Embryonic and fetal development of the collared peccary (Pecari tajacu)

Fetal external features and morphology of the umbilical cord of wild boars

This study aimed to describe the gestational and morphological aspects of the fetuses and their respective umbilical cords from two pregnant wild boars (Sus scrofa). Morphological descriptions were provided for 23 fetuses and the gestational ages were estimated through fetal characteristics and formula application. The specimens were fixed in 10% formalin for subsequent macroscopic and microscopic examination. Histological characterization was performed using haematoxylin-eosin (H&E), Masson's trichrome (MT) and Verhöeff's staining techniques. The wild boar fetuses exhibited an estimated gestational age of 55 days (in the larger uterus) and 45 days (in the smaller uterus). They displayed well-developed features consistent with domestic pig fetuses, except for the presence of five pairs of mammae. Additionally, the umbilical cord consisted of two arteries, one vein, an allantoic duct, and a vitelline duct (the latter two identified only microscopically), located in the juxtafetal, intermediate and juxtaplacental portions. The arteries and veins were comprised of endothelium, smooth muscle and collagen fibres, with no elastic fibres observed in the vessel walls. The allantoic duct was lined with simple cuboidal epithelium, while the vitelline duct featured a simple squamous epithelium. In conclusion, the morphological characteristics observed in the examined structures align with the expected patterns for species of the Suidae family. Furthermore, these findings contribute substantially to the morphological characterization of the wild boar, yielding valuable insights into the fetal morphology and the structure of the umbilical cord.

Prenatal post-implantation development of collared peccaries (Pecari tajacu Linnaeus, 1758)

Given the importance of information on intrauterine development in diagnosing anomalies in the gestational development of the species for the development of assisted reproduction technologies as well as understanding the autonomy and responsiveness of the newborn, the aim of the present study was to describe the external morphology of collared peccary conceptuses. For this study, two conceptuses were used per gestational age of 25-120 days post-copulation (dpc) and neonates with 145 dpc, totalling 22 animals. Females were euthanised, and embryos/foetuses were examined, measured, and photographed. During the first third of the gestational period (25-50 dpc, n = 8), a marked body curvature, brain vesicles, somites, internal organs, placid lens, auricular protrusion and limb buds are noted. In the second third of the gestational period (51-100 dpc, n = 10), foetuses lose their body curvature, displaying greater anatomical definition, including skeletal, external ears, nostrils, eyelids and tactile hair formation and cranial suture closure. In addition, dorsal scent gland and genital tubercle differentiation were visualized at 50 days post-copulation. In the third of the gestational period (101-145 dpc, n = 4), the organs become completely formed, alongside skin darkening, eyelid opening, dental eruption, dorsal odorous gland development, sexual organ externalization, and fanero attachment development. These data allowed for the construction of a prenatal growth curve, providing comparative anatomy information for ungulates and further contributing towards rational reproductive management and reproductive biotechnologies for this species.

Ultrasound evaluation of fetal bone development in the collared (Pecari tajacu) and white-lipped peccary (Tayassu pecari)

The study of fetal development allows for evaluating the different strategies adopted by mammal species to maximize neonatal survival. Autonomous locomotion is fundamental for newborns to perform foraging activities and increases newborn survival from predation. In this study, we assess the gestational bone development of 53 collared (CP, Pecari tajacu) and 61 white-lipped (WLP, Tayassu pecari) peccaries, collected through the collaboration of subsistence hunters in the Amazon. The bone mineralization and biometry of the axial and appendicular skeleton were assessed by ultrasound examinations, and the timing of the main bone developmental events was calculated in relation to the total dorsal length (TDL) and the percentage of the total gestational period (GP). The first US signs of mineralization of the axial skeleton in CP and WLP were observed in fetuses with 3.4 cm (42 gestation days, 30% GP_CP ) and 5.1 cm (51 gestation days, 32% GP_WLP ). The early development of the appendicular skeleton was observed by the synchronic appearance of the mineralized scapula, humerus, radius, ulna, ilium, ischium, femur, tibia, and fibula at 36% GP_CP (50 gestation days), and 35% GP_WLP (56 gestation days)_. The pubis was mineralized in fetuses at 55% GP_CP (75 gestation days) and 59% GP_WLP (94 gestation days). The mineralization was observed in all autopod bones at 79% GP_CP (109 gestation days) and 67% GP_WLP (106 gestation days). All primary ossification centers in long bones of thoracic and pelvic limbs were mineralized in advanced fetuses (GP_{CP and} GP_WLP ≥75%). The mineralized patella was not observed in advanced fetuses in either species. Secondary ossification centers first appeared at the distal epiphysis of the femur in the CP (99 gestation days, 72% GP_CP ) and the distal epiphysis of the radius, femur, and tibia in the WLP (106 gestation days, 67% GP_WLP ). Advanced fetuses of CP and WLP presented 60% (15/25) and 68% (17/25) of the total secondary ossification centers observed present in the adult domestic pig, while newborns from the domestic pig presented 52% (13/25). The early intrauterine development of the skeletal system in both peccary species suggests a precocial development strategy, which likely correlates with neonatal ability to escape predators and reduces the dependence on parental care.

