Estudo citogenético em duas espécies da família Callichthyidae (Callichthyinae, Siluriformes) da bacia do Rio de Contas/Bahia

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

09/02/2011

RESUMO

The family Callichthyidae is included in the order Siluriformes, is widely distributed by the Neotropical region and comprises 194 species and eight genera, distributed in two subfamilies, Corydoradinae and Callichthyinae. Aiming to expand the cytogenetics information of the ichthyofauna of the eastern Atlantic basins, this work was done in Callichthys callichthys and Hoplosternum littorale subfamily Callichthyinae collected in tributaries of the river basin Contas/BA and subjected to conventional and molecular cytogenetic studies. In C. callichthys, the two populations analyzed had 2n = 54 (16m+6sm +24st +8a) and the occurrence of a supernumerary chromosome of large size, which was detected in all samples of the population of Pedras River and 47.06% of individuals from the temporary pond. Multiple sites, and accentuated polymorphism of NORs, CMA3+/DAPI-, 18S rDNA and 5S with differences in the number, location and type of chromosomes were also observed in both populations and that, overall, the pond temporary showed less interindividual variation and a higher frequency of markers on chromosomes acrocentric. DAPI positive regions were detected in the centromeres of some chromosomes in both populations and the heterochromatin was observed in a discrete way in the centromeres of almost all chromosomes, indicating that some of these heterochromatic regions probably are rich in AT bases. Hoplosternum littorale exhibited 2n=60 (6m + 2SM + 52nd and NF = 68), simple and heteromorphic NORs in the terminal region of the short arm of pair 6, coincident with the constriction metastasis. The proccedure of double-FISH showed 18S rDNA sites in place of the short arm of pair 6, confirming the structural heteromorphism of NORs and the size, and 5S rDNA was located in the terminal portion of the short arm of two pairs of acrocentric chromosomes, not syntenic to bearing of NORs. The technique of double-FISH showed 18S rDNA sites in place of the short arm of pair 6, confirming the structural heteromorphism of NORs and the size, and 5S rDNA was located in the terminal portion of the short arm of two pairs of acrocentric chromosomes, not syntenic to bearing of NORs. The heterochromatin was shown to be distributed in chromosomal regions centromeric, interstitial and terminal. Four chromosomes were positive for CMA3, with a matching pair with NORs and the other with interstitial marking on the long arm, probably related to heterochromatin. The data presented here for C. callichthys confirm a large chromosomal variability in this species, which combined with the existence of taxonomic problems, reinforce the suggestion of a species complex for the group. In contrast, the results for H. littorale confirm a great karyotypic similarity among all the populations already studied, representing a species with low plasticity karyotype.

ASSUNTO(S)

peixe - citogenética ictiologia bagre (peixes) callichthyidae fish cytogenetics ichthyology

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