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Human aging is associated with senescence of the hypothalamic–pituitary–adrenal (HPA) axis, leading to progressive dysregulation characterized by increased cortisol exposure. This key hormone is implicated in the pathogenesis of many age‐related diseases. Common marmosets (Callithrix jacchus) display a wide spectrum of naturally occurring age‐related pathologies that compare similarly to humans and are increasingly used as translational models of aging and age‐related disease. Whether the marmoset HPA axis also shows senescence with increasing age is unknown. We analyzed hair cortisol concentration (HCC) across the lifespan of 50 captive common marmosets, ranging in age from approximately 2 months–14.5 years, via a cross‐sectional design. Samples were processed and analyzed for cortisol using enzyme immunoassay. HCC ranged from 1416 to 15,343 pg/mg and was negatively correlated with age. We found significant main effects of age group (infant, adolescent, adult, aged, very aged) and sex on HCC, and no interaction effects. Infants had significantly higher levels of HCC compared with all other age groups. Females had higher HCC than males. There was no interaction between age and sex. These results suggest marmosets do not show dysregulation of the HPA axis with increasing age, as measured via HCC. Highlights: We quantified hair cortisol concentration over the lifespan in marmosets.Infants displayed higher cortisol than all other age groups.Marmosets did not exhibit senescence of the hypothalamic–pituitary–adrenal (HPA) axis.HPA axis dysregulation may not be an inevitable consequence of aging. [ABSTRACT FROM AUTHOR]

Researchers and veterinarians often use hematology and clinical chemistry to evaluate animal health. These biomarkers are relatively easy to obtain, and understanding how they change across healthy aging is critical to clinical care and diagnostics for these animals. We aimed to evaluate how clinical biomarkers from a chemistry profile and complete blood count (CBC) change with age in common marmosets (Callithrix jacchus). We assessed blood samples collected during routine physical exams at the Southwest National Primate Research Center and the University of Texas Health San Antonio marmoset colonies from November 2020–November 2021. We found that chemistry and CBC profiles varied based on facility, sex, and age. Significant changes in albumin, phosphorus/creatinine ratio, albumin/globulin ratio, amylase, creatinine, lymphocyte percent, hematocrit, granulocytes percent, lymphocytes, hemoglobin, red cell distribution width, and platelet distribution width were all reported with advancing age. Aged individuals also demonstrated evidence for changes in liver, kidney, and immune system function compared with younger individuals. Our results suggest there may be regular changes associated with healthy aging in marmosets that are outside of the range typically considered as normal values for healthy young individuals, indicating the potential need for redefined healthy ranges for clinical biomarkers in aged animals. Identifying animals that exhibit values outside of this defined healthy aging reference will allow more accurate diagnostics and treatments for aging colonies. Research Highlights: The parameters that were reduced in peri‐geriatric or geriatric marmosets compared with younger marmosets were albumin, phosphorus/creatinine ratio, albumin/globulin ratio, calcium, glucose, lymphocytes, red blood cells, red cell distribution width, mean platelet volume, red cell distribution standard deviation, plateletcrit, platelet distribution width, and platelet distribution standard deviation.The parameters that were increased in peri‐geriatric and geriatric compared with young marmosets were amylase, creatinine,anion gap, granulocytes percent, and platelets.Our results suggest normal changes associated with healthy aging marmosets indicating the potential need for refinement of normal ranges for clinical biomarkers in aged marmosets. [ABSTRACT FROM AUTHOR]

Nonhuman primates exhibit sexual dimorphism in behavior, suggesting that there could be underlying differences in brain organization and function. Understanding this neuroanatomical variation is critical for enhancing our understanding of the evolution of sex differences in the human brain. Tufted capuchin monkeys (Sapajus [Cebus] apella) represent a phylogenetically diverse taxa of neotropical primates that converge on several behavioral characteristics with humans relevant to social organization, making them an important point of comparison for studying the evolution of sex differences in primates. While anatomical sex differences in gray matter have previously been found in capuchin monkeys, the current study investigates sex differences in white matter tracts. We carried out tract‐based spatial statistical analysis on fractional anisotropy images of tufted capuchin monkeys (15 female, 5 male). We found that females showed significantly higher fractional anisotropy than males in regions of frontal‐parietal white matter in the right cerebral hemisphere. Paralleling earlier findings in gray matter, male and female fractional anisotropy values in these regions were nonoverlapping. This complements prior work pointing toward capuchin sex differences in limbic circuitry and higher‐order visual regions. We propose that these sex differences are related to the distinct socioecological niches occupied by male and female capuchins. Capuchin neuroanatomical sex differences appear to be more pronounced than in humans, which we suggest may relate to human adaptations for prolonged neurodevelopmental trajectories and increased plasticity. [ABSTRACT FROM AUTHOR]

