Surface ultrastructural (SEM) characteristics of oropharyngeal cavity of house sparrow (Passer domesticus)

Comparative histological and ultrastructural features of the tongue of the mallard domestic duck, Anas platyrhynchos f. domestica, Anatidae (Linnaeus, 1758) in different two age stages (post-hatching [P2] and adult female) captured from Egypt

The domestic duck is classified as a specialist filter-feeder bird living in the water. These birds also use grazing and pecking as terrestrial feeding methods. The tongues of domestic ducks, similar to those of other Anseriformes, exhibit numerous types and shapes of mechanical papillae that serve a number of purposes when collecting food. The current study attempts to describe the morphological characteristics of the tongue as well as the mechanical papillae's development. In addition, the study aims to determine whether the papillae observed post-hatching (P2) exhibit similar morphology to those found in adult female avian species, as well as to investigate the readiness of the tongue to fulfill its feeding function following hatching. The comprehensive examination of lingual mucosa is examined about the structural modifications necessary for this variety of feeding activities. In this study, the tongues of nine young (P2) and adult female were used. The tongue had three distinct parts: the apex, which had a lingual nail on its ventral surface; the body, which exhibits numerous small and large conical papillae on its lateral sides and a lingual prominence in the caudal region; and the root, which is covered with numerous conical papillae of varying sizes. Conical, filiform, and hair-like mechanical papillae, the three types of food filtration apparatus, are present in both stages. The intraoral transfer involves several structures, including the median groove, lingual combs, and the rostral border of the lingual prominence. The rostral border of the lingual prominence is characterized by distinct rows of conical papillae. The histological analysis demonstrated the presence of both keratinized and nonkeratinized epithelium on different tongue regions. The lingual salivary glands in the rostral and caudal lingual salivary glands exhibit a pronounced periodic acid-Schiff-positive reaction. Additionally, the yellow adipose tissue and sensory receptors, namely the Grandry and Herbst corpuscles, which collectively form the bill-tongue organ that monitors the movement of food. These results conclude the presence of microstructural species-specific alterations in specific tongue areas of domestic ducks' lingual mucosa. These modifications are formed by the filtering mechanism and terrestrial feeding mechanisms, such as grazing or pecking. Following hatching, the tongue of the domestic duck undergoes significant development, primarily in preparation for grazing activities. The anatomical and histological structure of the young (P2) tongue exhibited similarities to that of the adult female domestic duck while also displaying certain variations that could potentially be attributed to the bird's habitat and mode of feeding. RESEARCH HIGHLIGHTS: The results of this study concluded that the domestic duck exhibit a complex tongue structure characterized by the arrangement and morphology of its mechanical papillae, the presence of the lingual prominence with distinctive shape and the lingual comb. These features are believed to be adaptations that enable the duck to actively and efficiently filter food particles from water, serving as its primary feeding mechanism. Additionally, the tongue of domestic ducks is specifically adapted to facilitate various terrestrial activities, such as grazing and pecking. This adaptation is achieved through the presence of conical papillae and a lingual nail. These investigations facilitate our comprehension of both the anatomical and histological characteristics of the domestic duck tongue, as well as enhance our understanding of bird adaptations to various feeding mechanisms.

Realistic three-dimensional avian vocal tract model demonstrates how shape affects sound filtering (Passer domesticus)

Despite the complex geometry of songbird's vocal system, it was typically modelled as a tube or with simple mathematical parameters to investigate sound filtering. Here, we developed an adjustable computational acoustic model of a sparrow's upper vocal tract (Passer domesticus), derived from micro-CT scans. We discovered that a 20% tracheal shortening or a 20° beak gape increase caused the vocal tract harmonic resonance to shift toward higher pitch (11.7% or 8.8%, respectively), predominantly in the mid-range frequencies (3-6 kHz). The oropharyngeal-oesophageal cavity (OEC), known for its role in sound filtering, was modelled as an adjustable three-dimensional cylinder. For a constant OEC volume, an elongated cylinder induced a higher frequency shift than a wide cylinder (70% versus 37%). We found that the OEC volume adjustments can modify the OEC first harmonic resonance at low frequencies (1.5-3 kHz) and the OEC third harmonic resonance at higher frequencies (6-8 kHz). This work demonstrates the need to consider the realistic geometry of the vocal system to accurately quantify its effect on sound filtering and show that sparrows can tune the entire range of produced sound frequencies to their vocal system resonances, by controlling the vocal tract shape, especially through complex OEC volume adjustments.

