Contributions of species Rineloricaria pentamaculata (Loricariidae:Loricariinae) in a karyoevolutionary context

Species of Rineloricaria demonstrate an interesting evolutionary history from a cytogenetic point of view, due to the occurrence of extensive variation in diploid number (2n=36 -70 chromosomes), with Robertsonian rearrangements mostly responsible for this karyotypic diversity. In this study we present the karyotypic data for a population of Rineloricaria pentamaculata, collected in the Itiz stream, a tributary of the Paraná River Basin (Paraná, Brazil), which exhibited 2n=56 chromosomes distributed in 8m/sm+48st/a (number fundamental equal to 64) and simple NOR system revealed by fluorescent in situ hybridization (FISH) with 18S rDNA probe, silver nitrate and positive C band, located on the first submetacentric chromosome pair (pair 5). In addition, the NOR pair showed a size heteromorphism for this region, rich in GC composition (positive CMA3). Clusters of 5S rDNA were located in 14 chromosomes and the FISH with a telomeric probe was used to map possible evidence of chromosomal fusions, however, it showed only telomeric sites. These results corroborate the data for the species R. pentamaculata and the genus Rineloricaria, showing that they are similar to most of the populations analyzed. About the cytogenetic data of R. pentamaculata, we reaffirm that most populations were conserved, but in those with derived characteristics, Robertsonian chromosomal rearrangements probably contributed to the karyotypic evolution of the group.