Exploiting flavour preferences of common marmosets to increase palatability of a dry pellet diet

Although commercially available complete diets exist for common marmosets, the animals’ consumption of these diets (available in dry pellet form) is typically very low. Increasing consumption of the pellet diet could have positive consequences for the welfare of the marmosets as the pellets are designed specifically to meet their full nutritional requirements, and therefore an increase in intake should help to ensure that they take in an appropriate balance of nutrients. We carried out a series of studies targeted towards improving the palatability, and hence increasing the intake, of a complete dry pellet diet for marmosets. In Study 1 we attempted to determine which of a wide range of flavours appeared to be preferred by the marmosets. In Study 2 we tested the marmosets’ preferences for a smaller number of highly preferred flavours (as determined in Study 1) when actually added to the dry pellet diet in a series of paired preference tests. Finally, in Study 3 we tested whether adding the most highly preferred flavours (as determined in Study 2) to the dry pellet diet would in fact increase consumption of these pellets in comparison with unflavoured pellets. Despite finding strong and consistent preferences for particular flavours amongst the marmosets, we found that adding these to the pellets did not significantly increase consumption. Reasons for this are discussed, along with other potential modifications which might prove more successful in increasing consumption of pellet diets for marmosets.     

Occurrence of a Carrier State for Herpesvirus tamarinus in Marmosets

The ecology of herpesviruses in marmosets and other nonhuman primates is important today, for colonies of these animals are being established for biomedical research. This paper presents the first reported isolations of Herpesvirus tamarinus from throat swabs of a healthy white-lipped marmoset carrier (Saguinus nigricollis) during a 2-month period. Infectivity studies with this virus in both white-moustached (S. mystax) and white-lipped marmosets demonstrated that the virus is not lethal to white-moustached marmosets (perhaps a more resistant species) at 1,000 TCID(50). Which environmental conditions trigger the unmasking of herpesviruses in marmosets is not known. Hoever, intermittent H. tamarinus shedding may help explain spontaneous infections in established colonies as well as suggest an additional mechanism for transmission of virus between marmosets under natural conditions.     

Changes in hematological and serum biochemical parameters in common marmosets (Callithrix jacchus) after inoculation with dengue virus

Background Marmosets are susceptible to dengue virus (DENV) infection. However, blood parameter data and clinical signs of DENV-infected marmosets are limited. Methods Blood hematological and serum biochemical values were obtained from twelve DENV-inoculated and four mock-infected marmosets. Additionally, body temperature and activity level were determined. Results Five DENV-inoculated marmosets demonstrated thrombocytopenia, nine demonstrated leucopenia, and five demonstrated an increase in the levels of AST, ALT, LDH, and BUN. Additionally, seven DENV-inoculated marmosets demonstrated clinical signs including fever and decreases in activity. None of the four mock-inoculated marmosets demonstrated changes in either hematological or biochemical parameters. Conclusions Marmosets inoculated with DENV exhibited clinical signs and changes in hematological and biochemical parameters. The results suggest that blood parameter data and clinical signs could potentially be useful markers for understanding the progress of DENV infection in studies using marmosets.     

Cage use and feeding height preferences of captive common marmosets (Callithrix j. jacchus) in two-tier cages

Determining appropriate feeding regimes has important welfare implications for captive primates. This study examined the preference of food bowl heights in 6 pairs of common marmosets (Callithrix jacchus) housed in a 2-tier cage system. Given that marmosets are arboreal and spend most of their time in the upper half of their cages, we predicted that the marmosets would prefer a food bowl positioned at the top of the cage over one positioned at the bottom. We further predicted that this would be more apparent for the marmosets housed in lower tier than upper tier cages. Given a choice regarding where to feed, marmosets did prefer the top bowl to the bottom bowl; however, when only 1 food bowl was presented, its position had no significant effect on the marmosets' feeding behavior. In addition, contrary to the prediction, there were few differences in the marmosets' feeding behavior in the upper and lower tier cages. Feeding the marmosets in a bowl at the bottom of their cage did not result in greater cage use. On the basis of this study, we recommend positioning captive marmosets' food bowls high in the cage.     

