Chromosomal rearrangements act as barriers to gene flow and can thus promote speciation. In moths and butterflies (Lepidoptera), which possess holocentric chromosomes facilitating karyotype changes, chromosome fusions are more common than fissions. Yet, limited evidence suggests that when speciation involves chromosomal rearrangements, it is most often linked to fissions. Notable karyotypic variation is observed in three clades of the subfamily Polyommatinae (Lycaenidae), with chromosome numbers ranging from n = 10 to 225. We investigated genome sizes and karyotypes in several species of the genera Polyommatus and Lysandra with modal and derived high chromosome numbers. Our findings showed no support for polyploidy, confirming previous conclusions about karyotypic diversification via chromosome fragmentation in this butterfly family. Species with high chromosome numbers have slightly larger genomes, which indicate a potential role of repetitive sequences but contradict the hypothesis of holocentric drive. Ends of fragmented chromosomes were healed with telomeres synthesized de novo, which were significantly larger than those of species with modal karyotype. No interstitial telomeric sequences were detected on autosomes. Internal telomeric signals on sex chromosomes, however, revealed multiple sex chromosome systems in Polyommatus (Plebicula) dorylas and Polyommatus icarus, with two karyotype races differing in sex chromosome constitution in the latter. Notably, the W chromosome resisted fragmentation, presumably due to its epigenetic silencing.

• Keywords
• Polyommatus, butterfly, fission, fusion, sex chromosomes, telomere,
• MeSH
• Chromosomes, Insect MeSH
• Karyotype MeSH
• Butterflies * genetics   MeSH
• Sex Chromosomes * genetics   MeSH
• Polyploidy MeSH
• Telomere * genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Zoraptera (also called "angel insects") is one of the most unexplored insect orders. However, it holds promise for understanding the evolution of insect karyotypes and genome organization given its status as an early branching group of Polyneoptera and Pterygota (winged insects) during the Paleozoic. Here, we provide karyotype descriptions of three Zorapteran species: Brazilozoros huxleyi (2n♂; ♀ = 42; 42), B. kukalovae (2n♂; ♀ = 43; 44) and Latinozoros cacaoensis (2n♂; ♀ = 36; 36). These species represent two of the four recently recognized Zorapteran subfamilies. Contrary to an earlier suggestion that Zoraptera has holocentric chromosomes, we found karyotypes that were always monocentric. Interestingly, we detected both X0 (B. kukalovae) and XY (B. huxleyi, L. cacaoensis) sex chromosome systems. In addition to conventional karyotype descriptions, we applied fluorescent in situ hybridization for the first time in Zoraptera to map karyotype distributions of 18S rDNA, histone H3 genes, telomeres and (CAG)n and (GATA)n microsatellites. This study provides a foundation for cytogenetic research in Zoraptera.

• Keywords
• Karyotype, Microsatellites, Sex chromosomes, Telomere, rDNA,
• MeSH
• Chromosomes, Insect * genetics   MeSH
• Cytogenetics methods   MeSH
• Histones genetics   MeSH
• Insecta genetics   classification   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Karyotype * MeSH
• Microsatellite Repeats genetics   MeSH
• Evolution, Molecular MeSH
• Sex Chromosomes genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH
• Names of Substances
• Histones MeSH

Genetic sexing strains (GSS), such as the Ceratitis capitata (medfly) VIENNA 8 strain, facilitate male-only releases and improve the efficiency and cost-effectiveness of sterile insect technique (SIT) applications. Laboratory domestication may reduce their genetic diversity and mating behaviour and hence, refreshment with wild genetic material is frequently needed. As wild males do not carry the T(Y;A) translocation, and wild females do not easily conform to artificial oviposition, the genetic refreshment of this GSS is a challenging and time-consuming process. In the present study, we report the development of a novel medfly GSS, which is based on a viable homozygous T(XX;AA) translocation using the same selectable markers, the white pupae and temperature-sensitive lethal genes. This allows the en masse cross of T(XX;AA) females with wild males, and the backcrossing of F1 males with the T(XX;AA) females thus facilitating the re-establishment of the GSS as well as its genetic refreshment. The rearing efficiency and mating competitiveness of the novel GSS are similar to those of the T(Y;A)-based VIENNA 8 GSS. However, its advantage to easily allow the genetic refreshment is of great importance as it can ensure the mass production of high-quality males and enhanced efficacy of operational SIT programs.

