Neuroscience: unveiling the brain of Saimiri collinsi (Squirrel Monkey).

Behavioral intelligence among non-human primates is a somewhat puzzling area to study, since it is closely linked to the morphology of the central nervous system. However, this morphology is still unknown to science in the case of Saimiri collinsi. As a means of assisting future studies on the social behavior of this species, we analyzed the brains of six adult females from the National Primate Center / Pará, which were sent to the Animal Morphological Research Laboratory at the Federal Rural University of Amazônia after death by natural causes. The animals were fixed in formaldehyde solution (10%) and dissected. The brains were covered externally by the dura mater, with long cerebral hemispheres, although there was a complete absence of gyri. The internal structures which form a part of the telencephalon, diencephalon, midbrain, hindbrain and myelencephalon were identified, with the exception of the mammillary bodies. This condition, when linked to the lissencephaly found in these individuals raises questions about the real learning abilities of this 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.