Serum Albumin and Body Weight as Biomarkers for the Antemortem Identification of Bone and Gastrointestinal Disease in the Common Marmoset

The increasing use of the common marmoset (Callithrix jacchus) in research makes it important to diagnose spontaneous disease that may confound experimental studies. Bone disease and gastrointestinal disease are two major causes of morbidity and mortality in captive marmosets, but currently no effective antemortem tests are available to identify affected animals prior to the terminal stage of disease. In this study we propose that bone disease and gastrointestinal disease are associated disease entities in marmosets and aim to establish the efficacy of several economical antemortem tests in identifying and predicting disease. Tissues from marmosets were examined to define affected animals and unaffected controls. Complete blood count, serum chemistry values, body weight, quantitative radiographs, and tissue-specific biochemical markers were evaluated as candidate biomarkers for disease. Bone and gastrointestinal disease were associated, with marmosets being over seven times more likely to have either concurrent bone and gastrointestinal disease or neither disease as opposed to lesions in only one organ system. When used in tandem, serum albumin <3.5 g/dL and body weight <325 g identified 100% of the marmosets affected with concurrent bone and gastrointestinal disease. Progressive body weight loss of 0.05% of peak body weight per day predicted which marmosets would develop disease prior to the terminal stage. Bone tissue-specific tests, such as quantitative analysis of radiographs and serum parathyroid hormone levels, were effective for distinguishing between marmosets with bone disease and those without. These results provide an avenue for making informed decisions regarding the removal of affected marmosets from studies in a timely manner, preserving the integrity of research results.     

Cage Use and Feeding Height Preferences of Captive Common Marmosets (Callithrix j. jacchus) in Two-Tier Cages

Determining appropriate feeding regimes has important welfare implications for captive primates. This study examined the preference of food bowl heights in 6 pairs of common marmosets (Callithrix jacchus) housed in a 2-tier cage system. Given that marmosets are arboreal and spend most of their time in the upper half of their cages, we predicted that the marmosets would prefer a food bowl positioned at the top of the cage over one positioned at the bottom. We further predicted that this would be more apparent for the marmosets housed in lower tier than upper tier cages. Given a choice regarding where to feed, marmosets did prefer the top bowl to the bottom bowl; however, when only 1 food bowl was presented, its position had no significant effect on the marmosets' feeding behavior. In addition, contrary to the prediction, there were few differences in the marmosets' feeding behavior in the upper and lower tier cages. Feeding the marmosets in a bowl at the bottom of their cage did not result in greater cage use. On the basis of this study, we recommend positioning captive marmosets' food bowls high in the cage.     

Environmental correlates of vocal communication of wild pygmy marmosets, Cebuella pygmaea

We quantified the acoustic characteristics of the habitats of two wild populations of pygmy marmosets, in Amazonian Ecuador to evaluate their effects on vocal signal structure. We obtained measures of ambient noise, sound attenuation and reverberation through recordings and broadcasts of exemplars of two short-range vocalizations and one long-range vocalization of the marmosets. Ambient noise levels differed among habitats. The calls of pygmy marmosets had frequencies that coincided with relatively quiet regions of the ambient noise spectra of the habitats. The three vocalization types were degraded similarly in all habitats. The two short-range signals, with a pulsatile structure, were more affected by reverberation than was the long-range, less pulsatile vocalization. This degradation could be used by the marmosets to estimate the distance of the caller animals. We obtained data on context of vocalizations from six groups of pygmy marmosets, three from each population, in both the dry and rainy seasons. The use of Trills, J calls and Long calls was related to the distance between the calling animal and the potential receivers suggesting that marmosets are using the calls in a way appropriate to the effects of habitat acoustics. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Age‐related changes in the marmoset gut microbiome

The gut microbiome is known to play a significant role in human health but its role in aging remains unclear. The objective of this study was to compare the gut microbiome composition between young adult and geriatric non‐human primates (marmosets) as a model of human health and disease. Stool samples were collected from geriatric (8+ years) and young adult males (2–5 years). Stool 16S ribosomal RNA V4 sequences were amplified and sequenced on the Illumina MiSeq platform. Sequences were clustered into operational taxonomic units and classified via Mothur's Bayesian classifier referenced against the Greengenes database. A total of 10 young adult and 10 geriatric marmosets were included. Geriatric marmosets had a lower mean Shannon diversity compared with young marmosets (3.15 vs. 3.46; p = 0.0191). Geriatric marmosets had a significantly higher mean abundance of Proteobacteria (0.22 vs. 0.09; p = 0.0233) and lower abundance of Firmicutes (0.15 vs. 0.19; p = 0.0032) compared with young marmosets. Geriatric marmosets had a significantly higher abundance of Succinivibrionaceae (0.16 vs. 0.01; p = 0.0191) and lower abundance of Porphyromonadaceae (0.07 vs. 0.11; p = 0.0494). In summary, geriatric marmosets had significantly altered microbiome diversity and composition compared with young adult marmosets. Further studies are needed to test microbiome‐targeted therapies to improve healthspan and lifespan.     

