The normal and abnormal owl monkey (Aotus sp.) heart: looking at cardiomyopathy changes with echocardiography and electrocardiography

Background Cardiovascular disease, especially cardiomyopathy, was the major cause of death among owl monkeys (Aotus sp.) at a major colony and threatened colony sustainability. For this study, echocardiography (echo) and electrocardiography (ECG) normal values were established, and cardiomyopathy animals identified. Methods Forty‐eight owl monkeys were studied, 30 older than 10 years of age (‘aged’) and 8 of age 5 years (‘young’). Eight aged owl monkeys had cardiomyopathy. Results and Conclusions Aged Aotus had increased left ventricular posterior wall thickness over young animals. Left ventricular diameter and ejection fraction appeared to be the best identifying measurements for cardiomyopathy. There were no differences in the ECG.     

Serum and urine biochemical diversity among wild-caught and colony-born Aotus nancymae

Serum and urine analytes were compared between adult wild-caught and adult colony-born owl monkeys (Aotus nancymae), to determine if normative clinical pathology data were similar. Significant differences (P ≤ 0.05) were noted in serum protein, glucose, sodium, urine calcium, calcium clearance, and fractional clearance of calcium between the two groups. The results suggest that reference data for feral owl monkeys is not completely applicable to colony-born animals, however, the differences are too small to be of clinical significance.     

Multifactorial etiology of anemia in SIV-infected rhesus macaques: Decreased BFU-E formation,serologic evidence of autoimmune hemolysis,and an exuberant erythropoietin response

We attempted to define the etiology of anemia in SIV-infected rhesus macaques. Bone marrow culture showed significantly decreased (75% reduction) burst forming unit-erythroid (BFU-E) growth in end-stage SIV⁺ “sick” animals. Direct antiglobulin tests (DAT) were positive in nine of 35 SIV⁺ “well” and 14 of 14 SIV⁺ “sick” monkeys (0 of 25 control animals had positive DATs). In animals with a positive DAT, moderate to severe anemia was observed, as was increased LDH and spherocytosis. Erythropoietin was measured in four control, eight SIV⁺ “well” and five SIV⁺ “sick” animals with mean levels of 4.0, 15.4, and 1176 mU/mL (r = .94) in the three groups. These data suggest that the cause of anemia in the SIV-infected rhesus macaque is multifactorial, that there may be a defect in erythropoiesis, and that, serologically, an IgG mediated autoimmune hemolytic anemia is also present.     

Cholelithiasis in owl monkeys: seven cases

Spontaneous cholelithiasis was found in seven owl monkeys (Aotus spp.) at necropsy. There were four male and three female animals. Antemortem clinicopathologic findings included weight loss, anemia, increased alanine aminotransferase and gamma glutamyl transpeptidase, and hyperbilirubinemia in several animals. Choleliths ranged in size from sand-like particles to 5 mm in diameter. Gallstones from five animals were analyzed by accepted analytical methods. Results showed the gallstones to be composed primarily of cholesterol (89%). The gallbladder was histologically normal in all cases examined. The etiopathogenesis of cholelithiasis in the owl monkey is unknown.     

Chromosome mapping of the owl monkey CSF1R and IL5 genes.

We mapped the owl monkey colony-stimulating factor 1 receptor (CSF1R) locus to the proximal region of chromosome 3q of karyotype VI(K-VI) and karyotype V(K-V) and the interleukin 5 (IL5) locus to the mid-region of chromosome 3q(K-VI) and 19q(K-IV) using a combination of Southern hybridization of somatic cells and in situ chromosomal hybridization methodologies. The findings support the proposed evolution of owl monkey chromosome 3(K-VI) from a fusion of two smaller structures, the homologs of chromosomes 6 and 19 (K-IV). The data also indicate genomic conservation of the HSA 5q23-q35 segment in the higher primates.     

