RESUMO
Analyses conducted using repetitive DNAs have contributed to better understanding the chromosome structure and evolution of several species of insects. There are few data on the organization, localization, and evolutionary behavior of repetitive DNA in the family Lygaeidae, especially in Brazilian species. To elucidate the physical mapping and evolutionary events that involve these sequences, we cytogenetically analyzed three species of Lygaeidae and found 2n (â) = 18 (16 + XY) for Oncopeltus femoralis; 2n (â) = 14 (12 + XY) for Ochrimnus sagax; and 2n (â) = 12 (10 + XY) for Lygaeus peruvianus. Each species showed different quantities of heterochromatin, which also showed variation in their molecular composition by fluorochrome staining. Amplification of the 18S rDNA generated a fragment of approximately 787 bp. The alignment of the consensus sequence with sequences from other species of Heteroptera deposited in the GenBank revealed a similarity of 98% with small differences. Fluorescent in situ hybridization with the 18S rDNA fragment revealed that this ribosomal gene was located in 1 autosomal pair at different positions in the three species. No cytogenetic data are available for these Brazilian species. The basal number and the possible chromosomal changes that occurred among the different species, as well as the evolution of these DNA sequences, are discussed.
Assuntos
Mapeamento Cromossômico , Hemípteros/genética , Heterocromatina , RNA Ribossômico 18S/genética , Animais , Sequência de Bases , Bandeamento Cromossômico , Cromossomos de Insetos , Feminino , Hibridização in Situ Fluorescente , Masculino , Dados de Sequência Molecular , Fenótipo , RNA Ribossômico 18S/química , Alinhamento de Sequência , Homologia de Sequência do Ácido NucleicoRESUMO
Heteroptera is the most numerous and diverse suborder of Hemiptera, with about 38,000 species. This diversity also involves cytogenetic features, including chromosome number and a sex determining system. Information about heterochromatin occurrence and distribution is scarce in heteropterans, but still, there is some evidence of variability. We determined the chromosome number and CMA3/DAPI-banding pattern of 179 individuals of 25 heteropteran species from Brazil. Eight species of Pentatomidae exhibited a constant chromosome number (2n = 12 + XY), but in Coreidae (12 species), Largidae (1 species), Rhopalidae (1 species), and Pyrrhocoridae (3 species), the numbers ranged from 2n = 10 + 2m + X0 to 2n = 24 + 2m + X0. Although there were no large differences in the chromosome size between species, the CMA3/DAPI-banding patterns differed markedly. Among the genera, species of Edessa, Spartocera, Hypselonotus, Phtia,Holhymenia and Euryophthalmus showed a large accumulation of heterochromatin, while the other species exhibited few or no heterochromatic bands. In general, when heterochromatin was more accumulated, this occurred preferentially at terminal positions, except in Holhymenia histrio, which exhibited intercalary bands. This study made it possible to identify some chromosome rearrangements and to enhance our knowledge of the evolutionary mechanisms that determine karyotype differentiation in Heteroptera.
