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Despite showing the greatest primate diversity on the planet, genomic studies on Amazonian primates show very little representation in the literature. With 48 geolocalized high coverage whole genomes from wild uakari monkeys, we present the first population-level study on platyrrhines using whole genome data. In a very restricted range of the Amazon rainforest, eight uakari species (Cacajao genus) have been described and categorized into the bald and black uakari groups, based on phenotypic and ecological differences. Despite a slight habitat overlap, we show that posterior to their split 0.92 Mya, bald and black uakaris have remained independent, without gene flow. Nowadays, these two groups present distinct genetic diversity and group-specific variation linked to pathogens. We propose differing hydrology patterns and effectiveness of geographic barriers have modulated the intra-group connectivity and structure of bald and black uakari populations. With this work we have explored the effects of the Amazon rainforests dynamism on wild primates genetics and increased the representation of platyrrhine genomes, thus opening the door to future research on the complexity and diversity of primate genomics.

Activity budget analyses are important for understanding how animals spend their time in daily activities like resting, foraging, moving and socializing. These behaviors are closely linked to energy management, so habitat quality and resource availability are known to influence the activity budgets of species. Therefore, many studies have examined the consequences of habitat loss and fragmentation on the energetic demands and activity budgets of species. However, we still have limited knowledge of how animals behave in large, continuous, and protected environments, as such habitats are currently rare. The present study analyzed how temporal variation, age, sex and reproductive status influenced the activity budget of wild red howler monkeys (Alouatta guariba clamitans), in one of the last Atlantic Forest remnants that remains large and protected. Between November 2017 and December 2018, we monitored two groups, G3 and G4, in Parque Estadual Carlos Botelho, São Paulo, Brazil. The groups were composed of one adult male, two adult females and their offspring and one (G3) or two (G4) subadult males, using scan sampling for behavioral for data collection every 20 min. The most common behavior was resting, followed by foraging, moving and social interactions, with inter-group differences. Temporal variation explained most of the fluctuations in the activity budget, so did age and sex, but to a lesser degree. The reproductive status of females did not alter their activity budget. These findings reveal that even neighboring groups display distinct and intricate relationships with their habitat. Future studies should be conducted in continuous forests to determine what is the expected range of variation in activity budget, particularly in those species considered as flexible and inhabiting endangered habitats, such as the Atlantic Forest. [ABSTRACT FROM AUTHOR]

Background: Oral focal epithelial hyperplasia (FEH) is an uncommon infection affecting humans, chimpanzees, bonobos, and howler monkeys. This study describes 10 cases of free‐ranging brown howler monkeys (Alouatta guariba clamitans) diagnosed with FEH and Alouatta guariba Papillomavirus 1 (AgPV 1). Methods: We analyzed demographic characteristics, rescue conditions, clinical and pathological findings, and species‐specific behavior factors in these cases. The study assessed the frequency of occurrence and potential contributing factors of FEH and AgPV 1 infection. Results: The frequency of FEH was 8.13%. Most affected howlers were adult or geriatric males with comorbidities or stressful conditions. Clinical and pathological observations were consistent with AgPV 1 infection. Species‐specific behaviors and environmental stressors were identified as contributing factors. Conclusions: FEH associated with AgPV 1 affected mainly adult or geriatric males with ongoing comorbidities or stressful conditions. Further research is needed to understand these factors for effective management. [ABSTRACT FROM AUTHOR]

The database of the IUCN SSC Primate Specialist Group currently (December 2023) registers 218 species and subspecies of Neotropical primates in 24 genera and five families. In the early 1960s, the diversity of Neotropical primates was estimated to be around 200 species and subspecies. From then, through the 1970s to the mid-1990s, however, the perception of the region's primate diversity dropped, and reached an all-time low at 83 species and subspecies in 1980 (A World List of Mammalian Species, G. B. Corbet and J. E. Hill, British Museum (Natural History), Comstock Publishing, Cornell University Press, London and Ithaca). Interest in taxonomy and primate field research in the Neotropics was subdued up to the late 1970s. Change was sparked by the burgeoning capture of primates for biomedical research in the 1950s and 1960s, and the increasing destruction of the Amazon rainforests from the late 1970s. The numbers increased, at first slowly, but then, in 1995, they leapt back to the 200s in anticipation of a book by C. P. Groves (2001, Primate Taxonomy, Smithsonian Institution Press, Washington, DC). The species' counts (not including subspecies) rose due to the adoption of the Phylogenetic Species Concept over the Biological Species Concept, the former favoring the category of species over subspecies. In this article, we discuss the changes in species and subspecies numbers in the classification of the Neotropical primates, and report on the taxonomic changes resulting from taxonomic research ongoing since 2012. We emphasize the importance of taxonomic research for an understanding of the diversity of primates, and for conservation planning, not least in identifying the populations that are threatened. [ABSTRACT FROM AUTHOR]

New World monkeys (NWM) comprise a group of extant and extinct taxa exclusive to the Neotropics. Lineage dispersal modeling was employed to test the validity of previously reported biogeographic patterns in NWM. Specifically, this research sought to confirm whether the dispersal timings of these patterns were supported by the modeling results. Species geographic distributions of extant platyrrhines were used to obtain a bioregionalization scheme. A lineage dispersal model was constructed based on multiple-area range, likelihood inference of rate, and stochastic mapping under likelihood. Based on published phylogenies, ten trees were randomly sampled and, for each tree, ten stochastic mappings were simulated. Results were presented as event counts and averages across the 100 stochastic mappings, and the timings of the inferred dispersal routes were compared to the timings of 12 biogeographic pattern hypotheses gathered from the literature. The modeling analysis provided directional and temporal support for eleven of the twelve patterns. Lineages most frequently dispersed from Western Amazonia towards other bioregions. For four dispersal routes, events initiated earlier than previously reported. The Western Amazonia bioregion served as both the ancestral area and primary source of platyrrhine lineages. Analyses revealed a novel biogeographic pattern, namely the “Amazonian eastward” dispersal route, which started in the Miocene epoch, during the establishment of the transcontinental Amazon River system, and lasted until recently in an increasing trend of dispersal rate. This route showed the greatest number of dispersal events during the macroevolution of NWM. [ABSTRACT FROM AUTHOR]

Rapid facial mimicry (RFM), the rapid and automatic replication of facial expression perceived, is considered a basic form of empathy and was investigated mainly during play. RFM occurs in Catarrhini (Old World primates), but it is not still demonstrated in Platyrrhini (New World primates). For this reason, we collected video data on playful interactions (Nplay_interactions = 149) in three species of spider monkeys (Ateles fusciceps—N = 11, Ateles hybridus—N = 14, and Ateles paniscus—N = 6) housed at La Vallée des Singes and the ZooParc de Beauval (France). For the first time, we demonstrated the occurrence of RFM in Platyrrhini (analyzing 175 events). Players' sex, age, species, relationship quality, and kinship did not modulate RFM probably due to the species' complex fission–fusion dynamics and flexible interindividual social relationships. Compared to the absence of any playful expressions or the presence of only not replicated play face, RFM prolonged the session duration and was sequentially associated with more types of more intense offensive playful patterns (patterns aimed at attacking/pursuing the playmate). We proposed that RFM may favor synchronization and context sharing between players, thus decreasing the risk of behavior misinterpretation while simultaneously fostering a more competitive nature of play. In conclusion, this study stimulates additional research on the evolutionary origins of motor mimicry in primates, possibly dating back to before the divergence of New and Old World monkeys. Furthermore, it also points toward the possibility that RFM may not always lead to cooperation but also to competition, depending on the context and species' social and cognitive features. Highlights: Rapid facial mimicry (RFM) occurred during play in three groups of different species of spider monkeys.RFM was not modulated by both individual (age, sex, and species) and social (relationship quality and kinship) factors.RFM prolonged playful session duration and fostered a more competitive nature of play, leading to competition rather than cooperation depending on context and species' socio‐cognitive features. [ABSTRACT FROM AUTHOR]