Susceptibility of Owl Monkeys (Aotus nancymaae) to Experimental Infection with Bartonella bacilliformis

Bartonellosis, caused by Bartonella bacilliformis, is a clinically significant disease in parts of South America, where it is characterized by fever and hemolytic anemia during the often-fatal acute stage and warty skin eruptions during chronic disease. In this study, we evaluated owl monkeys (Aotus nancymaae) as a potential model for studying the immunogenicity and pathology of bartonellosis. Two groups of animals (n = 3 per group) received either 9.5 × 10⁷ CFU B. bacilliformis by the ID route or 1.1 × 10⁶ CFU by the IV route and were followed for 140 d. Animals were evaluated by physical exam, complete blood count or hematocrit (or both); infection was confirmed by Giemsa staining of blood smears, PCR amplification, and blood culture. On days 7 and 21, Giemsa-stained blood smears from both groups contained organisms (1% to 4% of erythrocytes). All blood cultures and PCR tests were negative. Complete blood counts and chemistry panels showed no difference from baseline. Serology revealed a greater than 4-fold increase in the IgM titer (compared with baseline levels) in the 3 animals from the ID group and 1 animal from the IV group. On day 35, a dermal lesion was excised from the inguinal region of 1 monkey from each group, with a second lesion excised on day 84 from the same monkey in the IV group. However the histopathology and immunostaining of these samples were not consistent with B. bacilliformis. The present study shows that owl monkeys can be infected with B. bacilliformis, but additional dosage studies are necessary to evaluate the usefulness of this species as a disease model for human bartonellosis.Abbreviations: CBC, complete blood countBartonellosis (Carrion disease, Oroya fever, verruga peruana) is a complicated, multistage infectious disease caused by the bacterium Bartonella bacilliformis. B. bacilliformis-associated disease is limited almost exclusively to the Andes mountain region of South America because of the limited habitat of its sand fly vector, Lutzomia verrucarum. In the valleys of the Andes, approximately 60% of the human population is seropositive for the bacterium, and 5% to 10% of the population are active carriers of the disease.⁹ For 1997 through 2005, the Peruvian Ministry of Health reported a 10-fold increase in the incidence of bartonellosis (948 to 10,390 cases).¹⁶ Oroya fever is the hemolytic, immunosuppressive manifestation of acute infection¹ and has a case fatality rate of as high as 90% if left untreated; death is often associated with bacterial and protozoal superinfections.^2,20 The chronic stage of bartonellosis produces disfiguring warty, vascular nodules on the skin and is termed verruga peruana (Peruvian wart disease), which has a prolonged course but ultimately resolves and seldom results in death.⁴ To date, the organism has failed to be isolated from an animal reservoir, suggesting that eradication of the disease could be achieved by successful vaccination of the human population where the disease is endemic.Rhesus macaques can be infected with B. bacilliformis and develop Oroya fever (without the severe anemia) and granulomatous nodules resembling verruga peruana.¹⁴ Later experiments with mice, hamsters, guinea pigs, rabbits, and rhesus monkeys revealed their susceptibility to infection and found that the rabbit was the most susceptible.¹⁹ In these previous studies, however, the animals were inoculated by direct injection with biologic samples from infected patients, and no dose quantitation was performed. The purpose of the present study was to inoculate owl monkeys (Aotus nancymaae) with a defined inoculum of B. bacilliformis to determine their susceptibility to infection. We selected owl monkeys because they are native to Peru and are representative of New World nonhuman primates; previous studies with Old World primates produced conflicting results.^14,19 Small size, ease of handling, and lack of Cercopithicine herpesvirus 1 make owl monkeys an ideal nonhuman primate to use as an animal model. With the establishment of a nonhuman primate model that approximates the disease in humans, new strategies for the prevention and treatment of bartonellosis could be developed.     

