Chromosomes of the males of five species of Odontura, belonging to the subgenera Odontura and Odonturella, were analyzed. Intensive evolution of the karyotype was recorded, both in terms of changes in the numbers of chromosomes (from 2n = 31 to 27) and the sex chromosome system (from X0 to neo-XY and X0 to neo-X1X2Y). Karyotype evolution was accompanied by tandem autosome fusions and interspecific autosomal and sex chromosome differentiation involving changes in the locations of nucleolar organizer regions, NORs, which were revealed by silver impregnation and confirmed by FISH using an 18S rDNA probe. O. (Odonturella) aspericauda is a polytypic species with X0 and neo-X1X2Y sex determination. The latter system is not common in tettigoniids. It possibly originated by a translocation of a distal segment of the original X chromosome onto a medium sized autosome, resulting in a shortened neo-X1 and a metacentric neo-Y. The remaining autosome homologue became the neo-X2 chromosome. This shift from X0 to neo-X1X2Y is supported by the length of the X chromosome and location of the NOR/rDNA. and Elżbieta Warchałowska-Śliwa, Anna Maryańska-Nadachowska, Beata Grzywacz, Tatjana Karamysheva, Arne W. Lehmann, Gerlind U.C. Lehmann, Klaus-Gerhard Heller.
We report the karyotype characteristics including chromosome numbers of Saga campbelli campbelli, S. c. gracilis, and S. rammei using the following classical cytogenetic methods: C-banding, silver staining, and fluorochrome staining DAPI and CMA3. We also present FISH data showing the distribution of telomeric repeats and 18S rDNA on the chromosomes of these species and the results of similar studies cited in the literature on S. hellenica, S. natoliae, and S. rhodiensis. The five European Saga species exhibit a high rate of karyotype evolution. In addition to changes in chromosome number and morphology (by chromosomal inversion and/or chromosome fusion), interspecific autosomal differentiation involved changes in the distribution and quantity of constitutive heterochromatin and GC-rich regions, as well as the number and location of NORs. In the present study we focused on testing a hypothetical model of karyotype evolution in Saga, with particular reference to the cytogenetic mapping of rDNA and telomeric sequences. Variation in the distribution of rDNA and location of Ag-NORs are novel phylogenetic markers for the genus Saga.
The present study focused on the evolution of the karyotype in 21 taxa of the genus Isophya, which was done by mapping the location on the chromosomes of ribosomal RNA (rRNA) coding genes using fluorescence in situ hybridization (FISH) with an 18S rDNA probe and using silver staining (AgNO3) to evaluate the activity of major rDNA clusters. Since the chromosome number and sex determination do not vary in this genus, the above markers were used in a detailed comparison of the cytogenetic features of species of Isophya. The species analyzed were placed into three groups based on the location of rDNA on their chromosomes: (1) rDNA-FISH signals only on the two long pairs of autosomes, (2) rDNA-FISH signals on one long and one short pair of autosomes, and (3) rDNA-FISH signals on three to five different sized pairs of autosomes. These groupings partly correspond to the morphological groupings proposed in earlier studies. One long pair of autosomes frequently carried rDNA in all the Isophya species and probably is a plesiomorphic character for these taxa. The cytogenetic mapping revealed great variability among Isophya species in the chromosomal location of major rDNA clusters. Our results suggest that the observed variation in the number of rDNA clusters can be an important species-group specific phylogenetic marker. Analysis of 18S rDNA hybridization signals showed that the evolutionary dynamics of rDNA in this genus is remarkably high and accompanied by changes in the structure of chromosomes bearing rDNA at an inter- and intra-specific level. The telomeric sequence (TTAGG)n hybridized with the termini of most of chromosomes, however, some chromosome ends lacked signals probably due to a low copy number of telomeric repeats. and Beata Grzywacz, Anna Maryańska-Nadachowska, Dragan P. Chobanov, Tatjana Karamysheva, Elżbieta Warchałowska-Śliwa.