Gross Anatomical and Ultrastructural Characterization of the Oropharyngeal Cavity of the Egyptian Nightjar Caprimulgus aegyptius: Functional Dietary Implications

Abstract Much literature exists on the comparative oral morphology of birds in relation to dietary niche, but little research has been done on the nightjars, (Caprimulgidae, Caprimulgiformes). Herein, we describe the oropharyngeal cavity of the Egyptian nightjar, Caprimulgus aegyptius, using gross anatomical analysis and scanning electron microscopy. The tongue of C. aegyptius is short with a blunt apex carrying numerous scale-like structures. The body of the tongue has both small and large conical papillae for capturing and retrieving insects, and is separated from the root by a distinct papillary crest. The laryngeal mound is bounded by a laryngeal groove with a median glottic fissure that bears two laryngeal folds rostrally and two conical papillary rows caudally. Salivary glands are scattered on the lingual body and root, the floor of the oropharyngeal cavity, and the anterior maxillary and posterior palatine regions. The palate is divided into papillary and non-papillary regions. Furthermore, the median portion of the papillary region has two main clefts: the choanal and infundibular clefts. At the rear edge of the palate, a single transverse row of large caudally-directed conical papillae is present. Our findings reveal multiple structural and functional adaptations of the lingual papillae, salivary gland distribution, and palatal architecture in C. aegypitus that reflect the species' insectivorous dietary habits.