A putative homoeolog of human chromosome 12 in the owl monkey

Analyses of Southern blots of rodent x owl monkey somatic cell hybrids permitted syntenic assignment of gene loci coding for triosephosphate isomerase (TPI), antigen CD4(T4), Kirsten rat sarcoma 2(KRAS2) virus, insulin-like growth factor 1 (IGF1), and alpha 2-macroglobulin (A2M) to chromosome 10 of owl monkey karyotype VI(2n = 49, 50). In addition, regional in situ localization of the T4 and KRAS2 loci on the proximal region of the long arm of this acrocentric chromosome and on the corresponding homologous region on the long arm of metacentric chromosome 1 of karyotype IV (2n = 52) substantiated our hypothesis that a single fusion or fission event is responsible for the polymorphism in chromosome number characteristic of owl monkeys from at least three allopatric populations. The study supports a putative homoeology between owl monkey chromosome 10 (K-VI) and human chromosome 12. The morphological differences between these two primate chromosomes indicate evolutionary rearrangements involving at least one pericentric inversion.     

Chromosome assignment of the gene loci ETS1 and THY1 in the owl monkey

Our previous assignment of the gene loci HBB, HRAS1, INS, PTH, LDHA, and CAT to owl monkey chromosome 19 of karyotype VI (K-VI) indicated a putative homology of this owl monkey chromosome with the short arm of human chromosome 11 (HSA 11p). To investigate further the extent of shared homology, we localized in the owl monkey complement two genes known to be on HSA 11q. Segregation analysis of ETS1 and THY1 homologous DNA in three karyotypically different panels of rodent x owl monkey somatic cell hybrids provided evidence for the syntenic assignment of these loci to homologous chromosomes of three owl monkey karyotypes, namely, chromosomes 4 (K-VI), 3 (K-II), and 5 (K-V). The results indicate a disruption of syntenic gene loci on the distal portion of HSA 11q from 11p during primate evolution.     

Infant Development and Parental Care in Free-Ranging <Emphasis Type="Italic">Aotus azarai azarai</Emphasis> in Argentina

Studies of infant development and parental behavior in free-ranging owl monkeys have been constrained by their nocturnal habits. Taking advantage of the cathemeral activity pattern of Aotus azarai azarai in the Argentinean Chaco, we describe the development of a cohort of free-ranging infants born in an owl monkey population in Formosa Province. We observed 7 infants, whose birth dates are known to the nearest week, to record details of their development and care between October 1999 and March 2000. We collected 92 h of behavioral data in 76 sessions. The infants were almost never off the parents during the first 4 wk of life, and we observed no infant being transported by a nonadult. The parent carrying the infant traveled most frequently in the middle of the group, sometimes first, but rarely last. The mean duration of 33 nursing episodes is 69 sec. After nursing, the infant was more likely to return to the nonnursing adult than to remain with the mother suggesting that in owl monkeys the infant may be primarily attached to the adult male in the group. Infants began to explore, to manipulate and to consume solid foods during the second month. Our observations are comparable to ones on captive breeding groups of Colombian owl monkeys (Aotus lemurinus) and Bolivian owl monkeys (A. azarai boliviensis) under controlled conditions of temperature, illumination and food availability.     

Serum and urine biochemical diversity among adult wild-caught Aotus nancymae and Saimiri peruviensis

Serum and urine analytes were compared between adult wild-caught owl monkeys (Aotus nancymae) and adult wild-caught squirrel monkeys (Saimiri peruviensis) to determine if normative clinical pathology data were similar. An objective of the study was to confirm that species of neotropical primates are distinct with regard to physiologic parameters, and should not be considered interchangeable in biomedical research. Significant differences (P < 0.05) were noted in many serum and urine analytes between the two groups. The results suggest that reference data for wild-caught owl monkeys are not applicable to squirrel monkeys, and the differences are sufficiently large to be of clinical significance. These findings illuminate the diversity among species of neotropical primates.     

Hypertrophic Cardiomyopathy in Owl Monkeys (Aotus spp.)

