Cytogenetics of Howler Monkeys

MUDRY, MARTA D.; NIEVES, MARIELA; STEINBERG, ELIANA R.

Howler Monkeys Volume I

Springer

Año: 2014;

Cytogenetic studies of howler monkeys show diploid numbers ranging from 2N = 43 in Alouatta seniculus to 2N = 58 in A. pigra with several interspecific chromosomal rearrangements such as translocations and inversions. Other remarkable genetic features are the multiple sex chromosome systems and the presence of microchromosomes. Multiple sexual systems are originated by Y-autosome translocations, resulting in the formation of trivalents X1X2Y in males of A. belzebul and A. palliata and quadrivalents X1X2Y1Y2 in males of A. seniculus, A. pigra, A. macconnelli, and A. caraya. Fluorescent in situ hybridization (FISH) analyses in the South American species have revealed that segments with homeology to human chromosomes #3 and #15 (synteny 3/15) are involved in these sexual systems. Different authors agreed with the assumption that these diverse sex chromosome systems share the same autosomal pair and the rearrangement may have occurred once. Recent cytogenetic characterization of A. pigra and A. palliata has shown that the autosomes involved in the translocation that formed the sex chromosome systems in the Mesoamerican and South American species are different. Two independent events of Y-autosome translocations might have led to different sexual systems. Together with the multiple autosomal rearrangements found in the genus, the howler monkey?s sex chromosome systems constitute an illustrative example of the possible chromosomal evolutionary mechanisms in Platyrrhini.