Lab cognition going wild: Implementing a new portable touchscreen system in vervet monkeys.

Touchscreen technology has provided researchers with opportunities to conduct well-controlled cognitive tests with captive animals, allowing researchers to isolate individuals, select participants based on specific traits, and control aspects of the environment. In this study, we aimed to investigate the potential utility of touchscreen technology for the study of cognition in wild vervet monkeys. We assessed the viability of touchscreen testing by comparing rates of participation between wild and sanctuary-housed vervets. Additionally, we compared performance on a simple associative learning task in order to verify that wild participants are able to engage meaningfully with a touchscreen task presented in their natural environment. We presented eight groups of vervet monkeys (four wild and four sanctuary groups, totalling 240 individuals) with a portable touchscreen device. The touchscreen displayed tasks in which food rewards could be gained by touching a stimulus displayed on the screen. We assessed individuals' likelihood of interacting with the touchscreen, their frequency of participation, and their performance on a simple associative learning task. We found that sanctuary-housed monkeys were more likely to interact with the touchscreen. Participation in wild vervet monkeys was influenced by sex and age. However, monkeys in the two contexts (sanctuary vs. wild) did not differ in their performance on a simple associative learning task. This study demonstrates that touchscreen technology can be successfully deployed in a population of wild primates. This gives us a starting point to test animal cognition under natural conditions that include varying group composition, environmental challenges and ongoing activities such as foraging, which are challenging to recreate in captivity. While rates of participation were lower than those found in captivity, reasonable sample sizes can be achieved, and wild primates can successfully learn touchscreen tasks in a manner comparable to their captive counterparts.

Proprotein convertase subtilisin/kexin type 9 genetic screening using the vervet (Chlorocebus aethiops) model.

BACKGROUND: The proprotein convertase subtilisin/kexin type 9 (PCSK9) gene has come to prominence due to its reported function in the clearance of low-density lipoprotein cholesterol. The vervet monkey (Chlorocebus aethiops) was utilized to study the genetics of PCSK9 gene. METHOD: Sixteen vervet monkeys were selected to screen for possible PCSK9 polymorphisms and to determine gene expression. RESULTS: Four PCSK9 sequence variants (T112T, R148S, H177N and G635G) were identified and three of these variants (H177N, R148S, and G635G) were categorized as loss of function mutations. A decline in gene expression levels was also observed in animals harboring these three variants. Although the selected variants might have affected the level of gene expression in the selected animals, individual variation was also noticed in some of these individuals with the G635G variant. CONCLUSION: Based on the findings obtained from this study, it is suggestive that the activity of PCSK9 was hindered.

Evidence of selection in the uncoupling protein 1 gene region suggests local adaptation to solar irradiance in savannah monkeys (Chlorocebus spp.).

In the last 300 thousand years, the genus Chlorocebus expanded from equatorial Africa into the southernmost latitudes of the continent, where colder climate was a probable driver of natural selection. We investigated population-level genetic variation in the mitochondrial uncoupling protein 1 (UCP1) gene region-implicated in non-shivering thermogenesis (NST)-in 73 wild savannah monkeys from three taxa representing this southern expansion (Chlorocebus pygerythrus hilgerti, Chlorocebus cynosuros and Chlorocebus pygerythrus pygerythrus) ranging from Kenya to South Africa. We found 17 single nucleotide polymorphisms with extended haplotype homozygosity consistent with positive selective sweeps, 10 of which show no significant linkage disequilibrium with each other. Phylogenetic generalized least-squares modelling with ecological covariates suggest that most derived allele frequencies are significantly associated with solar irradiance and winter precipitation, rather than overall low temperatures. This selection and association with irradiance is demonstrated by a relatively isolated population in the southern coastal belt of South Africa. We suggest that sunbathing behaviours common to savannah monkeys, in combination with the strength of solar irradiance, may mediate adaptations to thermal stress via NST among savannah monkeys. The variants we discovered all lie in non-coding regions, some with previously documented regulatory functions, calling for further validation and research.

The thermal consequences of primate birth hour and its evolutionary implications.

