Anatomical study of the hind limb of capybaras (Hydrochoerus hydrochaeris)

Abstract

The present study aims to describe the anatomical bone, muscular, and nervous components of the capybara’s pelvic limb, associating dissections with radiographic imaging findings. Four animals (two adult females, one adult male, and one young male) were used for macroscopic dissections, and one adult male for radiographic acquisitions. A specimen was prepared for bone descriptions using a maceration procedure. The results demonstrated an elongated thigh bone, the obturator foramen obturator, the ilial wing, and the iliac body straight. The anatomical variations of the pelvic limb of capybaras found were: in the femur, the third trochanter is absent; in the tarsal–metatarsal complex, the I tarsal and the I and V metatarsals are vestigial, and a single portion of the M. sartorius and M. gracilis muscles was demonstrated. Furthermore, variations were found in the origin and insertion of each muscle. Macroscopic musculoskeletal descriptions associated with radiographic analyses made it possible to establish a standard of comparative normality for knowledge of species examinations. The pelvic limb was innervated by nerves that emerge from the lumbosacral plexus, which gives rise to the following nerves: N. gluteus cranialis, N. gluteus caudalis, N. genitofemoralis, N. obturatorius, ischiadicus—rami musculares, N. cutaneus surae lateralis, N. cutaneus surae caudallis, N. pudendus, N. femoralis, N. saphenous, N. tibialis, and N. fibularis communis. In conclusion, the anatomy of the capybara’s pelvic limb locomotor system presents particular characteristics related to its aquatic behavior and the absence of arboreal habits.