Chromosomal number and evolution in two Brazilian species of Callithrix

Abstract

The Karyotypes of the Brazilian marmosets C. jacchus and C. penicillafa are very similar. Both have 2n = 46. C. jacchus has one more metacentric pair and C. penicillata has one more submetacentric pair, while the sex chromosomes show distinct morphological differences. On the basis of the chomosome complement of these species some considerations about the process ofchromosomal evolution are presented. A short comparative study of these and other species of the same genus shows that basic mechanisms such as centric fusion and pericentric inversions can explain the observed morphologic chromosomal variations.