The southern black-horned capuchin, Sapajus nigritus cucullatus, is considered Near Threatened on the IUCN Red List and Vulnerable in Argentina. The species is mainly threatened by habitat loss and fragmentation. The aim of this study was to compare range size, group size, and density in S. n. cucullatus groups between areas of continuous and fragmented habitat in the Atlantic Forest in Argentina. The study was carried out in two areas in northern Misiones province, one continuous and one anthropogenic fragment. Fieldwork was carried out for 5 days each month from November 2019 to March 2020 and from November 2020 to March 2021. SARS-CoV-2 restrictions meant we could not survey in the intervening period. Group counts were made on existing trails and subsequent group follows. We georeferenced encounters and follows to estimate home range sizes. We calculated density based on home range modeling using 100% minimum convex polygons (MCP), and compared these using generalized linear models (GLM). Smaller groups and lower density of S. n. cucullatus were found in continuous forest, with group sizes between 12 and 23 individuals, and density of 0.14 ind/ha, whereas in the fragmented forest, group sizes were between 32 and 36, with density of 0.62 ind/ha (n = 107; zero-inflated negative binomial regression [ZINB], p < 0.05). The higher density in forest fragments may be due to reduced dispersal ability. This work highlights data on species plasticity that could contribute to the development of conservation management strategies for S. n. cucullatus and its habitat. [ABSTRACT FROM AUTHOR]

Abstract Many aspects of the ecology, evolution and social behavior of wild-living primates remain un-explored and require further investigation. While long-term field studies are crucial for addressing conservation concerns for many primates’ species, acquiring the necessary data is often challenging, often due to difficulties in locating study groups. Radio-telemetry has significantly facilitated the study of primates and other animals living in tropical forests. However, there are important practical challenges in the process of capturing and releasing animals after placement of telemetry collars. In this study, we report guidelines and considerations for capturing and collaring wild capuchin monkeys, Sapajus nigritus cucullatus, in the Atlantic Forest of Argentina. Our ultimate goal is to contribute to making captures safer, preventing harm and stress to animals when using radio-telemetry in monitoring strategies for conservation of this primate species. These methods can be useful for researchers using field capture and radio-telemetry for monitoring groups or populations of wild primates, specifically wild Sapajus.

The database of the IUCN SSC Primate Specialist Group currently (December 2023) registers 218 species and subspecies of Neotropical primates in 24 genera and five families. In the early 1960s, the diversity of Neotropical primates was estimated to be around 200 species and subspecies. From then, through the 1970s to the mid-1990s, however, the perception of the region’s primate diversity dropped, and reached an all-time low at 83 species and subspecies in 1980 (A World List of Mammalian Species, G. B. Corbet and J. E. Hill, British Museum (Natural History), Comstock Publishing, Cornell University Press, London and Ithaca). Interest in taxonomy and primate field research in the Neotropics was subdued up to the late 1970s. Change was sparked by the burgeoning capture of primates for biomedical research in the 1950s and 1960s, and the increasing destruction of the Amazon rainforests from the late 1970s. The numbers increased, at first slowly, but then, in 1995, they leapt back to the 200s in anticipation of a book by C. P. Groves (2001, Primate Taxonomy, Smithsonian Institution Press, Washington, DC). The species’ counts (not including subspecies) rose due to the adoption of the Phylogenetic Species Concept over the Biological Species Concept, the former favoring the category of species over subspecies. In this article, we discuss the changes in species and subspecies numbers in the classification of the Neotropical primates, and report on the taxonomic changes resulting from taxonomic research ongoing since 2012. We emphasize the importance of taxonomic research for an understanding of the diversity of primates, and for conservation planning, not least in identifying the populations that are threatened.

Recent fossil discoveries in Western Amazonia revealed that two distinct anthropoid primate clades of African origin colonized South America near the Eocene/Oligocene transition (ca. 34 Ma). Here, we describe a diminutive fossil primate from Brazilian Amazonia and suggest that, surprisingly, a third clade of anthropoids was involved in the Paleogene colonization of South America by primates. This new taxon, Ashaninkacebus simpsoni gen. et sp. nov., has strong dental affinities with Asian African stem anthro- poids: the Eosimiiformes. Morphology- based phylogenetic analyses of early Old World anthropoids and extinct and extant New World monkeys (platyrrhines) support rela- tionships of both Ashaninkacebus and Amamria (late middle Eocene, North Africa) to the South Asian Eosimiidae. Afro-Arabia, then a mega island, played the role of a biogeographic stopover between South Asia and South America for anthropoid primates and hystricognathous rodents. The earliest primates from South America bear little adaptive resemblance to later Oligocene-early Miocene platyrrhine monkeys, and the scarcity of available paleontological data precludes elucidating firmly their affinities with or within Platyrrhini. Nonetheless, these data shed light on some of their life history traits, revealing a particularly small body size and a diet consisting primarily of insects and possibly fruit, which would have increased their chances of survival on a natural floating island during this extraordinary over-water trip to South America from Africa. Divergence-time estimates between Old and New World taxa indicate that the trans- atlantic dispersal(s) could source in the intense flooding events associated with the late middle Eocene climatic optimum (ca. 40.5 Ma) in Western Africa. [ABSTRACT FROM AUTHOR]

This study provides the first morphological description of the male genital organs of black‐crowned dwarf marmoset (Callibella humilis). Internal and external genital organs were similar to other species of non‐human primates. However, some shape and size differences were noted. The penile shaft was laterally flattened and comprised of two corpus cavernosus. These were split by a septum up to the level of the glans and then merged to form a single structure. The glans penis had small, keratinized spicules arising from epidermal or dermal projections. The small, fully ossified and well‐mineralized penile bone, located at the distal end of the penis, consisted of a bone matrix surrounded by sparse osteoblasts and well‐developed internal osteocytes. The penile urethra was lined with columnar pseudostratified epithelium, with areas of simple cuboidal epithelium. The testes were small relative to the body compared to other primate species. The findings of this work may support comparative studies of primate reproductive ecology. [ABSTRACT FROM AUTHOR]

The history of Alu retroposons has been choreographed by the systematic accumulation of inherited diagnostic nucleotide substitutions to form discrete subfamilies, each having a distinct nucleotide consensus sequence. The oldest subfamily, AluJ, gave rise to AluS after the split between Strepsirrhini and what would become Catarrhini and Platyrrhini. The AluS lineage gave rise to AluY in catarrhines and to AluTa in platyrrhines. Platyrrhine Alu subfamilies Ta7, Ta10, and Ta15 were assigned names based on a standardized nomenclature. However, with the subsequent intensification of whole genome sequencing (WGS), large scale analyses to characterize Alu subfamilies using the program COSEG identified entire lineages of subfamilies simultaneously. The first platyrrhine genome with WGS, the common marmoset (Callithrix jacchus; [caljac3]), resulted in Alu subfamily names sf0 to sf94 in an arbitrary order. Although easily resolved by alignment of the consensus sequences, this naming convention can become increasingly confusing as more genomes are independently analyzed. In this study, we reported Alu subfamily characterization for the platyrrhine three-family clade of Cebidae, Callithrichidae, and Aotidae. We investigated one species/genome from each recognized family of Callithrichidae and Aotidae and of both subfamilies (Cebinae andSaimiriinae) of the family Cebidae. Furthermore, we constructed a comprehensive network of Alu subfamily evolution within the three-family clade of platyrrhines to provide a working framework for future research. Alu expansion in the three-family clade has been dominated by AluTa15 and its derivatives. [ABSTRACT FROM AUTHOR]