Virus-specific T-cell immunity correlates with control of GB virus B infection in marmosets

GB virus B (GBV-B) is a hepatotropic virus that is closely related to hepatitis C virus (HCV). GBV-B causes acute hepatitis in infected marmosets and tamarins and is therefore a useful small-animal model for the study of HCV. We investigated virus-specific T-cell responses in marmosets infected with GBV-B. Gamma interferon (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay responses in the peripheral blood of two marmosets were assessed throughout the course of GBV-B infection. These T-cell responses were directed against the GBV-B nonstructural proteins 3 (NS3), 4A (NS4A), and 5B (NS5B), and their appearance was temporally associated with clearance of viremia. These marmosets were then rechallenged with GBV-B at least 3 months after clearance of the primary infection to determine if the animals were protected from reinfection. There was no detectable viremia following reinfection, although a sharp increase in T-cell responses against GBV-B proteins was observed. Epitope mapping of T-cell responses to GBV-B was performed with liver and blood samples from both marmosets after rechallenge with GBV-B. Three shared, immunodominant T-cell epitopes within NS3 were identified in animals with multiple common major histocompatibility complex class I alleles. IFN-gamma ELISPOT responses were also detected in the livers of two marmosets that had resolved a primary GBV-B infection. These responses were high in frequency and were directed against epitopes within GBV-B NS3, NS4A, and NS5B proteins. These results indicate that virus-specific T-cell responses are detectable in the liver and blood of GBV-B-infected marmosets and that the clearance of GBV-B is associated with the appearance of these responses.     

Effects of training on stress-related behavior of the common marmoset (Callithrix jacchus) in relation to coping with routine husbandry procedures

Using positive reinforcement, J. McKinley trained 12 common marmosets (Callithrix jacchus) to provide urine samples on request. The study then exposed the marmosets to mildly stressful, routine husbandry procedures (i.e., capture and weighing). The nonhuman animals spent less time inactive poststressor as opposed to prestressor. L. Bassett collected matched behavioral data from 12 nontrained marmosets who were less accustomed to human interaction. These animals spent significantly more time self-scratching and locomoting as well as less time inactive, poststressor. Collapsed data from the 2 populations showed increased scent marking, poststressor. These results suggest that locomotion, self-scratching, and scent marking are useful, noninvasive behavioral measures of stress and, thus, reduced welfare in the common marmoset. Overall, nontrained animals showed more self-scratching than did their trained counterparts. It was not possible to collect urine from nontrained marmosets. In response to the stressor, however, trained animals showed no significant change in excreted urinary cortisol. These results suggest that training marmosets may allow them to cope better with routine laboratory procedures.     

Saliva sampling to assess cortisol levels in unrestrained common marmosets and the effect of behavioral stress

We report a method for taking saliva samples from unrestrained, captive marmosets (Callithrix jacchus) to assess levels of free cortisol. Saliva samples can be obtained reliably, without any habituation, by encouraging the marmosets to lick and chew a cotton-wool bud coated in banana. Saliva is thus left on the bud. We also tested sweetened fruit-drink crystals and a number of other substances, but none of these attracted all of the marmosets, and even flavors that were effective once soon lost their attraction. The presence of banana in the samples collected was found to lower the measured concentration of cortisol; however, as shown in samples taken with and without the banana coating on the bud, it did so in a linear and consistent way, and did not vary significantly among subjects. Therefore, a simple conversion factor could be applied to correct for the presence of banana. A first experiment showed that the marmosets exhibited a rise in salivary cortisol levels in response to social isolation. A second experiment showed elevation of cortisol during a period when the marmosets were disturbed by increased human activity and noise levels in the building in which they were housed. Hence, this method of saliva sampling is a convenient, noninvasive means of assessing cortisol levels in marmosets.     

