Obligate exudativory characterizes the diet of the pygmy slow loris Nycticebus pygmaeus: Pygmy Loris Diet in Cambodia

From masks to muscles: Mapping facial structure of Nycticebus

Facial musculature in mammals underlies mastication and nonverbal communicative facial displays. Our understanding of primate facial expression comes primarily from haplorrhines (monkeys and apes), while our understanding of strepsirrhine (lemurs and lorises) facial expression remains incomplete. We examined the facial muscles of six specimens from three Nycticebus species (Nycticebus coucang, Nycticebus javanicus, and Nycticebus menagensis) using traditional dissection methodology and novel three-dimensional facial scanning to produce a detailed facial muscle map, and compared these results to another nocturnal strepsirrhine genus, the greater bushbaby (Otolemur spp.). We observed 19 muscles with no differences among Nycticebus specimens. A total of 17 muscles were observed in both Nycticebus and Otolemur, with little difference in attachment and function but some difference in directionality of movement. In the oral region, we note the presence of the depressor anguli oris, which has been reported in other primate species but is absent in Otolemur. The remaining muscle is a previously undescribed constrictor nasalis muscle located on the lateral nasal alar region, likely responsible for constriction of the nares. We propose this newly described muscle may relate to vomeronasal organ functioning and the importance of the use of nasal musculature in olfactory communication. We discuss how this combined methodology enabled imaging of small complex muscles. We further discuss how the facial anatomy of Nycticebus spp. relates to their unique physiology and behavioral ecology.

Evaluating the Use of Chemical Weapons for Capturing Prey by a Venomous Mammal, the Greater Slow Loris (Nycticebus coucang)

Few mammals are venomous, including one group of primates-slow (Nycticebus spp.) and pygmy (Xanthonycticebus spp.) lorises. Hypotheses for the evolutionary function of venom in these primates include defense from predators or ectoparasites, communication or competition with conspecifics, and the capture of prey. We tested the prey capture hypothesis in 75 trials with 22 wild-caught greater slow lorises (N. coucang) housed in a rescue center in Java, Indonesia. We experimentally offered the slow lorises arthropod prey items varying in size, escape potential, and toxicity and recorded venom-related and predatory behaviors using live and video observations. The slow lorises visually targeted arthropod prey, approached it quickly and efficiently, and captured it with a manual grasping motion. They rarely performed venom-related behaviors and seemed to do so in a defensive context. The slow lorises exhibited little variation in pre-capture behavior as a function of prey size or escape potential. In response to noxious prey, the slow lorises performed tongue-flicking and other investigative behaviors that indicate they are using chemosensory input to assess prey characteristics. These data suggest it is unlikely that slow lorises use chemical weapons to subdue arthropod prey and may support, instead, a defensive function for slow loris venom.

CLINICAL FINDINGS OF DENTAL DISEASE AND POTENTIAL CONTRIBUTING FACTORS IN PYGMY SLOW LORISES (NYCTICEBUS PYGMAEUS) UNDER HUMAN CARE

Dental disease is a common finding in pygmy slow lorises (Nycticebus pygmaeus) under human care, but the etiology is not fully understood. The small oral cavity in this species can make diagnosis of dental disease difficult. This retrospective study evaluated medical records and diet and husbandry protocols from 18 participating institutions with the objective of describing the signalment, clinical signs, physical exam findings, tooth type, tooth location, diagnostics used, and treatments performed to help guide care for dental disease. In addition, the study aimed to identify potential contributing factors to dental disease in this species. Of 59 animals with medical records evaluated, 42 (71.2%) had dental disease: 19 (44.2%) males, 20 (46.5%) females, and 3 (9.3%) without gender documented. Average age at onset of dental disease was 7.6 yr in males and 9 yr in females. Multiple lorises with dental disease (n = 12; 28.6%) had no premonitory clinical signs, and dental disease was found incidentally on examination. On dental examination, 30 lorises (71.4%) had evidence of gingivitis. In 13 cases skull radiographs were taken, but the majority of images (n = 8; 61.5%) were nondiagnostic for pathologic dental changes. A small proportion of cases with dental abnormalities (n = 4; 9.5%) were diagnosed using computed tomography. In total, 175 teeth were extracted from 31 patients; molars were the most frequently extracted tooth (n = 55; 31.4%). No substantial differences in diets were noted among many of the participating institutions, and not all slow lorises evaluated developed dental disease (n = 17; 28.8%). This retrospective study provides clinical findings on slow loris dental disease and guidance for the veterinary care and management of slow lorises under human care.

