Evidence for TTAGG telomere repeats and rRNA gene clusters in leafhoppers of the genus Alebra (Hemiptera: Auchenorrhyncha: Cicadellidae)

摘要

The leafhopper genus Alebra Fieber, 1872 comprises a complex of morphologically similar species. The chromosome complements (karyotypes) of five Alebra species, i.e. A. albostriella, A. coryli, A. viridis, A. wahlbergi and a new, yet undescribed species, provisionally named Taxon 1, were here investigated, three of these species (A. coryli, A. viridis, and Taxon 1) for the first time. The techniques applied included standard chromosome staining, fluorescence in situ hybridization (FISH) for mapping of 18S rDNA and telomeric repeats (in every species), C-banding, AgNOR-banding and CMA(3)/DAPI-staining (in A. viridis). The species have a holokinetic type of chromosomes, as in other hemipterans. Karyotypes of all species are remarkably conserved with 2n = 22 + X(0)/XX(male/female), one large and 10 medium pairs of autosomes and the X chromosome similar in size to larger chromosomes within this group. In every species, FISH identified the "classical" insect telomere repeat of TTAG and rRNA gene clusters located on the homologues of a medium-sized pair of autosomes, presumably number 5. Thus, speciation in Alebra has apparently not involved significant karyotypic changes. In A. viridis, rDNA sites were both Ag- and CMA(3)-positive and were located at an interstitial position. C-banding revealed heterochromatic bands in the X chromosome and also in all but four pairs of autosomes, the bands were located at one telomere of a chromosome. C-bands were positive for CMA(3) and negative for DAPI, suggesting that C-heterochromatin is mainly enriched in GC-pairs.