Chromosome studies of seven species of Oligoryzomys (Rodentia : Sigmodontinae) from Brazil

Karyotypes of 7 taxa of the rodent genus Oligoryzomys trapped in 33 localit ies from an area ranging from 01 degreesN to 32 degreesS in Brazil were ana lyzed. Three species were trapped exclusively in the Cerrado biome: O. stra mineus, diploid number (2n) 52, fundamental number (herein, number of autos omal arms; FN) = 68; O. eliurus, 2n = 62, with 2 fundamental numbers, FN = 64 and 66; and Oligoryzomys sp., 2n = 70, FN = 74. In the Amazon, we caught O. cf. messorius, 2n = 56, FN = 58, and O. microtis, 2n = 66, FN = 74. Oli goryzomys nigripes (2n = 61, 62, FN = 80-82) was trapped in 24 localities i n various biomes, and O. flavescens from several sites in southern Brazil p resented the same karyotypes as those already described at other sites. The C- and NOR-banding were performed for all species, and the (T(2)AG(3))(n) telomeric probe hybridized in situ to both the short and long arms of all p airs of karyotypes of O. cf. messorius, O. eliurus, and Oligoryzomys sp. An analysis performed with 11 microsatellite DNA heterologous primers improve d differentiation of O. nigripes from O. eliurus individuals, 2 species tha t presented 2n = 62 and that were trapped at the same site.