Slowly Making Sense: A Review of the Two-Step Venom System within Slow (Nycticebus spp.) and Pygmy Lorises (Xanthonycticebus spp.)

Since the early 2000s, studies of the evolution of venom within animals have rapidly expanded, offering new revelations on the origins and development of venom within various species. The venomous mammals represent excellent opportunities to study venom evolution due to the varying functional usages, the unusual distribution of venom across unrelated mammals and the diverse variety of delivery systems. A group of mammals that excellently represents a combination of these traits are the slow (Nycticebus spp.) and pygmy lorises (Xanthonycticebus spp.) of south-east Asia, which possess the only confirmed two-step venom system. These taxa also present one of the most intriguing mixes of toxic symptoms (cytotoxicity and immunotoxicity) and functional usages (intraspecific competition and ectoparasitic defence) seen in extant animals. We still lack many pieces of the puzzle in understanding how this venom system works, why it evolved what is involved in the venom system and what triggers the toxic components to work. Here, we review available data building upon a decade of research on this topic, focusing especially on why and how this venom system may have evolved. We discuss that research now suggests that venom in slow lorises has a sophisticated set of multiple uses in both intraspecific competition and the potential to disrupt the immune system of targets; we suggest that an exudate diet reveals several toxic plants consumed by slow and pygmy lorises that could be sequestered into their venom and which may help heal venomous bite wounds; we provide the most up-to-date visual model of the brachial gland exudate secretion protein (BGEsp); and we discuss research on a complement component 1r (C1R) protein in saliva that may solve the mystery of what activates the toxicity of slow and pygmy loris venom. We conclude that the slow and pygmy lorises possess amongst the most complex venom system in extant animals, and while we have still a lot more to understand about their venom system, we are close to a breakthrough, particularly with current technological advances.

Functional genomics analysis reveals the evolutionary adaptation and demographic history of pygmy lorises

Lorises are a group of globally threatened strepsirrhine primates that exhibit many unusual physiological and behavioral features, including a low metabolic rate, slow movement, and hibernation. Here, we assembled a chromosome-level genome sequence of the pygmy loris (Xanthonycticebus pygmaeus) and resequenced whole genomes from 50 pygmy lorises and 6 Bengal slow lorises (Nycticebus bengalensis). We found that many gene families involved in detoxification have been specifically expanded in the pygmy loris, including the GSTA gene family, with many newly derived copies functioning specifically in the liver. We detected many genes displaying evolutionary convergence between pygmy loris and koala, including PITRM1. Significant decreases in PITRM1 enzymatic activity in these two species may have contributed to their characteristic low rate of metabolism. We also detected many evolutionarily convergent genes and positively selected genes in the pygmy loris that are involved in muscle development. Functional assays demonstrated the decreased ability of one positively selected gene, MYOF, to up-regulate the fast-type muscle fiber, consistent with the lower proportion of fast-twitch muscle fibers in the pygmy loris. The protein product of another positively selected gene in the pygmy loris, PER2, exhibited weaker binding to the key circadian core protein CRY, a finding that may be related to this species' unusual circadian rhythm. Finally, population genomics analysis revealed that these two extant loris species, which coexist in the same habitat, have exhibited an inverse relationship in terms of their demography over the past 1 million years, implying strong interspecies competition after speciation.

