Chromosome studies in the red howler monkey, <i>Alouatta seniculus stramineus</i> (Platyrrhini, Primates): description of an X₁X₂Y₁Y₂/X₁X₁X₂X₂sex-chromosome system and karyological comparisons with other subspecies

Abstract

In the red howler monkey, Alouatta seniculus stramineus (2n = 47, 48, or 49), variations in diploid chromosome number are due to different numbers of microchromo-somes. Males exhibit a Y autosome translocation involving the short arm of an individual biarmed autosome. Consequently, the sex-chromosome constitution in the male is X₁X₂Y₁Y₂with X₁ representing the original X chromosome, X₂ the biarmed autosome (No. 7), Y₁ the Y;7p translocation product, and Y₂ the acrocentric homolog of 7q. In the first meiotic division, a quadrivalent with a chain configuration can be observed in spermatocytes. Females have an X₁X₁X₂X₂sex-chromosome constitution. Chromosome heteromorphisms were observed in pair 13, due to a pericentric inversion, and pair 19, due to the presence of constitutive heterochromatin. Microchromosomes, which varied in number between individuals, were also heterochromatic. NOR-staining was observed at two separate sites on a single chromosome pair (No. 10). A comparison of A. s. stramineus with A.s. macconnelli shows that these two subspecies have identical diploid chromosome numbers (47, 48, or 49), again due to a varying number of microchromosomes, and that they share a similar sex-chromosome constitution. Their karyotypes, however, are not identical, but can be derived from each other by a reciprocal translocation. Further comparisons with other A. seniculus subspecies reported in the literature indicate that this taxon is not karyologically uniform and that substantial chromosome shuffling has occurred between populations that have been considered to be subspecies by taxonomic criteria based on their morphometric attributes.

Taxonomia e variação geográfica das espécies do gênero Alouatta Lacépède (Primates, Atelidae) no Brasil

“…Desde então Alouatta tem sofrido pequenas revisões na tentativa de esclarecer sua taxonomia e nomenclatura, com melhor tratamento dos dados biométricos mediante testes estatísticos, e com o emprego de caracteres moleculares e citogenéticos complementares aos morfológicos, para as proposições de relações de parentesco e a definição dos táxons (LIMA & SEUÁNEZ 1991, CONSIGLIERE et al 1996, SAMPAIO et al 1996, CORTÉS-ORTIZ et al 2003. Dentre os trabalhos, destaca-se o de BONVICINO et al (1989) cujo estudo minucioso da variação da pelagem no complexo A. belzebul, com a conseqüente redefinição das subespécies e seus respectivos limites geográficos, é referência até o presente.…”

“…O número diplóide variou de 47 a 49 de acordo com a presença de um a três micro-cromossomos (YUNIS et al 1976, LIMA & SEUÁNEZ 1991.…”

Phylogenetic relationships among Brazilian howler monkeys, genus Alouatta (Platyrrhini, Atelidae), based on <FONT FACE=Symbol>g</FONT>1-globin pseudogene sequences

“…In addition to other unresolved questions, the karyotype of Alouatta varies from 2n = 43 to 2n = 54 (Armada et al, 1987;Lima and Seuánez, 1991;Stanyon et al, 1995). Of the four Brazilian species, only A. caraya has a fixed number of chromosomes, with 2n = 52 (Pargament et al, 1984), whereas in A. seniculus, 2n varies from 43 to 49 (Yunis et al, 1976;Lima and Seuánez, 1991).…”

“…Of the four Brazilian species, only A. caraya has a fixed number of chromosomes, with 2n = 52 (Pargament et al, 1984), whereas in A. seniculus, 2n varies from 43 to 49 (Yunis et al, 1976;Lima and Seuánez, 1991). A. belzebul and A. fusca, on the other hand, share both the same diploid number (2n = 49/50) and a translocation on the Y chromosome (Koiffmann and Saldanha, 1974;Armada et al, 1987).…”

The primates of the Neotropics: genomes and chromosomes

“…In some species, like A. seniculus the diploid number may vary due to presence of different numbers of microchromosomes. Several sex chromosome systems have also been described in different species like XX/XY, X 1 X 1 X 2 X 2 /X 1 X 2 Y,X 1 X 1 X 2 X 2 /X 1 X 2 Y 1 Y 2 and X 1 X 1 X 2 X 2 X 3 X 3 /X 1 X 2 X 3 Y 1 Y 2 (see Yunis et al, 1976;Armada et al, 1987;Lima and Seuá nez, 1991;de Oliveira et al, 2002). A correlation of molecular and karyotypic data provides some clues on how Alouatta species evolved.…”