Most primates, including humans, give birth during the inactive phase of the daily cycle. Practical constraints therefore limit our knowledge of the precise timing of nocturnal birth in wild diurnal primates and so limit our understanding of selective pressures and consequences. We measured maternal core body temperature (Tb) across 24 births in a population of wild vervet monkeys using biologgers. We identified distinct perturbations in Tb during the birth period, including declining Tb during labour and the rapid recovery of Tb post-parturition. Vervet monkeys typically gave birth during their inactive phase in synchrony with the nadir of the maternal nychthemeral Tb rhythm but also showed remarkable inter-individual variability in their absolute Tb during birth. Our findings support the view that selection may have favoured a nocturnal timing of primate birth to coincide with lower night-time Tb and environmental temperatures, which improve thermal efficiency during birth.

Rectal prolapse associated with enlarged seminal vesicles in a Vervet monkey (Chlorocebus pygerythrus).

A 7-year-old vervet monkey (Chlorocebus pygerythrus) died 8 days after surgery to repair the rectal prolapse. The animal had a history of tenesmus in a week leading up to the rectal prolapse. At necropsy enlargement and dilatation of seminal vesicles that appeared to cause posterior compression of the rectum leading to luminal narrowing. It was concluded that enlargement of the seminal vesicles may have serious consequences such as rectal obstruction and tenesmus leading to prolapse of the rectum in vervet monkeys and should be considered a rare cause of lower gastrointestinal disorders in this species and probably other species of nonhuman primates as well.

A Fine-Scale Genetic Map for Vervet Monkeys.

Despite its important biological role, the evolution of recombination rates remains relatively poorly characterized. This owes, in part, to the lack of high-quality genomic resources to address this question across diverse species. Humans and our closest evolutionary relatives, anthropoid apes, have remained a major focus of large-scale sequencing efforts, and thus recombination rate variation has been comparatively well studied in this group-with earlier work revealing a conservation at the broad- but not the fine-scale. However, in order to better understand the nature of this variation, and the time scales on which substantial modifications occur, it is necessary to take a broader phylogenetic perspective. I here present the first fine-scale genetic map for vervet monkeys based on whole-genome population genetic data from ten individuals and perform a series of comparative analyses with the great apes. The results reveal a number of striking features. First, owing to strong positive correlations with diversity and weak negative correlations with divergence, analyses suggest a dominant role for purifying and background selection in shaping patterns of variation in this species. Second, results support a generally reduced broad-scale recombination rate compared with the great apes, as well as a narrower fraction of the genome in which the majority of recombination events are observed to occur. Taken together, this data set highlights the great necessity of future research to identify genomic features and quantify evolutionary processes that are driving these rate changes across primates.

The expression of type I and II gonadotropin-releasing hormone receptors transcripts in Vervet monkey (Chlorocebus aethiops) spermatozoa.

Gonadotropin-Releasing Hormone (GnRH), acting via the GnRH receptor (GnRHR), and a member of G-protein coupled receptor (GPCR), plays an essential role in the control of reproduction while operating primarily at the hypothalamic level of the gonadotropic axis. GnRH and its receptor are co-expressed in certain specific cells, suggesting an autocrine regulation of such cells. In the male reproductive system, two forms of GnRH (I and II) and its receptors (GnRHR) are present in the human and non-human primate (NHP) testis, prostate, epididymis, seminal vesicle, and human spermatozoa. In humans, the GnRHR-II receptor gene is disrupted by a frameshift in exon 1 and a stop codon in exon 2, rendering the receptor non-functional, whereas a fully functional GnRHR-II receptor is present in New-World and Old-World monkeys. There is no evidence of the existence of a GnRH receptor in NHP sperm. Since the NHP has a phylogenetic relationship to man and is often used as models in reproductive physiology, this present study aimed to determine GnRHR-I and GnRHR-II in Vervet monkey (Chlorocebus aethiops) spermatozoa. A total of 24 semen samples were obtained from four adult Vervet monkeys through electro-ejaculation and utilized for genotyping and gene expression analysis of GnRHR-I and II. Here we report that both receptors were successfully identified in the Vervet monkey sperm with the abundance of GnRHR-I gene expression compared to GnRHR-II. In comparison to the human, there is no evidence of such a stop codon at position 179 in exon 2 of the Vervet GnRHR-II. These findings suggest that both receptors are transcriptionally functional in Vervet spermatozoa.