We conducted a dose–response study of dexamethasone to investigate an optimal dexamethasone suppression test for common marmosets. Twelve marmosets received 0.1, 0.5, or 1.0 mg/kg dexamethasone. Doses of 0.5 and 1.0 mg/kg both suppressed endogenous cortisol for at least 18 h with greater individual variability in the lower 0.5 mg/kg dose. [ABSTRACT FROM AUTHOR]

This study reports an analysis of 20 T1‐weighted magnetic resonance imaging scans from tufted capuchin monkeys (5 male, 15 female). We carried out a data‐driven, whole‐brain volumetric analysis on regional gray matter anatomy using voxel‐based morphometry. This revealed that males showed statistically significant expansion of a region of the hypothalamus, while females showed significant expansion in a distributed set of regions, including the cerebellum, early visual cortex, and higher‐order visual regions spanning occipital and temporal cortex. In order to elucidate the network connectivity of these regions, we employed probabilistic tractography on diffusion tensor imaging data. This showed that the female‐enlarged regions connect with distributed association networks across the brain. Notably, this contrasts with rodent studies, where sex differences are focused in deep, ancestral limbic regions involved in the control of reproductive behavior. Additionally, in our data set, for several regions, male and female volumetric measures were completely nonoverlapping. This contrasts with human studies, where sex differences in cortical regions have been reported but are characterized by overlapping rather than divergent male and female values. We suggest that these results can be understood in the context of the different lifetime experiences of males and females, which may produce increased experience‐dependent cortical plasticity in capuchins compared to rodents, and in humans compared to capuchins. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article offers information on membership trends of the American Society of Primatologists in 2015 and the organization's future plans. It discusses events in scientific primatology between 2012 and 2015 that have influenced decisions concerning membership in the organization, a decline in the total number of its members and the failure of the organization to convert student members into full members.

Meissner's corpuscles ( MCs) are tactile mechanoreceptors found in the glabrous skin of primates, including fingertips. These receptors are characterized by sensitivity to light touch, and therefore might be associated with the evolution of manipulative abilities of the hands in primates. We examined MCs in different primate species, including common marmoset ( Callithrix jacchus, n = 5), baboon ( Papio anubis, n = 2), rhesus macaque ( Macaca mulatta, n = 3), chimpanzee ( Pan troglodytes, n = 3), bonobo ( Pan paniscus, n = 1) and human ( Homo sapiens, n = 8). Fingertips of the first, second and fourth digits were collected from both hands of specimens, dissected and histologically stained using hematoxylin and eosin. The density ( MCs per 1 mm2) and the size (cross-sectional diameter of MCs) were quantified. Overall, there were no differences in the densities of MCs or their size among the digits or between the hands for any species examined. However, MCs varied across species. We found a trend for higher densities of MCs in macaques and humans compared with chimpanzees and bonobos; moreover, apes had larger MCs than monkeys. We further examined whether the density or size of MCs varied as a function of body mass, measures of dexterity and dietary frugivory. Among these variables, only body size accounted for a significant amount of variation in the size of MCs. [ABSTRACT FROM AUTHOR]

