Morphological Characteristics of the Oropharyngeal Cavity (Tongue, Palate and Laryngeal Entrance) in the Eurasian Coot (Fulica atra, Linnaeus, 1758)

Abstract

The present study represents the first definitive anatomical description of the oropharyngeal cavity of the coot Fulica atra. For this purpose, the organs of six birds were prepared to examine grossly and by SEM and stereomicroscope. The oval lingual apex had multiple overlapping branched acicular processes on its anterior and lateral border. The lingual apex and body had multiple caudally directed filiform-like papillae. By stereomicroscopy, the lingual root had a characteristic appearance and consisted of four parts. The openings of the anterior glands were present on the dorsal lingual surface of the body, while the projected papillae with wide openings of the posterior glands were present on the dorsal surface of lingual root. There was a row of caudally directed pharyngeal papillae at the caudal border of the laryngeal mound. Grossly, the pharyngeal papillae arrangement took a W-shape, while by stereomicroscopy was observed to be heart shape. The palate was divided into two regions: a small rostral non-papillary and a large caudal papillary region, but the rostral region was characterized by the presence of three longitudinal ridges. The papillary crest had two paramedian longitudinal papillary rows, which continued caudally until the beginning of the third median row. The freely distributed papillae took a caudolateral direction, while the papillae encircling the rostral part of choanal cleft took a caudomedial direction. There was a transverse papillary row between the two parts of choanal cleft. There was a transverse papillary row between the caudal border of the infundibular cleft and oesophagus.

Surface ultrastructural descriptions of the oropharyngeal cavity of Anas querquedula

“…The current study observed that the median longitudinal lingual sulcus extended along the dorsal surface of the lingual apex and body, in which it is deep in the rostral ⅔ of the tongue and shallow in the caudal ⅓ of the tongue on the lingual prominence, similar position of the groove reported in Eurasian coot (Abumandour & El‐Bakary, ), and common kestrel (Abumandour & El‐Bakary, ). While, the shallow median lingual sulcus located along the dorsal surface of the lingual body including the lingual prominence observed in the Northern pintail (El Bakary, ) and domestic duck (Skieresz‐Szewczyk & Jackowiak, ), while it is present only on the dorsal surface of the lingual body (Jackowiak et al, ) in the domestic goose, but it is present on the anterior region of the lingual body and absent in the lingual apex and prominence of the Middendorff's bean goose (Iwasaki et al, ), but present in the caudal part of the lingual body as noted in the house sparrow (Abumandour, ).…”

“…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, ).…”

“…According to the previously published data, the presence of the papillary crest not correlated with the feeding behavior or types of available food particles (Abumandour & El‐Bakary, , ). The evidence of this, it is found in the carnivorous, omnivorous, and herbivorous birds as noted in the Eurasian coot (Abumandour & El‐Bakary, ), domestic duck (Marzban Abbasabadi & Sayrafi, ; Skieresz‐Szewczyk et al, ; Skieresz‐Szewczyk & Jackowiak, ), goose (Iwasaki et al, ; Jackowiak et al, ), house sparrow (Abumandour, ), quail (Parchami et al, ), Egyptian laughing dove (Abumandour & El‐Bakary, ), cormorant (Jackowiak et al, ), Eurasian Hobby (Abumandour, ), and common kestrel and Hume's tawny owl (Abumandour & El‐Bakary, ). Although, the lingual papillary crest absent in the penguin (Kobayashi et al, ), woodpecker (Emura et al, ), and ratite birds (Santos et al, ).…”

“…The lingual shape is species‐specific among avian species and related to the shape of the lower jaw, feeding styles, types of available food particles (Abumandour & El‐Bakary, , ; Jackowiak, Skieresz‐Szewczyk, Godynicki, Iwasaki, & Meyer, ). 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 focused point for the most researchers is the studying the morphological appearance of the tongue and their adaptation with the different feeding styles (Abumandour & El‐Bakary, ; Al‐Ahmady Al‐Zahaby, ; Jackowiak, Andrzejewski, & Godynicki, ; Pasand, Tadjalli, & Mansouri, ). Recently, there are some morphological articles designed to study the morphological characterization of the oropharyngeal cavity (tongue, laryngeal mound, and the palate) and its adaptations with the feeding behavior and the available food materials (Abumandour, ; Abumandour & El‐Bakary, ; Abumandour & Gewaily, ; Kobayashi, Kumakura, Yoshimura, Inatomi, & Asami, ; Santos et al, ).…”