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.

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 (Acromyrmexambiguus (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.

Chromosomal polymorphism has been studied in 31 natural populations of Ch.borokensis. 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 Ch.borokensis 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 Ch.borokensis is 40. Twenty six banding sequences are described for the first time for the species.

Recently, hypotheses regarding the evolutionary patterns of ribosomal genes in ant chromosomes have been under discussion. One of these hypotheses proposes a relationship between chromosomal location and the number of rDNA sites, suggesting that terminal locations facilitate the dispersion of rDNA clusters through ectopic recombination during meiosis, while intrachromosomal locations restrict them to a single chromosome pair. Another hypothesis suggests that the multiplication of rDNA sites could be associated with an increase in the chromosome number in Hymenoptera due to chromosomal fissions. In this study, we physically mapped rDNA sites in 15 new ant species and also reviewed data on rDNA available since the revision by Teixeira et al. (2021a). Our objectives were to investigate whether the new data confirm the relationship between chromosomal location and the number of rDNA sites, and whether the increase in the chromosome number is significant in the dispersion of rDNA clusters in ant karyotypes. Combining our new data with all information on ant cytogenetics published after 2021, 40 new species and nine new genera were assembled. Most species exhibited intrachromosomal rDNA sites on a single chromosome pair, while three species showed these genes in terminal regions of multiple chromosome pairs. On one hand, the hypothesis that the chromosomal location of rDNA clusters may facilitate the dispersion of rDNA sites in the ant genome, as previously discussed, was strengthened, but, on the other hand, the hypothesis of chromosomal fission as the main mechanism for dispersion of ribosomal genes in ants is likely to be refuted. Furthermore, in certain genera, the location of rDNA sites remained similar among the species studied, whereas in others, the distribution of these genes showed significant variation between species, suggesting a more dynamic chromosomal evolution.

The current study analyzed the chromosomal karyotype of Quasipaaspinosa David, 1875 from Hunan Province, China. The karyotype, C-banding, BrdU-banding pattern were characterized using direct preparation of bone-marrow cells and hemocyte cultures. The findings indicated that Q.spinosa was a diploid species (2n = 26) that lacked heteromorphic chromosomes and secondary constrictions. C-banding analysis revealed an abundance of positive signals in the centromere regions, while the BrdU-banding pattern showed three phases in both male and female, occurring consistently and in chronological sequence during S-phase. Notably, there was no asynchronous replication in the late phase. This study enhanced our understanding of the karyotypic structure of Q.spinosa by conventional cytogenetic techniques, thus providing essential scientific insights into the cytogenetics of Q.spinosa.

Results of the chromosome study of 12 sawfly species of the genus Arge Schrank, 1802 are reviewed, including new data on the karyotypes of A.ciliaris (Linnaeus, 1767) and A.enodis (Linnaeus, 1767) with n = 10. Moreover, the same chromosome number, n = 10, is found in A.ustulata (Linnaeus, 1758), for which n = 8 was previously reported. In addition, n = 8 is confirmed in A.gracilicornis (Klug, 1814). The results of the morphometric analysis of chromosome sets of these four species are given. In the genus Arge, haploid chromosome numbers of n = 8, 10, 11 and 13 were found. Among these sawflies, n = 8 appeared to be the most frequent chromosome number, followed by n = 10. The known data of the chromosome study of these insects are summarized and discussed in the light of phylogeny and taxonomy of the genus Arge.

The karyotype and reproductive features of Orbuspedummachinator Gavrilov-Zimin, 2017 (Pseudococcidae) were studied for the first time. Diploid chromosome number is 18 in females. Reproduction is probably bisexual, as indicated by the presence of characteristic Lecanoid heterochromatinization of the paternal set of chromosomes in embryonic cells of about 50% of the embryos studied. The female reproductive system has a pair of lateral oviducts merged into enlarged common oviduct; the spermatheca and accessory glands are connected to the common oviduct in its proximal part. Complete ovoviviparity occurs in ontogenesis.

The mitotic metaphases of five Andean species of genus Drosophila are described for the first time. The evolutionary and interspecific genetic relationships within three Neotropical Drosophila species groups are analyzed. The diploid chromosome number for each species is as follows: D.cashapamba Céspedes et Rafael, 2012 2n = 6 (2V, 1J) (X = J, Y = R), D.ecuatoriana Vela et Rafael, 2004 2n = 10 (3R, 2V) (X = V, Y = R), D.ninarumi Vela et Rafael, 2005 2n = 10 (3R, 1V, 1D) (X = V, Y = R), D.urcu Vela et Rafael, 2005 2n = 12 (4R, 2V) (X = V, Y = R), D.valenteae Llangarí-Arizo et Rafael, 2018 2n = 8 (3R, 1J) (X = J, Y = R).