Chromosomal differentiation among bisexual European species of Saga (Orthoptera: Tettigoniidae: Saginae) detected by both classical and molecular methods

Abstract

Abstract. 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.

Comparative analysis of the location of rDNA in the Palaearctic bushcricket genus Isophya (Orthoptera: Tettigoniidae: Phaneropterinae)

“…For example in most Tettigoniinae (see Warcha owska-liwa et al, 2005) and Saginae (Warcha owska-liwa et al, 2009) the active NOR with rDNA loci is located only on a single bivalent. In the African species Lunidia viridis (Phaneropteridae) a cluster of rDNA repeats corresponding to an active NOR occur on a single large bivalent (Hemp et al, 2010).…”

“…tiger beetles (Zacaro et al, 2004), grasshoppers (e.g. Loreto et al, 2008 and bushcrickets (Warcha owska-liwa et al, 2009). Other repetitive sequences, the so-called telomeric DNA, are located mainly at chromosome termini.…”

“…Telomeres were used as markers for identifying the ends of chromosomes and in the majority of insect orders, including Orthoptera, are composed of multiple copies of short, tandemly arranged TTAGG sequences. Clusters of telomeric repeats are thought to indicate chromosomal rearrangements related to changes in chromosome number and evolution in insects (López-Fernández et al, 2004, Warcha owska-liwa et al, 2009.…”

“…López-Fernández et al, 2004;Warcha owska-liwa et al, 2009;Hemp et al, 2010). Differences in the intensity of the hybridization signal detected among some autosomes and X chromosomes between species may be related to the presence of a different number of repeats of ribosomal sequences.…”

Changes in the numbers of chromosomes and sex determination system in bushcrickets of the genus Odontura (Orthoptera: Tettigoniidae: Phaneropterinae)

“…The silver staining method (Ag-NO3) for localization of the nucleolus organizer regions (NORs) was performed as previously reported (Warcha owska-liwa & Marya skaNadachowska, 1992). The fluorescence in situ hybridization (FISH) technique with ribosomal 18S DNA (rDNA) and telomeric (TTAGG)n DNA probes was performed according to Warcha owska-liwa et al (2009). Spermatogonial metaphases and meiotic stages were analyzed and photographed with a Nikon Eclipse 400 microscope fitted with a CCD DS-U1 camera and equipped with sets of standard filters.…”