Cytogenetics and systematic approach on a new Oryzomys species, of the nitidus group (Sigmodontinae, Rodentia) from Northeastern Brazil

摘要

The diploid number 2n=76 was found in five specimens (four males and one female) of a new species of Oryzomys belonging to the nitidus group (Sigmodontinae, Rodentia) from Pacoti, state of Ceara, Northeastern Brazil. Cytogenetic data included CBG and GTG-banding, Ag-NOR staining as well as fluorescence in situ hybridization (FISH) with (T(2)AG(3))(n) as probe, which revealed exclusive signals in all telomeres of all chromosomes. The karyotype comprises two large pairs (1 and 3) and four small metacentric pairs (34 to 37); 31 acrocentric pairs from large to small (pairs 2, and pairs 4 to 33). The X chromosome is a large subtelocentric and the Y is a medium size chromosome with two different morphologies: acrocentric and submetacentric. Pairs 1 and 3 are the result of Robertsonian rearrangements when compared with the 2n=80 karyotypes observed in Oryzomys russatus, O. nitidus and O. emmonsae. Interstitial telomeric sites (ITS) after FISH were not detected in those specific chromosomes. [References: 22]