Radiological and osteological study of the pelvic limbs in free-ranging capybaras (Hydrochoerus hydrochaeris)

Radiological Anatomy of the Pelvis and Pelvic Limb of the Greater Cane Rat (Thryonomys swinderianus)

Greater cane rats (Thryonomys swinderianus) are now being captive reared and domesticated in the sub-Saharan Africa because of increase in their demand for biomedical research and traditional medicine and as a source of meat. This research was performed to provide the normal radiological anatomy of the pelvis and pelvic limb in greater cane rats for a reference in biomedical research, in anatomical studies, and in clinical use. Radiological examination of the pelvis and right pelvic limb was done in five greater cane rats. Radiological results were correlated with bones of the pelvis and right pelvic limb. The pelvic bone had a prominent caudoventral iliac spine. The pelvic symphysis was long and obturator foramina appeared teardrop-shaped elongated craniocaudally. The prominent major trochanter extended proximally higher than the femoral head. The middle third of the body of the tibia presented a very prominent tuberosity. In all specimens, the tarsal sesamoid bone was visualised. Mineralised popliteal sesamoid bone was not visualised. In male greater cane rats, the os penis was visualised. The lateral and medial menisci of the stifle joint were seen with ossicles. The first metatarsal bone was rudimentary with greater plantar divergence. Despite of the pelvic limb and pelvis of greater cane rats sharing anatomical structures with other rodents, it retains some exceptional anatomical features. Findings of this study will serve as a reference for anatomical studies, clinical veterinary practice, and in biomedical research.

Anatomy of the skull in the capybara (Hydrochoerus hydrochaeris) using radiography and 3D computed tomography

The capybaras (Hydrochoerus hydrochaeris) are the largest rodent found throughout South America and are present in almost all the Brazilian territory, however, still lack basic descriptions about the species, such as about their cranial anatomy. This study was carried out to investigate the anatomical features in the capybara skull. Eight skulls and two heads, without sexual distinction, were used for the osteological, radiographic and tomographic identification of their structures. The skull of the capybara could be divided into a neurocranium and a viscerocranium. The capybara had a more robust and rectangular skull, elongated face caudally, thinned in the nasal region and slightly convex in the parietal region. The zygomatic arch was expanded and wide, the orbit had a circular shape, the infraorbital foramen was well developed, external acoustic meatus and tympanic bulla were relatively small, and the paracondylar process was large. These anatomical characteristics are compatible with the eating habit and semi-aquatic life of capybaras, which can be compared with characteristics reported for animals of similar habits. The radiographic image allowed to identify structures such as the frontal sinus, whereas 3D tomographic reconstruction was essential to have a spatial view of the skull of the capybara.

Hind foot drumming: morphological adaptations of the muscles and bones of the hind limb in three African mole-rat species

Seismic signalling in the form of hind foot drumming plays an integral role in the communication of several species of African mole-rats (Bathyergidae). To produce these vibrational signals, alternating hind limbs strike the ground repetitively at high speeds by flexion and extension of the hip and knee. This descriptive study aimed to determine whether anatomical differences in hind limb osteology and/or musculature between drumming and non-drumming species of three Bathyergidae species could be detected. Formalin-fixed left and right hind limbs of 24 animals (N = 48) consisting of three species (n = 16 each) of two drumming species, Georychus capensis and Bathyergus suillus, and one non-drumming species, Cryptomys hottentotus natalensis, were dissected to determine the origins and insertions of individual muscles. After dissection, all soft tissue was removed by maceration. Hind limb bones, including the pelvis, were photographed, and the exact muscle origin and insertion points were electronically mapped onto the images using imaging software. On lateral view, the acetabular position was parallel to the sacrum in G. capensis, while being more ventral in position in the other two species. The shape of the femur head was spherical and the neck defined in all species. The distal shaft of the femur was gracile and the epicondyles were robust and prominent in the non-drumming C. h. natalensis compared with the drumming species. Shallow and relatively wide patellar grooves were observed in all three species. In the two drumming species, m. gracilis was single, whereas it was double in C. h. natalensis. In all three species, m. tensor fasciae latae was absent. The more dorsal positioning of the acetabulum in G. capensis may be needed to increase the stability of the spine and allow for more force to be exerted on the pelvis during drumming. It is unlikely that m. gracilis plays a role in drumming, as the singularity or doubling thereof is variable among rodents. It is additionally postulated that m. gluteus superficialis has taken the hip rotator role of m. tensor fasciae latae as it partially inserted onto the lateral fascia of the thigh. The more robust ilia, femoral shafts and tibiae observed in the two drumming species studied here are possible adaptations for hind foot drumming, as robust bones are able to withstand the additional biomechanical loading during drumming.