Research involving nonhuman primates (NHPs) has played a vital role in many of the medical and scientific advances of the past century. NHPs are used because of their similarity to humans in physiology, neuroanatomy, reproduction, development, cognition, and social complexity-yet it is these very similarities that make the use of NHPs in biomedical research a considered decision. As primate researchers, we feel an obligation and responsibility to present the facts concerning why primates are used in various areas of biomedical research. Recent decisions in the United States, including the phasing out of chimpanzees in research by the National Institutes of Health and the pending closure of the New England Primate Research Center, illustrate to us the critical importance of conveying why continued research with primates is needed. Here, we review key areas in biomedicine where primate models have been, and continue to be, essential for advancing fundamental knowledge in biomedical and biological research. Am. J. Primatol. 76:801-827, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT We describe an atypical neuroanatomical feature present in several primate species that involves a fusion between the temporal lobe (often including Heschl's gyrus in great apes) and the posterior dorsal insula, such that a portion of insular cortex forms an isolated pocket medial to the Sylvian fissure. We assessed the frequency of this fusion in 56 primate species (including apes, Old World monkeys, New World monkeys, and strepsirrhines) by using either magnetic resonance images or histological sections. A fusion between temporal cortex and posterior insula was present in 22 species (seven apes, two Old World monkeys, four New World monkeys, and nine strepsirrhines). The temporoinsular fusion was observed in most eastern gorilla ( Gorilla beringei beringei and G. b. graueri) specimens (62% and 100% of cases, respectively) but was seen less frequently in other great apes and was never found in humans. We further explored the histology of this fusion in eastern gorillas by examining the cyto- and myeloarchitecture within this region and observed that the degree to which deep cortical layers and white matter are incorporated into the fusion varies among individuals within a species. We suggest that fusion between temporal and insular cortex is an example of a relatively rare neuroanatomical feature that has become more common in eastern gorillas, possibly as the result of a population bottleneck effect. Characterizing the phylogenetic distribution of this morphology highlights a derived feature of these great apes. J. Comp. Neurol. 522:844-860, 2014. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Skilled motor actions are associated with handedness and neuroanatomical specializations in humans. Recent reports have documented similar neuroanatomical asymmetries and their relationship to hand preference in some nonhuman primate species, including chimpanzees and capuchin monkeys. We investigated whether capuchins displayed significant hand preferences for a tool-use task and whether such preferences were associated with motor-processing regions of the brain. Handedness data on a dipping tool-use task and high-resolution 3T MRI scans were collected from 15 monkeys. Capuchins displayed a significant group-level left-hand preference for this type of tool use, and handedness was associated with asymmetry of the primary motor cortex. Left-hand preferent individuals displayed a deeper central sulcus in the right hemisphere. Our results suggest that capuchins show an underlying right-hemisphere bias for skilled movement. Am. J. Primatol. 75:435-440, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The frequency of anointing bouts and the materials used for self- and social anointing vary across capuchin species in captivity, but there is little published data on capuchin anointing in the wild. Here we present previously unpublished data on anointing behaviors from capuchin monkey populations at ten different field sites and incorporate these data into a review of the anointing literature for captive and wild capuchins. Using a comparative phylogenetic framework, we test four hypotheses derived primarily from captive literature for variation in anointing between wild untufted capuchins ( Cebus) and tufted capuchins ( Sapajus), including that (1) the frequency of anointing is higher in Cebus, (2) Cebus uses a higher proportion of plant species to insect species for anointing compared with Sapajus, (3) anointing material diversity is higher in Cebus, and (4) social indices of anointing are higher in Cebus. We found that wild Cebus anoints more with plant parts, including fruits, whereas wild Sapajus anoints more with ants and other arthropods. Cebus capucinus in particular uses more plant species per site for anointing compared with other capuchins and may specialize in anointing as an activity independent from foraging, whereas most other capuchin species tend to eat the substances they use for anointing. In agreement with captive studies, we found evidence that wild Cebus anoints at a significantly higher frequency than Sapajus. However, contrary to the captive literature, we found no difference in the range of sociality for anointing between Cebus and Sapajus in the wild. We review anointing in the context of other Neotropical primate rubbing behaviors and consider the evidence for anointing as self-medication; as a mechanism for enhanced sociality; and as a behavioral response to chemical stimuli. Am. J. Primatol. 74:299-314, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Urine washing (UW) consists of depositing urine on the hands and vigorously rubbing the body. As urine contains chemical and pheromonal cues, UW may convey socially relevant information. Although ritualized UW is observed in many New World primates, including capuchin monkeys, the functional significance of UW remains unclear. In this experiment, we investigated the social signaling hypothesis of UW. Specifically, we hypothesized that UW by males conveys socially relevant signals that females can detect. We used functional magnetic resonance imaging (fMRI) to test whether adult female capuchins show differential brain activation in response to adult male and juvenile male capuchin urine. We expected to see changes in activation of structures involved in olfactory processing, including the piriform cortex, medial preoptic and anterior hypothesis, orbitofrontal cortex, hippocampus, and cerebellum. Data were acquired from four adult female capuchin monkeys. Presentations of odor stimuli (obtained from unfamiliar males) were made during fMRI acquisition using a standard ON-OFF design. All fMRI data were spatially normalized to a template and analyzed using the FMRI Expert Analysis Tool Version 5.98, part of the FMRIB's Software Library (). Whole brain analyses revealed significant activations in the inferior temporal cortex, parahippocampal gyrus, precuneus, hippocampus, pulvinar, and cerebellum when females were presented with the adult male urine. Notably, significantly greater signal activation was observed in several regions associated with olfactory processing, when subjects were presented with adult male urine as compared with urine from juvenile males. Our results indicate that UW serves a social communicative function in capuchins, providing support for the sexual signaling hypothesis. Am. J. Primatol. 73:578-584, 2011. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The diet of capuchin monkeys consists largely of fruits, but these monkeys commonly prey upon insects and other invertebrates as well as vertebrates such as lizards, birds, and fish. Capturing small fast-moving prey requires the ability to process complex visuospatial information such as motion detection, shape, and pursuit. Here we report the results of an experimental investigation into whether capuchins display sex differences in prey capture efficiency, and whether these differences are associated with the morphology of regions of the corpus callosum (CC) involved in visuospatial ability. We examined the prey capture behavior of seven capuchin subjects (four female, three male) in the laboratory by providing subjects opportunities to fish. Additionally, we obtained structural magnetic resonance images from these subjects to determine if spatial-ability was related to CC anatomy. Over 30 fishing trials, we recorded the number of prey capture attempts, success rate in capturing fish, and hand techniques used in these attempts. Males were significantly faster and more successful than females at capturing prey. In addition, males had smaller total CC:brain ratios than females. Males displayed a left hand bias, as well as significant unimanual usage, whereas females displayed no significant preference for hand usage. Individual capture times were correlated with total CC:brain ratio. Taken together, our results suggest a relationship between prey capture efficiency, sex, and the degree of brain lateralization. Am. J. Primatol. 72:502–508, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The CC is the major white matter tract connecting the cerebral hemispheres and provides for interhemispheric integration of sensory, motor and higher-order cognitive information. The midsagittal area of the CC has been frequently used as a marker of brain development in humans. We report the first investigation into the development of the corpus callosum and its regional subdivisions in chimpanzees (Pan troglodytes). Magnetic resonance images were collected from 104 chimpanzees (female n = 63, male n = 41) ranging in age from 6 years (pre-pubescent period) to 54 years (old age). Sustained linear growth was observed in the area of the CC subdivision of the genu; areas of the posterior midbody and anterior midbody displayed nonlinear growth during development. After adjusting for total brain size, we observed linear growth trajectories of the total CC and CC subdivisions of the genu, posterior midbody, isthmus and splenium, and nonlinear growth trajectories of the rostral body and anterior midbody. These developmental patterns are similar to the development of the CC in humans. As the growth curves of the CC mirrors growth seen in the percentage of white matter in humans, our results suggest chimpanzees show continued white matter development in regions related to cognitive development. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52:133–141, 2010 [ABSTRACT FROM AUTHOR]