The sticky tasty: the nutritional content of the exudativorous diet of the Javan slow loris in a lowland forest

Plant exudates are an important food source for many primates. The Critically Endangered Javan slow loris (Nycticebus javanicus) was previously found to prefer Acacia decurrens exudate in an anthropogenically disturbed site, while its feeding habits in secondary natural forest remain unknown. Knowledge of the chemical characteristics of the plant exudates that Javan slow lorises consume is limited, especially with respect to those that they feed on in natural forests. As plant exudates may contain plant secondary metabolites (PSM), which are considered unpalatable in high concentrations, differences in PSM composition may drive feeding preferences. This research aims firstly to confirm exudate consumption by the Javan slow loris in a lowland tropical forest in Central Java, and secondly to identify the chemical characteristics of the exudates consumed. We followed wild slow lorises in Kemuning Forest, Central Java and observed their behaviour. We investigated the gum-producing trees that were utilized by the slow lorises by tapping the exudates and examining their nutritional and PSM contents. We found that exudates are the predominant food source for the Javan slow loris in this lowland forest, and that their nutritional contents are similar to those of exudates consumed by lorises in anthropogenically disturbed areas. Significant differences in polysaccharide and flavonoid contents were found between consumed and unconsumed exudates. Knowledge of the diet of the Javan slow loris is crucial to its conservation, and our findings confirm the importance of exudates in its diet. We also highlight the need to preserve natural slow loris habitat, and to manage the diets of these species in captivity. The results of this study indicate that plant exudates should constitute a significant portion of the diet of captive slow lorises, and that the presence of exudate-producing trees is vital in areas into which slow lorises are to be translocated.

Functional and ecological correlates of the primate jaw abductors

While the adductor musculature of the primate jaw has been extensively analyzed within the context of dietary and social ecology, little is known about the corresponding muscles of jaw abduction. Nonetheless, these muscles significantly contribute to a species' maximum gape potential, and thus might constrain dietary niche diversity and impact social display behaviors. In this study, we quantify the architectural properties of the digastric (a jaw abductor) and lateral pterygoid (a jaw abductor and anterior translator) across a broad sample of male and female anthropoid primates. We test the hypothesis that the abductor musculature reflects specialization to dietary and behavioral ecology. Our sample comprises 14 catarrhine and 13 platyrrhine species spanning a wide range of dietary and social categories. All specimens were sharp dissected and muscles subsequently chemically digested using a standardized protocol. Our findings demonstrate that relative fascicle lengths within the lateral pterygoid (but not the digastric) are significantly greater within species that habitually consume larger food items. Meanwhile, canine length is more strongly associated with fascicle lengths in the digastric than in the lateral pterygoid, particularly within males. Neither dietary mechanical resistance nor the intensity of social competition relates to the size or architectural properties of the jaw abductors. These findings suggest that dietary-and to a lesser extent, socioecological-aspects of a primate's life history may be reflected in the architecture of these muscles, albeit to varying degrees. This underlines the importance of considering the complete masticatory apparatus when interpreting the evolution of the primate jaw.

Beyond Description: The Many Facets of Dental Biomechanics

Teeth lie at the interface between an animal and its environment and, with some exceptions, act as a major component of resource procurement through food acquisition and processing. Therefore, the shape of a tooth is closely tied to the type of food being eaten. This tight relationship is of use to biologists describing the natural history of species and given the high instance of tooth preservation in the fossil record, is especially useful for paleontologists. However, correlating gross tooth morphology to diet is only part of the story, and much more can be learned through the study of dental biomechanics. We can explore the mechanics of how teeth work, how different shapes evolved, and the underlying forces that constrain tooth shape. This review aims to provide an overview of the research on dental biomechanics, in both mammalian and non-mammalian teeth, and to synthesize two main approaches to dental biomechanics to develop an integrative framework for classifying and evaluating dental functional morphology. This framework relates food material properties to the dynamics of food processing, in particular how teeth transfer energy to food items, and how these mechanical considerations may have shaped the evolution of tooth morphology. We also review advances in technology and new techniques that have allowed more in-depth studies of tooth form and function.

