified in univalent B chromosomes: (1) associating with a nonhomologous chromosome, (2) accumulating near spindle poles, and (3) contributing to unequal spindle formation. Based on the abundant chromosomal changes of A chromosomes and stable XX/XO sex determination, we infer that the B chromosomes likely originated from multiple A chromosomes in . The roles of B chromosomes in the cell cycle and individual fitness are briefly discussed, and the evolutionary scenario is putatively put forward for the diversification of B chromosomes.

Birds are one of the most diverse groups among terrestrial vertebrates. They evolved from theropod dinosaurs, are closely related to the sauropsid group and separated from crocodiles about 240 million years ago. According to the IUCN, 12% of bird populations are threatened with potential extinction. Classical cytogenetics remains a powerful tool for comparing bird genomes and plays a crucial role in the preservation populations of endangered species. It thus makes it possible to detect chromosomal abnormalities responsible for early embryonic mortalities. Thus, in this work, we have provided new information on part of the evolutionary history by analysing high-resolution GTG-banded chromosomes to detect inter- and intrachromosomal rearrangements in six species. Indeed, the first eight autosomal pairs and the sex chromosomes of the domestic fowl Linnaeus, 1758 were compared with five species, four of which represent the order Galliformes (Common and Japanese quail, Gambras and Chukar partridge) and one Otidiformes species (Houbara bustard). Our findings suggest a high degree of conservation of the analysed ancestral chromosomes of the four Galliformes species, with the exception of (double, terminal, para and pericentric) inversions, deletion and the formation of neocentromeres (1, 2, 4, 7, 8, Z and W chromosomes). In addition to the detected rearrangements, reorganisation of the Houbara bustard chromosomes mainly included fusions and fissions involving both macro- and microchromosomes (especially on 2, 4 and Z chromosomes). We also found interchromosomal rearrangements involving shared microchromosomes (10, 11, 13, 14 and 19) between the two analysed avian orders. These rearrangements confirm that the structure of avian karyotypes will be more conserved at the interchromosomal but not at intrachromosomal scale. The appearance ofa small number of inter- and intrachromosomal rearrangements that occurred during evolution suggests a high degree of conservatism of genome organisation in these six species studied. A summary diagram of the rearrangements detected in this study is proposed to explain the chronology of the appearance of various evolutionary events starting from the ancestral karyotype.

Data on chromosomal polymorphism in two natural populations from the Inya River in Western Siberia (Novosibirsk province) of sp. J (Kiknadze, 1991) -one of the sibling species from the 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 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 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 sp. J is indeed closest to , 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 sp. J and other species from the group was discussed.