Estudo citogenetico de duas especies de dipteros de interesse medico-veterinario : Haematobia irritans e Muscina stabulans (Diptera, Muscidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The flies Muscina stabulans and Haematobia irritans are exceptions among Muscidae since both present one less pair of chromosomes and thus do not follow the mIe 2n=12. The objectives of this study were:describing the karyotype of M. stabulans, re-analyzing the karyotype of H. irritans and locating NORs and constitutive heterochromatic regions in mitotic and meiotic chromosomes of both species. The nucleolus was also examined by comparing its number and morphQlogy in different tissues. To characterize the M. stabulans karyotype, chromosomes from L3 larval brain preparations were measured. Pairs I, 11, 111 e V are metacentric and pair IV is submetacentric. The long arm of chromosome I presents two secundary constrictions and the short arm of chromosome n presents one constriction. The description of the karyotype of H. irritans was performed using the same methods. Chromosomes I, 11 and Vare metacentric and the other two are submetacentric. The nucleolar organizer regions were studied through silve r staining. As a result, the method has very often shown to be unspecific for mitotic chromosomes in both species, since detection of centromeric, telomeric and sometimes intersticial was possible. As for meiotic chromosomes, the method was more specific, allowing clear detection of one dense black dot in chromosome 111 of H. irritans. C-banding allowed the identification of constitutive heterochromatin regions. In M. stabulans brain preparations the centromeric regions of all chromosomes and one region of the short arm of the chromosome 11, which seems to be related to the secundary constriction, were all C-band positive. In H. irritans chromosomes, however, centromeric regions could not be distinguished as C-band positive. Only one intercalary band was seen in pair 11. Cells possessing one or two nucleoli were observed in testes, brain and embryonic tissues. Nucleoli in testes of M. stabulans are seen either as multiple or single units, which could be the results of either fission or aggregation throughout the development of these cells. The results obtained were compared to those available for Diptera and other insects. The C-band and NO R patterns obtained for both mitotic and meiotic chromosomes of the two flies as well as the number and morphology of their chromosomes contribute to the cytotaxonomic studies of Muscidae and add up to data that can help to understand the reduction of chromosomes from 12 to 10 in certain species

ASSUNTO(S)

mosca-do-chifre diptero - citologia

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