Although the Amazon has the greatest diversity of primates, there are still taxonomic uncertainties for many taxa, such as the species of the Saguinus mystax group. The most geographically broadly distributed and phenotypically diverse species in this group is S. mystax, and its phenotypic diversity has been recognized as three subspecies--S. mystax mystax, S. mystax pileatus and S. mystax pluto--with non-overlapping geographic distributions. In this sense, we carried out an extensive field survey in their distribution areas and used a framework of taxonomic hypothesis testing of genomic data combined with an integrative taxonomic decision-making framework to carry out a taxonomic revision of S. mystax. Our tests supported the existence of three lineages/species. The first species corresponds to Saguinus mystax mystax from the left bank of the Juruá River, which was raised to the species level, and we also discovered and described animals from the Juruá-Tefé interfluve previously attributed to S. mystax mystax as a new species. The subspecies S. m. pileatus and S. m. pluto are recognized as a single species, under a new nomenclatural combination. However, given their phenotypic distinction and allopatric distribution, they potentially are a manifestation of an early stage of speciation, and therefore we maintain their subspecific designations. [ABSTRACT FROM AUTHOR]

A 10‐year‐old black howler monkey presented with a 36‐day subacute clinicopathological picture of fever, prostration, inappetence, intestinal hypomotility, and emaciation. Therapy was trimethoprim‐sulfamethoxazole with streptomycin. The liver, lungs, lymph nodes, and spleen presented lesions. Toxoplasma gondii isolation and PCR determined the diagnosis, and indirect fluorescent antibody tests confirmed an increase in antibody titers. [ABSTRACT FROM AUTHOR]

Neotropical Primates (Platyrrhini) show great diversity in their life histories, ecology, behaviour and genetics. This diversity extends to their chromosome complements, both to autosomes and to sex chromosomes. In this contribution, we will review what is currently known about sex chromosomes in this group, both from cytogenetic and from genomic evidence. The X and Y chromosomes in Neotropical Primates, also known as New World Monkeys, have striking structural differences compared with Old World Monkeys when Catarrhini sex chromosomes are considered. The XY bivalent displays a different meiotic behaviour in prophase I, and their Y chromosome shows extensive genomic differences. Even though the most widespread sex chromosome system is the XX/XY and thus considered the ancestral one for Platyrrhini, modifications of this sexual system are observed within this group. Multiple sex chromosome systems originated from Y‐autosome translocations were described in several genera (Aotus, Callimico and Alouatta). In the howler monkeys, genus Alouatta, an independent origin of the sexual systems in South American and Mesoamerican species was postulated. All the above‐mentioned evidence suggests that the Y chromosome of Platyrrhini has a different evolutionary history compared with the Catarrhini Y. There is still much to understand regarding their sex chromosome systems. [ABSTRACT FROM AUTHOR]

Here we describe new fossil material of Antillothrix bernensis , a Pleistocene-Holocene primate taxon from Hispaniola. It is now represented by seven crania, five mandibles, and dozens of postcranial elements from several paleontologically rich cave systems. The five adult crania included here share a similar overall profile as well as specific features such as a deep depression at the glabella. The complete anterior dentition of Antillothrix can now be described for the first time; short canine crowns, in the apicobasal dimension, compare well with titi monkeys, but the new crania and mandibles lack the specialized tall-crowned incisors of the extant pitheciids. They do, however, have a diastema between the lateral maxillary incisors and canines, a feature not present in the previously known crania. The new mandibles deepen posteriorly and have a medial inflection of the mandibular ramus, as in some pitheciids, but also share with Xenothrix a significant vertical narrowing of the corpus under P 4 /M 1 not observed among extant taxa. Two of the specimens, a cranium and a mandible that do not fit together, exhibit congenitally absent third molars—a rarity among extant, noncallitrichine taxa. There is an approximately 1-kg range in the estimated body mass among the full Antillothrix sample (from 2.4 to 3.4 kg), as well as a range of approximately 5 cm3 of endocranial volume (from 40 to 45 cm3). With these extended ranges from the new specimens, Antillothrix can no longer be described as a taxon with a brain size smaller than that expected for its body size. Neither of these ranges in the brain size or body size is large enough to indicate a substantial level of sexual dimorphism or to necessitate separating the sample into male and female individuals. Given this, and the similar canine sizes for all specimens where they are present, the sample is consistent with a morphologically variable but monomorphic species. [ABSTRACT FROM AUTHOR]

Although the Amazon has the greatest diversity of primates, there are still taxonomic uncertainties for many taxa, such as the species of the Saguinus mystax group. The most geographically broadly distributed and phenotypically diverse species in this group is S. mystax, and its phenotypic diversity has been recognized as three subspecies—S. mystax mystax, S. mystax pileatus and S. mystax pluto—with non-overlapping geographic distributions. In this sense, we carried out an extensive field survey in their distribution areas and used a framework of taxonomic hypothesis testing of genomic data combined with an integrative taxonomic decision-making framework to carry out a taxonomic revision of S. mystax. Our tests supported the existence of three lineages/species. The first species corresponds to Saguinus mystax mystax from the left bank of the Juruá River, which was raised to the species level, and we also discovered and described animals from the Juruá–Tefé interfluve previously attributed to S. mystax mystax as a new species. The subspecies S. m. pileatus and S. m. pluto are recognized as a single species, under a new nomenclatural combination. However, given their phenotypic distinction and allopatric distribution, they potentially are a manifestation of an early stage of speciation, and therefore we maintain their subspecific designations.

The evolution of human right-handedness has been intensively debated for decades. Manual lateralization patterns in non-human primates have the potential to elucidate evolutionary determinants of human handedness, but restricted species samples and inconsistent methodologies have so far limited comparative phylogenetic studies. By combining original data with published literature reports, we assembled data on hand preferences for standardized object manipulation in 1786 individuals from 38 species of anthropoid primates, including monkeys, apes, and humans. Based on that, we employ quantitative phylogenetic methods to test prevalent hypotheses on the roles of ecology, brain size, and tool use in primate handedness evolution. We confirm that human right-handedness represents an unparalleled extreme among anthropoids and found taxa displaying population-level handedness to be rare. Species-level direction of manual lateralization was largely uniform among non-human primates and did not strongly correlate with any of the selected biological predictors, nor with phylogeny. In contrast, we recovered highly variable patterns of hand preference strength, which show signatures of both ecology and phylogeny. In particular, terrestrial primates tend to display weaker hand preferences than arboreal species. These results challenge popular ideas on primate handedness evolution, including the postural origins hypothesis. Furthermore, they point to a potential adaptive benefit of disparate lateralization strength in primates, a measure of hand preference that has often been overlooked in the past. Finally, our data show that human lateralization patterns do not align with trends found among other anthropoids, suggesting that unique selective pressures gave rise to the unusual hand preferences of our species.