Numerous studies investigating behavioral lateralization in capuchins have been published. Although some research groups have reported a population-level hand preference, other researchers have argued that capuchins do not show hand preference at the population level. As task complexity influences the expression of handedness in other primate species, the purpose of this study was to collect hand preference data across a variety of high- and low-level tasks to evaluate how task complexity influences the expression of hand preference in capuchins. We tested eleven captive brown capuchin monkeys (Cebus apella) to determine if they show consistent hand preferences across multiple high- and low-level tasks. Capuchins were expected to display high intertask consistency across the high-level tasks but not the low-level tasks. Although most individuals showed significant hand preferences for each task, only two of the high-level tasks that involved similar hand motions were significantly positively correlated, indicating consistency of hand preference across these tasks only. None of the tasks elicited a group-level hand preference. High-level tasks elicited a greater strength of hand preference than did low-level tasks. No sex differences were found for the direction or strength of hand preference for any task. These results contribute to the growing database of primate laterality and provide additional evidence that capuchins do not display group-level hand preferences. Am. J. Primatol. 70:254–260, 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

In several studies of social monitoring in primates, subordinate animals directed more visual attention toward dominant animals than vice versa. This behavior is thought to enable subordinate animals to avoid conflict. We sought to clarify whether visual attention behavior functions in this manner in a small captive group of brown capuchin monkeys, Cebus apella. We tested the hypothesis that social monitoring is related to dominance status. Dominance status was determined based on the directionality of aggressive behavior, and visual attention was quantified by using focal animal sampling. Subordinate animals directed significantly more visual attention toward others than dominant animals. Subordinate animals also looked more frequently at the animals that attacked them and others the most. The results indicate that social monitoring behavior in this captive group was driven by conflict-avoidance. [ABSTRACT FROM AUTHOR]