Field data confirm the ability of a biophysical model to predict wild primate body temperature.

In the face of climate change there is an urgent need to understand how animal performance is affected by environmental conditions. Biophysical models that use principles of heat and mass transfer can be used to explore how an animal's morphology, physiology, and behavior interact with its environment in terms of energy, mass and water balances to affect fitness and performance. We used Niche Mapper™ (NM) to build a vervet monkey (Chlorocebus pygerythrus) biophysical model and tested the model's ability to predict core body temperature (Tb) variation and thermal stress against Tb and behavioral data collected from wild vervets in South Africa. The mean observed Tb in both males and females was within 0.5 °C of NM's predicted Tbs for 91% of hours over the five-year study period. This is the first time that NM's Tb predictions have been validated against field data from a wild endotherm. Overall, these results provide confidence that NM can accurately predict thermal stress and can be used to provide insight into the thermoregulatory consequences of morphological (e.g., body size, shape, fur depth), physiological (e.g. Tb plasticity) and behavioral (e.g., huddling, resting, shade seeking) adaptations. Such an approach allows users to test hypotheses about how animals adapt to thermoregulatory challenges and make informed predictions about potential responses to environmental change such as climate change or habitat conversion. Importantly, NM's animal submodel is a general model that can be adapted to other species, requiring only basic information on an animal's morphology, physiology and behavior.

Endemicity of Yaws and Seroprevalence of Treponema pallidum Antibodies in Nonhuman Primates, Kenya.

Human yaws has historically been endemic to Kenya, but current epidemiologic data are lacking. We report seroprevalence for Treponema pallidum antibodies in olive baboons (Papio anubis) and vervet monkeys (Chlorocebus pygerythrus) in Laikipia County, Kenya. Our results suggest endemicity of the yaws bacterium in monkeys, posing a possible zoonotic threat to humans.

Evaluation of tuberculin skin test (TST) in vervet monkeys (Chlorocebus pygerythrus) using experimentally tuberculin sensitized animals.

BACKGROUND: Nowadays, several test methods with different useful values are available for diagnosis of the tuberculosis (TB) in non-human primates (NHPs). Despite some limitations of tuberculin skin test (TST), it is still the most commonly used method for TB testing of NHPs. METHODS: During this investigation, TST was performed upon three groups of experimentally tuberculin sensitized and one group of non-sensitized vervet monkeys (Chlorocebus pygerythrus) by means of two types of old tuberculin (OT) and two types of purified protein derivative (PPD) tuberculin. RESULTS: The data obtained from this study revealed that PPD tuberculin prepared from both Mycobacterium tuberculosis and Mycobacterium bovis has more advantages over OT in tuberculin testing of the vervet monkeys. The potency of the PPD tuberculin prepared from M bovis was estimated almost twice as much of the M tuberculosis. CONCLUSIONS: Intrapalpebral injection of 0.1 mL of a concentration of ≥1 mg/mL of PPD tuberculin prepared from M bovis is the preferred method for TST of vervet monkeys.

The effect of hyperglycinemic treatment in captive-bred Vervet monkeys (Chlorocebus aethiops).

Nonketotic hyperglycinemia (NKH) is a neuro-metabolic disorder caused by a deficiency in the glycine cleavage system (GCS) and glycine transporter 1 (GlyT1). A case of atypical late onset of NKH has been reported in a colony of captive-bred Vervet monkeys. The purpose of this study was to evaluate the effect of sodium benzoate and dextromethorphan in reducing glycine levels in hyperglycinemic monkeys. Twelve captive-bred Vervet monkeys were assigned into three groups consisting of four animals (control, valproate induced and cataract with spontaneous hyperglycinemia). Valproate was used to elevate glycine levels and the induced group was then treated with sodium benzoate and dextromethorphan together with group three to normalise glycine levels in cerebrospinal fluid (CSF) and plasma. Valproate induction elicited changes in phosphate, alkaline phosphatase and platelet count, however, no significant changes in the glycine levels were observed, and this might be due to the individual variability within the group. The treatment intervention was only obtained in the spontaneous group whereby the glycine levels were normalised in CSF and plasma. Therefore, it can be concluded that sodium benzoate and dextromethorphan treatment was effective and beneficial to the hyperglycinemic group.

