Scanning Electron Microscopy of the Oropharyngeal Floor of Northern Bobwhite (Colinus virginianus, Linnaeus, 1758) Focusing on the Numerical and Regional Distribution of the Taste Buds.

Abstract

The architecture of the avian oropharynx corresponds to the feeding pattern. The present study aims to provide data on morphology, morphometry, and spatial distribution of taste buds in the oropharyngeal floor of the northern bobwhite (Colinus virginianus) using gross anatomy, morphometric, and scanning electron microscopy. The lower beak tip and tomia revealed the presence of variably-sized dermal papillae. The prefrenular part of the oral floor had an interrupted median groove. Numerous taste buds and rostral submandibular salivary gland openings were detected alongside this groove. The tongue partially filled the oral floor. Its rostral end formed a median pointed process, the lingual nail. The dorsolateral aspects of the lingual apex and body showed hair-like and rosette-shaped filiform papillae of variable densities and sizes. However, these parts were devoid of taste buds. On the other hand, the surface mucosa of the lingual root presented numerous scale-like cellular elevations and a large number of taste buds. Examination of cross sections in the lingual root suggested the presence of two groups of caudal lingual salivary glands, central and lateral. The laryngeal mound contained taste buds that protruded from the surface epithelium into the lumen. The mucosa of the pharyngeal floor contained many taste buds that appeared similar to those detected on the laryngeal mound, except for the large taste pores, excessive cellular porosity, and denser microvilli. The total proportions of the taste buds in the oral and pharyngeal floors were 34.1% and 65.81%, respectively. The proportions of taste buds were 34.1%, 57.26%, 4.27%, and 4.27% in the sublingual floor, lingual root, laryngeal mound, and pharyngeal wall, respectively. In conclusion, this study provides comprehensive data on the oropharynx of northern bobwhite and will help to understand mechanisms governing food gustation in the studied bird and other related birds.