Análise citogenômica em Hypostomus soniae Carvalho & Weber, 2004 (siluriformes - loricariidae) do Rio Tapajós, Pará, Brasil.

Abstract

The present study addreresses the cytogenetic characterization of Hypostomus soniae Carvalho & Weber, 2004, this specie is endemic to the Tapajós river basin, know as acari violet, is an importante natural resource marketed in the aquarium market in the West region of Paraense. The present study aims to investigate the karyoevolution of H. soniae from Tapajós River. Were analyzed ten specimens, of these six were females, three males and one unidentified specimen. Were used techniques of Giemsa staining, C-banding, Ag-NOR, Cromomycin A3 (CMA3) and fluorescent in situ hydribridization (FISH) with rDNA 5S and 18S, telomeric, histone H1 and H3, snRNA U2 probes. The results revealed karyotype with 2n=64, NF=112 e FC=12m+22sm+14st+16a. The C-banding evidenced heteromorphism of heterochromatic blocks in the pairs 25 and 26, that may related with development of a nascent XX/XY sex chromosome system. NORs were detected in the telomeric regions of an acrocentric, except to the specimen PMT-36 that showed two labeled pairs, in agreement with CMA3 and rDNA 18S evidences. Three pairs showed marks to rDNA 5S probes and the telomeric probes labeled the extremity of all the chromosomes. We mapped for the first time H1 and H3 histones and snRNA U2 in the karyotype of H. soniae, and then H1 and H3 revealed clusters in two chromosomal pairs, pointed to conservative status of these sequences; snRNA U2 probes were detected in the distal portions in the most of the chromosomes. The results confirm the conservatism of H. soniae karyotypic macrostructure between Tapajós and Teles Pires Rivers populations and reinforces the hypothesis of occurrence of sex chromosome system and intraspecific polymorphism.