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Nursery rearing has well-known consequences for primate species. Relative to some other primate species, research has indicated a reduced impact of nursery rearing on squirrel monkeys, particularly in terms of rates, severity, and persistence of abnormal behavior. We administered the Primate Neonatal Neurobehavioral Assessment to 29 dam-reared and 13 nursery-reared squirrel monkeys (Saimiri boliviensis boliviensis) at 2 and 6 weeks of age. Mixed-model ANOVAs comparing composite scores and individual assessment items across age, rearing status, and sex revealed a number of developmental differences. Dam-reared infants scored higher on all four composite measures compared to nursery-reared infants (p < .05) indicating that nursery-reared animals had slower motor development, were less active and attentive, and were more passive than their dam-reared counterparts. Consistent with infant rhesus macaques, nursery-reared squirrel monkeys showed an increased sensitivity to tactile stimulation (p < .05). Altogether, these results suggest a disruption of species-typical development when squirrel monkey infants are reared in a nursery setting, with activity, orientation, and state control areas most affected, though experimental research is needed to determine if this is a causal relationship. Contrary to previous behavioral research, there are likely developmental differences between dam-reared infant squirrel monkeys and those reared in a nursery setting.

Assuntos

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BACKGROUND: How are morphological evolution and developmental changes related? This rather old and intriguing question had a substantial boost after the 70s within the framework of heterochrony (changes in rates or timing of development) and nowadays has the potential to make another major leap forward through the combination of approaches: molecular biology, developmental experimentation, comparative systematic studies, geometric morphometrics and quantitative genetics. Here I take an integrated approach combining life-history comparative analyses, classical and geometric morphometrics applied to ontogenetic series to understand changes in size and shape which happen during the evolution of two New World Monkeys (NWM) sister genera. RESULTS: Cebus and Saimiri share the same basic allometric patterns in skull traits, a result robust to sexual and ontogenetic variation. If adults of both genera are compared in the same scale (discounting size differences) most differences are small and not statistically significant. These results are consistent using both approaches, classical and geometric Morphometrics. Cebus is a genus characterized by a number of peramorphic traits (adult-like) while Saimiri is a genus with paedomorphic (child like) traits. Yet, the whole clade Cebinae is characterized by a unique combination of very high pre-natal growth rates and relatively slow post-natal growth rates when compared to the rest of the NWM. Morphologically Cebinae can be considered paedomorphic in relation to the other NWM. Geometric morphometrics allows the precise separation of absolute size, shape variation associated with size (allometry), and shape variation non-associated with size. Interestingly, and despite the fact that they were extracted as independent factors (principal components), evolutionary allometry (those differences in allometric shape associated with intergeneric differences) and ontogenetic allometry (differences in allometric shape associated with ontogenetic variation within genus) are correlated within these two genera. Furthermore, morphological differences produced along these two axes are quite similar. Cebus and Saimiri are aligned along the same evolutionary allometry and have parallel ontogenetic allometry trajectories. CONCLUSION: The evolution of these two Platyrrhini monkeys is basically due to a size differentiation (and consequently to shape changes associated with size). Many life-history changes are correlated or may be the causal agents in such evolution, such as delayed on-set of reproduction in Cebus and larger neonates in Saimiri.

Assuntos

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Physiological parameters of laboratory animals used for biomedical research is crucial for following several experimental procedures. With the intent to establish baseline biologic parameters for non-human primates held in closed colonies, hematological and morphometric data of captive monkeys were determined. Data of clinically healthy rhesus macaques (Macaca mulatta), cynomolgus monkeys (Macaca fascicularis), and squirrel monkeys (Saimiri sciureus) were collected over a period of five years. Animals were separated according to sex and divided into five age groups. Hematological data were compared with those in the literature by Student's t test. Discrepancies with significance levels of 0.1, 1 or 5% were found in the hematological studies. Growth curves showed that the sexual dimorphism of rhesus monkeys appeared at an age of four years. In earlier ages, the differences between sexes could not be distinguished (p < 0.05). Sexual dimorphism in both squirrel monkeys and cynomolgus monkeys occurred at an age of about 32 months. Data presented in this paper could be useful for comparative studies using primates under similar conditions.

Assuntos

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A functional skeletal criterion, as an extension of the van der Klaauw's cranial theory, was adopted in the present study. The null hypothesis tested was: "The major skeletal components of the platyrrhine body grow linearly, regardless of their functional dependence to different demands." The acceptance of the hypothesis will imply that all Saimiri skeletal growth may be satisfactorily explained by independent variables in a single equation. The rejection will suggest that such skeletal growth patterns have to be explained by variables in several different equations, and perhaps these equations may vary with the effect of sex and undernutrition. Control and undernourished squirrel monkeys were radiographed monthly for 2 years; they were also measured; and their volumetric and morphometric neurocranial, facial, and pelvic indices were calculated. The curves that best described each of the 24-point sequences were obtained. Three main growth patterns were observed: 1) Simple linear (femur length for all groups, and pelvic index for control and undernourished females), for which the simple regression equation explained more than 95% of the variation; 2) Complex linear (pelvic index for control and undernourished males, and neurocranial and facial indices for all of the groups), for which more than 95% of the variation was explained by one of the four four-function type equations; and 3) Noncorrelated with age (neurofacial index for undernourished males, and pelviofemoral index for control females and undernourished males and females), which showed nonsignificant correlations with respect to age. The food intake and the oscillations of the environmental temperature might help to explain the undulating growth trajectory observed in the complex linear components.

