COMPARATIVE CYTOGENETICS OF 3 SPECIES OF SOUTH-AMERICAN FIELD MICE OFTHE GENUS AKODON (RODENTIA, CRICETIDAE)

A karyological analysis of three species of South American field mice of the genus Akodon from four different localities of the Department o f Tarija, Bolivian Republic, was performed, In Akodon simulator, 2n = 40 - 42, NFa = 42. The variation of the diploid number is caused by a polymorphism of the Robertsonian type involving six pairs of acrocentr ic chromosomes. Five variants of karyotypes were revealed. The chromos ome set of A. sp. has 2n = 36, NFa = 40; in A, toba, 2n = 42 - 43, NFa = 44 - 46, The variation of the diploid number and the number of auto somal arms is caused by the polymorphism of the first autosomal pair. A comparative karyological analysis of A. simulator, A, sp., and A. to ba revealed a high level of similarity of all karyotypic elements. Fif teen autosomal pairs of these three species have identical G-banding p atterns; the others are involved in formation of larger chromosomes, r epresenting one possible combination of the same chromosomal material. The set of rearrangements is limited only to tandem chromosome fusion s.