The domestic duck, as a representative of birds living in the water, is considered as a specialist filter-feeder. Behavioral observations of foraging revealed that these birds also use a terrestrial feeding mechanism such as grazing and pecking. This study examined the entirety of the lingual mucosa in relation to the structural adaptations required for this range of feeding activities. The structures on the lateral surfaces of the tongue, the conical and filiform papillae, constitute the food filtration apparatus. The process of pecking involves the spatula-shaped apex of the tongue and a specific horny plate—the lingual nail. In the grazing mechanism, large conical papillae and lamellae in the beak are required. Structures engaged in intra-oral transport include the median groove, lingual combs, the rostral border of the lingual prominence and distinct rows of conical papillae on the lingual prominence. Two types of keratinized epithelia, the ortho- and parakeratinized epithelium, as well as nonkeratinized epithelium cover individual areas of the tongue. The rostral and caudal lingual glands present in the lamina propria of the body, lingual prominence and root of the tongue produce mucus. The specific arrangement of Grandry and Herbst corpuscles form so-called bill-tongue organ monitoring food transportation. Our research confirm that the lingual mucosa in domestic duck is characterized by microstructural species-specific modifications of particular areas of the tongue, which is formed not only under the influence of the filtering mechanism, but also by terrestrial feeding mechanisms such as grazing or pecking.
Skieresz-Szewczyk, K., & Jackowiak, H. (2016). Morphofunctional study of the tongue in the domestic duck (Anas platyrhynchos f. domestica, Anatidae): LM and SEM study. Zoomorphology, 135(2), 255–268. https://doi.org/10.1007/s00435-016-0302-2