Fetal development of the urinary tract of Cuniculus paca

The species Cuniculus paca is highly subject to predation, whether natural or anthropogenic, and the ability of species to withstand different levels of depredation depends directly on their reproductive dynamics. However, there is little literature on the developmental biology of this species, and so the aim of this paper was to describe the fetal development of the urinary tract of C. paca through morphological analysis. Twelve specimens with estimated gestational ages of between 75 and 157 days were used, divided into 3 groups. We found the urinary tract in pelvic-abdominal topography with macroscopic differentiation between the organs already present in the first ages studied; in addition, the microscopic structural pattern changed little between the groups. This evidence reinforces the precocial development of these individuals. Research Highlights: With the results obtained for development of urinary tract in Cuniculus paca reinforces the precocial development of these individuals. The urinary tract had pelvic-abdominal topography with macroscopic differentiation between the organs already present in the first ages studied. The microscopic structural pattern changed little between the groups. At all analyzed fetal ages, the cortical region of kidney was characterized by the presence of glomeruli arranged throughout the region, formed by capillary plexuses surrounded by a glomerular capsule. In addition, the cortical region also presented convoluted tubules with cubic epithelial tissue cells and a brush border. The presence of a developed macula densa was observed next to the glomeruli, suggesting the initial formation of the fetal juxtaglomerular apparatus.