Primate tool use is of great interest but has been reported only in a limited number of species. Here we report tool use in crested capuchin monkeys (Sapajus robustus), an almost completely unstudied robust capuchin species. Crested capuchins and their sister species, the yellow‐breasted capuchin, diverged from a common ancestor over 2 million years ago, so this study fills a significant gap in understanding of tool use capacity and variation within the robust capuchin monkey radiation. Our study group was a captive population of seven individuals at the Santa Ana Zoo in California. The monkeys were given no prior training, and they were provided with a variety of enrichment items, including materials that could be used as tools as well as hard‐to‐access resources, for open‐ended interactions. In 54 observation hours, monkeys performed eleven tool use actions: digging, hammering, probing, raking, sponging, striking, sweeping, throwing, waving, wedging, and wiping. We observed tool modification, serial tool use, and social learning opportunities, including monkeys' direct observation of tool use and tolerated scrounging of foods obtained through tool use. We also observed significant individual skew in tool use frequency, with one individual using tools daily, and two individuals never using tools during the study. While crested capuchins have never been reported to use tools in the wild, our findings provide evidence for the species' capacity and propensity for tool use, highlighting the urgent need for research on this understudied, endangered primate. By providing detailed data on clearly identified S. robustus individuals, this study marks an effort to counteract the overgeneralization in the captive literature in referring to any robust capuchins of unknown provenance or ancestry as Cebus apella, a practice that obfuscates potential differences among species in tool use performance and repertoire in one of the only species‐rich tool‐using genera in the world. Highlights: Untrained captive crested capuchin monkeys performed 11 distinct types of tool use.Digging and hammering were performed by the most individuals (5 of 7 and 4 of 7, respectively), and raking was the tool action most frequently performed (53 times).We observed tool modification, serial tool use, and tolerated scrounging of foods obtained through tool use. [ABSTRACT FROM AUTHOR]

Robust capuchin monkeys (Sapajus spp.) are distributed widely in the Neotropics and may be able to survive in modified landscapes because of their omnivorous, opportunistic diet. The poorly known and endangered crested capuchin monkey (Sapajus robustus) is endemic to the Atlantic Forest in Bahia, Minas Gerais and Espírito Santo states, Brazil. We collected data on diet and home range for a crested capuchin group with access to forest and cultivated areas. We hypothesized that with access to cultivated exotic fruit, capuchins would use cultivated areas more for feeding during the season of fruit scarcity in the surrounding forest and have a small home range size because of higher fruit availability. Both the forest and the cultivated areas peaked in fruit availability in the wet season, with a low proportion of trees producing fruit in the dry season; cultivated areas had a higher proportion of trees in fruit compared to the forest throughout the study. While monkeys consumed exotic fruits like jackfruit and oil palm, we recorded more samples of them eating forest fruits than exotic fruits in all but 1 month, and they consumed a more diverse array of forest fruits (56 species) but only six exotic species. Home range size was relatively small compared with other studies: 120.5 ha across the year (wet season 102 ha, dry season 111.5 ha). Natural and human‐intensified fruit sources in a protected area without hunting may have allowed monkeys to maintain a smaller home range size. The group composition changed during the study; this also likely influenced home range use. Studies focused on robust capuchin groups that utilize agricultural or cultivated foods may underestimate home range needs for groups without access to human‐intensified food sources. Studying crested capuchin ecology in additional locations will be important for establishing a sound species conservation program. Research Highlights: Crested capuchins (Sapajus robustus) in Espírito Santo state, Brazil used forest and cultivated areas every month.Despite higher cultivated fruit availability, monkeys spent more time‐consuming forest fruit each month based on a number of scan samples.The number of feeding scans on cultivated fruits only exceeded that for forest fruits in January.Home range was smaller than for most Sapajus sites, and smaller in the dry season compared to the wet season. [ABSTRACT FROM AUTHOR]

Reports of spontaneous hematopoietic neoplasms in Platyrrhines species are scarce. We present the gross, histological, and immunohistochemical findings of disseminated T‐cell lymphoma in a male 25‐year‐old Sapajus xanthosternos kept in a Brazilian conservation center. No molecular evidence of betaherpesvirus or gammaherpesvirus was associated with the occurrence of this neoplasm. [ABSTRACT FROM AUTHOR]

Abstract Primate colour vision depends on a matrix of photoreceptors, a neuronal post receptoral structure and a combination of genes that culminate in different sensitivity through the visual spectrum. Along with a common cone opsin gene for short wavelengths (sws1), Neotropical primates (Platyrrhini) have only one cone opsin gene for medium-long wavelengths (mws/lws) per X chromosome while Paleotropical primates (Catarrhini), including humans, have two active genes. Therefore, while female platyrrhines may be trichromats, males are always dichromats. The genus Alouatta is inferred to be an exception to this rule, as electrophysiological, behavioural and molecular analyses indicated a potential for male trichromacy in this genus. However, it is very important to ascertain by a combination of genetic and behavioural analyses whether this potential translates in terms of colour discrimination capability. We evaluated two howler monkeys (Alouatta spp.), one male A. caraya and one female A. seniculus, using a combination of genetic analysis of the opsin gene sequences and a behavioral colour discrimination test not previously used in this genus. Both individuals completed the behavioural test with performances typical of trichromatic colour vision and the genetic analysis of the sws1, mws, and lws opsin genes revealed three different opsin sequences in both subjects. These results are consistent with uniform trichromacy in both male and female, with presumed spectral sensitivity peaks similar to Catarrhini, at ~ 430 nm, 532 nm, and 563 nm for S-, M- and L-cones, respectively.

Abstract Background Callitrichids comprise a diverse group of platyrrhine monkeys that are present across South and Central America. Their secondarily evolved small size and pointed claws allow them to cling to vertical trunks of a large diameter. Within callitrichids, lineages with a high affinity for vertical supports often engage in trunk-to-trunk leaping. This vertical clinging and leaping (VCL) differs from horizontal leaping (HL) in terms of the functional demands imposed on the musculoskeletal system, all the more so as HL often occurs on small compliant terminal branches. We used quantified shape descriptors (3D geometric morphometrics) and phylogenetically-informed analyses to investigate the evolution of the shape and size of the humerus and femur, and how this variation reflects locomotor behavior within Callitrichidae. Results The humerus of VCL-associated species has a narrower trochlea compared with HL species. It is hypothesized that this contributes to greater elbow mobility. The wider trochlea in HL species appears to correspondingly provide greater stability to the elbow joint. The femur in VCL species has a smaller head and laterally-oriented distal condyles, possibly to reduce stresses during clinging. Similarly, the expanded lesser trochanters visible in VCL species provide a greater lever for the leg retractors and are thus also interpreted as an adaptation to clinging. Evolutionary rate shifts to faster shape and size changes of humerus and femur occurred in the Leontocebus clade when a shift to slower rates occurred in the Saguinus clade. Conclusions Based on the study of evolutionary rate shifts, the transition to VCL behavior within callitrichids (specifically the Leontocebus clade) appears to have been an opportunity for radiation, rather than a specialization that imposed constraints on morphological diversity. The study of the evolution of callitrichids suffers from a lack of comparative analyses of limb mechanics during trunk-to-trunk leaping, and future work in this direction would be of great interest.