Cardiac hypertrophy is a common postmortem finding in owl monkeys. In most cases the animals do not exhibit clinical signs until the disease is advanced, making antemortem diagnosis of subclinical disease difficult and treatment unrewarding. We obtained echocardiograms, electrocardiograms, and thoracic radiographs from members of a colony of owl monkeys that previously was identified as showing a 40% incidence of gross myocardial hypertrophy at necropsy, to assess the usefulness of these modalities for antemortem diagnosis. No single modality was sufficiently sensitive and specific to detect all monkeys with cardiac hypertrophy. Electrocardiography was the least sensitive method for detecting owl monkeys with hypertrophic cardiomyopathy. Thoracic radiographs were more sensitive than was electrocardiography in this context but cannot detect animals with concentric hypertrophy without an enlarged cardiac silhouette. Echocardiography was the most sensitive method for identifying cardiac hypertrophy in owl monkeys. The most useful parameters suggestive of left ventricular hypertrophy in our owl monkeys were an increased average left ventricular wall thickness to chamber radius ratio and an increased calculated left ventricular myocardial mass. Parameters suggestive of dilative cardiomyopathy were an increased average left ventricular myocardial mass and a decreased average ratio of left ventricular free wall thickness to left ventricular chamber radius. When all 4 noninvasive diagnostic modalities (physical examination, echocardiography, electrocardiography, and thoracic radiography) were used concurrently, the probability of detecting hypertrophic cardiomyopathy in owl monkeys was increased greatly.Abbreviations: LVFWTd, left ventricular free wall thickness at end-diastole; STd, interventricular septal thickness at end-diastole; EDD, left ventricular chamber diameter at end-diastole; ESD, left ventricular chamber diameter at end-systole; VHS, vertebral heart scaleOwl monkeys (Aotus spp.) are maintained and used primarily as a nonhuman primate model for the study of malaria.^17,38,45 These neotropical monkeys have also been shown to be useful for the study of visceral leishmaniasis,⁵ various viruses,^1,20-22,27 streptotrichosis,¹⁹ campylobacteriosis,¹⁶ and toxoplasmosis.³⁴ Owl monkeys are naturally susceptible to a variety of internal parasites,^37,39 hemolytic anemia, and glomerulonephritis.^8,13,40Approximately 40% of Aotus monkeys dying from all causes in a colony maintained for dispersement to investigators for the study of malaria have gross evidence of myocardial hypertrophy at necropsy.⁴⁰ This incidence is similar to the 41% mortality ascribed to cardiovascular disease in captive adult lowland gorillas,²⁵ and the report that, in humans, cardiovascular disease represents 42% of all deaths in the United States.⁹ The hypertrophy in owl monkeys almost obliterates the left ventricular chamber and causes marked thickening of the left ventricular free wall and interventricular septum. A similar incidence of myocardial hypertrophy has previously been reported in other owl monkey colonies.^13,31,32Most of the deaths in the owl monkey colony at our institution can be attributed to various identifiable causes typical for this species.⁴⁰ However, several monkeys in this colony had gross evidence of myocardial hypertrophy at death but had shown no clinical signs of disease and displayed no gross or microscopic etiology for death. A prominent feature of the spontaneous deaths within this particular colony of Aotus monkeys was ‘sudden death,’ particularly during periods of high physical and psychologic stress.⁴⁰ Ventricular arrhythmias have been hypothesized as possible cause of sudden death in chimpanzees with cardiomyopathy,¹⁰ and a similar mechanism might be responsible for sudden death in captive owl monkeys.Gross hypertrophy of the left ventricle has many causes in humans and animals. In the absence of gross evidence of resistive lesions (that is, coarctation of the aorta, aortic stenosis) or shunting lesions (that is, ventricular septal defect, patent ductus arteriosus, atrial septal defect), hypertrophic cardiomyopathy and hypertension are the 2 most likely causes of or stimulus for the left ventricular hypertrophy observed in our colony.^4,18 Because no gross lesions that contribute to myocardial hypertrophy have been found at necropsy, we presumed that the hypertrophic changes in our monkeys are due to hypertrophic cardiomyopathy or to increased afterload secondary to hypertension. Spontaneous hypertension has been reported as causing dilated cardiomyopathy in wooly monkeys,¹¹ and vitamin E deficiency is a cause of cardiomyopathy (primarily dilative) in gelada baboons as well as other primates.^23,24 Cardiac changes secondary to experimental trypanosomiasis have occurred in vervet²⁸ and squirrel monkeys²⁹ and after group A streptococcal infection in rhesus monkeys.²⁶ However, only a few reports detail spontaneous myocardial hypertrophic changes in nonhuman primates.^3,10,13,32 Because of the high incidence of cardiac hypertrophy in clinically normal owl monkeys, it is difficult to establish ‘normal’ reference values for the species. One group of authors³¹ was reluctant to suggest reference intervals for normal echocardiographic variables in owl monkeys due to inability to confirm that monkeys classified as normal were free of cardiac disease.The left ventricular hypertrophy in the owl monkey colony we present has been speculated to be the result of renal-induced hypertension. Many of these monkeys have evidence of glomerular lesions at necropsy. Spontaneous primary systemic hypertension has been suggested as the etiology of the cardiomyopathy and renal disease in owl monkeys,¹³ however, no relationship between antemortem blood pressure and the presence or absence of renal lesions and myocardial hypertrophy in these monkeys had been established until recently. A recent study³⁵ using chronically implanted pressure transducers in A. nancymae found that 30% of the monkeys had resting mean arterial pressures in the hypertensive range (>110 mm Hg), and all animals had exaggerated pressor responses in response to routine husbandry procedures (mean arterial pressure, 125 to 196 mm Hg). These same authors concluded that the hypertension observed was consistent with a neural-based essential hypertension that possibly was engendered by the frequent hyperreactive responses of the sympathetic nervous system of these animals to environmental events.³⁵This study was undertaken to identify individual owl monkeys with left ventricular hypertrophy by using noninvasive diagnostic techniques antemortem. Physical examination, echocardiography, electrocardiography, and thoracic radiography were selected as potential diagnostic modalities with the greatest probability of yielding sensitive and specific information regarding left ventricular hypertrophy in individual monkeys prior to postmortem examination.     

