More effective induction of anesthesia using midazolam-butorphanol-ketamine-sevoflurane compared with ketamine-sevoflurane in the common marmoset monkey (Callithrix jacchus)

The common marmoset has been increasingly used for research in the biomedical field; however, there is little information available regarding effective methods of anesthesia in this species. This study retrospectively analyzed 2 regimens of anesthesia induction: intramuscular injection of ketamine followed by inhalation of 5% sevoflurane, and intramuscular injection of midazolam, butorphanol and ketamine followed by inhalation of 5% sevoflurane. Anesthetic depth did not reach the surgical anesthesia stage in 7 out of 99 animals receiving the former regimen, whereas there were only 2 such animals out of 273 receiving the latter regimen. The latter regimen, when followed by maintenance anesthesia with 3% sevoflurane inhalation, was successfully used in various nociceptive procedures. These results indicate that the injection of a combination of midazolam, butorphanol and ketamine followed by inhalation of a high concentration of sevoflurane is effective for anesthesia induction in marmosets.     

A short note on extractive foraging behavior in gray snub‐nosed monkeys

Extractive foraging (EF) involves the exploitation of hidden or embedded foods, generally any food that is not visible to the naked eye. Therefore, EF is particularly important for survival in marginal habitats as it provides seasonal fallback foods in low food availability seasons. Although many studies consider primates’ EF behavior and category, colobine species are usually categorized as non‐extractive foragers and few studies quantitatively examine their EF behavior. In this study, we examined the EF behavior of one colobine species, the gray snub‐nosed monkey (Rhinopithecus brelichi), at Yangaoping in Fanjingshan National Nature Reserve, Guizhou. We recorded 6 categories of EF behaviors. The most frequently sought‐out foods were seeds, young bamboo and invertebrates. Extracted foods accounted for an average of 26.02% of feeding records. As the monkey engages in little EF behavior in the winter when the food availability is low, these results seem to do not support the hypothesis that EF serves to secure additional resources during lean times in marginal or seasonal habitats. According to these findings, we suggest R. brelich should be considered as an extractive forager. Our study also highlights the need for increased representation of colobines in the EF literature to better inform the discussion concerning its link to primate brain evolution.     

Genetic polymorphism as a background of animal behavior

Various studies have shown the associations between differences in human behavioral traits and genetic polymorphism of neurotransmitter-related proteins such as receptors, transporters and monoamine oxidase. To clarify the genetic background of animal behavior, corresponding regions in animals have been analyzed. The study has been especially focused on primates, as the evolutionally closest animal to humans, and on dogs, as the socially closest animal to humans. In primates, polymorphisms were discovered between or within species, and the functional effects on neural transmission were found to be different by alleles. Even in apes, the closest species to humans, function was different from that in humans. In dogs, allele distributions of several genes were different among breeds showing different behavioral traits, and genes associated with individual differences in aggressiveness and aptitude of working dogs were surveyed. The survey of behavior-related genes has also been carried out in other mammals such as horses and cetaceans. Genes controlling various behaviors in birds have also been reported. The marker genes for behavior will provide useful information for human evolution, welfare of zoo animals and effective selection of working dogs and industry animals.     

Comparative retinal ganglion cell and optic nerve morphology

The optic nerve is divided in four regions: intraocular, intraorbital, intracanalicular, and intracranial. The vertebrate retinal ganglion cells are classified by morphology, physiology and soma size. Species differences and similarities occur with retinal ganglion cells. Alpha retinal ganglion cells have large somata, large dendritic fields, large-diameter axons, and are most dense in the peripheral retina. Beta retinal ganglion cells have smaller diameter somata, smaller dendritic fields, small diameter axons, and predominate in the central retina. Gamma retinal ganglion cells are a heterogenous class of cells and have small diameter axons, and slow axon conduction velocities. The spatial distribution and organization of the retinal ganglion cells extends retinotopically through the nerve fiber layer, optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, and visual cortex. The retinal nerve fiber layer thickness decreases from the optic disk toward the periphery of the retina. The retrobulbar optic nerve axon counts and axon density vary by species, with larger nerves having higher axon counts. Decussation of the optic nerve axons at the optic chiasm varies with 100% decussation in most birds and fish, 65% in cats, 75% in dogs, 80–90% in large animals, and 50% in primates. Centrifugal axons also occur in the optic nerve and may represent a method by which the brain can influence retinal activity.     

Fundus pigment distribution in rhesus monkeys

There is growing evidence for an interaction among fundus pigmentation, character, geography and the function and structure of the outer retina. We examined three inbred groups of rhesus macaques (132 eyes) including all ages. One was a smaller (18 eyes) group. Coat colors were variations of brown-tan however, the smaller group had lighter 'golden' coats and colors. Fundus images were classified for pigmentation and its geographic distribution. In golden-coated animals there was bias toward nasal fundus hypopigmentation with the optic disk as a watershed demarcation zone, which extended in the superior-inferior direction. Temporal fundus hypopigmentation did not occur in the absence of nasal hypopigmentation. More common, darker coated samples showed a characteristic diffuse fundus pigmentation. There was no evidence for albinism or large variations in macular pigmentation. Rhesus monkeys can exhibit geographically controlled genetic development of fundus pigmentation. Hypopigmentation provides for access to the choroidal infrastructure.     

