Alterações na estrutura cromossomica de Aplastodiscus perviridis e Hyla albopunctata (Amphibia, Anura) provenientes do Morro do Ferro (MG), região de alta radioatividade natural

AUTOR(ES)
DATA DE PUBLICAÇÃO

1989

RESUMO

Morro do Ferro, located in the Poços de Caldas Plateau in the State of Minas Gerais, has a radiation level as high as 131.4 mSv/year, suggesting on of the highest mean levels reported anywhere in the world. In this research the possible effect of the natural radiation in the Morro do Ferro on chromosomal structures was studied in two species of Anura Amphibia, Aplastodiscus perviridis and Hyla albopunctata. For A: perviridis the controls were collected in the Botucatu (SP) and Serra da Bocaina (SP) regions and for H. albopunctata in Botucatu (SP) and Campinas (SP). Considering the hypothesis that the Morro do Ferro population of A. perviridis might not be the same species as that of Serra da Bocaina. the karyotypes of both were determined. The chromosomes were obtained from the testicles, intestine, spleen, oesophagus and bone marrow. The slides were prepared by conventional squashing techniques and hy cell suspensions. The results showed that A. perviridis from Morro do Ferro, Serra da Bocaina and Botucatu presented the same diploid number 2n = 24 chromosomes and karyotipic similarity amongst the three populations. The chromosomic alterations appearing in both species were characterized as: condensation, decondensation, breaks, faults, deletions, acentric fragments and dicentric chromosomes. The majority of these alterations could probably be attributed to the high level of natural radiation in Morro do Ferro. The frequency of altered metaphases for some animais collected at UNICAMP (Campinas) was relatively higher than in the other controls. This was attributed to the presence of some mutagenic chemicals in the lagoon where the animais developed and were collected. Differences in the frequency of altered metaphases amongst the vanous individuals from all the localities studied were found. This was probably related to genotipic differences inherent to each animal and /or its age and radiation exposure. As expected, in the intestine and testicles the number of altered metaphases was greater than in the other organs analysed. In the germinative cell lineage only the spermatogonia presented altered metaphases. The compacted and decompacted chromosomic portions were those which showed the least drastic alterations, due to the possibility of reversion. Deletions and breaks were the more frequent alterations in both species, and a great number of these occurred in the centromeric hetero­chromatin neighborhood. The types of alteration encountered represent all enormous potential for chromosomic arrangements. These could bring about consequences not only for the individual itself, but principally in the diversification of the natural populations

ASSUNTO(S)

radioatividade atmosferica citologia

ACESSO AO ARTIGO

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