Quantification of hair cortisol concentration in common marmosets (Callithrix jacchus) and tufted capuchins (Cebus apella)

Quantifying cortisol concentration in hair is a non‐invasive biomarker of long‐term hypothalamic‐pituitary‐adrenal (HPA) activation, and thus can provide important information on laboratory animal health. Marmosets (Callithrix jacchus) and capuchins (Cebus apella) are New World primates increasingly used in biomedical and neuroscience research, yet published hair cortisol concentrations for these species are limited. Review of the existing published hair cortisol values from marmosets reveals highly discrepant values and the use of variable techniques for hair collection, processing, and cortisol extraction. In this investigation we utilized a well‐established, standardized protocol to extract and quantify cortisol from marmoset (n = 12) and capuchin (n = 4) hair. Shaved hair samples were collected from the upper thigh during scheduled exams and analyzed via methanol extraction and enzyme immunoassay. In marmosets, hair cortisol concentration ranged from 2,710 to 6,267 pg/mg and averaged 4,070 ± 304 pg/mg. In capuchins, hair cortisol concentration ranged from 621 to 2,089 pg/mg and averaged 1,092 ± 338 pg/mg. Hair cortisol concentration was significantly different between marmosets and capuchins, with marmosets having higher concentrations than capuchins. The incorporation of hair cortisol analysis into research protocols provides a non‐invasive measure of HPA axis activity over time, which offers insight into animal health. Utilization of standard protocols across laboratories is essential to obtaining valid measurements and allowing for valuable future cross‐species comparisons.     

Evolution of an intronic microsatellite polymorphism in Toll-like receptor 2 among primates

Nonhuman primates express varying responses to Mycobacterium tuberculosis: New World monkeys appear to be resistant to tuberculosis (TB) while Old World monkeys seem to be particularly susceptible. The aim of this study was to elucidate the presence of the regulatory guanine–thymine (GT) repeat polymorphisms in intron 2 of Toll-like receptor 2 (TLR2) associated with the development of TB in humans and to determine any variations in these microsatellite polymorphisms in primates. We sequenced the region encompassing the regulatory GT repeat microsatellites in intron 2 of TLR2 in 12 different nonhuman primates using polymerase chain reaction amplification, TA cloning, and automatic sequencing. The nonhuman primates included for this study were as follows: chimpanzee (Pan troglodytes), bonobo (Pan paniscus), gorilla (Gorilla gorilla), orangutan (Pongo pygmaeus), Celebes ape (Macaca nigra), rhesus monkey (Macaca mulatta), pigtail macaque (Macaca nemestrina), patas monkey (Erythrocebus patas), spider monkey (Ateles geoffroyi), Woolly monkey (Lagothrix lagotricha), tamarin (Saguinus labiatus), and ring-tailed lemur (Lemur catta). Nucleotide sequences encompassing the regulatory GT repeat region are similar across species and are completely conserved in great apes. However, Old World monkeys lack GT repeats altogether, while New World monkeys and ring-tailed lemurs have much more complex structures around the position of the repeats. In conclusion, the genetic structures encompassing the regulatory GT repeats in intron 2 of human TLR2 are similar among nonhuman primates. The sequence is most conserved in New World monkeys and less in Old World monkeys.     

Abundance, diversity, and patterns of distribution of primates on the Tapiche River in Amazonian Peru

This work presents data on the relative diversity, abundance, and distribution patterns of primates in a 20 km2 area of the Tapiche River in the Peruvian Amazon. Population data were collected while the study area was both inundated and dry (March to September 1997) using conventional line-transect census techniques. Survey results reflected the presence of 11 primate species, but population parameters on only eight of the species will be presented, including saddleback tamarins (Saguinus fuscicollis), Bolivian squirrel monkeys (Saimiri boliviensis), brown capuchins (Cebus apella), white-fronted capuchins (Cebus albifrons), monk sakis (Pithecia monachus), red titi monkeys (Callicebus cupreus), red uakaris (Cacajao calvus), and red howler monkeys (Alouatta seniculus). Woolly monkeys (Lagothrix lagotricha), night monkeys (Aotus nancymaae), and pygmy marmosets (Callithrix pygmaea) were also seen in the area. The data for the smaller-bodied primates is similar to that reported almost 18 years earlier, but the data for the larger-bodied primates reflect a loss in the number of animals present in the area. Pressure from hunters and the timber industry may account for declining numbers of large-bodied primates, while it appears that natural features peculiar to the conservation area contribute to the patchy pattern of distribution.     