• MeSH
• Pest Control, Biological methods   MeSH
• Ceratitis capitata * genetics   MeSH
• Humans MeSH
• Infertility, Male * genetics   MeSH
• Reproduction genetics   MeSH
• Translocation, Genetic MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Genes for major ribosomal RNAs (rDNA) are present in multiple copies mainly organized in tandem arrays. The number and position of rDNA loci can change dynamically and their repatterning is presumably driven by other repetitive sequences. We explored a peculiar rDNA organization in several representatives of Lepidoptera with either extremely large or numerous rDNA clusters. We combined molecular cytogenetics with analyses of second- and third-generation sequencing data to show that rDNA spreads as a transcription unit and reveal association between rDNA and various repeats. Furthermore, we performed comparative long read analyses among the species with derived rDNA distribution and moths with a single rDNA locus, which is considered ancestral. Our results suggest that satellite arrays, rather than mobile elements, facilitate homology-mediated spread of rDNA via either integration of extrachromosomal rDNA circles or ectopic recombination. The latter arguably better explains preferential spread of rDNA into terminal regions of lepidopteran chromosomes as efficiency of ectopic recombination depends on the proximity of homologous sequences to telomeres.

• Keywords
• Lepidoptera, major ribosomal RNA genes, mobile elements, satellite,
• MeSH
• Chromosomes MeSH
• Moths * genetics   MeSH
• Repetitive Sequences, Nucleic Acid * MeSH
• DNA, Ribosomal genetics   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Ribosomal MeSH

Odonata have holokinetic chromosomes. About 95% of species have an XX/X0 sex chromosome system, with heterogametic males. There are species with neo-XX/neo-XY sex chromosomes resulting from an X chromosome/autosome fusion. The genus Rhionaeschna includes 42 species found in the Americas. We analyzed the distribution of the nucleolar organizer region (NOR) using FISH with rDNA probes in Rhionaeschna bonariensis (n = 12 + neo-XY), R. planaltica (n = 7 + neo-XY), and Aeshna cyanea (n = 13 + X0). In R. bonariensis and A. cyanea, the NOR is located on a large pair of autosomes, which have a secondary constriction in the latter species. In R. planaltica, the NOR is located on the ancestral part of the neo-X chromosome. Meiotic analysis and FISH results in R. planaltica led to the conclusion that the neo-XY system arose by insertion of the ancestral X chromosome into an autosome. Genomic in situ hybridization, performed for the first time in Odonata, highlighted the entire neo-Y chromosome in meiosis of R. bonariensis, suggesting that it consists mainly of repetitive DNA. This feature and the terminal chiasma localization suggest an ancient origin of the neo-XY system. Our study provides new information on the origin and evolution of neo-sex chromosomes in Odonata, including new types of chromosomal rearrangements, NOR transposition, and heterochromatin accumulation.

• Keywords
• FISH, GISH, dragonflies, holokinetic chromosomes, meiosis, neo-sex chromosome evolution, nucleolar organizer region, ribosomal DNA, structural rearrangements,
• Publication type
• Journal Article MeSH