A comparative study of gut microbiomes in captive nocturnal strepsirrhines

Feeding strategy and diet are increasingly recognized for their roles in governing primate gut microbiome (GMB) composition. Whereas feeding strategy reflects evolutionary adaptations to a host's environment, diet is a more proximate measure of food intake. Host phylogeny, which is intertwined with feeding strategy, is an additional, and often confounding factor that shapes GMBs across host lineages. Nocturnal strepsirrhines are an intriguing and underutilized group in which to examine the links between these three factors and GMB composition. Here, we compare GMB composition in four species of captive, nocturnal strepsirrhines with varying feeding strategies and phylogenetic relationships, but nearly identical diets. We use 16S rRNA sequences to determine gut bacterial composition. Despite similar husbandry conditions, including diet, we find that GMB composition varies significantly across host species and is linked to host feeding strategy and phylogeny. The GMBs of the omnivorous and the frugivorous species were significantly more diverse than were those of the insectivorous and exudativorous species. Across all hosts, GMBs were enriched for bacterial taxa associated with the macronutrient resources linked to the host's respective feeding strategy. Ultimately, the reported variation in microbiome composition suggests that the impacts of captivity and concurrent diet do not overshadow patterns of feeding strategy and phylogeny. As our understanding of primate GMBs progresses, populations of captive primates can provide insight into the evolution of host-microbe relationships, as well as inform future captive management protocols that enhance primate health and conservation.

Nutrient-based diet modifications impact on the gut microbiome of the Javan slow loris (Nycticebus javanicus)

Environment and diet are key factors which shape the microbiome of organisms. There is also a disparity between captive and wild animals of the same species, presumably because of the change in diet. Being able to reverse the microbiome to the wild type is thus particularly important for the reintroduction efforts of Critically Endangered animals. The Javan slow loris (Nycticebus javanicus) is a suitable model, being kept in the thousands within rescue centres throughout Southeast Asia. With next-generation sequencing, we show how a naturalistic diet impacts the gut microbiome of captive slow lorises (Primates: Nycticebus). A comparison of the microbiome of wild animals with captive animals that had been fed a standard captive or improved diet reveals strong microbiome differences between wild and captive animals; however, diet changes failed to alter the microbiome of captive populations significantly. Bifidobacterium was the most abundant genus in wild animals (46.7%) while Bacteroides (11.6%) and Prevotella (18.9%) were the most abundant in captive animals fed the captive and improved diets, respectively. Correlation analyses of nutrients with microbial taxa suggest important implications in using nutrition to suppress potential pathogens, with soluble fibre and water-soluble carbohydrates both being associated with opposing microbiome profiles. The improved diet significantly increased microbe diversity, which exemplifies the importance of high fibre diets; however, wild individuals had lower diversity, which contradicts recent studies. Detection of methanogens appeared to be dependent on diet and whether the animals were living in captivity or in the wild. This study highlights the potential of nutrition in modulating the microbiome of animals prior to release. Unexpectedly, the results were not as significant as has been suggested in recent studies.

Sources of morbidity in lorises and pottos in North American zoos: A retrospective review, 1980-2010

Delineating patterns of morbidity can reveal management practices in need of reassessment to improve individual welfare, as well as population health and sustainability. We reviewed medical records from 38 North American zoological institutions for 276 slender lorises, slow lorises, and pottos born between January 1, 1980 and December 31, 2010. This sample included animals identified as 116 Nycticebus pygmaeus, 84 N. coucang, 48 Loris tardigradus tardigradus, 6 L.t. nordicus (now classified as L. lydekkerianus nordicus), and 22 Perodicticus potto. Taxonomy for lorises and pottos is developing, and two of these populations (N. coucang and P. potto) likely included hybrids and/or multiple species. Our focus was to examine trends based on species and age. Across all species, whole body disease events, abnormalities of bloodwork, and dental diseases were the most common sources of morbidity. Other major sources of morbidity varied by species and included trauma, respiratory disease, and ocular disease. A recent upsurge in research has informed feeding practices for slow lorises living in human care, and a similar, evidence-based approach is needed to improve diets for other species. Given the prevalence of trauma in this sample, social needs and reproductive management practices are also important areas for further investigation. Species-level health trends reveal risk factors for individual welfare that can guide husbandry practices in zoos, as well as in sanctuaries caring for the influx of lorises and pottos rescued from the growing wildlife trade.