Data on the spatiotemporal distribution of resources can be collected and plotted using GPS (global positioning system) and GIS (geographical information system) technologies. By combining such data with information on foraging and ranging behavior of nonhuman primates, one can analyze the influence of resource distribution on social organization and group cohesion. We investigated the abilities of a three-channel GPS receiver to collect location data under varying canopy densities in both temperate and tropical forests. Eighty randomly selected points were sampled in a beech–maple forest in northeast Ohio, USA; 65 points also were sampled at several tropical forests in Costa Rica and Trinidad. At each point we attempted to obtain a GPS position fix; we also determined the speed of satellite acquisition and measured canopy density using a spherical densiometer. The ability to obtain a reading differed greatly between the two forest types (χ[sup 2] = 53.79, P < 0.001). Ninety-seven percent of all attempts were successful in the temperate forest, whereas only a 34% acquisition rate was obtained in the tropical forests. Logistic regression showed that the probability of obtaining a reading in Neotropical forests was 75% but only when canopy cover was less than 20%. Thus, these minimal-channel GPS units may be of limited utility for behavioral ecologists working in closed-canopy Neotropical forests. Am. J. Primatol. 46:167–172, 1998. © 1998 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Eight capuchins were trained in a capture and venipuncture procedure. Samples taken immediately following capture indicated that subjects experienced rising cortisol levels over the first 5 weeks of training followed by a return to baseline (equivalent to day 1 levels) in the sixth and seventh weeks. After 7 weeks, samples taken 60 min after initial capture revealed that behaviorally habituated animals exhibited significantly lower cortisol levels in response to venipuncture as opposed to naive and experienced but nonbehaviorally habituated subjects. [ABSTRACT FROM AUTHOR]

White-fronted capuchins were observed to use leaves as cups to retrieve water from tree cavities. On multiple occasions several individuals performed this behavior. Thus, these capuchins engage in habitual tool use, as defined by McGrew's classificatory scheme of tool using behavior. Am. J. Primatol. 46:259–261, 1998. © 1998 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Executive control is a higher‐level cognitive function that involves a range of different processes that are involved in the planning, coordination, execution, and inhibition of responses. Many of the processes associated with executive control, such as response inhibition and mental flexibility, decline with age. Degeneration of white matter architecture is considered to be the one of the key factors underlying cognitive decline associated with aging. Here we investigated how white matter changes of the corpus callosum were related to cognitive aging in common marmosets (Callithrix jacchus). We hypothesized that reduction in myelin thickness, myelin density, and myelin fraction of axonal fibers in the corpus callosum would be associated with performance on a task of executive function in a small sample of geriatric marmosets (n = 4) and young adult marmosets (n = 2). Our results indicated declines in myelin thickness, density, and myelin fraction with age. Considerable variability was detected on these characteristics of myelin and cognitive performance assessed via the detoured reach task. Age‐related changes in myelin in Region II of the corpus callosum were predictive of cognitive performance on the detoured reach task. Thus the detoured reach task appears to also measure aspects of corticostriatal function in addition to prefrontal cortical function. We investigated age‐related changes in the white matter of the corpus callosum, and if such changes were related to cognitive aging in common marmosets. Age‐related declines in myelin thickness, density, and myelin fraction were detected. Changes in white matter in Region II of the corpus callosum were associated with cognitive performance. [ABSTRACT FROM AUTHOR]

The development of the marmoset as a translational model for healthspan and lifespan studies relies on the characterization of health parameters in young and geriatric marmosets. This cross‐sectional study examined health phenotypes in marmosets for five domains of interest for human health and aging: mobility, cognition, metabolism, homeostasis, and immune function. Geriatric marmosets were found to have significant executive function impairment when compared to young animals. While geriatric animals did not show gross abnormalities in mobility and measures of locomotion, their types of movement were altered from young animals. Geriatric marmosets had alterations in cardiac function, with significantly increased mean arterial pressures; metabolism, with significantly lower VO2; and suppressed immune function. Further, this study sought to characterize and describe histopathology for both young and geriatric healthy marmosets. Overall this study provides a characterization of health parameters for young and geriatric marmosets which will greatly enhance future aging and interventional testing in marmosets. This research provides a cross‐sectional examination of parameters of health in young and geriatric marmosets. Geriatric marmosets are found to have significant impairments of health for each of the five domains examined: mobility, cognition, metabolism, homeostasis, and immune function. As a non‐human primate model, marmosets offer many advantages for the study of aging and healthspan. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the author discusses various reports within the issue on topics including primatology, animal behavior, and animal food.