Social Change Affects Vocal Structure in a Callitrichid Primate (Callithrix kuhlii)

Vocal plasticity in the face of changing social context is well‐documented in passerine birds, but the degree to which changes in social environment affect the vocal structure of non‐human primates is a topic which has remained largely unexplored. We assessed whether modification of social environments, in this case the presence of marmosets in neighboring cages, influenced the vocal morphology of phee calls, which possess ‘signature’‐like features, in Wied's black tufted‐ear marmosets (Callithrix kuhlii). Individual phee calls were obtained over a period of 8 wk from 11 animals maintained in rooms with stable social environments. After this baseline phase, seven marmosets were housed for an additional 8 wk in rooms that contained cages with unfamiliar marmosets, while four marmosets maintained the same neighbors as the first phase. Calls were digitized and both frequency and temporal parameters were measured. Multivariate discriminant function analyses (DFA) generated from vocalizations collected in the first phase produced functions that accurately classified calls to the correct individual, showing that calls had significant individual distinctiveness. DFAs generated from vocalizations in the first phase of the study continued to show high classification accuracy for marmosets in a stable social environment, but DFAs from the first phase were significantly less likely to correctly classify vocalizations in marmosets that were housed next to novel conspecifics. These data show that phee calls, which have signature‐like properties in marmosets, can be modified by changes in social context. The results suggest a degree of plasticity in vocal signals that is rare among non‐human primates.     

精制甲型肝炎灭活疫苗的狨猴保护实验

目的　检测精制甲型肝炎 (甲肝 )灭活疫苗的保护效果。方法　甲型肝炎病毒 (YN5株 )经Vero细胞培养制成精制甲肝灭活疫苗 ,采用普通狨猴进行疫苗的免疫原性和保护性研究。结果　 7只狨猴均有特异性抗体产生 ,无血清酶活性升高和肝组织学病理改变 ,接种疫苗的狨猴能抵抗甲肝病毒强毒 (Han ZD)株的攻击。但是 ,对照组狨猴均出现血清酶异常升高和肝组织学病理改变。结论　甲肝灭活疫苗 (YN5株 )具有良好的免疫原性和保护效果。     

In search of a meaningful classification for Amazonian marmosets: Should dwarf marmosets be considered Mico congenerics?

The criteria to classify the diversity of Neotropical Primates have recently taken the discussion boards due to the reappraisal on the phylogenetic relationship of some groups. Such controversial and arbitrary decisions, however, can hamper conservation actions in as much as it becomes difficult to prioritise and set meaningful targets. It is the case for dwarf marmosets from central Amazonia. Today, the classification of dwarf marmosets in Mico or Callibella genus has not been satisfactorily settled. Aiming to contribute to the taxonomic and conservation assessment of dwarf marmosets, we conducted new data collection during 3‐year fieldwork in the Aripuanã River, where the species was discovered. We present the first phylogenomic analysis of the evolutionary relationships between marmosets, new data from mitochondrial DNA and morphology, as well new records to clarify geographic distribution. With this new evidence, we support dwarf marmosets as the genus Callibella. We further discuss the implications for the conservation of this marmoset.     

Bromocriptine administration lowers serum prolactin and disrupts parental responsiveness in common marmosets (Callithrix j. jacchus)

The influence of prolactin on parental responsiveness was investigated in eight unpaired, parentally inexperienced common marmosets (Callithrix jacchus; 6 female, 2 male). The marmosets were prescreened with infants (1-10 days of age) and required to exhibit short latency retrieval and infant carrying in at least three consecutive pretests as criterion for inclusion in this study. The marmosets were then administered the dopamine agonist bromocriptine (0.5 mg/0.5ml vehicle subcutaneously) and the vehicle alone (0.5 ml 10% ethanol solution) twice daily for 3 consecutive days in random order. Bromocriptine treatment reduced circulating prolactin to nondetectable levels. Bromocriptine treatment eliminated infant retrieval in four of the eight marmosets and was associated with significantly increased retrieval latencies and significantly reduced carrying durations in the four monkeys that continued to retrieve following bromocriptine treatment. When given the vehicle alone, the marmosets retrieved infants significantly faster than during pretests, suggesting a handling effect of the injection series. Bromocriptine treatments were associated with significantly increased movement during the tests. The results of this study indicate that prolactin and/or its regulatory neurotransmitters are involved in the control of the spontaneous display of parental responsiveness in common marmosets.     

Variation in circulating and excreted estradiol associated with testicular activity in male marmosets.

