Reproductive physiology with emphasis on endometrial cycles of woolly and uakari monkeys-A literature review.

The ability of a species to withstand human impact depends on its life history characteristics, including social, ranging, and reproductive activity. The genera Lagothrix and Cacajao are more susceptible to anthropic action than small-sized primates due to their slower life histories, more restricted geographical ranges, and lower population densities. This narrative literature review aimed to gather scientific information available from the last 60 years on the reproductive biology of females of the genera Lagothrix and Cacajao. Most studies on the genus Lagothrix, mainly focused on L. lagothricha and L. l. poeppigii, present important advances on reproductive strategies, reproductive productivity, functional morphology and physiology, including seasonality, sexual cycle, gestation and fetal development in captive and free-living populations. Contrary, there is much less known about the reproductive biology of the genus Cacajao, with studies on free-living C. calvus and C. melanocephalus highlighting reproductive behavior, and basic description of the sexual cycle, gestation, and lactation. Unfortunately, the morphology of the female genital organs is only described in C. calvus, and there is still scarce information about the menstrual activity and the placenta. This literature review encourages primatologists, morphophysiologists, reproductive specialists, and ecologists to conduct comprehensive studies of these species to better understand the gaps in knowledge about reproduction, their relationship with their environment, including climatic and social variables. Understanding the integrative reproductive biology of these species will be a clue for improving the assessment of the resilience capacity of free-living populations and, consequently, establishing more appropriate management programs, and for the development of ex situ management techniques for the conservation of the species.

Embryonic and fetal development of the white-lipped peccary (Tayassu pecari).

The white-lipped peccary (Tayassu pecari) is an endangered large-sized Neotropical ungulate that is one of the most hunted mammals in the Amazon. Here, we used two embryos and 102 white-lipped peccary fetuses originated from animals hunted for subsistence in the Peruvian and Brazilian Amazon to describe the intrauterine development of external and internal morphology of this Neotropical ungulate. Logistic regressions were used to estimate the probability of occurrence of main external characteristics in relation to the total dorsal length (TDL), while multiple linear and non-linear regressions were conducted to assess the relationship between external and visceral biometry with TDL. External characteristics appeared in the following chronological order: limbs, differentiated genitalia and opened eyelids (≥5.1 cm TDL), fused eyelids (≥6.2 cm TDL), hooves and outer ear (≥7.9 cm TDL), dorsal gland (≥9.4 cm TDL), skin (≥11.5 cm TDL); tactile pelage (≥13.8 cm TDL), covering pelage (≥20.9 cm TDL), tooth eruption (≥26.4 cm TDL) and opened eyelids (≥27.8 cm TDL). The formula of fetal age was ∛W = 0.084 (t - 31.80), with a high linear relationship between TDL and gestational age. All external biometric parameters and absolute volume of visceral organs showed strong positive relationship with TDL. Except for the liver, we found differences in the relative volume of most visceral organs between advanced fetuses (≥34.2 cm TDL) and adults. The most important events during the intrauterine development in the white-lipped peccary show that, in contrast with the domestic pig, it is a highly precocial species producing newborns with a high fetal growth velocity which allows newborns to achieve an early autonomous functionality. Our results are relevant to improve imaging techniques and assist the reproductive and clinical management for the white-lipped peccary both in captivity and in the wild.

Fetal development of the Poeppig's woolly monkey (Lagothrix poeppigii).

The intrauterine development is an evolutionary strategy that prepares the neonate for extra-uterine life, thus providing important information on the life history of species. In this study, we described the external and internal morphology of 25 fetuses of Poeppig's woolly monkeys (Lagothrix poeppigii) by taking advantage of a 10-year participatory collection of biological samples originated from animals hunted for subsistence purposes in the Peruvian Amazon. Logistic regressions estimated the probability of occurrence of each external morphological characteristic in relation to the crown-rump length (CRL). The presence of nails, closed eyelids, differentiated genitalia and formed limbs with separation of the digits were observed in all analyzed fetuses (≥4.2 cm CRL). The other characteristics appeared in the following order: skin with epidermal pigmentation, oral and nasal mucosal pigmentation, tactile pelage and covering pelage. Although advanced fetuses (>15.8 cm CRL) showed most fetal external characteristics, they were not fully developed and no specimen showed tooth eruption or opened eyelids. The growth formula used to determine fetal age was ∛W = 0.042 (t - 45), with a high linear relationship between CRL and gestational age. All associations between the external biometry, absolute volume of internal organs and the CRL had a high coefficient of determination. Advanced fetuses and adults showed similar relative volume of thoracic and abdominal organs, except for thymus and the liver with a higher and lower relative volume, respectively. The relative volume of the tubular gastrointestinal tract and the thymus had a constant increase along fetal development, and the liver showed a significant decrease. This study describes important morphological events for understanding the gestational development in the Lagothrix genus. In addition, these results may be useful to improve imaging techniques, contributing to the in situ and ex situ reproductive management of this highly hunted species in the Amazon.

Embryonic and fetal morphology in the lowland paca (Cuniculus paca): A precocial hystricomorph rodent.

In mammals, the embryonic and fetal development of a species has evolved to maximize neonatal survival. In this study, we use a sample of 132 embryos/fetuses of wild lowland paca (Cuniculus paca), obtained over a period of 15 years through collaborative methods with local hunters in the Amazon to describe the intrauterine development of external and internal morphology of this Neotropical rodent. We also compare the newborn survival strategy in this species with other rodents. The crown-rump length (CRL) ranged between 0.6 and 24.6 cm. External features appeared in the following chronological order: limbs, eyelid buds, fusioned eyelids, genitalia, outer ear, tactile pelage, claws, skin, skin spots, covering pelage, teeth and open eyelids. Fetuses with CRL >19.5 cm presented all external features fully developed. The growth formula of fetal age was calculated as ∛W = 0.082 (t - 37.25), and age was accurately associated with CRL. We described the relationship between CRL and external and internal biometry. The liver declined in proportion within the internal cavity, while the relative volume of tubular gastrointestinal organs increased significantly along the embryo/fetal development. All organs, except the heart and the thymus, had similar relative volumes in advanced fetuses and adults. Our comparison of the intrauterine development in several rodent species indicates that the paca's reproductive strategy is comparable to species that are subject to low natural predation. Given that C. paca is perhaps the most hunted animal in Latin America, sustainable hunting throughout its range must take into account its relative reproductive performance.