Comparative cytogenetics of four species of Thrichomys (Rodentia: Echimyidae).

Thrichomys Trouessart, 1880 is a genus of echimyid rodents endemic to South America, distributed from northeastern Brazil to Paraguay and Bolivia. Although all the recognized species of this genus have already been karyotyped, detailed comparative cytogenetic analyses have not been performed yet. We karyologically analyzed four species of Thrichomys from different Brazilian states. Our analyses included GTG- and CBG-banding, silver-staining of the nucleolar organizer regions (Ag-NORs), and fluorescent in situ hybridization (FISH) with telomeric and 45S rDNA probes. Comparative GTG-banding suggested that the interspecific variation may result from Robertsonian rearrangements, pericentric and paracentric inversions, centromere repositioning, and heterochromatin variation. FISH with a telomeric probe showed interspecies variation in interstitial telomeric sequences (ITs) distribution. Our results represent the most complete data on the cytogenetics of Thrichomys reported to date and give an insight into the chromosome evolution of this genus.