Haplogyne araneomorphs are a diverse spider clade. Their karyotypes are usually predominated by biarmed (i.e., metacentric and submetacentric) chromosomes and have a specific sex chromosome system, X1X2Y. These features are probably ancestral for haplogynes. Nucleolus organizer regions (NORs) spread frequently from autosomes to sex chromosomes in these spiders. This study focuses on pholcids (Pholcidae), a highly diverse haplogyne family. Despite considerable recent progress in pholcid cytogenetics, knowledge on many clades remains insufficient including the most species-rich pholcid genus, Pholcus Walckenaer, 1805. To characterize the karyotype differentiation of Pholcus in Europe, we compared karyotypes, sex chromosomes, NORs, and male meiosis of seven species [P.alticeps Spassky, 1932; P.creticus Senglet, 1971; P.dentatus Wunderlich, 1995; P.fuerteventurensis Wunderlich, 1992; P.phalangioides (Fuesslin, 1775); P.opilionoides (Schrank, 1781); P.silvai Wunderlich, 1995] representing the dominant species groups in this region. The species studied show several features ancestral for Pholcus, namely the 2n♂ = 25, the X1X2Y system, and a karyotype predominated by biarmed chromosomes. Most taxa have a large acrocentric NOR-bearing pair, which evolved from a biarmed pair by a pericentric inversion. In some lineages, the acrocentric pair reverted to biarmed. Closely related species often differ in the morphology of some chromosome pairs, probably resulting from pericentric inversions and/or translocations. Such rearrangements have been implicated in the formation of reproductive barriers. While the X1 and Y chromosomes retain their ancestral metacentric morphology, the X2 chromosome shows a derived (acrocentric or subtelocentric) morphology. Pairing of this element is usually modified during male meiosis. NOR patterns are very diverse. The ancestral karyotype of Pholcus contained five or six terminal NORs including three X chromosome-linked loci. The number of NORs has been frequently reduced during evolution. In the Macaronesian clade, there is only a single NOR-bearing pair. Sex chromosome-linked NORs are lost in Madeiran species and in P.creticus. Our study revealed two cytotypes in the synanthropic species P.phalangioides (Madeiran and Czech), which differ by their NOR pattern and chromosome morphology. In the Czech cytotype, the large acrocentric pair was transformed into a biarmed pair by pericentric inversion.

• Keywords
• NOR, Synspermiata, haplogyne, inversion, rDNA, sex chromosome, speciation,
• Publication type
• Journal Article MeSH

Whip spiders (Amblypygi) represent an ancient order of tetrapulmonate arachnids with a low diversity. Their cytogenetic data are confined to only a few reports. Here, we analyzed the family Charinidae, a lineage almost at the base of the amblypygids, providing an insight into the ancestral traits and basic trajectories of amblypygid karyotype evolution. We performed Giemsa staining, selected banding techniques, and detected 18S ribosomal DNA and telomeric repeats by fluorescence in situ hybridization in four Charinus and five Sarax species. Both genera exhibit a wide range of diploid chromosome numbers (2n = 42-76 and 22-74 for Charinus and Sarax, respectively). The 2n reduction was accompanied by an increase of proportion of biarmed elements. We further revealed a single NOR site (probably an ancestral condition for charinids), the presence of a (TTAGG)n telomeric motif localized mostly at the chromosome ends, and an absence of heteromorphic sex chromosomes. Our data collectively suggest a high pace of karyotype repatterning in amblypygids, with probably a high ancestral 2n and its subsequent gradual reduction by fusions, and the action of pericentric inversions, similarly to what has been proposed for neoamblypygids. The possible contribution of fissions to charinid karyotype repatterning, however, cannot be fully ruled out.

• Keywords
• Charinus, Sarax, chromosome fusion, fluorescence in situ hybridization, heterochromatin, nucleolar organizer region, telomere,
• Publication type
• Journal Article MeSH

Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.