Macroscopic, morphometric and tomographic features of the mandible of the collared peccary (Pecari tajacu) applied to clinical morpho-physiology and imaging

Veterinary dentistry is one of the specialties with the greatest potential to contribute to animal welfare; however, it requires a deep anatomical knowledge of the region to be treated. Therefore, the aim was to describe the macroscopic, morphometric and tomographic anatomy of the mandible of the collared peccary in order to provide support for a better understanding of local morpho-physiology and to improve clinical procedures and interpretation of imaging exams in live adult specimens. Four mandibles from wild adult Pecari tajacu were used. The mandibles were submitted to CT scanning, and comparative analyses were performed using multiplanar views. Afterwards, mandibular morphometry was conducted following the literature. Each hemimandible is composed of body, angle and ramus. The main bony landmarks are the mandibular foramen, three main lateral mental foramina, two medial mental foramina, condylar and coronoid processes, and mandibular and angular notches. The teeth are bunodont, and the dental formula is I3/C1/PM3/M3. All bony structures were observed both in the prepared mandible and in the tomographic images and their 3D reconstruction. No obvious differences were observed in the morphometric data between males and females, or between right and left hemimandibles. It can be concluded that the mandible of the collared peccary may be anatomically structured to favor its omnivorous feeding habit. CT scan proved to be an excellent tool for evaluating the teeth and mandible, and it also provides reliable 3D bone reconstructions that can be helpful in the structural identification and in planning of oral care in live adult animals. This article is protected by copyright. All rights reserved.

Fetal bone development in the lowland paca (Cuniculus paca, Rodentia, Cuniculidae) determined using ultrasonography

Studying the timing of the main events of embryonic and fetal development may clarify the strategies adopted by species to maximize neonatal survival and the consequences of these events for their life history. This study describes bone development during the fetal phase of the lowland paca (Cuniculus paca), comparing it with other precocial or altricial species, and its relationship with the species' adaptive strategies. A total of 102 embryos/fetuses obtained over the course of 17 years through collaboration with local subsistence hunters in the Amazon were analyzed. Measurements of mineralization of the axial and appendicular skeletons were performed by ultrasonography using a 10-18-MHz linear transducer. The chronological order of occurrence of mineralization in relation to the total dorsal length (TDL) was: skull (TDL = 4.1 cm); vertebral bodies (TDL = 4.6 cm); scapula, humerus, radius, ulna, ilium, ischium, femur, tibia, and fibula (TDL = 6.7 cm); ribs (TDL = 7.8 cm); clavicle (TDL = 8.5 cm); metacarpi/metatarsi (TDL = 11 cm); phalanges (TDL = 15 cm); tarsus (TDL = 18 cm); patella (TDL = 23 cm); and carpus (TDL = 27.2 cm). Secondary ossification centers first appeared in the femoral distal epiphysis (TDL = 16.6 cm) and tibial proximal epiphysis (TDL = 18.4 cm). Advanced fetuses (TDL > 30 cm, 97% gestational period) presented mineralization in all primary and most secondary centers. Compared to other species, paca neonates have a well-developed skeletal system at birth, which is important for their independent postnatal locomotion. Our results may contribute to the monitoring of bone development in other wild species, helping us to understand their life history, and serving as parameters for comparisons between precocial and altricial mammals.