The neuropeptide oxytocin is part of a neuroendocrine system that has physiological effects ranging from ensuring uterine myometrial contractions at parturition and post-partum mammary gland milk ejection to the modulation of neural control of social relationships. This initial study was performed to investigate the potential use of positron emission tomography (PET) for localizing oxytocin receptors in two New World primates. Three biomarkers for PET (1-3) that are known to have high affinity and selectivity for the human oxytocin receptor were investigated in the common marmoset (Callithrix jacchus) via PET imaging. Brain penetration, and uptake in the salivary gland area were both observed with biomarkers 2 and 3. No brain penetration was observed with 1, but uptake was observed more specifically in several peripheral endocrine glands compared to 2 or 3. Biomarker 2, which displayed the best brain penetration of the three biomarkers in the marmoset, was then investigated in the monogamous coppery titi monkey (Callicebus cupreus) in a brain scan and a limited full body scan. No significant brain penetration of 2 was observed in the titi monkey, but significant uptake was observed in various locations throughout the periphery. Metabolism of 2 was suspected to have been significant based upon HPLC analysis of blood draws, but parent compound was still present near the end of the scan. Follow-up investigations will focus on next generation biomarkers bearing improved binding characteristics and brain penetrability as well as investigating tissue in regions where biomarker uptake was observed.

We describe a well-preserved humerus of Homunculus patagonicus, a stem platyrrhine from the late early Miocene of the Santa Cruz Formation, Santa Cruz Province, Argentina. The distal part of a humerus was collected by Carlos Ameghino and figured in the 19th Century, but is now lost. Other described postcranial elements, also collected by him include a femur and a partial radius. Comparative observations are made with living and extinct platyrrhines, Oligocene African anthropoids, and extant strepsirrhines. Homunculus patagonicus was a robustly built arboreal quadruped that weighed between 2.2 and 2.6 kg. There is no evidence that the elbow could be fully extended as in living suspensory platyrrhines like Ateles. The medial orientation of the epicondyle suggests that the finger and wrist flexors were not aligned with the long axis of the limb, a distinction from more cursorial monkeys (extant cercopithecoids and the Cuban Pleistocene fossil platyrrhine Paralouatta have retroflexed medial epicondyles). Overall, the morphology is typically platyrrhine although the bone is quite robust. The robustness of the humerus is most comparable to that of early anthropoids from Africa rather than any extant platyrrhine. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to examine primate postcanine tooth root surface area (TRSA) in the context of two ecological variables (diet and bite force). We also assess scaling relationships within distinct taxonomic groups and across the order as a whole. Materials and Methods: Mandibular postcanine TRSA was measured using a three‐dimensional computed tomography (CT) method for catarrhine (N = 27), platyrrhine (N = 21), and strepsirrhine (N = 24) taxa; this represents the first sample of strepsirrhines. Two different body size proxies were used: cranial geometric mean (GM) using nine linear measurements, and literature‐derived body mass (BM). Results: TRSA correlated strongly with body size, scaling with positive allometry or isometry across the order as a whole; however, scaling differed significantly between taxa for some teeth. Among Strepsirrhini, molar TRSA relative to GM differed significantly between folivores and pliant‐object feeders. Additionally, P4 TRSA relative to BM differentiated folivores from both hard‐ and pliant‐object feeders. Among Cercopithecoidea, P4 TRSA adjusted by GM differed between hard‐ and pliant‐object feeders. Discussion: Dietary signals in TRSA appear primarily driven by high frequency loading experienced by folivores. Stronger and more frequent dietary signals were observed within Strepsirrhini relative to Haplorhini. This may reflect the constraints of orthognathism within the latter, constraining the adaptability of their postcanine teeth. Finally, because of the strong correlation between TRSA and BM for each tooth locus (mean r2 = 0.82), TRSA can be used to predict BM in fossil primates using provided equations. [ABSTRACT FROM AUTHOR]

Abstract Background Endogenous Retroviruses (ERVs) constitute approximately 8% of every human genome and are relics of ancestral infections that affected the germ line cells. The ERV-W group contributed to primate physiology by providing an envelope protein (Syncytin-1) that has been adopted for placenta development in hominoids. Expression of Human ERV-W (HERV-W) sequences is investigated for a pathological role in various human diseases. Results We previously characterized ERV-W group genomic sequences in human and non-human Catarrhini species. We now investigated ERV-W-like sequences in the parvorder Platyrrhini, especially regarding two species with complete genome assemblies, namely marmoset (Callithrix jacchus) and squirrel monkey (Saimiri boliviensis). We identified in both species proviral sequences, annotated as ERV1–1 in respective genome assemblies, sharing high sequence similarities with Catarrhini ERV-W. A total of 130 relatively intact proviruses from the genomes of marmoset and squirrel monkey were characterized regarding their structural and evolutionarily relationships with Catarrhini ERV-W elements. Platyrrhini ERV-W sequences share several structural features with Catarrhini ERV-W elements and are closely related phylogenetically with the latter as well as with other ERV-W-related gammaretrovirus-like ERVs. The ERV-W group colonized Platyrrhini primates of both Callitrichidae and Atelidae lineages, with provirus formations having occurred mostly between 25 and 15 mya. Two LTR subgroups were associated with monophyletic proviral bodies. A pre-gag region appears to be a sequence feature common to the ERV-W group: it harbors a putative intron sequence that is missing in some ERV-W loci, holding a putative ORF as well. The presence of a long pre-gag portion was confirmed among all gammaretroviral ERV analyzed, suggesting a role in the latter biology. It is noteworthy that, contrary to Catarrhini ERV-W, there was no evidence of L1-mediated mobilization for Platyrrhini ERV-W sequences. Conclusions Our data establish that ERV-W is not exclusive to Catarrhini primates but colonized both parvorders of Simiiformes, providing further insight into the evolution of ERV-W and the colonization of primate genomes.

• Information about Platyrrhine IgG subclasses molecular characterisation is scarce. • A conserved IGHG genetic organisation (exon - intron) between NWM and OWM was found. • The amount of Catarrhine and Platyrrhine immunoglobulin G isotypes is different. • 2–3 IGHG gene variants in parvorder Platyrrhine were identified. Non-human primates (NHP) are essential in modern biomedical research; New World monkeys (NWM) are mainly used as an experimental model regarding human malaria as they provide useful information about the parasite's biology and an induced immune response. It is known that a vaccine candidate's efficacy is mediated by a protection-inducing antibody response (IgG). Not enough information is available concerning IgG subclasses' molecular characteristics regarding NHP from parvorder Platyrrhini. Understanding the nature of the humoral immune response and characterising the IgG subclasses' profile will provide valuable information about the immunomodulator mechanisms of vaccines evaluated using an NHP animal model. This article has characterised IgG subclasses in NWM (i.e. genera Aotus , Cebus , Ateles and Alouatta) based on the amplification, cloning and sequencing of the immunoglobulin heavy constant gamma (IGHG) gene's CH1 to CH3 regions. The resulting sequences enabled elucidating IGHG gene organisation; two IgG variants were found in the Aotus and Ateles monkey group and three IgG variants in the Cebus and Alouatta group. The sequences were highly conserved in Platyrrhini and had a similar structure to that reported for monkeys from parvorder Catarrhini. Such information will help in developing tools for a detailed characterisation of the humoral immune response in an NWM experimental animal model. [ABSTRACT FROM AUTHOR]

