Karyotypic comparison among Cebuella pygmaea, Callithrix jacchus and C. emiliae (Callitrichidae, Primates) and its taxonomic implications

The karyotype of Cebuella pygmaea (2n = 44) obtained by G-, C-banding, and NOR-staining is described. This species presents a heteromorphic C band in the intersticial region of the short arm of chromosome 2. The data obtained were compared with those previously described for the karyotypes of Callithrix jacchus and Callithrix emiliae. The three species differ in the amount and distribution of non-centromeric constitutive heterochromatin. The importance of the variation in constitutive heterochromatin for the phylogeny of the group is discussed. Comparison of the karyotypes in terms of G-banding patterns showed that C. pygmaea and C. emiliae differ from C. jacchus by a Robertsonian translocation and a paracentric inversion, whereas C. pygmaea and C. emiliae differ from each other by a reciprocal translocation between an acrocentric autosome and the short arm of the submetacentric chromosomes that distinguishes their karyotypes from that of C. jacchus. The possible evolutionary paths followed by the karyotypes of the three species are discussed.

Chromosomal evolution in Callithrix emiliae

We studied the karyotype of specimens of Callithrix emiliae (Callithricidae, Primates) from Rondonia, Brazil. Comparison with the karyotype of Callithrix jacchus showed that, even though these two species show many karyotypic similarities, they differ by a Robertsonian translocation, a paracentric inversion and large-scale addition of heterochromatin. The C. emiliae species appears to be in an active phase of chromosome evolution by the addition of constitutive heterochromatin.