Chromosomal characterization and relationship between two new species of Ctenomys (Rodentia, Ctenomyidae) from northern Cordoba province, Argentina

Karyotypes of two recently described species of Ctenomys from northern Cord oba province (Argentina) were studied. C. osvaldoreigi is only known from t he type locality in the high valleys of the Sierras Grandes at more than 20 00 m above sea level. The karyotype consists of 2n = 52 chromosomes with FN = 56 and includes 22 pairs of telocentric autosomes that decrease graduall y in size, a pair of subtelocentric autosomes (n degrees 8), two pairs of s mall metacentrics and a pair of sex chromosomes. Three populations from the northeastern plains of Cordoba province (including one from the type local ity) of C. rosendopascuali were analyzed. All individuals were 2n = 52 but FNs of the three populations were different. Individuals from Los Mistoles showed FN = 62 and the karyotype consists of a large subtelocentric autosom al pair, a medium-sized subtelocentric (n degrees 8), twenty telocentric an d three small metacentric pairs plus a pair of sex chromosomes. Candelaria specimens had FN = 64; the karyotype includes a second large subtelocentric pair which replaces a large telocentric, the remainder of the complement b ring similar to Los Mistoles. A further large subtelocentric occurs in the Mar Chiquita population, thus FN = 66; the remainder of the karyotype does not differ from the two other populations In order to compare the new speci es to a known species of the same general geographical area, four populatio ns of C. bergi from northwestern Cordoba were karyotyped. All specimens had 2n = 48, FN = 90. The: three karyotypes found in C. rosendopascuali are re markably similar and obviously related to that of C. osvaldoreigi through r elatively simple chromosomal rearrangements, which confirms their morpholog ical and molecular proximity.