Structural adaptations of the beak and oropharyngeal cavity roof in migratory Anas crecca: Distinctive scanning electron microscopic pattern of its filter feeding apparatus

Abstract

There is insufficient data about the migratory duck Anas crecca, especially the beak and oropharyngeal cavity roof. This study aimed to characterize the beak and palatine adaptations and relate the morphological features with the species-specific feeding behavior of A. crecca collected near Lake Nasser (Egypt). Our study was carried out with the help of gross, scanning electron microscopy (SEM), and morphometric analysis. The lower median papillary teeth-like region corresponded to the lower papillary region in terms of food particle capture. The serrated gnathotheca surface exhibited transverse, wedge-like, cap-like, and serrated border-like processes. The lower mandibular space had four spaces: the rostral smooth, the middle folded, the long sublingual, and the caudal sublaryngeal space. The palate showed two major regions, the rostral long beak (beak nail, middle part, and the caudal papillary part) and the connecting region. The choana consists of the rostral narrow part, which has rostral non-papillated and caudal papillated parts, and the caudal papillated wide part, which has three papillary rows. The infundibular plate had numerous small papillae and sphenopterygoid salivary gland openings. Functionally, the beak plays an important role in the sieving filter feeding mechanism, and the palate is involved in the fixation of the captured food particles inside the oral cavity. Consequently, beak and palate structures exhibit anatomical adaptations for efficiently filtering feeding mechanisms.