Posthatching ultrastructural development of the oropharyngeal cavity roof in five age-stages of Coturnix coturnix (Linnaeus, 1758)

Recent literature has demonstrated only adult avian palate, albeit there has been only limited focus on the postnatal development of the avian oropharyngeal cavity roof. Hence, the current investigation was designed to obtain the full ultrastructure postnatal description of the oropharyngeal roof during the five developmental age-stages of Coturnix coturnix by employing assessments using gross morphometric analysis and stero and scanning electron microscopy. The elongated triangular oropharyngeal roof has a spoonful rounded beak tip. The palate region is subdivided into the rostral ridged area and the choanal area. The palate has eight longitudinal palatine ridges (seven nonpapillated and one papillated median) and four transverse papillary rows (one slightly oblique row and three transverse papillary crests). The median palatine ridge continuous caudally and is then divided into three ridges: one median and two paramedian ridges (forming the lateral boundaries of the choanal field). The choanal field had three regions (rostral, middle, and caudal). The finger-like projection papillary region has five papillae. The choanal cleft has two unequal parts (rostral and caudal). The rostral nonpapillated short choanal part is subdivided by transverse papillary row into rostral narrow straight and caudal diamond portions. The caudal wide papillated choanal part is further divided by a second transverse crest into rostral long (encircled by interdigitated papillae) and caudal short wider part (not encircled by interdigitated papillae). The infundibular cleft is not bordered by any papillae, while the pharyngeal region has numerous papillae and openings of the salivary glands. Moreover, the morphometric analysis revealed a higher value with increasing age for all dimensions. Our findings indicated a higher degree of functional adaptation between the five developmental age stages of quail. Our observations suggest that adaptations such as these may increase the efficiency of food prehension with increasing age.

Ultrastructural and histological descriptions of the oropharyngeal cavity of the rock pigeon Columba livia dakhlae with special refer to its adaptive dietary adaptations

The current investigation gave a full ultrastructural and histological description of the oropharyngeal cavity of the rock-pigeon Columba livia dakhlae. Our study carried on 10 heads of adult rock pigeons by gross, scanning, and light microscopic examination, in addition to the immunohistochemical analysis of the cytokeratin of the dorsal surface mucosa epithelium and the proliferating cell nuclear antigen expression (PCNA) immunoreactivity. The pointed apex of the elongated tongue covered rostrally and laterally with numerous caudally directed scales-like papillae. The dorsal surface of the apex and body was covered with numerous caudally directed scales-like filiform papillae. The U-shaped transverse papillary crest carried caudally directed pointed triangular conical papillae with two giant papillae. The elevated caudal area of the lingual body contains little numbers of the opening of the lingual gland. The laryngeal mound is divided into two symmetrical halves by rostral fissure and caudal laryngeal fissure into the right and left half. There were four palatine ridges: two lateral, middle, and median ridges. The choanal field bounded by the two lateral palatine ridges and containing the median choanae. The rostral part of the palatine cleft bounded laterally by a line of the small caudally directed conical papillae, while the caudal part was free from these papillae. There was a little number of taste buds in the palate. The high magnification of the rostral part of the beak is covered with directed rods-like projections. In conclusion, the obtained results described the adaptations of the tongue and its belonged structures with the feeding demand of the rock-pigeon.

Biological Aspects of the Tongue and Oropharyngeal Cavity of the Eurasian Collared Dove (Streptopelia decaocto, Columbiformes, Columbidae): Anatomical, Histochemical, and Ultrastructure Study

