The structure of the holocentric chromosomes of the rosy apple aphid, Dysaphis plantaginea (2n = 12), and pear-grassaphid, Melanaphis pyraria (2n = 8), was studied using C-banding, NOR, Giemsa and fluorochrome staining, and fluorescent in situhybridization (FISH). Contrary to the equilocal distribution of heterochromatin typical of monocentric chromosomes, in both species C-banding evidenced a tendency of highly repetitive DNAs to be restricted to the X chromosomes. Silver staining and FISH, using a 28S rDNA probe, located rDNA genes on one telomere of each X chromosome, the only brightly fluorescent C-positive sites revealed by CMA3 staining, whereas all other heterochromatic C-bands were DAPI positive. Both species showed a noticeable amount of rDNA heteromorphism. Mitotic recombination is proposed as a possible mechanism responsible for the variation in size of rDNA.

Distribution of heterochromatin and rDNA on the holocentric chromosomes of the aphids Dysaphis plantaginea and Melanaphis pyraria (Hemiptera: Aphididae) / Angela, Criniti; Gabriele, Simonazzi; Cassanelli, Stefano; Mario, Ferrari; Davide, Bizzaro; Manicardi, Gian Carlo. - In: EUROPEAN JOURNAL OF ENTOMOLOGY. - ISSN 1210-5759. - STAMPA. - 106:2(2009), pp. 153-157. [10.14411/eje.2009.018]

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