Reproduction of the owl monkey (Aotus spp.) in captivity

Abstract: The reproduction performance of captive owl monkeys, a breed used extensively in biomedical research, was observed at the Battelle Primate Facility (BPF). The colony grew through captive breeding, imports from the Peruvian Primatological Project, and others to a peak size of 730. It included seven karyotypes of Aotus sp. Results showed that owl monkeys can breed successfully in a laboratory in numbers sufficient to sustain modest research programs. Reproductive success increases when pairs are compatible, of the same karyotype, and stabilized; however, mated pairs of different karyotype are also productive. Under conditions of controlled lighting and heating, owl monkeys at BPF showed no birth peak nor birth season.     

Pattern of maternal circulating CRH in laboratory‐housed squirrel and owl monkeys

The anthropoid primate placenta appears to be unique in producing corticotropin‐releasing hormone (CRH). Placental CRH is involved in an endocrine circuit key to the production of estrogens during pregnancy. CRH induces cortisol production by the maternal and fetal adrenal glands, leading to further placental CRH production. CRH also stimulates the fetal adrenal glands to produce dehydroepiandrostendione sulfate (DHEAS), which the placenta converts into estrogens. There are at least two patterns of maternal circulating CRH across gestation among anthropoids. Monkeys examined to date (Papio and Callithrix) have an early‐to‐mid gestational peak of circulating CRH, followed by a steady decline to a plateau level, with a possible rise near parturition. In contrast, humans and great apes have an exponential rise in circulating CRH peaking at parturition. To further document and compare patterns of maternal circulating CRH in anthropoid primates, we collected monthly blood samples from 14 squirrel monkeys (Saimiri boliviensis) and ten owl monkeys (Aotus nancymaae) during pregnancy. CRH immunoreactivity was measured from extracted plasma by using solid‐phase radioimmunoassay. Both squirrel and owl monkeys displayed a mid‐gestational peak in circulating CRH: days 45–65 of the 152‐day gestation for squirrel monkeys (mean±SEM CRH=2,694±276 pg/ml) and days 60–80 of the 133‐day gestation for owl monkeys (9,871±974 pg/ml). In squirrel monkeys, circulating CRH declined to 36% of mean peak value by 2 weeks before parturition and then appeared to increase; the best model for circulating CRH over gestation in squirrel monkeys was a cubic function, similar to previous results for baboons and marmosets. In owl monkeys, circulating CRH appeared to reach plateau with no subsequent significant decline approaching parturition, although a cubic function was the best fit. This study provides additional evidence for a mid‐gestational peak of maternal circulating CRH in ancestral anthropoids that has been lost in the hominoid lineage. Am. J. Primatol. 72:1004–1012, 2010. © 2010 Wiley‐Liss, Inc.     

