Cytogenetic Characterization of Brown Howler Monkeys, <b><i>Alouatta guariba clamitans </i></b>(Atelidae, Platyrrhini): Meiotic Confirmation of an X₁X₁X₂X₂X₃X₃/X₁X₂X₃Y₁Y₂ Sex Chromosome System

Abstract

For brown howler monkeys (Alouatta guariba clamitans), diploid chromosome numbers varying from 2n = 45 to 2n = 52, with XX/XY, X₁X₁X₂X₂/X₁X₂Y, and X₁X₁X₂X₂X₃X₃/X₁X₂X₃Y₁Y₂ sex chromosome systems have been described by mitotic studies but still await confirmation by meiotic analyses. We analyzed 3 male individuals sampled in the wild (in the municipality of Santa Maria, RS, Brazil) as well as 1 male and 1 female individual in captivity at the São Braz breeding center. Peripheral blood samples and testicular biopsies were taken. We found different diploid numbers for both sexes in somatic cells, 2n = 45,X₁X₂X₃Y₁Y₂ in males and 2n = 46,X₁X₁X₂X₂X₃X₃ in females, with 4 metacentric (9-12), 7 submetacentric (1-6, 8), and 9 acrocentric autosomal chromosome pairs (13-20, 22). X₁ and X₂ were submetacentric chromosomes, while X₃, Y₁, and Y₂ were acrocentric ones. Spermatocyte microspreads were examined for synaptonemal complexes. Pachytene spermatocyte analysis was done to verify the chromosome number and morphologies observed in mitotic karyotypes. Immunodetection was performed using anti-SMC3 and anti-CREST antibodies. The presence of a sex chromosome pentavalent X₁X₂X₃Y₁Y₂ in the males was confirmed by C-banding in metaphase I and by immunodetection in prophase I by the clear identification of 5 centromeres. The G-banded karyotype corresponded to that previously described for A. g. clamitans in the south of Brazil (Curitiba, Parana State, and Blumenau, Santa Catarina State) and for the Misiones Province, Argentina.

Rapid emergence of independent “chromosomal lineages” in silvered-leaf monkey triggered by Y/autosome translocation

“…Other cases of Y/autosome translocations have been reported in the New World Monkey genera Aotus 27 , Callimico 28 , and Alouatta 29,30 . However, these cases have at best only been studied with chromosome painting and others only with chromosome banding.…”

Sex chromosome quadrivalents in oocytes of the African pygmy mouse Mus minutoides that harbors non-conventional sex chromosomes

“…Within Artiodactyla, a chain of four is characteristic of the genera Nanger and Eudorcas following the translocations of the X and Y chromosomes on different autosomes (Vozdova et al 2016), and in the black muntjac Muntiacus crinifrons, complex rearrangements between sex chromosomes and autosomes have contributed to the origin of a pentavalent at meiosis (Huang et al 2006). Among the New World howler monkeys, some species of the genus Alouatta show a quadrivalent due to translocations between the Y and autosomes, and an additional rearrangement has led to a pentavalent in A. guariba (Rahn et al 1996;Mudry et al 2001;Steinberg et al 2017). The most striking multivalents are observed in monotremes, with sex chromosome chains of nine in echidna and ten in platypus (Rens et al 2004(Rens et al , 2007Daish et al 2009;Casey et al 2017).…”