Ants are the dominant group of animals in many habitats, particularly in tropical rainforests. High abundance and formation of large colonies convert them into a potential food source for a broad spectrum of animals. In this paper we review myrmecovory (consumption of ants) in Neotropical primates. Myrmecovory has been reported from 57 taxa (species + subspecies) out of 217 species of Neotropical primates, representing 18 out of 22 genera. The proportion of ants in the animal portion of the diet is highest amongst members of the genera Cebus, Sapajus, Cheracebus and Plecturocebus, but generally low in callitrichids, large pitheciids (Cacajao, Chiropotes) and atelids. Ants from seven subfamilies of Formicidae (out of 13 subfamilies found in the Neotropics) are consumed, including taxa with and without functional sting and with varying other defences. Foraging technics employed in myrmecovory range from picking ants from open substrates to extractive foraging involving the destruction of ant nests or shelters, but tool use has not been reported. We conclude that myrmecovory is widespread amongst Neotropical primates but on average contributes only a minor proportion of the diet. The diversity of foraging technics employed and lack of tool use in Neotropical primate myrmecovory, even for ants with functional stings and aggressive biting, suggests that tool use for myrmecovory in hominids has not evolved in response to ant defences but is a consequence of enhanced cognitive skills that evolved under other selection pressures. [ABSTRACT FROM AUTHOR]

The Convention on Biological Diversity and the International Union for Conservation of Nature emphasize that ex situ conservation efforts are unavoidable. However, inappropriate management or insufficient knowledge of species physiology can lead to behavioral signs of stress and low breeding success in ex situ populations. We assessed fecal steroids across 12 months in captive Brachyteles arachnoides. We collected data on five males and three females living in three different group compositions. We combined reproductive behavior with data on estrogen and progestin metabolite levels in females, and with testosterone (fTM) and glucocorticoid (fGCM) metabolite levels in males. For females, we detected ovulations, pregnancy, and resumption of ovarian activity following parturition. Additionally, all females were acyclical during late spring, suggestive of seasonality. In males, we did not observe annual variation in fTM or fGCM, but males housed together showed higher fGCM and lower fTM, copulated less, and were more aggressive than an isolated male or a male in a unimale—multifemale group. These results suggest that B. arachnoides presents traits consistent with reproductive competition. By including its particular reproductive behavior in management practice guidelines, we can not only prevent possible fights, injuries, and death of captive individuals, but also increase their welfare and reproductive success. [ABSTRACT FROM AUTHOR]

"Conversation rules" such as overlap avoidance and coordinated overlap have been reported in nonhuman animals, and seem to be adaptive responses to the requirements of social life. Some species display both patterns in an apparently flexible way, but the social factors mediating their respective usage remain poorly documented. We investigated the potential social factors guiding the usage of these temporal rules during collective howling in six free‐ranging groups of black howler monkeys (Alouatta pigra). First, we found that adult males' vocalizations rarely overlap those of other callers while most adult females' calls overlap other members' calls, especially that of other females. Second, whereas some call types (notably affiliative calls) are typically emitted without overlap, roars (agonistic loud calls) overlap more frequently. Third, coordinated overlap is more frequent during intergroup competition. Our findings support the hypothesis that overlap avoidance and coordinated overlap are two different (here sex‐related) vocal alliance social behaviors, at least for some nonhuman primates. More comparative investigations are now needed to explore further their evolutionary trajectories in this lineage. Research highlights: Howling bouts of howler monkey are temporally structured vocal interactionsAlthough adult females overlap most of their calls, males avoid overlapOverlap rate depends on the social context [ABSTRACT FROM AUTHOR]

Primate colour vision depends on a matrix of photoreceptors, a neuronal post receptoral structure and a combination of genes that culminate in different sensitivity through the visual spectrum. Along with a common cone opsin gene for short wavelengths (sws1), Neotropical primates (Platyrrhini) have only one cone opsin gene for medium-long wavelengths (mws/lws) per X chromosome while Paleotropical primates (Catarrhini), including humans, have two active genes. Therefore, while female platyrrhines may be trichromats, males are always dichromats. The genus Alouatta is inferred to be an exception to this rule, as electrophysiological, behavioural and molecular analyses indicated a potential for male trichromacy in this genus. However, it is very important to ascertain by a combination of genetic and behavioural analyses whether this potential translates in terms of colour discrimination capability. We evaluated two howler monkeys (Alouatta spp.), one male A. caraya and one female A. seniculus, using a combination of genetic analysis of the opsin gene sequences and a behavioral colour discrimination test not previously used in this genus. Both individuals completed the behavioural test with performances typical of trichromatic colour vision and the genetic analysis of the sws1, mws, and lws opsin genes revealed three different opsin sequences in both subjects. These results are consistent with uniform trichromacy in both male and female, with presumed spectral sensitivity peaks similar to Catarrhini, at ~ 430 nm, 532 nm, and 563 nm for S-, M- and L-cones, respectively. [ABSTRACT FROM AUTHOR]

Background: Callitrichids comprise a diverse group of platyrrhine monkeys that are present across South and Central America. Their secondarily evolved small size and pointed claws allow them to cling to vertical trunks of a large diameter. Within callitrichids, lineages with a high affinity for vertical supports often engage in trunk-to-trunk leaping. This vertical clinging and leaping (VCL) differs from horizontal leaping (HL) in terms of the functional demands imposed on the musculoskeletal system, all the more so as HL often occurs on small compliant terminal branches. We used quantified shape descriptors (3D geometric morphometrics) and phylogenetically-informed analyses to investigate the evolution of the shape and size of the humerus and femur, and how this variation reflects locomotor behavior within Callitrichidae. Results: The humerus of VCL-associated species has a narrower trochlea compared with HL species. It is hypothesized that this contributes to greater elbow mobility. The wider trochlea in HL species appears to correspondingly provide greater stability to the elbow joint. The femur in VCL species has a smaller head and laterally-oriented distal condyles, possibly to reduce stresses during clinging. Similarly, the expanded lesser trochanters visible in VCL species provide a greater lever for the leg retractors and are thus also interpreted as an adaptation to clinging. Evolutionary rate shifts to faster shape and size changes of humerus and femur occurred in the Leontocebus clade when a shift to slower rates occurred in the Saguinus clade. Conclusions: Based on the study of evolutionary rate shifts, the transition to VCL behavior within callitrichids (specifically the Leontocebus clade) appears to have been an opportunity for radiation, rather than a specialization that imposed constraints on morphological diversity. The study of the evolution of callitrichids suffers from a lack of comparative analyses of limb mechanics during trunk-to-trunk leaping, and future work in this direction would be of great interest. [ABSTRACT FROM AUTHOR]

Yellow Fever (YF) is a viral arbovirosis of Public Health importance. In Brazil, surveillance is focused mainly on detecting epizootic events of Platyrrhini. Herein, we compared the detection and phylogenetic analysis of YF virus in two neotropical primates (NTP), a Callithrix detected in the previous epidemic period (2016–2020), and a Callicebus nigrifons , showing a new introduction of YF in 2023. This paper illustrates the importance of joint actions of laboratory and field teams to ensure quick response to Public Health emergencies, such as the intensification of vaccination of susceptible human populations. [ABSTRACT FROM AUTHOR]

Se lleva a cabo un abordaje de las generalidades correspondientes al primate Callicebus caquetensis, actualmente denominado Plecturocebus caquetensis, el cual se encuentra en el departamento de Caquetá en la amazonia colombiana. La descripción de su sistemática permite entender las especies que se encuentran en la región con las cuales se asocia en su evolución. Igualmente, se indican las características propias de la especie, generando un conocimiento de la misma, sin dejar de un lado que su descubrimiento no alcanza una década, y la destrucción de su hábitat es más rápida que los procesos de investigación, razón por la cual es poca la información disponible sobre la misma.

