Caracterização cromossômica de seis espécies de peixes da família Curimatidae (Characiformes) da Amazônia

Abstract

The Curimatidae family Gill 1858 are a group of fishes, that among the Characiformes, are easily indentified by not having teeth in their jaws. Currently, the family has 117 valid species in eight genera, widely distributed in Central and South America, being found in greater abundance in the Amazon Region. Classics cytogenetics analysis have already been carried out in 38 species of this family, however molecular cytogenetic studies are still incipient. Therefore, this study aimed contribute to the knowledge of chromosomal evolution of curimatids species, on this way contributing to clarify the diversification process of these fishes karyotypes, three species collected at the Amazon basin (Curimata vittata, Curimatella meyeri and Psectrogaster rutiloides) and the others three species from the Tocantins-Araguaia basin (Curimata inornata, Curimatella dorsalis and Psectrogaster falcata). We highlight the first Psectrogaster falcata cytogenetics data and the first molecular cytogenetics data for the others six species here studied. All species here studied had a diploid number with 54 chromosomes, meta and submetacentric types (FN = 108), presenting species-specific karyotypes formulas. The heterochromatin pattern was evident in centromeric and terminal regions of some chromosomes, in addition to conspicuous blocks in the Psectrogaster species. The nucleolus organizing region (Ag-NOR) was single in five species and multiple only in C. vittata, all with positive heterochromatin. The chromosomal location of NOR was confirmed using the 18S ribosomal DNA mapping, showing an additional chromosomal pair in the species C. meyeri. rDNA 5S was found only in a chromosome pair from 5 species, however the specie P. rutiloides have two pairs. In our analysis, we foud the first case of synteny between 18S and 5S in the Curimatidae family, in the C. dorsalis specie. Telomerics sequences (TTAGGG)n were highlighted in terminal regions of the chromosomes from species of Curimata genus, however the presence of interstitial telomeric sequences (ITS) were evidenced in several chromosomes from species of Curimatella and Psectrogaster genera. Given this, despite a conserved chromosomal macrostructure, the molecular cytogenetic data obtained to these species suggest the occurrence of non-Robertsonian rearrangements, showing that the karyotype microstructure of these species is involved in the chromosomal diversification process.