Genetic influences on behavioral inhibition and anxiety in juvenile rhesus macaques

In humans and other animals, behavioral responses to threatening stimuli are an important component of temperament. Among children, extreme behavioral inhibition elicited by novel situations or strangers predicts the subsequent development of anxiety disorders and depression. Genetic differences among children are known to affect risk of developing behavioral inhibition and anxiety, but a more detailed understanding of genetic influences on susceptibility is needed. Nonhuman primates provide valuable models for studying the mechanisms underlying human behavior. Individual differences in threat-induced behavioral inhibition (freezing behavior) in young rhesus monkeys are stable over time and reflect individual levels of anxiety. This study used the well-established human intruder paradigm to elicit threat-induced freezing behavior and other behavioral responses in 285 young pedigreed rhesus monkeys. We examined the overall influence of quantitative genetic variation and tested the specific effect of the serotonin transporter promoter repeat polymorphism. Quantitative genetic analyses indicated that the residual heritability of freezing duration (behavioral inhibition) is h ² = 0.384 ( P  = 0.012) and of 'orienting to the intruder' (vigilance) is h ² = 0.908 ( P  = 0.00001). Duration of locomotion and hostility and frequency of cooing were not significantly heritable. The serotonin transporter polymorphism showed no significant effect on either freezing or orienting to the intruder. Our results suggest that this species could be used for detailed studies of genetic mechanisms influencing extreme behavioral inhibition, including the identification of specific genes that are involved in predisposing individuals to such behavior.     

Serotonin Transporter Genotype Modulates Social Reward and Punishment in Rhesus Macaques

Background

Serotonin signaling influences social behavior in both human and nonhuman primates. In humans, variation upstream of the promoter region of the serotonin transporter gene (5-HTTLPR) has recently been shown to influence both behavioral measures of social anxiety and amygdala response to social threats. Here we show that length polymorphisms in 5-HTTLPR predict social reward and punishment in rhesus macaques, a species in which 5-HTTLPR variation is analogous to that of humans.

Methodology/Principal Findings

In contrast to monkeys with two copies of the long allele (L/L), monkeys with one copy of the short allele of this gene (S/L) spent less time gazing at face than non-face images, less time looking in the eye region of faces, and had larger pupil diameters when gazing at photos of a high versus low status male macaques. Moreover, in a novel primed gambling task, presentation of photos of high status male macaques promoted risk-aversion in S/L monkeys but promoted risk-seeking in L/L monkeys. Finally, as measured by a “pay-per-view” task, S/L monkeys required juice payment to view photos of high status males, whereas L/L monkeys sacrificed fluid to see the same photos.

Conclusions/Significance

These data indicate that genetic variation in serotonin function contributes to social reward and punishment in rhesus macaques, and thus shapes social behavior in humans and rhesus macaques alike.     

Increased positive selection pressure within the complementarity determining regions of the T‐cell receptor β gene in New World monkeys

Because of the long‐term co‐evolution of TCR and MHC molecules, numerous nucleotide substitutions have accumulated within the domains of TCRβ genes. We previously found that nonsynonymous nucleotide substitutions occurred more frequently in complementarity determining region (CDR)β than in CDRα, even though only a limited number of common marmoset (Callithrix jacchus) and human T‐cell receptor β variable (TRBV) sequences were compared. This interesting finding raised the question of whether the increased selective pressure within CDRβ was species‐specific. In this study, we identified 21 TRBV region sequences from the common marmoset and performed comparative sequence analyses of the T‐cell receptor α variable (TRAV) and TRBV regions from human, chimpanzee, rhesus monkey, cotton‐top tamarin, Ma's night monkey, and common marmoset. The ratios of the number of nonsynonymous nucleotide substitutions per site (d_N) to the d_S values (d_N/d_S) were less than 1 within the framework regions (FRs) of TRAV and TRBV region sequences, suggesting that purifying selection is largely dominant within the FRs. In contrast, the d_N values were statistically significantly greater for CDRβ than for CDRα only in New World monkeys. Also, increased d_N/d_S ratios (d_N/d_S>1) were observed within CDRβ between humans and New World monkeys and, interestingly, between New World monkeys, which share a relatively recent common ancestor. Moreover, phylogenetic analysis by maximum likelihood analysis provided firm evidence to support that positive selection occurred within CDRβ along New World monkey lineages. These results suggest that increased positive selection pressure within CDRβ is common in New World monkeys rather than being species‐specific. This study provides an intriguing insight into the co‐evolution of TCR and MHC molecules within primates. Am. J. Primatol. 73:1082–1092, 2011. © 2011 Wiley‐Liss, Inc.     