• Keywords
• Geometridae, Lepidoptera, W chromosome, comparative genomic hybridization, intraspecific chromosomal variability, neo-sex chromosomes, sex chromatin, sex chromosome evolution,
• MeSH
• Species Specificity MeSH
• In Situ Hybridization, Fluorescence MeSH
• Karyotype MeSH
• Moths genetics   MeSH
• Sex Chromosomes genetics   MeSH
• Sex Chromatin metabolism   MeSH
• Comparative Genomic Hybridization MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Sex determination in the silkworm, Bombyx mori, is based on Feminizer (Fem), a W-linked Fem piRNA that triggers female development in WZ individuals, and the Z-linked Masculinizer (Masc), which initiates male development and dosage compensation in ZZ individuals. While Fem piRNA is missing in a close relative of B. mori, Masc determines sex in several representatives of distant lepidopteran lineages. We studied the molecular mechanisms of sex determination in the Mediterranean flour moth, Ephestia kuehniella (Pyralidae). We identified an E. kuehniella Masc ortholog, EkMasc, and its paralog resulting from a recent duplication, EkMascB. Both genes are located on the Z chromosome and encode a similar Masc protein that contains two conserved domains but has lost the conserved double zinc finger domain. We developed PCR-based genetic sexing and demonstrated a peak in the expression of EkMasc and EkMascB genes only in early male embryos. Simultaneous knock-down experiments of both EkMasc and EkMascB using RNAi during early embryogenesis led to a shift from male- to female-specific splicing of the E. kuehniella doublesex gene (Ekdsx), their downstream effector, in ZZ embryos and resulted in a strong female-biased sex-ratio. Our results thus confirmed the conserved role of EkMasc and/or EkMascB in masculinization. We suggest that the C-terminal proline-rich domain, we have identified in all functionally confirmed Masc proteins, in conjunction with the masculinizing domain, is important for transcriptional regulation of sex determination in Lepidoptera. The function of the Masc double zinc finger domain is still unknown, but appears to have been lost in E. kuehniella.

• MeSH
• Alternative Splicing MeSH
• Gene Duplication * MeSH
• Insect Proteins chemistry   genetics   MeSH
• Dosage Compensation, Genetic MeSH
• Moths embryology   genetics   MeSH
• Organ Specificity MeSH
• Sex Chromosomes genetics   MeSH
• Sex Determination Processes MeSH
• Protein Domains MeSH
• Gene Expression Profiling MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Insect Proteins MeSH

Fluorescence in situ hybridization (FISH) allows identification of particular chromosomes and their rearrangements. Using FISH with signal enhancement via antibody amplification and enzymatically catalysed reporter deposition, we evaluated applicability of universal cytogenetic markers, namely 18S and 5S rDNA genes, U1 and U2 snRNA genes, and histone H3 genes, in the study of the karyotype evolution in moths and butterflies. Major rDNA underwent rather erratic evolution, which does not always reflect chromosomal changes. In contrast, the hybridization pattern of histone H3 genes was well conserved, reflecting the stable organisation of lepidopteran genomes. Unlike 5S rDNA and U1 and U2 snRNA genes which we failed to detect, except for 5S rDNA in a few representatives of early diverging lepidopteran lineages. To explain the negative FISH results, we used quantitative PCR and Southern hybridization to estimate the copy number and organization of the studied genes in selected species. The results suggested that their detection was hampered by long spacers between the genes and/or their scattered distribution. Our results question homology of 5S rDNA and U1 and U2 snRNA loci in comparative studies. We recommend the use of histone H3 in studies of karyotype evolution.

• MeSH
• Cytogenetic Analysis methods   MeSH
• Genome MeSH
• In Situ Hybridization, Fluorescence MeSH
• Chromosome Mapping MeSH
• Evolution, Molecular * MeSH
• Butterflies genetics   MeSH
• Moths genetics   MeSH
• DNA, Ribosomal genetics   MeSH
• RNA, Small Nuclear genetics   MeSH
• RNA, Ribosomal, 18S genetics   MeSH
• RNA, Ribosomal, 5S genetics   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Ribosomal MeSH
• RNA, Small Nuclear MeSH
• RNA, Ribosomal, 18S MeSH
• RNA, Ribosomal, 5S MeSH
• U2 small nuclear RNA MeSH Browser