Repetitive Sequence Distribution on Saguinus, Leontocebus and Leontopithecus Tamarins (Platyrrhine, Primates) by Mapping Telomeric (TTAGGG) Motifs and rDNA Loci

Tamarins are a distinct group of small sized New World monkeys with complex phylogenetic relationships and poorly studied cytogenetic traits. In this study, we applied molecular cytogenetic analyses by fluorescence in situ hybridization with probes specific for telomeric sequences and ribosomal DNA loci after DAPI/CMA3 staining on metaphases from five tamarin species, namely Leontocebus fuscicollis, Leontopithecus rosalia, Saguinus geoffroyi, Saguinus mystax and Saguinus oedipus, with the aim to investigate the distribution of repetitive sequences and their possible role in genome evolution. Our analyses revealed that all five examined species show similar karyotypes, 2n = 46, which differ mainly in the morphology of chromosome pairs 16–17 and 19–22, due to the diverse distribution of rDNA loci, the amplification of telomeric-like sequences, the presence of heterochromatic blocks and/or putative chromosomal rearrangements, such as inversions. The differences in cytogenetic traits between species of tamarins are discussed in a comparative phylogenetic framework, and in addition to data from previous studies, we underline synapomorphies and apomorphisms that appeared during the diversification of this group of New World monkeys.

The chondrocranial key: Fetal and perinatal morphogenesis of the sphenoid bone in primates

The sphenoid bone articulates with multiple basicranial, facial, and calvarial bones, and in humans its synchondroses are known to contribute to elongation of the skull base and possibly to cranial base angulation. Its early development (embryological, early fetal) has frequently been studied in a comparative context. However, the perinatal events in morphogenesis of the sphenoid have been explored in very few primates. Using a cross-sectional age sample of non-human primates (n=39; 22 platyrrhines; 17 strepsirrhines), we used microcomputed tomographic (µCT) and histological methods to track age changes in the sphenoid bone. In the midline, the sphenoid expands its dimensions at three growth centers, including the sphenooccipital, intrasphenoidal (ISS) and presphenoseptal (PSept) synchondroses. Bilaterally, the alisphenoid is enlarged via appositional bone growth that radiates outward from cartilaginous parts of the alisphenoid during midfetal stages. The alisphenoid remains connected to the basitrabecular process of the basisphenoid via the alibasisphenoidal synchondrosis (ABS). Reactivity to proliferating cell-nuclear antigen is observed in all synchondroses, indicating active growth perinatally. Between mid-fetal and birth ages in Saguinus geoffroyi, all synchondroses decrease in the breadth of proliferating columns of chondrocytes. In most primates, the ABS is greatly diminished by birth, and is likely the earliest to fuse, although at least some cartilage may remain by at least one-month of age. Unlike humans, no non-human primate in our sample exhibits perinatal fusion of ISS. A dichotomy among primates is the orientation of the ABS, which is more rostrally directed in platyrrhines. Based on fetal Saguinus geoffroyi specimens, the ABS was initially oriented within a horizontal plane, and redirects inferiorly during late fetal and perinatal stages. These changes occur in tandem with forward orientation of the orbits in platyrrhines, combined with downward growth of the midface. Thus, we postulate that active growth centers direct the orientation of the midface and orbit before birth.

Rain forests and movement ecology of neotropical primates

Movement ecology of arboreal monkeys in Central America involves the action of diverse body postures to address challenges in rain forests, where scattered resources and complex habitat structure demand that a primate frequently employ extreme physical finesse to survive. What is not clearly understood about this area of study is the connection between primate body postures as responses to specific types of forest architecture and how forest structure may influence a monkey’s continued capacity for wide-ranging mobility over time. We studied tree canopy structure and branch connectivity associated with the movement ecology of black-handed spider monkeys (Ateles geoffroyi), mantled howling monkeys (Alouatta palliata), Geoffroy’s tamarins (Saguinus geoffroyi), and white-faced capuchins (Cebus capucinus) in Panama and Costa Rica. Laboratory study of primate cadaver pelvises was done at UC Davis, Oregon Osteology Lab, and the Denver Museum. Rain forests appear to induce wide-ranging leg movements in wild neotropical monkeys that were not observed in the same species of monkeys inhabiting artificial environments. We also found that a wild primate employs frequent wide-ranging leg movement that result in widely dispersed contacts between the articulating surfaces within the hip, potentially maintaining cartilage and contributing to the longevity of that joint. Thus, a connection may exist between rain forests, the leg action of wild monkeys, and the continued capacity to move over time in this group of long-lived animals.

Rain forests and movement ecology of neotropical primates

Movement ecology of arboreal monkeys in Central America involves the action of diverse body postures to address challenges in rain forests, where scattered resources and complex habitat structure demand that a primate frequently employ extreme physical finesse to survive. What is not clearly understood about this area of study is the connection between primate body postures as responses to specific types of forest architecture and how forest structure may influence a monkey’s continued capacity for wide-ranging mobility over time. We studied tree canopy structure and branch connectivity associated with the movement ecology of black-handed spider monkeys (Ateles geoffroyi), mantled howling monkeys (Alouatta palliata), Geoffroy’s tamarins (Saguinus geoffroyi), and white-faced capuchins (Cebus capucinus) in Panama and Costa Rica. Laboratory study of primate cadaver pelvises was done at UC Davis, Oregon Osteology Lab, and the Denver Museum. Rain forests appear to induce wide-ranging leg movements in wild neotropical monkeys that were not observed in the same species of monkeys inhabiting artificial environments. We also found that a wild primate employs frequent wide-ranging leg movement that result in widely dispersed contacts between the articulating surfaces within the hip, potentially maintaining cartilage and contributing to the longevity of that joint. Thus, a connection may exist between rain forests, the leg action of wild monkeys, and the continued capacity to move over time in this group of long-lived animals.

Rain-forest canopy-connectivity and habitat selection by a small neotropical primate, Geoffroy's tamarin (Saguinus geoffroyi)

Wild populations of a small neotropical primate, Geoffroy's tamarin (Saguinus geoffroyi), were studied through 30-s instantaneous observational sampling to identify different canopy habitats used by this tamarin. Tree and shrub canopies were sampled in randomly selected plots and in nearby plots that tamarins were observed to use in the forests of Agua Clara, Panama (28 d, 59 100-m2 plots, 32.25 h of tamarin observations, 27 tamarins in total), and in the nearby forests of Barro Colorado Island (49 d, 29 100-m2 plots, 29.6 h of tamarin observations, 14 tamarins in total). Light penetration through the canopy, ambient temperature and humidity, presence of other primates, stem diameters, plant life-forms, distribution of woody flora, abundance of fleshy fruits and arthropods typically consumed by tamarins and abundance of thorny vegetation and biting arthropods in plots used by tamarins were compared with control plots. Habitats used by tamarins had significantly shorter distances between adjacent tree canopies and between canopies and the ground. There was a random distribution of large insects and fleshy fruits that tamarins are known to eat. Habitat selection by tamarins may not be influenced by spiny vegetation, but tamarins may avoid areas with abundant hooked thorns and blood-sucking arthropods. Mobility along runways in various tiers of a rain-forest canopy may be of primary importance, with local abundance of food being a secondary consideration in habitat selection by this small primate.