BACKGROUND: Marmosets, Callithrix spp, are small New World monkeys that have gained importance as an experimental animal model for human. Despite its use, information on its renal morphometry, vascularization, and location are limited. Therefore, this study will supply basic anatomy for applied studies and for comparative anatomy.
METHODS: Fifty cadavers of Callithrix spp were collected on highways from the Atlantic Forest biome, identified and injected with a 10% formaldehyde solution. Later, the specimens were dissected and the measurements and topography of the kidneys and renal vessels were recorded. Both left and right kidneys were significantly larger in females.
RESULTS: In the specimens studied, the average body length was 20.00 ± 2.46 cm in males and 20.50 ± 1.98 cm in females (p = .43). The kidneys of the Callithrix spp. were symmetrical in shape and resembled a \"bean.\" They were also pale brown with a smooth surface. In males, the most frequent location of the right kidney was at the L1-L2 level (92%), while the location of the left kidney was between L2 and L3 (76%). In females, the most frequent location of the right kidney was at the L1-L2 level (56%), while the location of the left kidney was between L2 and L3 (32%) (Table 1). However, in seven (28%) males and nine (36%) females, the kidneys were at the same level.
CONCLUSIONS: In both sexes, there was a positive and significant linear correlation between body length and kidney length. Regardless of the variable location of the kidneys in both sides and in either sexe, the right kidney was always located more cranially than the left, similar to observations in other non-human primates.

BACKGROUND: Platynosomiasis in non-human primates kept under human care causes chronic disease of the bile ducts and liver, which initially presents with nonspecific signs and can culminate in the death of the animal. Diagnosing this disease is a challenge, and an ultrasound examination can be an excellent tool when it is suspected.
METHODS: This study describes the ultrasound findings from 57 marmosets with suspected infection by Platynosomum sp., the correlated hepatobiliary changes, and the anatomopathological findings that confirmed the occurrence of platynosomiasis.
RESULTS: In six marmosets (one C. aurita, two C. jacchus, and three Callithrix sp.), Platynosomum infection was confirmed macroscopically (presence of adult trematodes in the gallbladder) and microscopically (adults, larvae, and eggs in histological examinations and eggs in bile and feces). These findings were compatible with the hepatobiliary changes and with images suggestive of parasitic structures in ante-mortem assessments.
CONCLUSIONS: Ultrasound examination demonstrated its usefulness within the clinical routine for investigating this parasitosis.

Fleas are ectoparasites affecting many animal species but reports in captive nonhuman primates are rare and mainly concern pet monkeys. Moreover, to the authors\' knowledge, a detailed report on marmosets is not known at present. This case describes the clinical signs, diagnosis, treatment and follow-up of a flea infestation by Ctenocephalides felis in a captive colony of common marmosets. Fleas, flea feces and skin lesions were identified on two animals during annual health screening. Subsequently, the entire colony was examined, and nearly half of the colony showed signs of infestation. Consequently, treatment was initiated for the entire colony and the environment. Animals received two topical administrations of imidacloprid (5 mg for animals <200 g and 10 mg for animals weighing >200 g) three weeks apart, and their enclosures were decontaminated using vaporizers containing permethrin, piperonyl butoxide, and pyriproxyfen. Subsequently, skin lesions were resolved and no evidence of fleas were noticed. No side effects of the treatment were observed. Stray cats were identified as the source of the infestation. Their access to the animal-related rooms was stopped. No reinfestation has been reported for 3 years. The topical application of imidacloprid appeared effective with no adverse events occurring, so may be appropriate for use in other non-human primates.

Reports of sarcomas in nonhuman primates are scarce and, specifically, primary hepatic sarcomas are rare, as in humans. This is the first report of an aggressive hepatic fibrosarcoma in a young adult Callithrix jacchus. The final postmortem diagnosis was obtained by means of immunohistochemical analysis, which confirmed the tumor histogenesis.

Recent research has proposed new approaches to investigate color vision in Old World Monkeys by measuring suprathreshold chromatic discrimination. In this study, we aimed to extend this approach to New World Monkeys with different color vision genotypes by examining their performance in chromatic discrimination tasks along different fixed chromatic saturation axes. Four tufted capuchin monkeys were included in the study, and their color vision genotypes were one classical protanope, one classical deuteranope, one non-classical protanope, and a normal trichromat. During the experiments, the monkeys were required to perform a chromatic discrimination task using pseudoisochromatic stimuli with varying target saturations of 0.06, 0.04, 0.03, and 0.02 u\'v\' units. The number of errors made by the monkeys along different chromatic axes was recorded, and their performance was quantified using the binomial probability of their hits during the tests. Our results showed that dichromatic monkeys made more errors near the color confusion lines associated with their specific color vision genotypes, while the trichromatic monkey did not demonstrate any systematic errors. At high chromatic saturation, the trichromatic monkey had significant hits in the chromatic axes around the 180° chromatic axis, whereas the dichromatic monkeys had errors in colors around the color confusion lines. At lower saturation, the performance of the dichromatic monkeys became more challenging to differentiate among the three types, but it was still distinct from that of the trichromatic monkey. In conclusion, our findings suggest that high saturation conditions can be used to identify the color vision dichromatic phenotype of capuchin monkeys, while low chromatic saturation conditions enable the distinction between trichromats and dichromats. These results extend the understanding of color vision in New World Monkeys and highlight the usefulness of suprathreshold chromatic discrimination measures in exploring color vision in non-human primates.