We characterized the morphological and anatomical adaptations of the lingual microstructures of the Eurasian collared dove and discussed their implications for its dietary niche. We analyzed tongues of nine S. decaocto using histological, histochemical, stereomicroscopic, and scanning electron microscopic techniques. Our findings showed that the tongue is relatively short with a tapered apex that carries a terminal lingual nail. However, the lingual body has median scales and is bordered laterally by filiform papillae. Further, the tongue body bears a distinctive papillary crest. The tongue root is nonpapillate and infiltered with orifices of the posterior salivary glands. The bulky laryngeal mound has a circular glottic fissure, carrying a single row of papillae at the rear edge. Concurrently, our histological and histochemical findings demonstrate that the tongue has taste buds, anterior and posterior salivary glands, along with an elongated entoglossum that extends from lingual apex to root. Besides, ovoid and globular mucous glands displayed intense alcianophilic reactions. More substantially, the palate is made up of three palatine ridges with a caudal choanal cleft that was bounded by two rows of palatine papillae. Our data indicate multiple and novel structural variations for the lingual and palatal sculptures coopted for their feeding style.

Recessive white plumage color mutation of Japanese quail (Coturnix coturnix japonica) revealed morphological variations in the oropharyngeal roof structures, accompanied by behavioral differences

Genetic background of experimental animals contributes mainly to the variations in the experimental outcomes. Therefore, quails of two lines of plumage color (brown and recessive white) were studied to investigate the impact of plumage color mutations on the morphological structures of the oropharyngeal roof and also on the ingestive behavior and quail performance. Feeding intake and feed conversion ratio were higher in the brown quails, associated with nonsignificant increase of the live body weight and body weight gain. In the recessive white quails, ingestive behaviors revealed significant declines. The roof of the oropharynx roof was significantly longer in the recessive white quails; however, the upper beak was significantly longer and narrower in the brown ones. The length of the palate and pharynx showed nonsignificant increase in the recessive white quails. The median palatine ridge was formed of rostral continuous and caudal interrupted parts, and the lengths of these parts were slightly higher in the recessive white quails, meanwhile the lateral palatine ridge length showed a slight increase in the brown birds. Openings of intraepithelial glands were more numerous in the recessive white quails. The brown quails demonstrated more detectable and larger caudally directed conical shaped palatine and pharyngeal papillae, in addition to more considerable palatine salivary glands openings. The infundibular cleft was significantly wider in the recessive white quails, where its edges were characterized by lack of the pharyngeal papillae. The findings of this study will be beneficial for the breeders during selection the suitable quail lines for meat production purposes.

Ultrastructural comparison between the tongue of two reptilian species endemic in Egyptian fauna; Bosc's fringe-toed lizard Acanthodactylus boskianus and Sinai fan-fingered gecko Ptyodactylus guttatus

The current observations focused on the ultrastructure comparison between the tongue of two reptile species endemic the Egyptian fauna; Bosc's fringe-toed lizard Acanthodactylus boskianus and Sinai fan-fingered gecko Ptyodactylus guttatus to exhibit the relationship between the lingual epithelium and its function according to their specific feeding strategy. A. boskianus possessed triangular elongated tongue with bifurcated tapering apex and wide base while; the P. guttatus had a triangular flattened tongue with conical shallow bifurcated apex and broad base. The ventral surface of the lingual apex of A. boskianus had transverse while in P. guttatus had two oval pads and median ventral groove. Both surfaces of the tongue of both examined species are covered by stratified squamous epithelium with great variability of degree of keratinization. The dorsal epithelium formed flattened and conical filiform papillae in A. boskianus, while in P. guttatus formed cylindrical papillae, conical, and tall filiform ones. Few taste buds are observed on the fore-tongue but increase on the mid-tongue of A. boskianus, while in P. guttatus, numerous taste buds are distributed on the fore-tongue and mid-tongue. Both surfaces of the laryngeal mound of both examined species provided with numerous of cilia and orifices of laryngeal gland. The present results confirmed that the tongue of A. boskianus acts as a chemoreceptor organ to follow pheromone trails of prey and mates. While in P. guttatus the tongue may play an important role in the feeding mechanism and act as a chemoreceptor organ.

