Structural and functional specializations of the tongue in the desert-dwelling Arabian jerboa (Jaculus loftusi): Anatomical, histological, and histochemical study.

The current study aimed to characterize the structural, histological, and histochemical features of the Arabian jerboa's tongue, correlating it with the feeding habit and environmental pressure. Macroscopically, the tongue was elongated and categorized into apex, body, and root. It lacked the median sulcus, while the lingual body possessed a prominent torus linguae. The tongue dorsum carried five main types of papillae, categorized into mechanical and gustatory forms. The filiform papillae were the most prevalent type, situated at the lingual apex. The fungiform papillae were distributed randomly among filiform papillae, while the circumvallate papillae were three in number and localized at the lingual root. The tongue epithelium was composed of stratified squamous epithelium, covered by a heavy keratinized layer, especially at the lingual apex. The keratin layer gradually decreased toward the root, suggesting regional specialization, with the apex and body performing mechanical roles while the root carried gustatory purposes. Histological analysis revealed that the tongue consisted of a central core of intercalated muscle strands, bordered by lamina propria representing the main tongue framework. Two glandular populations were distinctly intercalated between the muscle strands, especially at the lingual root, while the apex was devoid of glands. The histochemical affinities of the lingual glands prevail in the acidic components of the serous acini (von Ebner's gland) and the pure mucous Weber's gland. Collectively, the Arabian Jerboa's tongue exhibited some structural modifications to survive in the arid conditions of the desert habitat. These modifications include robust keratinization, especially at the lingual apex, the distribution pattern of the lingual papillae, and the spatial arrangement of the glandular components. All of these modifications aimed to efficiently process the hard plant-based diet, soften the swallowing of dry food, and significantly contribute to water conservation.