Syncytin-2 is a membrane fusion protein involved in placenta development that is derived from the endogenous retrovirus envelope gene acquired in the common ancestral lineage of New World and Old World monkeys (OWMs). It is known that syncytin-2 is conserved between apes and OWMs, suggesting its functional importance; however, syncytin-2 of common marmosets (Callithrix jacchus) exhibits lower fusogenic activity than those of humans and OWMs in human cell lines. To obtain insight into the functional diversity of syncytin-2 genes in primates, we examined the syncytin-2 gene in New World monkeys (NWMs). We experimentally evaluated the cell fusion ability of syncytin-2 in humans, C. jacchus, and tufted capuchins (Sapajus apella). We found that the cell fusion ability of S. apella was lower than that of human syncytin-2. Chimeric syncytin-2 constructs revealed that the amino acid differences in the surface unit of S. apella syncytin-2 were responsible for the weak cell fusion activity. In addition, genomic sequence analyses of syncytin-2 revealed that the open reading frames (ORFs) of syncytin-2 were highly conserved in seven apes and 22 OWMs; however, the syncytin-2 ORFs of three of 12 NWM species were truncated. Our results suggest that syncytin-2 in several NWMs may be of less importance than in OWMs and apes, and other syncytin-like genes may be required for placental development in various NWM species.

The emergence of spillover pathogens such as SARS-CoV-2 is a risk to vulnerable human populations. We report natural SARS-CoV-2 infection in a free-ranging adult female black-tailed marmoset (Mico melanurus) from an urban area of Cuiabá, Mato Grosso State, Brazil. The animal was found after a motor vehicle collision without previous clinical history. Necropsy confirmed polytrauma. Severe multifocal to coalescent haemorrhage and mild multifocal peribronchial lymphocytic hyperplasia were seen in lung sections. The alveolar septa were multifocally expanded by a few lymphocytes. Mild lymphocytic periportal hepatitis and interstitial nephritis were found. The lymphoid nodules of the large intestine showed marked lymphocytic hyperplasia. Infection by SARS-CoV-2 was established by viral RNA detection in a pool of nasopharyngeal and oropharyngeal swabs and liver samples. Immunohistochemistry detected the viral nucleocapsid protein in sections of lung, liver, spleen, lymph nodes and large intestine, and spike protein antigen in lung tissue. This is the first report of naturally occurring SARS-CoV-2 infection in a New World monkey. Platyrrhine species should be included as potential hosts of natural infection of SARS-CoV-2.

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.

OBJECTIVE: To characterize the cardiopulmonary and anesthetic effects of alfaxalone at three dose rates in comparison with a ketamine-dexmedetomidine-midazolam-tramadol combination (KDMT) for immobilization of golden-headed lion tamarins (GHLTs) (Leontopithecus chrysomelas) undergoing vasectomy.
METHODS: Prospective clinical trial.
METHODS: A total of 19 healthy, male, wild-caught GHLTs.
METHODS: Tamarins were administered alfaxalone intramuscularly (IM) at 6, 12 or 15 mg kg-1, or KDMT, ketamine (15 mg kg-1), dexmedetomidine (0.015 mg kg-1), midazolam (0.5 mg kg-1) and tramadol (4 mg kg-1) IM. Immediately after immobilization, lidocaine (8 mg kg-1) was infiltrated subcutaneously (SC) at the incision site in all animals. Physiologic variables, anesthetic depth and quality of immobilization were assessed. At the end of the procedure, atipamezole (0.15 mg kg-1) was administered IM to group KDMT and tramadol (4 mg kg-1) SC to the other groups; all animals were injected with ketoprofen (2 mg kg-1) SC.
RESULTS: A dose-dependent increase in sedation, muscle relaxation and immobilization time was noted in the alfaxalone groups. Despite the administration of atipamezole, the recovery time was longer for KDMT than all other groups. Muscle tremors were noted in some animals during induction and recovery with alfaxalone. No significant differences were observed for cardiovascular variables among the alfaxalone groups, whereas an initial decrease in heart rate and systolic arterial blood pressure was recorded in KDMT, which increased after atipamezole administration.
CONCLUSIONS: Alfaxalone dose rates of 12 or 15 mg kg-1 IM with local anesthesia provided good sedation and subjectively adequate pain control for vasectomies in GHLTs. KDMT induced a deeper plane of anesthesia and should be considered for more invasive or painful procedures. All study groups experienced mild to moderate hypothermia and hypoxemia; therefore, the use of more efficient heating devices and oxygen supplementation is strongly recommended when using these protocols.

Spontaneous endometriosis is common in women, great apes and Old World monkeys, but rare in New World monkeys. We report on the clinical diagnosis and successful combination of surgical and medical treatment in a case of spontaneous endometriosis in a diabetic hooded capuchin. Addressing this painful condition had a positive welfare impact.