Evolution of a repeat sequence in the parathyroid hormone-related peptide gene in primates

A polymorphism of the variable number of tandem repeat (VNTR) type is located 97 bp downstream of exon VI of the parathyroid hormone-related peptide (PTHrP) gene in humans. The repeat unit has the general sequence G(TA)_nC, where n equals 4–11. In order to characterize the evolutionary history of this VNTR, we initially tested for its presence in 13 different species representing four main groups of living primates. The sequence is present in the human, great apes, and Old World monkeys, but not in New World monkeys; and this region failed to PCR amplify in the Loris group. Thus, the evolution of the sequence as part of the PTHrP gene started at least 25–35 millions years ago, after divergence of the Old World and New World monkeys, but before divergence of Old World monkeys and great apes and humans. The structural changes occurring during evolution are characterized by a relatively high degree of sequence divergence. In general, the tandem repeat region tends to be longer and more complex in higher primates with the repeat unit motifs all being based on a TA-dinucleotide repeat sequence. Intra-species variability of the locus was demonstrated only in humans and gorilla. The divergence of the TA-dinucleotide repeat sequence and the variable mutation rates observed in different primate species are in contrast to the relative conservation of the flanking sequences during primate evolution. This suggests that the nature of the TA-dinucleotide repeat sequence, rather than its flanking sequences, is responsible for generating variability. Particular features of the sequence may allow it to form stable secondary structures during DNA replication, and this, in turn, could promote slipped-strand mispairing to occur.     

ASPM and the Evolution of Cerebral Cortical Size in a Community of New World Monkeys

The ASPM (abnormal spindle-like microcephaly associated) gene has been proposed as a major determinant of cerebral cortical size among primates, including humans. Yet the specific functions of ASPM and its connection to human intelligence remain controversial. This debate is limited in part by a taxonomic focus on Old World monkeys and apes. Here we expand the comparative context of ASPM sequence analyses with a study of New World monkeys, a radiation of primates in which enlarged brain size has evolved in parallel in spider monkeys (genus Ateles) and capuchins (genus Cebus). The primate community of Costa Rica is perhaps a model system because it allows for independent pairwise comparisons of smaller- and larger-brained species within two taxonomic families. Accordingly, we analyzed the complete sequence of exon 18 of ASPM in Ateles geoffroyi, Alouatta palliata, Cebus capucinus, and Saimiri oerstedii. As the analysis of multiple species in a genus improves phylogenetic reconstruction, we also analyzed eleven published sequences from other New World monkeys. Our exon-wide, lineage-specific analysis of eleven genera and the ratio of rates of nonsynonymous to synonymous substitutions (d_N/d_S) on ASPM revealed no detectable evidence for positive selection in the lineages leading to Ateles or Cebus, as indicated by d_N/d_S ratios of <1.0 (0.6502 and 0.4268, respectively). Our results suggest that a multitude of interacting genes have driven the evolution of larger brains among primates, with different genes involved in this process in different encephalized lineages, or at least with evidence for positive selection not readily apparent for the same genes in all lineages. The primate community of Costa Rica may serve as a model system for future studies that aim to elucidate the molecular mechanisms underlying cognitive capacity and cortical size.     

Human speech reduces pygmy marmoset (Cebuella pygmaea) feeding and resting at a Peruvian tourist site,with louder volumes decreasing visibility

Although potentially beneficial in terms of raising awareness and conservation funding, tourist visitation of wild primates can have negative impacts on visited groups. Tourism‐generated noise is a relatively understudied facet of ecotourism research, and the effects of tourist‐generated speech on free‐ranging, wild primates has never been explored previously. This study investigates the behavioral responses of 10 groups of pygmy marmosets (Cebuella pygmaea) to human speech. Through the use of an experimental playback study using recorded human speech, we show that pygmy marmosets within the Tamshiyacu‐Tahuayo Reserve, Peru, are significantly less visible, and often move completely out of sight after louder playbacks. Although no consistent differences were found in other behaviors with playback duration and volume, playbacks of human speech tended to increase the amount of time individuals were alert and decrease feeding and resting behaviors. Our results demonstrate that human speech can alter the behavior of visited primates, and identifies a decrease in primate visibility within the increasing volume. As all trials in this study took place near a marmoset group's feeding tree, moving out of sight from the visible study area is a particularly energetically costly behavior, and also has a negative effect on visitor enjoyment as it limits the time that they are able to view the target species. This response was not observed (nor was any other consistent behavior change) in control trials where the marmosets were exposed to human presence but not to speech, suggesting that negative tourist impacts can be reduced by encouraging tourists to refrain from speaking in the presence of visited primate groups.     

