Microanatomy and Spatial Distribution of the Tongue Musculature of the Lesser Bamboo Rat (Cannomys badius)

The mammalian tongue consists of complex arrays of intertwining muscle fibers, the functions of which are based upon hydrostatic deformation and are directly responsible for food processing. The anatomy of tongue musculature has been well-described in the laboratory rat and mouse, representative of other rodents, but is lacking in wild species. Accordingly, this study presents a detailed description of the muscular structures of the lesser bamboo rat’s tongue, a wild rodent distributed in Indochina. Primarily, serial coronal sections of three tongues were taken, stained, and histologically examined. The outlines and configurations of tongue muscles were observed and then used to construct three-dimensional (3D) visuals that facilitated evaluation of the interrelated anatomical orientation of muscles. Sagittal sections in one specimen reinforced the 3D depiction by providing details of the intricate myoarchitecture along the entire tongue length. As by-products of serial sectioning, the distributions of the lingual artery and the hypoglossal nerve were also traced at the posterior part of the tongue. The overall anatomy of the lesser bamboo rat’s tongue is similar to that of the rat and mouse, but two principal noticeable differences among the three rodents were found in the anterior tongue: (i) the arrangement of the transversus muscle pertaining to longitudinal muscles and (ii) the end point of the genioglossus muscle. These orientations may be associated with movements of the tongue tip. Based on the anatomy of the tongue musculature in conjunction with its arterial and nerve supplies, types of tongue movements in the lesser bamboo rat are also proposed and explained in relation to food manipulation; enlightening the structure-function relationships for this complex muscle organ.