Concentrations of estradiol (E2) are high in the urine of male marmosets, and links between E2 and paternal behavior have been proposed in black tufted-ear marmosets, Callithrix kuhlii. However, it is not clear whether urinary E2 in male marmosets: 1) represents production of E2 associated with testicular activity, 2) is associated with adrenal steroid production, or 3) merely reflects peripheral conversion of T to E2 prior to excretion. We tested the hypothesis that urinary E2 in male marmosets represents estrogen production-associated activity in the hypothalamus-pituitary-gonad (HPG) axis. We treated adult male marmosets with gonadotropin-releasing hormone (GnRH), and used saline-treated males as controls. We collected blood and urine samples from males before and after treatment, and assayed them for testosterone (T), estradiol (E2), and cortisol (CORT). Treatment with GnRH increased circulating T and E2, and prevented decreases in levels of urinary T and E2. Moreover, changes in plasma and urinary E2 after treatment were positively correlated with post-treatment changes in T. Thus, our data are consistent with both plasma and urinary E2 in male marmosets increasing as a result of testicular stimulation. However, treatment with GnRH did not affect plasma or urinary CORT concentrations of males, suggesting that the E2 excreted by males is not of adrenal origin. We also compared urinary T, E2, and CORT levels between intact and castrated male common marmosets (Callithrix jacchus). Urinary concentrations of T and E2, but not CORT, were significantly lower in castrated than in intact males, further suggesting that E2 in male marmosets varies with testicular activity.     

Hemolytic complement in nonhuman primates

Hemolytic serum complement activity was quantitatively compared in baboons, squirrel monkeys, cebus monkeys, and cotton-top marmosets. Squirrel monkeys showed the highest activity, and marmosets had the lowest activity. The complement level in squirrel monkeys and tenfold greater than marmosets and almost four times higher than that of man. Cebus monkeys had levels most similar to that of man while the baboon exhibited activity almost as low as that of the marmoset.     

Induction of β(A4)-amyloid in primates by injection of Alzheimer’s disease brain homogenate

Amyloid plaques, associated with argyrophilic dystrophic neurites, and cerebral amyloid angiopathy (CAA), but no neurofibrillary tangles, were found in the brains of three middle-aged marmoset monkeys that had been injected intracerebrally (ic) 6–7 yr earlier with brain tissue from a patient with early-onset Alzheimer’s disease. Such changes were not found in the brains of three age-matched control marmosets. Immunochemically the amyloid plaques and CAA stained with antibody to β(A4)-protein. The plaques and CAA displayed dichroic birefringence when stained with Congo red and viewed under polarized light. β(A4)-amyloid plaques and CAA were also found in the brain of one of two marmosets injectd ic 6 yr previously with brain tissue from a patient with prion disease with concomitant β(A4)-amyloid plaques and CAA. An occasional β(A4)-amyloid plaque was found in the brains of two of four marmosets injected ic >4.5 yr previously with brain tissue from three elderly patients, two of whom had suspected (but untransmitted) CJD. No β(A4)-amyloid plaques or CAA were found in six marmosets who were older than the injected animals, in four marmosets that had not developed spongiform encephalopathy (SE) having been injected several years previously with human brain tissue from three younger patients with suspected or atypical prion disease, or in 10 younger marmosets who had undergone various neurosurgical procedures. Seventeen marmosets injected in the same way with brain tissue from patients or animals with SE developed SE 17–49 mo after injection. These results suggest that β(A4)-amyloidosis is a transmissible process comparable to the transmissibility of SE.     

Isoimmunizations among marmosets to identify leucocyte antigens.

Saguinus fuscicollis ssp., S.o. oedipus, and S. nigricollis marmosets were immunized with white blood cells (WBC) from S.f. illigeri marmosets. Of the three genetic donor-host combinations attempted, only an interspecies immunization of S.o oedipus marmosets resulted in antibody formation which was detectable by agglutination or cytotoxicity tests. Analysis of one of the antisera with a panel of WBC from S.f. illigeri marmosets indicated varying specificities, reactions ranging from strong, intermediate, to completely negative. That the serum was detecting genotypic as well as phenotypic markers was suggested by the similarity of reactions of WBC from co-twin pairs and in preliminary testing of individual families.     

Neurovirulence of mumps virus: intraspinal inoculation test in marmosets.

An intraspinal inoculation test of mumps virus using marmosets was performed in order to develop a neurovirulence test of mumps vaccines. In the group inoculated with non-neurovirulent Jeryl Lynn vaccine strain at 10(2.0) pfu/dose, there were only minimal histopathological changes in 3 of the 5 marmosets. In contrast, all marmosets inoculated with neurovirulent Urabe and NK-M46 vaccine strains developed extensive encephalitis and meningitis. Thus, this marmoset model, which can distinguish between non-neurovirulent and neurovirulent vaccine strains, is useful for evaluating neurovirulence of vaccine strains and elucidating the molecular pathogenesis of mumps.