Skeletal fragments of ursine howler monkeys (Alouatta, A. cf. arctoidea) recovered from two archaeological sites in northern Venezuela are discussed in this article. Osteological remains, material culture evidence, and historical records are put together using an archaeoprimatological approach in order to investigate the relationships between the pre‐Hispanic human societies in this region of South America and this primate taxon. The remains of howler monkeys studied suggest that Indigenous peoples of Arawakan linguistic affiliation of Orinocan origin interacted with nonhuman primates in northern Venezuela before AD 800. This interaction encompasses different meanings: the howler as a possible pet or hunting prey and thus a source of food, and the howler as a reference with symbolic value. [ABSTRACT FROM AUTHOR]

Despite strong support from the media, the reintroduction of animals into natural environments does not always achieve its goal. Alouatta caraya is the primate species facing the greatest hunting pressure due to the illegal pet trade in Argentina. Confiscations of this species are common, as is the voluntary surrender of animals by owners no longer able or willing to care for them. These animals ultimately arrive at rehabilitation centers and, in many cases, are released into natural environments that may differ from the original sites where they were captured. Until recently, the lack of genetic analysis of the individuals involved led to biased relocation decisions. We followed the reintroduction of 12 A. caraya individuals in a protected area (Isla Palacio, Misiones, Argentina). The presence of potential predators such as pumas (Puma concolor) and jaguars (Panthera onca) in this area was confirmed by camera traps, footprints and feces. After the disappearance of four A. caraya at the reintroduction site, we investigated the applicability of genetic assignment tests based on genotypic data to accurately identify predated individuals. Genetic analyses allowed us to determine the predator species (P. onca) and to identify the predated individuals as two of the reintroduced animals. This procedure is promising for identifying the remains of predated individuals, and can contribute to the design of reintroduction policies based on scientific evidence. [ABSTRACT FROM AUTHOR]

Oxytocin is a mammalian neuropeptide hormone that mediates behaviours important to reproduction. Despite almost universal amino acid sequence conservation across most groups of mammals, several unique forms have been reported across Neotropical primates. To explore sequence diversity, we investigated the genes encoding oxytocin and its receptor across the Atelidae, which was known to contain at least three unique oxytocin sequences. Additionally, we included the genus Cebus , within the Cebidae, to further explore the ubiquity of the Pro8 variant in this family. We found a novel amino acid variant (Val3) within the Atelidae radiation, bringing the total number of oxytocin sequences within Neotropical primates to seven. Analyses of physicochemical properties revealed conservative substitutions that are likely tolerated within the selective constraints imposed by receptor binding. Furthermore, we report radical substitutions at the eighth codon and evidence for co-evolution between Pro8 and a ligand-binding region of the oxytocin receptor in the Atelidae, supporting the notion that this variant may affect binding specificity. Overall, we suggest that selective constraint on binding specificity may maintain proper oxytocin function and that the diversification of amino acid sequence is likely due to a variety of processes such as relaxed constraint, neutral mutation, positive selection and coevolution. [ABSTRACT FROM AUTHOR]

The black-tailed marmoset, Mico melanurus, occurs in Brazil, Bolivia, and Paraguay. There are some gaps in our understanding of its distribution in the Brazilian states of Mato Grosso and Rondônia. Based on field surveys and a literature review, we present new records and an updated distribution map for the species. We also assess geographic and individual variation in the pelage of M. melanurus. For the surveys, we used the linear-transect method, adapted to include the use of playback. We also examined 11 specimens from museum collections--four from the mammal collection of the Cáceres campus of the Mato Grosso State University, and seven from the Goeldi Museum, Belém, Pará. Specimens from Vilhena and Chupinguaia had the darkest pelage, representing a previously unrecorded phenotype for the species, while specimens from the Guaporé, São Miguel, and Cautário river basins were of the palest phenotype. The thigh stripe, otherwise prominent, is inconspicuous or absent in some specimens. The new records extend the geographic distribution of M. melanurus to the northwest, suggesting contact zones with Mico nigriceps and Mico intermedius. [ABSTRACT FROM AUTHOR]

Four specimens of primates were collected from the Santa Cruz Formation (Early–Middle Miocene) during expeditions undertaken by the Museo de la Plata, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, and Duke University in 2013, 2014, and 2017. A new species of Homunculus Ameghino, H. vizcainoi (Platyrrhini, Homunculidae), was identified at Barrancas Blancas, and Segundas Barrancas Blancas localities on the right bank of the Río Santa Cruz (Santa Cruz Province, Argentina). The Barrancas Blancas specimen comes from a tuff dated at 17.04 Ma; those from Segundas Barrancas Blancas are older than a tuff dated at 16.32 Ma and younger than a tuff dated at 17.36 Ma. A Río Bote specimen is confidently identified as Homunculus, but of uncertain species. All these fossil primates are temporally equivalent to those from the coastal Santa Cruz Formation, and younger than those from the Pinturas Formation to the north. By contrast, the lower and middle strata of the Pinturas Formation contain a different but closely related taxon, Carlocebus Fleagle. All known records of Carlocebus from the Pinturas Formation in north central Santa Cruz Province are older than the known occurrences of Homunculus in the Santa Cruz Formation in the Río Santa Cruz valley, Río Bote and elsewhere.

The muscle–tendon arrangement of the m. flexor digitorum superficialis (FDS) varies among different primate groups. Recent developmental investigations revealed that the primordium of FDS emerges in the hand region first and relocates to the forearm later. The relationship between the diverse muscle–tendon arrangement and the characteristic developmental process of FDS is important for understanding the evolutionary changes of the FDS. Moreover, the innervation pattern cannot go unremarked when discussing the muscle homology and evolution. We examined the muscle–tendon arrangement and intramuscular nerve distribution of the FDS in three genera of Platyrrhini: three common marmosets (Callithrix jacchus), two squirrel monkeys (Saimiri sciureus) and two spider monkeys (Ateles sp.). We observed that the FDS consisted of multiple muscle bellies. The origin of the muscle bellies to digits II and V varied, whereas muscle bellies to digits III and IV consistently originated from the medial epicondyle. The muscle–tendon arrangement of the FDS differed among the three genera owing to the different origins of muscle bellies to digits II and V. In all the examined specimens, the muscle bellies to digits II and/or III were innervated by the direct nerve branches from the median nerve. However, the muscle bellies to digits IV and V never received direct nerve branches from the median nerve. Nerve branches within the belly to digit III extended into the belly to digit IV, and one nerve branch within the belly to digit IV extended into the belly to digit V. These consistent nerve distribution patterns suggest that different patterns of FDS muscle–tendon arrangement have changed from that of a common ancestral condition. It is plausible that the diverse origins of muscle bellies in the FDS are attributable to the difference in the destination for the relocation of the muscle bellies during developmental processes. [ABSTRACT FROM AUTHOR]

Many primates intentionally consume earth. This geophagy has probable health benefits, such as mineral supplementation or gastrointestinal tract protection, and is likely to be an important behavior for a species' ecology, health, diet, and conservation. We investigated geophagy in the Critically Endangered yellow-tailed woolly monkey (Lagothrix flavicauda). We collected observational data and camera trap records over 2 years at La Esperanza study site, northern Peru. Geophagy was rare, with 67 events recorded during the study. All age/sex classes engaged in geophagy, but adult males spent significantly less time consuming earth in situ than adult females did. Geophagy occurred predominantly during the dry season and was a solitary behavior. The forest floor is presumably a high-risk environment for these predominantly arboreal primates and our study animals employed various strategies to minimize predation risk. These included using a single route to access and leave geophagy sites, displaying increased vigilance behaviors before and during geophagy events, and minimizing the time spent on the forest floor (mean: 15 ± SD 9 s). They also maximized the benefits of being on the forest floor by removing earth to consume ex situ. These findings provide the first steps in the systemic approach required to understand the role geophagy plays in our study species, whose almost exclusive arboreality, coupled with the increased predation risk associated with terrestriality, suggests that geophagy confers an important benefit. [ABSTRACT FROM AUTHOR]

