Amplification of a GC-rich heterochromatin in the freshwater fish Leporinus desmotes (Characiformes, Anostomidae)

This is the first description of the karyotype of Leporinus desmotes. The d iploid female number was 2n = 54 meta- and submetacentric chromosomes. The nucleolar organizing regions (NORs) were studied by sliver nitrate staining and rDNA fluorescence ir? situ hybridization (FISH) and were found to be l ocated in the telomeric region of the long arm of the 9th pair. C-banding r evealed centromeric and telomeric heterochromatin segments in most chromoso mes. Intercalar blocks of heterochromatin were observed in the long arm of six chromosome pairs. Besides a NOR-adjacent heterochromatin, all of the in tercalar heterochromatic segments were brightly fluorescent by mithramycin staining. These data suggest that a unique amplification of a primordial GC -rich heterochromatin, probably NOR-associated, may have taken place in the karyotype diversification of this Leporinus species.