Behavior,Ecology, and Demography of <Emphasis Type="Italic">Aotus vociferans</Emphasis> in Yasuní National Park,Ecuador

Given its broad geographical distribution, Aotus is a productive genus for comparative studies that evaluate how different ecological factors influence the morphology, behavior, ecology, and demography of closely related species. During 18 mo we collected demographic, ranging, and activity data from owl monkeys (Aotus vociferans) in Yasuní National Park in eastern Ecuador. To collect demographic data, we monitored the trail system several times per week searching for groups. To characterize patterns of activity, we recorded the time when the subjects began and ended their nocturnal activity, and we collected data on range use and daily path length during 12 full-moon and 12 new-moon night follows of 1 radiocollared group. They ranged in size between 3 and 5 individuals (n = 4 groups). All groups were strictly nocturnal, beginning their activity between 1800 and 1900 h and finishing it between 0500 and 0600 h. The territory size of the radiocollared group was 6.3 ha. On average, the subjects traveled 645 m per night (±286 m) and ranged farther during full-moon than new-moon nights. The owl monkeys used a small number of preferred daytime sleeping trees. Our data conform well with previous studies of other tropical owl monkeys from Colombia and Perú. A comparison of tropical owl monkeys with more temperate Aotus azarai from the Argentinean Gran Chaco reveals that grouping patterns, day range length, and territory size are relatively conserved across the genus despite dramatic differences in body size and activity pattern.     

Mapping of five human chromosome 19 DNA markers to owl monkey chromosomes.

Hybridization of DNA from three panels of karyotypically distinct owl monkey x rodent somatic cell hybrids with human DNA probes resulted in the syntenic assignments of INSR-LDLR-TGFB1-APOE-D19S8 to owl monkey chromosome 25 of karyotype VI (2n = 49/50), INSR-LDLR-TGFB1-D19S8 to chromosome 2 of karyotype II (2n = 54), and INSR-APOE to chromosome 2 of karyotype V (2n = 46). The APOE and D19S8 loci are on adjacent regions proximal to the centromere of chromosomes 25q (K-VI) and 2p (K-II), as determined by in situ chromosomal hybridization analysis. These findings support our previous proposals on (1) the homology of these chromosomes of three owl monkey karyotypes, (2) the evolutionary derivation of chromosome 2 of karyotypes II and V as the result of two separate centric fusion events, and (3) the likelihood that owl monkey chromosome 25 (K-VI) (and its homologs) is a conserved genetic homoeolog of human chromosome 19.     