Geophagy is the intentional consumption of soil and has been observed in various animal taxa including human and nonhuman primates. Among the numerous adaptive hypotheses proposed to explain this behavior, two of them stand out: soil either protects the gastrointestinal tract from secondary plant compounds, parasites and pathogens, and/or supplements micronutrients in the diet. Few studies have characterized the physical and chemical characteristics of soils consumed by nonhuman primates. Here, we describe the composition of soils consumed by yellow-tailed woolly monkeys (Lagothrix flavicauda) in comparison with soils taken from surrounding areas. We also studied the physical aspects of geophagy sites in terms of accessibility, dimensions and vegetation density. This study took place at the La Esperanza field site, in northern Peru, between 2016 and 2018. We conducted focal follows, placed camera traps at geophagy sites and sampled soils. In total, we recorded 77 geophagy events. Our results highlight some aspects of soil and site selection in these arboreal primates, who face an increased predation risk when descending to the ground. Animals preferred smaller sites with denser surrounding vegetation. Composition of consumed soils was similar between geophagy sites. Soils were poor in micronutrients, but contained around 20% clay. High clay content, coupled with the fact that geophagy was performed significantly more in the dry season, when leaf consumption is highest, lends support to geophagy as a mechanism for protection of the gastrointestinal tract in L. flavicauda. [ABSTRACT FROM AUTHOR]

Aim: Addressing the phylogenetic relationship among species has been insightful to understand evolutionary and biogeographical processes shaping the distribution of diversity across broad geographical gradients. Here we determine the geographical distribution and the variables correlated with the phylogenetic component of diversity and endemism for primates, as well as their relationships with the taxonomic component of diversity. Location: New World. Taxon: New World monkeys, Platyrrhini. Methods: We mapped primate occurrence in cells of 110 × 110 km. For each cell, we calculated phylogenetic diversity (PD) and endemism (PE), as well as how much these indices deviate from their expected values based on species richness (SR) and endemism (SE), respectively. Using simultaneous autoregressive models, we tested the effects of mean annual temperature, forest structure and climate history on the current patterns of primate phylogenetic diversity. Results: We found that most primate phylogenetic diversity is found in the tropical forests of South America. Tropical forests also present much higher PD and PE than predicted by SR and SE, respectively, demonstrating their importance in producing and maintaining primate phylogenetic diversity in the New World. Furthermore, regions presenting low SR and SE nevertheless show high PE, likely because these areas have witnessed the evolution of many clades occurring exclusively therein. Overall, mean annual temperature had the highest influence in explaining phylogenetic indices. Main conclusions: Our results suggest a strong influence of primate biogeography throughout the New World on the geographical distribution of the phylogenetic component of their diversity, with the Amazon, Atlantic Forest and Central America containing the greatest amount and endemism of phylogenetic diversity. Our study contributes to a better understanding of the dynamics underlying the geographical distribution of New World's primate diversity, especially in a phylogenetic context in which their biogeographical history has deeply affected current patterns of primate diversity in this region. Our results provide essential information for the conservation of primate evolutionary history, especially considering the forecast effects of habitat loss and climate change on the dynamics of tropical forests. [ABSTRACT FROM AUTHOR]

Background: Endogenous Retroviruses (ERVs) constitute approximately 8% of every human genome and are relics of ancestral infections that affected the germ line cells. The ERV-W group contributed to primate physiology by providing an envelope protein (Syncytin-1) that has been adopted for placenta development in hominoids. Expression of Human ERV-W (HERV-W) sequences is investigated for a pathological role in various human diseases. Results: We previously characterized ERV-W group genomic sequences in human and non-human Catarrhini species. We now investigated ERV-W-like sequences in the parvorder Platyrrhini, especially regarding two species with complete genome assemblies, namely marmoset (Callithrix jacchus) and squirrel monkey (Saimiri boliviensis). We identified in both species proviral sequences, annotated as ERV1–1 in respective genome assemblies, sharing high sequence similarities with Catarrhini ERV-W. A total of 130 relatively intact proviruses from the genomes of marmoset and squirrel monkey were characterized regarding their structural and evolutionarily relationships with Catarrhini ERV-W elements. Platyrrhini ERV-W sequences share several structural features with Catarrhini ERV-W elements and are closely related phylogenetically with the latter as well as with other ERV-W-related gammaretrovirus-like ERVs. The ERV-W group colonized Platyrrhini primates of both Callitrichidae and Atelidae lineages, with provirus formations having occurred mostly between 25 and 15 mya. Two LTR subgroups were associated with monophyletic proviral bodies. A pre-gag region appears to be a sequence feature common to the ERV-W group: it harbors a putative intron sequence that is missing in some ERV-W loci, holding a putative ORF as well. The presence of a long pre-gag portion was confirmed among all gammaretroviral ERV analyzed, suggesting a role in the latter biology. It is noteworthy that, contrary to Catarrhini ERV-W, there was no evidence of L1-mediated mobilization for Platyrrhini ERV-W sequences. Conclusions: Our data establish that ERV-W is not exclusive to Catarrhini primates but colonized both parvorders of Simiiformes, providing further insight into the evolution of ERV-W and the colonization of primate genomes. [ABSTRACT FROM AUTHOR]

Primates are characterized by specializations for manual manipulation, including expansion of posterior parietal cortex (PPC) and, in Catarrhines, evolution of a dexterous hand and opposable thumb. Previous studies examined functional interactions between motor cortex and PPC in New World monkeys and galagos, by inactivating M1 and evoking movements from PPC. These studies found that portions of PPC depend on M1 to generate movements. We now add a species that more closely resembles humans in hand morphology and PPC: macaques. Inactivating portions of M1 resulted in all evoked movements being reduced (28%) or completely abolished (72%) at the PPC sites tested (in areas 5L, PF, and PFG). Anterior parietal area 2 was similarly affected (26% reduced and 74% abolished) and area 1 was the least affected (12% no effect, 54% reduced, and 34% abolished). Unlike previous studies in New World monkeys and galagos, interactions between both nonanalogous (heterotopic) and analogous (homotopic) M1 and parietal movement domains were commonly found in most areas. These experiments demonstrate that there may be two parallel networks involved in motor control: a posterior parietal network dependent on M1 and a network that includes area 1 that is relatively independent of M1. Furthermore, it appears that the relative size and number of cortical fields in parietal cortex in different species correlates with homotopic and heterotopic effect prevalence. These functional differences in macaques could contribute to more numerous and varied muscle synergies across major muscle groups, supporting the expansion of the primate manual behavioral repertoire observed in Old World monkeys. NEW & NOTEWORTHY Motor cortex and anterior and posterior parietal cortex form a sensorimotor integration network. We tested the extent to which parietal areas could initiate movements independent of M1. Our findings support the contention that, although areas 2, 5L, PF, and PFG are highly dependent on M1 to produce movement, area 1 may constitute a parallel corticospinal pathway that can function somewhat independently of M1. A similar functional architecture may underlie dexterous tool use in humans.