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

Anatomical and Surface Electron Microscopic Investigation of the Tongue and Laryngeal Prominence in the Red-Eyed Turtle Dove (Streptopelia semitorquata, Rüppel 1837)

This study investigated the morphology of tongue and laryngeal structures in red-eyed dove and related it to feeding habits. Samples were examined using gross anatomy, scanning electron microscopy (SEM), and histological techniques. The tongue conformed to the shape of the lower beak, and the apex with a pointed tip, body, and root were distinguished. A median grove was apparent, and a papillary crest with pointed triangular papillae separated the body from the root. The length of the tongue, its width (body), and the percentage of the length of the lower jaw occupied by the tongue were, on average, 12.5 mm, 2.3 mm, and 57.3%, respectively. SEM showed highly desquamated dorsal epithelium with pointed papillae-like projections. The papillary crest presented pointed papillae of about 20-22. Salivary openings were apparent in the root, surrounded by mucosal folds and blunt papillae. Laryngeal prominence was irregularly triangular shaped and elevated. The rim of the glottis showed glandular pinpointed marks. Typical cornified multilayered mucosal epithelium was present in the apex and decreased caudally. Hyaline entoglossal cartilage and adjoining connective tissue were present in the body and apex. Numerous tubuloalveolar glands were seen in the body and root. The rim of the glottis showed mucous intraepithelial glands. The rostral and caudal lingual glands indicated positive reaction to neutral and acidic mucins. This study demonstrated a morphofunctional relationship of the tongue of a red-eyed dove to its diet.

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.

Histo-morphological Characterization of the Tongue and Oropharyngeal Cavity of the Shining Sunbird (Cinnyris habessinicus)

Sunbirds, as specialized nectarivores, have developed multiple lingual and oropharyngeal peculiarities imposed by this dietary specialization that particularly extract floral nectar. We have described the functional morphology of the tongues and palates of the shining sunbird, Cinnyris habessinicus, using gross anatomical, histological, and scanning electron microscopic methods. The tongue was bifurcated with fringed lamella and extended posteriorly, forming a broad trough at the lingual body and terminating in two fleshy, alae linguae. The lingual apex and body are nonpapillate and nonglandular, and its root had a muscular pad followed by a conspicuous laryngeal mound bordered by three prominent rows of conical papillae. The lingual root had clusters of mucoid glands with rich acidic mucins, and the laryngeal region had complex papillary distribution at the back margins. Both the lingual body and root had well-developed skeletal elements, musculature, and connective tissues. Furthermore, the palate was membranous and made up of four main ridges with a central choanal slit guarded by choanal papillae. Overall, the presented results showed structural and anatomical features that are the results of the nectarivory dietary niche.

Scanning electron microscopic and histological features of the oral cavity of the Egyptian tortoise (Testudo kleinmanni)

This investigation was led to depict the structural and functional adaptations of the oral cavity of herbivorous Egyptian tortoises using scanning electron and light microscopes. The SEM showed that the triangular papillary tongue possessed three conical papillary subtypes: the rectangular conical on the tip, the round conical on the rest of the dorsal lingual surface and the elongated conical on the caudal portion of the lingual wing. The presence of the serrated lips with their valves compensated for the absence of the teeth. The rostral part had a vomeronasal opening while the middle part had the choana, but the caudal part had numerous openings of the salivary glands. There are three palatine folds: a single median palatine fold, two peripheral palatine folds and the choanal fold. The current histological results show the keratinized dorsal lingual surface, in which the keratinized layer extended to cover the papillae. Two types of lingual glands, according to their position, are papillary superficial and deep lingual glands. Papillary or superficial glands open in the interpapillary spaces via narrow openings, while the deep glands are surrounded by well-developed muscles and open via wide openings on the dorsal lingual surface. An entoglossal cartilaginous structure of hyaline cartilage was found in the mid- and hindtongue, with numerous chondrocytes lodged within the lacunae. Our results conclude that the oral cavity of the herbivorous Egyptian tortoise was adapted to the dietary and vigorous demands of the Egyptian fauna.

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.

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.

Morphology of the tongue and laryngeal entrance in the Common pheasant (Phasianus colchicus); a light and scanning electron microscopic study

The present work was carried out to describe morphological features of the tongue and laryngeal entrance of the Common pheasantPhasianus colchicus, using light and scanning electron microscopy. The lingual apex was taper-shaped with a shallow median sulcus. A V-shaped papillary crest with 15-20 caudally directed conical papillae was located between the radix and corpus linguae. The second row of papillae consisting of three caudolaterally directed conical papillae was arranged caudal to the main papillary crest. The mons laryngealis was equipped caudally with a double-layer of large conical papillae as pharyngeal crest, and few small conical papillae were seen around the glottis. Scanning electron microscope (SEM) observation showed that the apex linguae and corpus were covered with compact filiform papillae, while the radix linguae were free of papillae. Numerous openings of salivary gland can be seen on the radix linguae and mons laryngealis at higher magnification. On histological sections, all parts of the tongue and mons laryngealis were covered with a keratinised stratified squamous epithelium. The keratinised layer became thinner rostro-caudally. The simple alveolar salivary glands were distributed in the submucosa from the apex linguae to the radix linguae as well as the mons laryngealis. PAS staining revealed mucin-secreting activity of this glands. According to the findings, although the tongue and laryngeal entrance of the Common pheasant is characteristics of a galliform bird, it has some features similar to passeriformes and falconiformes.

Anatomical features of the tongue of two chiropterans endemic in the Egyptian fauna; the Egyptian fruit bat (Rousettus aegyptiacus) and insectivorous bat (Pipistrellus kuhlii)

The current study aimed to investigate the tongue (lingual) morphometry, histology, and histochemistry of two chiropterans endemic in the Egyptian fauna, and having different feeding preferences. The tongues of nine adult individuals of each species were utilized in our investigation. The tongue of fruit-eating bat was observed relatively longer than the one of insect-eating bat. Grossly, the insect-eating bat had a lingual prominence on the dorsum of lingual body, while the fruit-eating bat had a concave midline over the lingual body. Histologically, numerous forms of lingual papillae were scattered along the dorsal epithelium of the tongue. The lingual papillae of the fruit-eating bat seem to be well adapted for piercing the skin of a fruit and liquid sap retention. The lingual glands of both species were lodged in the muscular layer. Two main sets were identified; the serous von Ebner's gland usually seen accompanied by the circumvallate papillae and Weber's gland with mixed mucoserous secretions. Von Ebner's gland showed more prominent acidic mucins, while Weber's gland expressed neutral mucins. The lingual epithelium of the fruit-eating bat had an outer covering of cornified non-nucleated epithelium. On the other hand, the insect-eating bat had an outer covering of nucleated epithelium. It is for the first time to record the existence of the entoglossal plates of both species which consisted of a bony core in the fruit-eating bat and a cartilaginous element in the insect-eating bat. The current study represents an attempt to shed more light on the tongue evolution among mammalian vertebrates.

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.