Composition and stability of the vervet monkey milk microbiome.

The human milk microbiome is vertically transmitted to offspring during the postnatal period and has emerged as a critical driver of infant immune and metabolic development. Despite this importance in humans, the milk microbiome of nonhuman primates remains largely unexplored. This dearth of comparative work precludes our ability to understand how species-specific differences in the milk microbiome may differentially drive maternal effects and limits how translational models can be used to understand the role of vertically transmitted milk microbes in human development. Here, we present the first culture-independent data on the milk microbiome of a nonhuman primate. We collected milk and matched fecal microbiome samples at early and late lactation from a cohort of captive lactating vervet monkeys (N = 15). We found that, similar to humans, the vervet monkey milk microbiome comprises a shared community of taxa that are universally present across individuals. However, unlike in humans, this shared community is dominated by the genera Lactobacillus, Bacteroides, and Prevotella. We also found that, in contrast to previous culture-dependent studies in humans, the vervet milk microbiome exhibits greater alpha-diversity than the gut microbiome across lactation. Finally, we did not find support for the translocation of microbes from the gut to the mammary gland within females (i.e., "entero-mammary pathway"). Taken together, our results show that the vervet monkey milk microbiome is taxonomically diverse, distinct from the gut microbiome, and largely stable. These findings demonstrate that the milk microbiome is a unique substrate that may selectively favor the establishment and persistence of particular microbes across lactation and highlights the need for future experimental studies on the origin of microbes in milk.

The Demographic and Adaptive History of the African Green Monkey.

Relatively little is known about the evolutionary history of the African green monkey (genus Chlorocebus) due to the lack of sampled polymorphism data from wild populations. Yet, this characterization of genetic diversity is not only critical for a better understanding of their own history, but also for human biomedical research given that they are one of the most widely used primate models. Here, I analyze the demographic and selective history of the African green monkey, utilizing one of the most comprehensive catalogs of wild genetic diversity to date, consisting of 1,795,643 autosomal single nucleotide polymorphisms in 25 individuals, representing all five major populations: C. a. aethiops, C. a. cynosurus, C. a. pygerythrus, C. a. sabaeus, and C. a tantalus. Assuming a mutation rate of 5.9 × 10-9 per base pair per generation and a generation time of 8.5 years, divergence time estimates range from 523 to 621 kya for the basal split of C. a. aethiops from the other four populations. Importantly, the resulting tree characterizing the relationship and split-times between these populations differs significantly from that presented in the original genome paper, owing to their neglect of within-population variation when calculating between population-divergence. In addition, I find that the demographic history of all five populations is well explained by a model of population fragmentation and isolation, rather than novel colonization events. Finally, utilizing these demographic models as a null, I investigate the selective history of the populations, identifying candidate regions potentially related to adaptation in response to pathogen exposure.

Identity Construction and Symbolic Association in Farmer-Vervet Monkey (Chlorocebus aethiops sabaeus) Interconnections in St. Kitts.

Primates occupy a liminal space between humans and animals. On the Caribbean island of St. Kitts, translocated vervet monkeys (Chlorocebus aethiops sabaeus) are respected creatures, yet they cause problems. Vervets regularly consume crops on farms and are considered "pests"; still, Kittitians express empathy and understanding for them based largely on the monkeys' display of human-like behaviours. Using data from interviews with 64 Kittitian farmers, we deconstruct the symbolism of the vervet monkey in St. Kitts and analyse how farmers give the monkeys identities that are meaningful only within human social expectations. Our findings reveal that Kittitian farmers consider monkeys to be clever and emotive, displaying complex intentions such as revenge and remorse. Yet, crop-foraging behaviour is a regular and negative experience for the majority of farmers in this study, and the monkeys' presence itself is a constant reminder of the multitude of challenges farmers face in a newly adopted tourism economy that no longer prioritises agriculture. Our results reveal that while vervet crop consumption is a significant problem in St. Kitts, it is the monkeys' boundary-crossing status that drives the growing mentality that "the monkey problem" is completely out of control.

Behavioral responses of vervet monkey Chlorocebus pygerythrus infants in a novel fostering program.