Comparison of marmoset and human FSH using synthetic peptides of the β‐subunit L2 loop region and anti‐peptide antibodies

Follicle stimulating hormone (FSH) is a glycoprotein hormone required for female and male gametogenesis in vertebrates. Common marmoset (Callithrix jacchus) is a New World primate monkey, used as animal model in biomedical research. Observations like, requirement of extremely high dose of human FSH in marmosets for superovulation compared to other primates and generation of antibodies in marmoset against human FSH after repeated superovulation cycles, point towards the possibility that FSH–FSH receptor (FSHR) interaction in marmosets might be different than in the humans. In this study we attempted to understand some of these structural differences using FSH peptides and anti‐peptide antibody approach. Based on sequence alignment, in silico modeling and docking studies, L2 loop of FSH β‐subunit (L2β) was found to be different between marmoset and human. Hence, peptides corresponding to region 32–50 of marmoset and human L2β loop were synthesized, purified and characterized. The peptides displayed dissimilarity in terms of molecular mass, predicted isoelectric point, predicted charge and in the ability to inhibit hormone–receptor interaction. Polyclonal antibodies generated against both the peptides were found to exhibit specific binding for the corresponding peptide and parent FSH in ELISA and Western blotting respectively and exhibited negligible reactivity to cross‐species peptide and FSH in ELISA. The anti‐peptide antibody against marmoset FSH was also able to detect native FSH in marmoset plasma samples and pituitary sections. In summary, the L2β loop of marmoset and human FSH has distinct receptor interaction ability and immunoreactivity indicating possibility of subtle conformational and biochemical differences between the two regions which may affect the FSH–FSHR interaction in these two primates. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Corticotropin-releasing hormone-binding protein in primates

In humans, placental corticotropin-releasing hormone (CRH) production has been linked to the determination of gestational length, and a late gestational fall in CRH-binding protein (CRH-BP) has been linked to the onset of parturition. Expression of placental CRH mRNA is limited to primates, and only in man has a circulating CRH-BP been described. As the fall in CRH-BP in late gestation has been associated with parturition in humans, we sought to determine whether a CRH-BP circulated in the plasma of other primates. It is unclear whether maternal plasma CRH concentrations are elevated in New World monkeys and prosimians. We have therefore performed CRH plasma measurements in the blood of pregnant marmosets, in several species of lemur, and in pregnant and fetal rhesus monkeys as a positive control. Using gel chromatography, CRH-BP was detected in the human, gorilla, chimpanzee, orangutan, gibbon, macaque, squirrel monkey, and marmoset, but was absent in the mandrill, spider monkey, and lemur. CRH was detected in the plasma of pregnant marmosets and rhesus monkeys. CRH was also detected in the fetal rhesus monkey, but at lower concentrations than in maternal plasma. CRH immunoreactivity was not detectable in the plasma of pregnant lemurs or in extracts of lemur placenta. In conclusion, a circulating binding protein for CRH exists in all species of apes but occurs variably among New World and Old World monkeys and is absent in lemurs. The variable occurrence of the CRH-BP does not support a role for this protein in the mechanism of parturition in primates. Maternal CRH is elevated in the pregnant marmoset and rhesus, and may play a role in the pregnancy of New and Old World monkeys.     

Camera Trap Observations of Nonhabituated Critically Endangered Wild Blonde Capuchins,Sapajus flavius (Formerly Cebus flavius)

