Absence of the guttural pouch in a newborn Indian rhinoceros demonstrated by three-dimensional image observations

Abstract. CT scanning and its related three-dimensional image techniques were applied for a carcass head of a newborn Indian rhinoceros (Rhinoceros unicornis) to clarify if the guttural pouch is well-developed or not in the early growth stages of this species. Observations from the sections of the CT three-dimensional reconstructed image reveal that the guttural pouch is not present around the stylohyoid bone in a new born Indian rhinoceros. Since the absence of the guttural pouch has been confirmed also in adult rhinoceros, we can point out that the guttural pouch does not disappear during the growth stages, but is originally absent in the newborn. Although the well-developed guttural pouch in the horse and ass has attracted anatomists, we can conclude that the guttural pouch is not commonly observed in the perissodactyls, but in a few species of Equus, and that the guttural pouch is adapted only to restricted roles in the smaller taxa within perissodactyls. Key words: CT, growth, guttural pouch, perissodactyls, Rhinoceros unicornis. The accessory apparatus of the respiratory system such as guttural pouch (auditory tube diverticulum) has remained morphologically unclear in large-sized mammals. The perissodactyls have attracted comparative anatomists since the well-developed guttural pouch was observed in the domesticated horse (Bourdelle and Bresso

Three-Dimensional CT Examination of the Mastication System in the Giant Anteater

The gross anatomy of the mastication system of the giant anteater (Myrmecophaga tridactyla) was examined by means of three-dimensional image analysis. The anteater rotates the mandibles medially and laterally to control its tongue when it is elongated and to house it when it is relaxed. Three-dimensional CT image analysis demonstrated that the shape and size of the oral cavity changes drastically when the mandibles are rotated. The oral cavity expands bilaterally when the dorsal part of the mandibles bend medially. Macroscopic observations and muscle-weight data supported the observation that the superficial temporal and medial pterygoid muscles act as the main medial and lateral rotators of the mandible, respectively. The low height of the mandibular ramus and the incomplete zygomatic arch in this species represent adaptations for the rotational movement of the mandibles, since they both contribute to the medially oriented transmission of force from the temporal muscles and to preventing collision between the mandibles and the cranium during the rotational movement

The Effect of 7.2% Hypertonic Saline Solution with 6% Dextran 70 on Cardiac Contractility as Observed by an Echoocardiography in Normovolemic and Anesthetized Dogs

We studied the effect of a small volume of 7.2% hypertonic saline solution (HSS) or HSS with 6% dextran 70 (HSD) on hemodynamic status, especially on cardiac contractility, in anesthetized dogs using the left ventricular end-systolic volume index (ESVI) and ejection fraction (EF), which can be obtained in noninvasive echocardiography. In the present study, the mean values of ESVI were unaffected by HSS and HSD infusion, whereas the left ventricular end-diastolic volume index (EDVI) was markedly and significant increased. As a result of the changes in EDVI but not in ESVI, EF increased transiently and significantly in the HSS and HSD group, whereas no such significant change was observed in the dogs that received isotonic saline solution. In addition, as a result of the increases in cardiac index but not arterial pressure, system vascular resistances (SVR) decreased transiently and significantly in the HSS and HSD groups, whereas no such significant change was observed in the ISS group. Therefore, the positive inotropic effects of HSS and HSD may be attributable to the increase in left ventricular preload and decreases in SVR rather than direct changes in myocardial contractility

Carpal bone movements in gripping action of the giant panda (Ailuropoda melanoleuca)

The movement of the carpal bones in gripping was clarified in the giant panda (Ailuropoda melanoleuca) by means of macroscopic anatomy, computed tomography (CT) and related 3-dimensional (3-D) volume rendering techniques. In the gripping action, 3-D CT images demonstrated that the radial and 4th carpal bones largely rotate or flex to the radial and ulnar sides respectively. This indicates that these carpal bones on both sides enable the panda to flex the palm from the forearm and to grasp objects by the manipulation mechanism that includes the radial sesamoid. In the macroscopic observations, we found that the smooth articulation surfaces are enlarged between the radial carpal and the radius on the radial side, and between the 4th and ulnar carpals on the ulnar side. The panda skilfully grasps using a double pincer-like apparatus with the huge radial sesamoid and accessory carpal