Vervet monkeys (Chlorocebus pygerythrus) are considered pests by farmers and homeowners. Consequent attempts to exterminate problem adult vervet monkeys often result in orphaned young offspring, which are sometimes taken to wildlife rehabilitation centers. We assessed the success of a novel fostering program at the Vervet Monkey Foundation, South Africa. Nine orphaned vervet monkeys were fostered to adult conspecific females of existing troops at the Foundation. The fostering protocol focused on reducing the time orphans spent in human rearing and involved a stepwise process of integration. We recorded the behaviors of orphans, including their interactions with their foster mother, to assess the process of fostering. Fostering success was high (89%). Orphans maintained close association with the foster mother and had little or no socio-negative and abnormal behavior. Comparison with literature showed a similar high fostering success in another vervet monkey study, regardless of the period and level of human-caregiving, and it is apparent that the duration of human care is less important than the protocol used for fostering. Nonetheless, our study has conservation relevance for vervet monkey rehabilitation.

Age-related degenerative functional, radiographic, and histological changes of the shoulder in nonhuman primates.

BACKGROUND: Nonhuman primates have similar shoulder anatomy and physiology compared to humans, and may represent a previously underutilized model for shoulder research. This study sought to identify naturally occurring bony and muscular degeneration in the shoulder of nonhuman primates and to assess relationships between structural and functional aspects of the shoulder and measures of physical function of the animals. We hypothesized that age-related degenerative changes in the shoulders of nonhuman primates would resemble those observed in aging humans. METHODS: Middle-aged (n = 5; ages 9.4-11.8 years) and elderly (n = 6; ages 19.8-26.4 years) female vervet monkeys were studied for changes in mobility and shoulder function, and radiographic and histologic signs of age-related degeneration. RESULTS: Four out of 6 (4/6) elderly animals had degenerative changes of the glenoid compared to 0/5 of the middle-aged animals (P = .005). Elderly animals had glenoid retroversion, decreased joint space, walked slower, and spent less time climbing and hanging than middle-aged vervets (P < .05). Physical mobility and shoulder function correlated with glenoid version angle (P < .05). Supraspinatus muscles of elderly animals were less dense (P = .001), had decreased fiber cross-sectional area (P < .001), but similar amounts of nuclear material (P = .085). Degenerative rotator cuff tears were not observed in any of the eleven animals. DISCUSSION AND CONCLUSION: The vervet monkey naturally undergoes age-related functional, radiographic and histological changes of the shoulder, and may qualify as an animal model for selected translational research of shoulder osteoarthritis.

A morphological study and the variability in the number of infraorbital foramina in the African green monkey (Grivet) (Chlorocebus aethiops) using microcomputed tomography.

Knowledge of the nonhuman primate morphology and anatomy related to craniofacial mechanoreception is essential for a fundamental understanding of the incidents that have occurred during the evolution of craniofacial features. The present study focuses on the variability in the number of infraorbital foramina and associated anatomical structures such as the infraorbital canal (IOC) and the infraorbital groove (IOG), as they are considered to play an important role in the behavioral ecology of these animals. A total of 19 skulls of Chlorocebus aethiops were analyzed. The number of infraorbital foramina was assessed macroscopically using a magnifying glass and a small diameter probe. Three dimensional (3D) projections and morphometric analysis of the infraorbital foramina, IOCs, and IOGs were performed using microcomputed tomography (micro-CT) for two skulls that represent one of the most common morphological types. Regardless of sex and body side, the most common morphological type observed in the studied species is the presence of three infraorbital foramina. The IOC takes a funnel or pinched shape. 3D projections were made to assess the course of the infraorbital vascular and nerve bundles in selected individuals. The results indicate a high morphological diversity within the species, although there appears to be a consistent distribution pattern of infraorbital neurovascular bundles in species of the Cercopithecidae family. The use of X-ray micro-CT allowed 3D visualization of the maxillary region to determine the variability of the infraorbital foramina and to track the division of the infraorbital neurovascular bundle in the case of the most common macroscopic expression of the number of the infraorbital foramen in C. aethiops, as well as the morphometric of the IOCs and IOGs which are related to mechanoreception of the primate's snout.

Using light and X-ray scattering to untangle complex neuronal orientations and validate diffusion MRI.