Habituation presents major challenges for the study of wild primates, particularly in areas where threats such as hunting pressure and increasing forest fragmentation exist. This study describes the use of ground camera trapping to investigate nonhabituated blonde capuchins. Capuchins are arboreal animals, but often use the ground when foraging. Thus, we hypothesized that a ground-baited camera trapping station would be an efficient method to document the presence of capuchins, and to collect information about aspects of their social behavior and ecology. We conducted 92 systematic trapping days over 15 months (from December 2010 to February 2011 and from August 2011 to July 2012). The capuchins visited the trapping stations 43 times. All visits occurred between 05:13h and 17:32h, and lasted 3 min-2:03 h. Sixty-five percent of the photographs included our target species. Groups contained up to 46 individuals and were multimale-multifemale. We recorded no monkeys at the trapping stations during August and November (2011) and January (2012). Infants were more likely to be carried than not. Infants were carried by both sexes; however, 96% of photographs showed females as carriers. Adult males always arrived first at the camera trapping stations, suggesting that males led the group’s movements. The ground-baited camera trapping stations proved effective for confirming the presence of the blonde capuchins in the study site and for documenting aspects of their social behavior. The technique could potentially be used to provide comparative data among populations of this and other primate species in areas where habituation is difficult or risky to the primates.     

Primate evolution of the alpha-globin gene cluster and its Alu-like repeats

The arrangement of alpha-globin genes in Old World and New World monkeys and a prosimian, galago, has been determined by restriction mapping. Recombinant DNAs containing galago and Old World monkey alpha-globin genes have been isolated and subjected to a partial sequence determination for comparison to alpha-globin genes in human, chimpanzee and non-primate mammals. The results of this extensive structural analysis are relevant to several topics concerning the evolution of primate alpha-globin genes and Alu family repeats. All orders of higher primates (i.e. Old and New World monkeys, chimpanzee and human) have the same arrangement of alpha-globin genes. In contrast, the arrangement and correction of galago alpha-globin genes differ from those of higher primates, but are similar to those of non-primate mammals. The 5' and 3'-flanking regions of the human alpha 1 gene are orthologous to the corresponding region in galago, identifying the human alpha 2 gene as the more recently duplicated gene. The human psi alpha 1 gene is found to be inactivated after divergence of the human and galago lineages but prior to the divergence of human and monkey. Orthologous Alu family members in human and monkey DNAs indicate that the dispersion of some Alu repeats occurred prior to the divergence of these lineages. However, the Alu-like repeats of prosimian and higher primates result from entirely independent events giving rise to different repeat elements inserted at distinct genomic positions.     

Life history patterns of new world monkeys

Allometric methods are used to investigate the life history patterns of New World monkeys. These patterns are compared to those found in other haplorhines and links with ecology are explored. The life history characteristics of the cebid monkeys suggest that these species are primarily slow breeding and slow developing for primates of their size. I suggest that these characteristics arose during a long period of adaptation to stable rainforest habitats. The capuchins and squirrel monkeys are a notable exception to the general rule that genera found outside primary forests will have a “fast” life history. In the marmosets and tamarins selection for small size and high birth rate has occurred, probably as a result of their adapting to more secondary habitats. It is this selection for rapid breeding, combined with the preadaptation of paternal care, that has probably led to twinning in these species. The evidence presented indicates that it is unlikely that twinning arose as a direct result of the mechanical constraints of small size but is more probably due to selection for increased reproductive output.     

Interspecific Infanticide and Infant‐Directed Aggression by Spider Monkeys (Ateles hybridus) in a Fragmented Forest in Colombia

Interspecific aggression amongst nonhuman primates is rarely observed and has been mostly related to scenarios of resource competition. Interspecific infanticide is even rarer, and both the ultimate and proximate socio‐ecological factors explaining this behavior are still unclear. We report two cases of interspecific infanticide and five cases of interspecific infant‐directed aggression occurring in a well‐habituated primate community living in a fragmented landscape in Colombia. All cases were initiated by male brown spider monkeys (Ateles hybridus) and were directed toward infants of either red howler monkeys (Alouatta seniculus: n = 6 cases) or white‐fronted capuchins (Cebus albifrons: n = 1 case). One individual, a subadult spider monkey male, was involved in all but one case of interspecific infanticide or aggression. Other adult spider monkeys participated in interspecific aggression that did not escalate into potentially lethal encounters. We suggest that competition for food resources and space in a primate community living in high population densities and restricted to a forest fragment of ca. 65 ha might partly be driving the observed patterns of interspecific aggression. On the other hand, the fact that all but one case of interspecific infanticide and aggression involved the only subadult male spider monkey suggests this behavior might either be pathological or constitute a particular case of redirected aggression. Even if the underlying principles behind interspecific aggression and infanticide are poorly understood, they represent an important factor influencing the demographic trends of the primate community at this study site. Am. J. Primatol. 74:990‐997, 2012. © 2012 Wiley Periodicals, Inc.