Morphofunctional study of the tongue in the domestic duck (Anas platyrhynchos f. domestica, Anatidae): LM and SEM study

Abstract

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.

Surface ultrastructural descriptions of the oropharyngeal cavity of Anas querquedula

“…Anatomically, there are numerous shape of the lingual apex among different avian species such as the round lingual apex appeared in the, quail, Egyptian laughing dove and ostrich (Abumandour & El‐Bakary, ; Parchami et al, ; Pasand et al, ), while a pointed apex appeared in the chicken and hoopoe (Iwasaki & Kobayashi, ), but a blunt round apex in ostrich (Pasand et al, ). The current work confirmed that reported by Skieresz‐Szewczyk and Jackowiak ()) that the Anatidae family use the round‐shaped lingual apex with the lingual nail in the pecking process to grabbing the grains with the beak, in which the lingual nail act as a spoon for raise the food particles.…”

“…The current work reported that the characteristic form of the lingual body that consists of three parts: rostral, middle, and caudal part. The rostral part have the region of the small conical and the filiform papillae on its lateral surfaces, similar to that reported by Skieresz‐Szewczyk, Jackowiak, and Kontecka () and Skieresz‐Szewczyk and Jackowiak (). While, the middle part carry the lingual comb on its dorsal surface, similar to that observed by Marzban Abbasabadi and Sayrafi () and Skieresz‐Szewczyk and Jackowiak (), while its lateral surfaces contain the region of the large conical and small filiform papillae, similar to that noted by Marzban Abbasabadi and Sayrafi (), Skieresz‐Szewczyk et al () and Skieresz‐Szewczyk and Jackowiak ().…”

“…The shape of the bird's tongue contains two possibilities for adaptation to a lower beak; the first possibility, include that it is closely correlated with the lower beak as observed in the current work and by Abumandour (), Abumandour and El‐Bakary (, ), Emura, Okumura, and Chen (), and Parchami, Dehkordi, and Bahadoran (), but the second possibility, include that there is no relationship between the shape of the tongue and the size of the lower beak in which there is two conditions of the tongue, may be short tongue such as the hoopoe (Abumandour & Gewaily, ), the ratite birds (Jackowiak et al, ; Santos et al, ), and the white stork (Jackowiak et al, ) or may be the tongue longer than the lower jaw such as in the wood‐peckers bird (Emura, Okumura, & Chen, ). The current investigation observed the presence of the elongated flat non‐protrusible tongue of the Garganey ( A. querquedula ) extended to fill the full limit of the lower beak, except the tip of the lower beak, similar to that reported in other water bird duck and goose (Jackowiak et al, ;Marzban Abbasabadi & Sayrafi, ; Skieresz‐Szewczyk & Jackowiak, ).…”

“…The lingual prominence consider as the main characteristic lingual structure in the dorsal surface of the ruminant tongue (El‐Bakary & Abumandour, ). Furthermore, this lingual prominence is the main characteristic part in the duck and goose tongue as observed in the current work and the duck and goose (Iwasaki et al, ; Jackowiak et al, ; Skieresz‐Szewczyk & Jackowiak, ). Only the rostral part of the lateral surface of the lingual prominence have the region of the large conical and small filiform papillae, while the caudal half of lateral surface occupied by the laterally situated spinated border from the lingual root, but in the domestic duck (Skieresz‐Szewczyk & Jackowiak, ) reported that all the lateral surface have the region of the conical and filiform papillae.…”

“…The lingual apex is the most lingual part that indicate the environmental adaptation with the feeding behavior and the different types of foods available, as the lingual apex is adapted to perform different action in the feeding mechanism as the foods collection, food manipulation, and help in the direction of the foods toward the esophagus (Abumandour & El‐Bakary, ). This is clear in the current study on the migratory omnivorous Garganey ( A. querquedula ), as the most water birds has the round‐shaped lingual apex with an anterior spatula‐like structure (Jackowiak et al, ; Marzban Abbasabadi & Sayrafi, ; Skieresz‐Szewczyk & Jackowiak, ), but there is another water birds not contain the lingual nail as the Eurasian coot (Abumandour & El‐Bakary, ), however, the tongue of the nutcracker (one of the passerine birds) has a pair of dagger‐like processes that play an important role in the raising and ejection the seeds toward the median longitudinal lingual sulcus (Jackowiak et al, ). Anatomically, there are numerous shape of the lingual apex among different avian species such as the round lingual apex appeared in the, quail, Egyptian laughing dove and ostrich (Abumandour & El‐Bakary, ; Parchami et al, ; Pasand et al, ), while a pointed apex appeared in the chicken and hoopoe (Iwasaki & Kobayashi, ), but a blunt round apex in ostrich (Pasand et al, ).…”