A comparative study of the adrenergic nerves to the anterior eye segment of some primates

Summary The distribution of adrenergic terminals to the anterior eye segment of humans, Cynomolgue monkeys, squirrel monkeys, owl monkeys, Cebus monkeys, vervets, tamarins, and baboons has been investigated. The cornea is normally devoid of adrenergic terminals, except in a plexus near the limbus. The trabecular meshwork contains varying numbers of adrenergic terminals: usually none in Cynomolgus monkeys, patas monkeys, vervets, and humans, although fibres have very rarely been observed in Cynomolgus monkeys, vervets, and humans; a few in owl monkeys, squirrel monkeys, and tamarins; and moderate numbers in Cebus monkeys and baboons. From the evidence, however, it seems premature to presume an adrenergic innervation of the trabecular mechanism regulating the outflow resistance. The dilatator pupillae is regularly supplied with numerous adrenergic terminals and in the iris stroma there is probably an adrenergic innervation of the melanophores. The sphincter pupillae regularly contains adrenergic terminals with notable species differences; most fibres occur in baboons and fewest in humans, with the remaining species forming a middle class. The ciliary processes in all species contain a moderate number of adrenergic terminals, presumably primarily associated with the epithelium. Intraepithelial adrenergic terminals have been observed on the pars plana of the ciliary body of humans, Cebus monkeys, vervets, baboons, and patas monkeys. The ciliary muscle of baboons and Cynomolgus monkeys contains numerous adrenergic terminals. Moderate numbers occur in Cebus monkeys and vervets, and still less in (in falling order) tamarins, squirrel monkeys, humans, and patas monkeys.     

Homologs of eleven loci on human chromosome 11 assigned to two owl monkey chromosomes

We localized 11 loci mapped to human chromosome 11 to two chromosomes, 4 and 19 of owl monkey karyotype VI (2n = 49/50), by the use of somatic cell hybrids. Furthermore, using in situ hybridization to chromosomes of two owl monkey karyotypes, the HSTF1 oncogene locus was precisely localized on homologs 19q (K-VI) and 2q (K-II). Comparative analysis of available gene-mapping data among human, mouse, and owl monkey chromosomes revealed a pattern of evolutionary change in a syntenic group on human chromosome 11. These structural changes could be explained as having derived from a pericentric inversion of human chromosome region 11cen----q13 and a translocation involving human region 11q22----qter during primate evolution.     

Two new karyotypes in the Peruvian owl monkey (Aotus trivirgatus)

The observation of remarkable karyotypic variation in owl monkeys (Aotus trivirgatus) stimulated us to study the chromosomal evolution of this New World genus. As an extension of this project, we examined the chromosome complement of a “phenotype-B” Aotus population from Peru. In addition to karyotype V(2n = 46), two new karyotypes with diploid numbers of 47 and 48 were identified. A G-band comparison of these karyotypes indicated that the chromosome number polymorphism in these Peruvian owl monkeys resulted from a single fusion or fission event involving a single metacentric and two acrocentric chromosome pairs. This mechanism is also known to be responsible for the chromosome number polymorphism in at least two other populations of phenotype B Aotus, one from Colombia and the other from Panama.     

AVPR1A Sequence Variation in Monogamous Owl Monkeys (Aotus azarai) and Its Implications for the Evolution of Platyrrhine Social Behavior

The arginine vasopressin V1a receptor gene (AVPR1A) has been implicated in increased partner preference and pair bonding behavior in mammalian lineages. This observation is of considerable importance for studies of social monogamy, which only appears in a small subset of primate taxa, including the Argentinean owl monkey (Aotus azarai). Thus, to investigate the possible influence of AVPR1A on the evolution of social behavior in owl monkeys, we sequenced this locus in a wild population from the Gran Chaco. We also assessed the interspecific variation of AVPR1A in platyrrhine species that represent a set of phylogenetically and behaviorally disparate taxa. The resulting data revealed A. azarai to have a unique genic structure for AVPR1A that varies in coding sequence and microsatellite repeat content relative to other primate and mammalian species. Specifically, one repetitive region that has been the focus in studies of human AVPR1A diversity, “RS3,” is completely absent in A. azarai and all other platyrrhines examined. This finding suggests that, if AVPR1A modulates behavior in owl monkeys and other neotropical primates, it does so independent of this region. These observations have also provided clues about the process by which the range of social behavior in the Order Primates evolved through lineage-specific neurogenetic variation.