Epiphyseal Closure of Femur, Tibia and Fibula of the Paca (Cuniculus Paca, Linnaeus, 1766)

Abstract

After capybara, paca (Cuniculus paca) is the largest rodent in the neotropical region and the body weight varies from 5 to 10 kg, and may reach up to 14 kg. They are animals that reach sexual maturity at around 10 months of age. The aim of this research is to examine, through radiography, the femur, tibia and fibula of the paca. The animals were anaesthetized for radiographic exams. At 6 months of age, the growth line of the femoral proximal epiphysis ceases to perform its functions. At 12 months of age, there is the closure of the line growth of distal femoral epiphysis. At the paca's tibia, at 12 months old, there was the closure of the growth of the proximal epiphysis. In the distal epiphysis, the closure of the line growth also occurred at 12 months old. At the paca's fibula, the bone activity of proximal epiphysis ceases with only 23 months old. The distal fibular epiphysis ends its development with 15 months. There are similarities and differences relative to the closure of the pacas' epiphysis femur, tibia and fibula comparing with dogs and cats.Keywords: Bones; Rodent; Wild animal; Morphology; Anatomy After capybara, paca (Cuniculus paca) is the largest rodent in the neotropical region [1][2][3]; the adult males measure from 60 to 80 centimeters, from nose to tip of tail, and the females from 55 to 70 centimeters [1,4]. The body weight varies from 5 to 10 kg, and may reach up to 14 kg [2], but it does not exceed 10 kg [5]. They are animals that reach sexual maturity at around 10 months of age [6].The moment of the epiphyseal cartilage closing varies according to the bone, some closing already in the uterine life and others remain present for several years [7]. Still, the whole axial correction deviations processes of limbs also depend on the age at which the closing of the growth plate closing occurs. Not only the non-surgical techniques but also the surgical ones for correction of conformations depend on the physiological activity of the growth plate of long bones [8].There are several recent researches on pacas and they involve teeth radiographic anatomy [10] and the axial [9] and appendicular [11] skeletons, heart topographic anatomy [12], dental eruption for age determination [13] and lumbo-sacral epidural anesthesia [14]. Other studies on this species are about the description of the structure, ultrastructure and morphometry of the superior vena cava [15] and morphology and topography of the male genital organs [16]. Still, recent study on miology demonstrates similarities between pacas and dogs [17]. The objective of this work is to determine the age of the epiphyseal closure of femur, tíbia and fibula in pacas, an animal that has shown great scientific recent interest.Regarding paca, anatomic-radiographic details have already been described. Paca's femur has long axis, round head, and apparent neck; the greater trochanter is well developed, unlike the lesser trochanter and the third trochanter. The tibia and fibula are equal in length and are partially melted by a fibrocartilage at their e...