The gut microbiome of nonhuman primates: Lessons in ecology and evolution

The mammalian gastrointestinal (GI) tract is home to trillions of bacteria that play a substantial role in host metabolism and immunity. While progress has been made in understanding the role that microbial communities play in human health and disease, much less attention has been given to host-associated microbiomes in nonhuman primates (NHPs). Here we review past and current research exploring the gut microbiome of NHPs. First, we summarize methods for characterization of the NHP gut microbiome. Then we discuss variation in gut microbiome composition and function across different NHP taxa. Finally, we highlight how studying the gut microbiome offers new insights into primate nutrition, physiology, and immune system function, as well as enhances our understanding of primate ecology and evolution. Microbiome approaches are useful tools for studying relevant issues in primate ecology. Further study of the gut microbiome of NHPs will offer new insight into primate ecology and evolution as well as human health.

Welfare impacts of the illegal wildlife trade in a cohort of confiscated greater slow lorises, Nycticebus coucang

Illegal harvesting and trade are major forces behind population declines of wild slow lorises (genus Nycticebus). The impacts of the wildlife trade on individual slow lorises have not been as well described. In this article, we describe quantitatively the consequences of the wildlife trade for 77 greater slow lorises, N. coucang, who were confiscated en masse and brought to Cikananga Wildlife Center in Indonesia. Medical records indicated that in total, 28.6% of the slow lorises died within the first 6 months, mostly due to traumatic injury, and all the infants died. The greatest sources of morbidity were external wounds (33.1% of 166 total medical events) and dental problems (19.3%). Of the surviving individuals, 25.4% displayed abnormal behavior. Behavioral observations indicated that healthy adults (n = 3) spent 48.2% of their active period performing stereotypies. These data illustrate the physical and behavioral impacts of the illegal wildlife trade on the welfare of slow lorises. We suggest that sharing these individual stories may help generate empathy and educate the public about the impacts of the exotic companion-animal (pet) trade on nonhuman animal welfare.

Does toxic defence in Nycticebus spp. relate to ectoparasites? The lethal effects of slow loris venom on arthropods

The venom produced by slow lorises (Nycticebus spp.) is toxic both intra- and inter-specifically. In this study we assessed the ecoparasite repellent properties of their venom. We tested venom from two Indonesian slow loris species: Nycticebus javanicus and Nycticebus coucang. Arthropods directly exposed to brachial gland secretions mixed with saliva from both species were immediately impaired or exhibited reduced activity (76%), and often died as a result (61%). We found no significant difference in the result of 60-min trials between N. coucang and N. javanicus [X(2)(1, n = 140) = 2.110, p = 0.3482]. We found evidence that the degree of lethality of the venom varies according to the arthropod taxa to which it is exposed. While most maggots (84%) were initially impaired from the venom after 10 min, maggots died after a 1 h trial 42% of the time. In contrast, at the end of 1 h trial, spiders died 78% of the time. For all arthropods, the average time to death from exposure was less than 25 min (M = 24.40, SD = 22.60). Ectoparasites including ticks, members of the arachnid order, are known to transmit pathogens to hosts and may be an intended target of the toxic secretions. Our results suggest that one function of slow loris venom is to repel parasites that affect their fitness, and that their topical anointing behaviour may be an adaptive response to ectoparasites.

Vegetable exudates as food for Callithrix spp. (Callitrichidae): exploratory patterns

Marmosets of the genus Callithrix are specialized in the consumption of tree exudates to obtain essential nutritional resource by boring holes into bark with teeth. However, marmoset preferences for particular tree species, location, type, and other suitable factors that aid in exudate acquisition need further research. In the current study, the intensity of exudate use from Anadenanthera peregrina var. peregrina trees by hybrid marmosets Callithrix spp. groups was studied in five forest fragments in Viçosa, in the state of Minas, Brazil. Thirty-nine A. peregrina var. peregrina trees were examined and 8,765 active and non-active holes were analyzed. The trunk of A. peregrina var. peregrina had a lower number of holes than the canopy: 11% were found on the trunk and 89% were found on the canopy. The upper canopy was the preferred area by Callithrix spp. for obtaining exudates. The intensity of tree exploitation by marmosets showed a moderate-to-weak correlation with diameter at breast height (DBH) and total tree height. The overall results indicate that Anadenanthera peregrina var. peregrina provides food resources for hybrid marmosets (Callithrix spp.) and these animals prefer to explore this resource on the apical parts of the plant, where the thickness, location, and age of the branches are the main features involved in the acquisition of exudates.