Sex chromosome systems in Neotropical Primates: What have we learnt so far from cytogenetics and genomics?

Neotropical Primates (Platyrrhini) show great diversity in their life histories, ecology, behaviour and genetics. This diversity extends to their chromosome complements, both to autosomes and to sex chromosomes. In this contribution, we will review what is currently known about sex chromosomes in this group, both from cytogenetic and from genomic evidence.

Sperm Morphology in Neotropical Primates.

The morphological and morphometric characterization of spermatozoa has been used as a taxonomic and phylogenetic tool for different species of mammals. We evaluated and compared the sperm morphometry of five neotropical primate species: , and of family Atelidae; and (=) and (=) of family Cebidae. After the collection of semen samples, the following parameters were measured on 100 spermatozoa from each specimen: Head Length, Head Width, Acrosome Length, Midpiece Length, Midpiece Width and Tail Length.

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

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.

Two cases of polydactyly in wild brown howler monkeys (Alouatta guariba clamitans).

We report the first two cases of polydactyly in an atelid species: (i) a wild ca. 16-week-old infant female presenting seven digits in both feet and other bone malformations and (ii) a wild newborn male presenting six digits in both feet with the extra digit fused to the hallux.

Primates karyological diagnosis and management programs applications.

Background: Captive primates are often maintained in groups without geographic origin or genetic heritage information. This could lead to an incorrect assignment of species, which could result in an inadequate management of the colonies.

Methods: We present a cytogenetic protocol adapted to be successfully used in an accurate taxonomic diagnosis of non-human primates (Platyrrhini), including lymphocyte culture, G- and C-banding, meiosis, and fluorescent in situ hybridization technique (FISH).

Multiple sex chromosome systems in howler monkeys (Platyrrhini, Alouatta).

In light of the multiple sex chromosome systems observed in howler monkeys (Alouatta Lacépède, 1799) a combined cladistic analysis using chromosomal and molecular characters was applied to discuss the possible origin of these systems. Mesoamerican and South American howlers were karyologically compared. FISH analysis using the chromosome painting probes for the #3 and #15 human chromosomes was applied to corroborate the homeology of the sexual systems.

A comparative study of the recombination pattern in three species of Platyrrhini monkeys (primates).

Homologous chromosomes exchange genetic information through recombination during meiotic synapsis, a process that increases genetic diversity and is fundamental to sexual reproduction. Meiotic studies in mammalian species are scarce and mainly focused on human and mouse. Here, the meiotic recombination events were determined in three species of Platyrrhini monkeys (Cebus libidinosus, Cebus nigritus and Alouatta caraya) by analysing the distribution of MLH1 foci at the stage of pachytene.

Pairing and recombination features during meiosis in Cebus paraguayanus (Primates: Platyrrhini).

Background: Among neotropical Primates, the Cai monkey Cebus paraguayanus (CPA) presents long, conserved chromosome syntenies with the human karyotype (HSA) as well as numerous C+ blocks in different chromosome pairs.In this study, immunofluorescence (IF) against two proteins of the Synaptonemal Complex (SC), namely REC8 and SYCP1, two recombination protein markers (RPA and MLH1), and one protein involved in the pachytene checkpoint machinery (BRCA1) was performed in CPA spermatocytes in order to analyze chromosome meiotic behavior in detail.

Results: Although in the vast majority of pachytene cells all autosomes were paired and synapsed, in a small number of nuclei the heterochromatic C-positive terminal region of bivalent 11 remained unpaired.

Meiotic characterization and sex determination system of neotropical primates: Bolivian squirrel monkey Saimiri boliviensis (primates: Cebidae).

The chromosomal sex determination system differs among platyrrhine monkeys more than any other group of primates. Although a number of studies have investigated mitotic chromosomes across platyrrhine species, the meiotic chromosomes of many genera have not yet been described. The goal of this study was to characterize the sex determination system of Saimiri boliviensis.