Cytogenetic characterization of brown howler monkeys, Alouatta guariba clamitans (Atelidae, Platyrrhini): confirmation of an X1X2X3Y1Y2 sex chromosome system

STEINBERG E.R; FORTES V.; ROSSI L.F.; MURER L.; LOVATO M.; MERANI, M.S.; MUDRY M.D.

Guarujá

Congreso; 60º Congreso Brasilero de Genética; 2014

Sociedad Brasilera de Genética

Alouatta guariba clamitans is one of the two subspecies currently recognized for brown howler monkeys. Its geographic distribution ranges from southeast Brazil to the north of Misiones, in Argentina. Diploid numbers ranging from 2N=45 to 2N=52, with a high degree of intraspecific chromosomal variability, and the presence of XX/XY, X1X1X2X2/X1X2Y and X1X1X2X2X3X3/X1X2X3Y1Y2 sex chromosome systems were described by mitotic studies. Cytogenetic studies that include both mitotic and meiotic analysis are necessary for the characterization of the species. With this objective, the present contribution shows the karyological analysis of 4 adult males and 1 adult female of A. guariba clamitans from the Santa Maria region, RS, Brazil, not yet described to this date. Three males were sampled in the wild within their natural distribution and 1 male and 1 female were sampled while in captivity at the São Braz breeding center. Animals were weighted and their morphometric measurements were taken. At the same time, peripheral blood samples and testicular biopsies were taken under anesthesia by veterinarians. Lymphocyte cultures were performed following standard techniques. The testicular tissue was divided in smaller pieces to perform two techniques: spermatocyte microspreads for synaptonemal complexes and the air-drying technique for the analysis of meiotic stages. Inmunodetection was performed in spermatocyte microspreads using antibodies anti-SMC3 and anti-CREST for the synaptonemal complex and the kinetochores respectively to illustrate the meiotic behaviour in early prophase. Mitotic studies showed a diploid number 2N=45, X1X2X3Y1Y2 in the males and a 2N=46, X1X1X2X2X3X3 in the female. The autosomal complement was constituted by 3 metacentric chromosomal pairs, 7 submetacentric and 10 acrocentric. X1 and X2 were submetacentric chromosomes, while X3, Y1 and Y2 were acrocentrics. The G-banding pattern was in agreement with previous descriptions for the species. The stages of meiosis were evaluated. At least 30 diakinesis/metaphase I were analysed per individual. Meiotic analysis confirmed the presence of a sexual pentavalent (X1X2X3Y1Y2) in the males. C-banding in metaphase I and inmunodetection in prophase I showed the clear presence of 5 centromeres in the sexual multivalent. The meiotic behaviour of the autosomal bivalents and the sexual pentavalent was analyzed. These results were compared with the karyological descriptions for other howlers and discussed in the framework of the chromosomal evolution hypothesis for the speciogenic process of the genus.