Posthatching developmental studies on the tongue and laryngeal entrance of the common quail (Coturnix coturnix, Linnaeus, 1758) in different five age-stages

The present study represents the first trial to characterize the ultrastructural of five ages of Coturnix coturnix. Lingual nail had membrane that differ in number among five studied ages. Filiform papillary system had four caudally directed papillae types; small (apex, rostral, and median part of body in 1 day, body in 10 and 20 days), long (apex and rostral part of body in 10 days, tip and two lateral area in 20, 30, 40-days, lateral border in 1 and 10 days, two lateral area of body in 40 days), broad (median area of body in 20, 30, 40 days). Scales on the ventral surface of apex, mound. Lingual sulci on the apex and body without reaching tip in 10, 20, 30, 40-days while, in 1 day the body had ridge caudally. Three papillae on posterior part of lateral border of body. W-shape crest had papillae on its median part while, its lateral part had two giant papillae on each side. Dorsal giant papillae terminated caudally with six processes, while ventral papillae terminated caudally with three processes. The unique root appearance, at 1 day had four papillae while in 10-day, it had one papilla however in 20, 30, 40 days, it had T-shaped ridge. Mound had one longitudinal row on each side of cleft and two transverse papillary rows at its caudal border and additional row at 40-days. Our findings exposed unique structural and functional characterizations of lingual and laryngeal entrance that reflected with feeding behavior.

Gross morphological, histological and scanning electron specifications of the oropharyngeal cavity of the hooded crow (Corvus cornix pallescens)

The present study was carried out on the oropharyngeal cavity of the hooded crow to investigate the gross and microscopic structures via gross anatomy, light microscopy and scanning electron microscopy (SEM). The gross anatomy clarified the elongated triangular shape of the oropharyngeal cavity with a non-protruding tongue with a bifid apex. The lingual body contained median groove rostrally and separated caudally from the root by a transverse papillary crest. The laryngeal mound located posterior to the lingual root, contained midline laryngeal cleft and bounded caudally by a transverse row of pharyngeal papillae. The palate contained choanal cleft rostrally and infundibular slit caudally in addition to five palatine ridges. By light microscopy, the dorsal lingual epithelium was highly keratinised stratified squamous with a lingual nail in the most rostral part of the apex. Then, the thickness of the keratin layer decreased caudally, while in the ventral surface, the lining epithelium became non-keratinised. The entoglossum supported the lingual body and root, but not extended to the apex. The lining epithelium of the palate was also keratinised stratified squamous and became none-keratinised at the oral side of the choanal cleft. There were numerous lobules of polystomatic salivary glands in the lingual root and the palate. SEM revealed the arrangement of different types of papillae covering both the floor and the roof of the oropharynx besides numerous openings of salivary glands in the lingual root, laryngeal mound and the palate. These findings reflect the functional relationship of the oropharyngeal cavity of the hooded crow during feeding.

Comparative morphological study of the oropharyngeal floor of squabs and adult domestic pigeons (Columba livia domestica)

The current study compared the morphological features of the oropharyngeal floor of squabs and adult domestic pigeons (Columba livia domestica). Samples from the oropharyngeal floor of both squabs and adult pigeons were collected directly after slaughtering. The collected samples were examined grossly, morphometrically, and by scanning electron microscopy (SEM). The lower beak had triangular shape with pointed rostral end. The tongue did not fill the entire oral floor in squabs as well as adult pigeons. The lingual apex of squabs had a small lingual nail while that of the adult pigeons had a well-developed lingual nail. The lingual body was separated from the lingual root by a transverse papillary crest, which was "V" shaped in squabs but "U"-shaped in adult pigeons. Filiform papillae were distributed on the dorsal surface of lingual apex, as well as, body, but were absent on the root. The lingual root presented fine elevations and low projections in squabs and adult pigeons, respectively. On the other hand, the tongue of adult pigeons had larger number of the lingual salivary glands openings compared to that of squabs. In addition, the edges of the glottis had numerous small projections in squabs bur presented large dome-shaped papillae in adult pigeons. Moreover, adult pigeons had longer pharyngeal papillae at pharyngoesophageal junction than those of squabs. In conclusion, these variations suggest that adult pigeons adapted well to their diet, which might reflect higher efficiency of food prehension.

