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 dip-loid 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 tribu-tary of the Parana River Basin (Parana, Brazil), which exhibited 2n=56 chromosomes distributed in 8m/sm+48st/a (number fundamental equal to 64) and simple NOR sys-tem 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 chromo-somes and the FISH with a telomeric probe was used to map possible evidence of chromosomal fusions, however, it showed only telomeric sites. These results corrobo-rate 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 contrib-uted to the karyotypic evolution of the group.

Automated summary

Based on the study of Rineloricaria pentamaculata population, it was found that their karyotypic data is similar to most populations, indicating that the cytogenetic characteristics of this species are relatively conservative. However, Robertsonian chromosomal rearrangements may have occurred in some populations with derived features.