Short term pharmacological immobilization in macaque monkeys

ObjectiveTo develop a safe and effective immobilization protocol in rhesus monkeys, which is not based on dissociative anaesthetic agent.Study designProspective, randomised, experimental trial.AnimalsTwenty rhesus monkeys, weighing 2.6–8.0 kg, 1–3 years of age, of both sexes.MethodsThe monkeys received 50 μg kg^?1 medetomidine, 0.25 mg kg^?1 midazolam and 5 μg kg^?1 fentanyl with 150 IU hyaluronidase intramuscularly (IM). The animals were closely observed for behavioural changes and reaction to sound stimulus. Pulse rate and oxygen saturation of haemoglobin (SpO₂) were monitored every 5 minutes, for 20 minutes. After this period, 250 μg kg^?1 atipamezole or a placebo was administered IM and behavioural changes were closely observed.ResultsFull immobilization was observed after mean 269 ± SD 116 seconds. Ten minutes after injection mean arterial oxygen saturation of haemoglobin was 94 ± 4%, but did not fall significantly further. The median pulse rate was 116 beats minute^?1 5 minutes after the administration of the drug. This level further decreased to a median level of 108 beats minute^?1 20 minutes after the drug's administration. The median time to recover from immobilization was significantly shorter after atipamezole administration when compared to placebo (2.7 versus 55 minutes). All animals awoke smoothly and no side effects such as vomiting or agitation were observed.ConclusionsShort term and reversible pharmacological immobilization was achieved using combination of midazolam, medetomidine, and fentanyl.Clinical relevanceThe present study demonstrates that 20-minute pharmacological immobilization with a combination of midazolam, medetomidine, and fentanyl is feasible in rhesus monkeys with minimal effect on heart rate.     

Drusen and lipid-filled retinal pigment epithelium cells in a rhesus macula

A middle-aged rhesus monkey with detailed clinical history exhibited progression of a macular abnormality with a variety of clinical drusen and pigment changes typical of the Cayo Santiago phenotype. Numerous frozen sections of one sample of the macular retina/retinal pigment epithelium (RPE)/choroid showed a single classical druse but extensive single and clustered lipid-filled RPE cells. The monkey exhibited functional outer retinal decline and an insignificant number of 'window defects' as found among signs of relatively benign human macular aging. The clinical and histologically defined results agree if lipid-filled RPE cells are included among the clinically apparent signs of drusen.     

Trialling nutrient recommendations for slow lorises (Nycticebus spp.) based on wild feeding ecology

Slow loris (Nycticebus spp.) captive diets have been based on routine and anecdotes rather than scientific fact. The growing body of evidence contradicts the high fruit diet supported by such anecdotes. Non‐human primate nutrient requirements are grouped into new (based on the common marmoset Callithrix jacchus) or old world (based on rhesus macaques Macaca mulatta) primates. Slow lorises are known to suffer from many health ailments in captivity such as dental disease, obesity, wasting and kidney issues all of which have been linked to diet. This study aimed to estimate nutrient intake from free‐ranging slow lorises and to determine whether this intake can be used as nutrient recommendations. We collected data of nutrient intake, food passage rate and digestibility of captive slow lorises on three diet treatments 1: current captive type diet which is mostly fruits, 2: wild‐type diet made only of food items from their natural diet, 3: new diet made to reflect wild slow loris nutrient intake. In order to validate our nutrient recommendations, diets 2 and 3 would have to be significantly different to Diet 1 in terms of nutrients, but not different from each other. Captive diets were significantly higher in soluble carbohydrates and lower in minerals and fibre fractions than both diets 2 and 3. Diets 2 and 3 led to a significantly increased food passage time and to more effective fibre and calcium digestion compared to Diet 1. We also observed obese individuals lost weight and underweight individuals gained weight. Our nutrient recommendations have been validated by our trials, and new or old world monkey nutrient recommendations are not consistent with our results. Diets should be high in protein and fibre and low in soluble carbohydrates and fats.     

Giardia duodenalis in primates: Classification and host specificity based on phylogenetic analysis of sequence data

Giardia duodenalis colonizes the gastrointestinal tract of a wide range of hosts, including humans and other primates. It is grouped into eight different Assemblages and, beyond that, into a number of sub‐Assemblages, defined ad hoc on the basis of genetic differences; these various groups are often considered to be associated with a specific restricted host range. The aim of this study was to use publicly available genotyping data to investigate the relatedness of human and non‐human primate (NHP) Giardia isolates in order to evaluate the usefulness of current taxonomic classification and to assess whether there is potential for zoonotic transmission between humans and NHP. Our final data set consisted of sequence data from 165 isolates, 111 from NHP and 54 from humans. Assemblages were well defined, but sub‐Assemblages across Assemblage B were not resolved. Although sub‐Assemblages AI and AII were resolved, the terms were not found to capture any useful molecular or host/deme properties. In the phylogenetic tree, NHP isolates were scattered among human isolates across Assemblages A and B, and were even found in Assemblage E. We conclude that there does not appear to be significant molecular distinction between human and NHP Giardia isolates across these four molecular markers. Thus, on the basis of these markers, we cannot exclude a risk for zoonotic and anthropozoonotic transmission of Assemblages A and B isolates, irrespective of sub‐Assemblage classification. We further evaluated the relative merit of the four genes used in genotyping studies. The tpi, gdh and bg genes gave relatively congruent tree topologies, but the SSU gene did not resolve Assemblages according to the current classification. Future genotyping efforts should aim for multilocus or whole‐genome approaches and, in particular, use of the SSU gene as the sole marker should be avoided when possible.