Surface ultrastructural descriptions of the oropharyngeal cavity of Anas querquedula

The current work considers the first anatomical description of oropharyngeal cavity of Garganey, which was performed on eight heads with the help of scanning electron microscopy (SEM). The round apex of elongated tongue has anterior spatula-like named lingual nail. SEM of dorsal surface of lingual nail carry microtubercles and micropores on its rostral part, while its caudal part carry numerous microridges and micropores, while lateral apical surface only without lingual nail carrying filiform papillae, but its ventral surface carry exfoliated scales-like projections. Lateral lingual tip carries numerous laterally directed hairs-like structures. Rostral part of body carry region of small conical papillae in between them small hairs-like papillae on its lateral surface. Middle part of body carry lingual comb on its dorsal surface, while its lateral surfaces carry region of small conical papillae in between them hairs-like papillae in addition to filiform papillae, and large conical with small filiform papillae begin to appear laterally to the heads of lingual comb. Lateral surface of lingual prominence carry region of large conical and small filiform papillae on its rostral part, while its caudal part occupied by laterally situated spinated border from the root. Lingual root has two triangular smooth middle and spinated lateral and caudal. Laryngeal entrance divided into papillary and nonpapillary regions. Roof of oropharyngeal cavity divided into lamellar and papillary regions. Choanal cleft divided into rostral narrow ¼ and wide caudal ¾ parts. In conclusion, feeding process depend on the filter feeding mechanism that performed by the help of lateral situated papillae with lingual prominence.

Gross morphological and ultrastructural characterization of the oropharyngeal cavity of the Eurasian hoopoe captured from Egypt

The present study aimed to give full morphological insight into the oropharyngeal cavity of Eurasian hoopoe at the level of gross morphology in addition to ultrastructural inspection including light- and scanning electron microscopy. The oropharyngeal cavity has a triangular appearance with a very long rostrally located beak, helping the bird achieve its feeding mechanism. The floor of the oropharyngeal cavity is divided into three parts; a pre-lingual part with a pre-lingual fold, a lingual part containing a rudimentary triangular tongue, and a laryngeal part, which contains a small elevated laryngeal mound. There are four giant papillae and numerous openings of lingual salivary glands on the root. The roof is divided into the pre-choanal and the choanal region. The pre-choanal region has two parallel palatine ridges, while the choanal region had an ovoid-shaped choanal cleft rostrally, followed caudally by a narrow infundibular slit. The mechanical papillae on the roof are arranged in two rows directed caudally; one row is located on the free border of rostral half of the choanal cleft, while the other row is located between the pharynx cavity and the esophagus. The histological study showed that the tongue was covered dorsally and ventrally by keratinized stratified squamous epithelium and supported centrally by entoglossum, which extends from the root until the rostral tip of the tongue. The entoglossum was mainly cartilaginous rostrally in the apex and ossified caudally in the lingual body and root. Numerous mucous glands scattered in the sub mucosa of the lingual root as well as in the palatine region convey their secretions to the surface through a duct guarded by diffuse lymphocytic infiltration.

Anatomical investigations of the tongue and laryngeal entrance of the Egyptian laughing dove Spilopelia senegalensis aegyptiaca in Egypt

In the present work, the first full anatomical description of the tongue and laryngeal entrance of the Egyptian laughing dove Spilopelia senegalensis aegyptiaca, which was obtained with the aid of scanning electron microscopy (SEM) and histological techniques, is provided. The lingual apex was rounded and the cranially convex papillary crest exhibited a transverse papillary row, in addition to another row consisting of two giant papillae. Papillae were not observed on the elevated, triangular laryngeal mound except for the glottic opening, which was bounded by two lateral elevated borders that presented a row of small papillae. Two fissures occurred on the laryngeal mound: a rostral fissure at the rostral border of the laryngeal mound, and a caudal fissure that occurred caudally to the glottic opening and continued caudally as the laryngeal fissure. SEM analysis showed filiform papillae on the dorsal surface of the apex and body, and indicated that each giant papilla was long with a pointed apex and exhibited one or two secondary papillae on its surface. The dorsal surface of the lingual root exhibited numerous openings of the lingual salivary glands. The caudal part of the laryngeal mound presented numerous openings of the laryngeal salivary glands. Histologically, the dorsal surface of the anterior and middle lingual part was covered with a thick and stratified squamous epithelium. The anterior and middle lingual part presented entoglossum cartilaginous ossification of the entoglossal bone, which had numerous chondrocytes lodged within the lacunae of the entoglossum. The lingual glands appeared in the middle and caudal lingual part.