Assuntos

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Ten male Saimiri sciureus boliviensis (Cebidae) born at the Centro Argentino de Primates (CAPRIM) were divided into a control group (five animals fed ad libitum on a 20% protein diet) and an undernourished group (five animals fed ad libitum on a 5% protein diet) at weaning (seven months old). Each animal was radiographed monthly from both later-lateral and dorsal-ventral views, from the first to the third year of age. The length, width and height of the optic, respiratory, and masticatory components of the face and anterior neural, middle neural, and posterior neural components were measured in the radiographs. Volumetric (VI) and morphometric (MI) indices were calculated for each component. Correlations and simple linear regressions with respect to age were performed. In the face, two components -respiratory and masticatory- showed the greatest growth rate. In the neurocranium, the middle neural component grew most, approaching the rate observed for the component of the lowest growth in the face (optic). The anterior neural and posterior neural components showed the lowest -although significant- growth rates of the skull. The determination coefficients showed that linearity explained from 12% (posterior neural component) to 74% (masticatory component) of the variation, the remainder being attributed to shape changes and noise effects. The neurofacial rate showed a high level (80%) of nonlinearity since the neurocranium grew almost 1/3 with respect to the face. The morphometric indices showed that only the masticatory component was linear to the face. While the respiratory component grew more, the optic one grew less than the whole face. Only the anterior neural component kept linearity with the neurocranium. While the middle neural component grew more, the posterior neural one grew less than the whole neurocranium. Significant alterations due to undernutrition were seen in both major components. While the three facial and the anterior neural components showed correlation coefficients lower -but significant- than in controls, in the remaining indices -morphometrics included- the correlation values were abruptly broken. The slopes of the regressions which remained significant showed that undernutrition affected mainly the components with greater growth rates (respiratory, masticatory, and middle neural). Secondarily affected were those with lower growth rates (optic, anterior neural and posterior neural), despite their function and according to the histology of the organs they support and protect.

Assuntos

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Ten male Saimiri sciureus boliviensis (Cebidae), born at the Centro Argentino de Primates (CAPRIM), were grown in captivity. At weaning (6 months old), five individuals were fed ad libitum on a 20% protein diet (controls). The other five animals were fed ad libitum on a 5% protein diet (malnourished). Animals were radiographed monthly. The length, width, and height of the anterior, middle, and posterior components of the neurocranium, and those of the masticatory, respiratory, and optic components of the face were measured. A pattern of high growth rate was observed in both the three facial and the middle neural components. The anterior and posterior neural components showed a pattern of low rate of growth. The growth behavior of each variable was also different. Lengths grew more than widths and heights in the facial components, whereas widths grew more than heights and lengths in the neurocranium. Malnutrition delayed growth in size and altered the normal shape changes. High-patterned variables, such as masticatory and respiratory lengths, and the anterior and middle neural widths were particularly affected. The masticatory and the middle neural components underwent the greatest growth arrest. The optic and the respiratory components suffered a mild effect. The anterior and the posterior neural components were affected to a lesser degree.

Assuntos

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Twenty weanling 6-month-old male squirrel monkeys were allotted to the following treatments: 1) first control animals were killed at weaning; 2) second control animals were killed when 24 months old; and 3) malnourished animals were fed on a low-protein diet and killed at age 24 months. Lateral and vertical teleradiographies were taken. Growth of the neurocranial and splanchnocranial components were measured by volumetric (size estimators) and morphometric (shape estimators) indices. All facial components grew. The neurocranial components showed a heterogeneous behavior: The anteroneural component remained stable, and the increase of the midneural component was compensated by a decrease in the posteroneural component. Malnutrition affected the growths of 1) the craniofacial complex, 2) the splanchnocranium, and 3) the respiratory and midneural components. Growth influenced skull shape through 1) increases of the splanchnocranium and the midneural component relative to the neurocranium; 2) decreases of the masticatory and optic components relative to the splanchnocranium, and 3) decreases of the anteroneural and posteroneural components relative to the neurocranium. Malnutrition influenced skull shape through the relationship between the anteroneural component and the neurocranium. These results confirmed the existence of functional interrelationships among the cranial components. A new approach to craniological studies is suggested.

Assuntos

Assuntos