Disentangling human brain connectivity requires an accurate description of nerve fiber trajectories, unveiled via detailed mapping of axonal orientations. However, this is challenging because axons can cross one another on a micrometer scale. Diffusion magnetic resonance imaging (dMRI) can be used to infer axonal connectivity because it is sensitive to axonal alignment, but it has limited spatial resolution and specificity. Scattered light imaging (SLI) and small-angle X-ray scattering (SAXS) reveal axonal orientations with microscopic resolution and high specificity, respectively. Here, we apply both scattering techniques on the same samples and cross-validate them, laying the groundwork for ground-truth axonal orientation imaging and validating dMRI. We evaluate brain regions that include unidirectional and crossing fibers in human and vervet monkey brain sections. SLI and SAXS quantitatively agree regarding in-plane fiber orientations including crossings, while dMRI agrees in the majority of voxels with small discrepancies. We further use SAXS and dMRI to confirm theoretical predictions regarding SLI determination of through-plane fiber orientations. Scattered light and X-ray imaging can provide quantitative micrometer 3D fiber orientations with high resolution and specificity, facilitating detailed investigations of complex fiber architecture in the animal and human brain.

Imaging crossing fibers in mouse, pig, monkey, and human brain using small-angle X-ray scattering.

Myelinated axons (nerve fibers) efficiently transmit signals throughout the brain via action potentials. Multiple methods that are sensitive to axon orientations, from microscopy to magnetic resonance imaging, aim to reconstruct the brain's structural connectome. As billions of nerve fibers traverse the brain with various possible geometries at each point, resolving fiber crossings is necessary to generate accurate structural connectivity maps. However, doing so with specificity is a challenging task because signals originating from oriented fibers can be influenced by brain (micro)structures unrelated to myelinated axons. X-ray scattering can specifically probe myelinated axons due to the periodicity of the myelin sheath, which yields distinct peaks in the scattering pattern. Here, we show that small-angle X-ray scattering (SAXS) can be used to detect myelinated, axon-specific fiber crossings. We first demonstrate the capability using strips of human corpus callosum to create artificial double- and triple-crossing fiber geometries, and we then apply the method in mouse, pig, vervet monkey, and human brains. We compare results to polarized light imaging (3D-PLI), tracer experiments, and to outputs from diffusion MRI that sometimes fails to detect crossings. Given its specificity, capability of 3-dimensional sampling and high resolution, SAXS could serve as a ground truth for validating fiber orientations derived using diffusion MRI as well as microscopy-based methods. STATEMENT OF SIGNIFICANCE: To study how the nerve fibers in our brain are interconnected, scientists need to visualize their trajectories, which often cross one another. Here, we show the unique capacity of small-angle X-ray scattering (SAXS) to study these fiber crossings without use of labeling, taking advantage of SAXS's specificity to myelin - the insulating sheath that is wrapped around nerve fibers. We use SAXS to detect double and triple crossing fibers and unveil intricate crossings in mouse, pig, vervet monkey, and human brains. This non-destructive method can uncover complex fiber trajectories and validate other less specific imaging methods (e.g., MRI or microscopy), towards accurate mapping of neuronal connectivity in the animal and human brain.

First Report of Massive Myocardial Calcifications in a Vervet Monkey (Chlorocebus pygerythrus).

A 13-years-old male vervet monkey that was kept in a primates breeding and research facility at Razi Vaccine and Serum Research Institute, Karaj, Iran (RVSRI) died suddenly. Massively scattered grayish-yellow mottling on both ventricles were the most significant gross necropsy findings. There was a gritty feeling on palpation and sectioning of the yellow areas. Microscopically, the lesions demonstrated scattered degeneration and necrosis of myocardial cells. Inside the affected areas, large calcium deposit plaques were detected using the Von kossa staining method. The development of myocardial calcification in the present case can be attributed to the dystrophic calcification following spontaneous myocardial necrosis or an undetected infection/inflammatory process. Persistent anxiety might trigger spontaneous biventricular necrosis in vervet monkeys. In conclusion, due to similarities between the clinical and histological presentation of the current case with sudden death syndrome associated with myocardial calcification in humans, it was suggested that vervet monkeys might be a relevant animal model for research on the pathophysiological processes of this complication.