Comparative phenotypic and structural adaptations of tongue and gastrointestinal tract in two bats having different feeding habits captured from Saudi Arabia: Egyptian fruit bat (Rousettus aegyptiacus) and Egyptian tomb bat (Taphozous perforatus)

Bat Tongues and Foraging: Linking Morphology to Hunting Strategies

On their dorsal surface, bat tongues show a raised muscular structure called mediodorsal lobe (MDL) or lingual prominence. It exhibits different mechanical papillae across species, which we hypothesized are linked to foraging strategies. We predicted that tall MDLs and prominent papillae pointing frontward would effectively trap prey items caught on the wing by aerial hawkers. We examined 904 high-resolution, close-up images of 239 individual bats from 24 European species, focusing on MDL height and morphology and arrangement of MDL papillae. Aerial hawkers such as Tadarida teniotis, Nyctalus lasiopterus, Miniopterus schreibersii, and pipistrelles displayed prominent forward-pointing papillae and taller MDLs, adaptations suited to high-speed aerial foraging. These traits may be part of a broader "ecomorphological syndrome", facilitating efficient prey capture in open-space foragers. In contrast, gleaning and trawling species lacked these specializations, exhibiting flatter MDLs and less prominent papillae. Phylogenetic analysis indicated evolutionary convergence in MDL morphology among aerial hawkers, with M. schreibersii showing similarities to vespertilionids despite its phylogenetic distance. This convergence highlights the influence of evolutionary pressures arising from foraging requirements on tongue morphology. Although possessing tall MDLs, rhinolophids are outliers, possibly reflecting their unique perch-hunting strategy or echolocation. If the patterns we found are confirmed for a larger number of species, MDL morphology could predict foraging style across bat species and be included in future descriptions of foraging guilds.

Gross and scanning electron microscopic features of the oral cavity (palate, tongue, and sublingual floor) of the Egyptian long-eared hedgehog (Hemiechinus auratus aegyptius)

The study was focused on the anatomical characteristics of the Egyptian long-eared hedgehog's oral cavity by using gross and scanning electron microscopic examinations. The upper lip had an elongated T-shaped snout-like structure. The hard palate had a triangular rostral part (which had a semicircular area and a caudal ridged area with the first 3 or 4 ridges) and a caudal part (which contained seven or eight slightly oblique ridges with raphae). The diamond-incisive papilla is flanked on both sides by a groove and a fissure. The hard palate surface had glandular openings and a microplicae system. The uneven, soft palate's surface had multiple grooves and folds with 12-16 Gemmal papillae. The Gemmal papillary surface had three to four taste pores with microplicae and glandular openings. The dorsal lingual surface had six filiform subtypes: pointed (on the tip, rostral border, and median apical region), triangular (on the lateral apical and circumvallate regions), bifurcated (on the median tip only), leaf-like (on the median body region), branched (on the lateral root region), and small pointed papillae (on the median root). There were two fungiform subtypes: ovals (on the rostral border and lateral region) and rounds (on the median apical region and body). The caudal root part had a triangular arrangement of three circumvallate papillae. In conclusion, the finding confirmed its oral cavity adaptation with its insectivorous feeding habits and Egyptian environment.

Lingual adaptations of the Tarentola annularis with new insights into its papillary system adaptations: Ultrastructure, histochemistry, and immunohistochemical observations

Our research aims to conduct a comprehensive ultrastructural, histochemical, and immunohistochemical examination of Tarentola annularis' tongue, utilizing various techniques such as light, scanning electron microscopy, and morphometric analysis. The complex papillary system consisted of four conical subtypes and one filiform type. The apex carried three conical subtypes (elongated, quadrilateral, and round); the midtongue carried two papillary types (quadrilateral conical and rectangular pointed filiform); and the hindtongue carried two conical subtypes (quadrilateral and elongated serrated). The dorsal papillary surface carried little taste pores on the foretongue and taste buds on the midtongue. The foretongue had a slightly stratum corneum that spread to coat the papillae, while the mid- and hindtongue did not. The glands are absent from the foretongue but are found in the interpapillary spaces of the mid- and hindtongue. Histochemical analysis reveals the presence of collagen fibers in the muscle bundles and the papillary core. The midtongue glands exhibited a strong reaction to AB and PAS, while the hindtongue showed moderate AB positivity and strong positive PAS. The cytokeratin expression in the foretongue papilla was positive, whereas the papillae in other regions were negative. The Tarentola annularis exhibits distinctive lingual structural characteristics due to its varied feeding habits influenced by available food particles.

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.

Tongue microarchitecture and functional characterization of the lingual papillae in the desert hedgehog (Paraechinus aethiopicus)

The present work attempted to provide a comprehensive description of the morphoanatomical, histological, and ultrastructural characteristics of the tongue in the desert hedgehog (Paraechinus aethiopicus), and to correlate lingual modifications to the feeding lifestyle. Five adult male hedgehogs were utilized in our investigation. The macroscopic observations revealed elongated, with a moderately pointed apex, tongue and the tongue dorsum lacks both lingual prominence and median sulcus. The main subdivisions of the tongue are radix linguae (root), corpus linguae (body), and apex linguae (apex). The tongue dorsum carries two types of mechanical (conical and filiform) and gustatory (fungiform and circumvallate) papillae. The lingual apex is characterized by the existence of a unique encapsulated muscular structure. Additionally, the lingual glands were interposed between the muscular strands and no lingual glands were detected on the lingual apex. The dorsal surface of the lingual apex exhibited the highest level of keratinization as revealed by histochemical staining while the root showed moderate staining. The topography of the tongue was investigated by scanning electron microscopy (SEM). The obtained results are important to provide basic knowledge that can contribute to better understanding of the nourishment, feeding habits and behavior in this species. Furthermore, the addition of the newly investigated species may help us to determine the evolutionary relationships among species.

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.

Morphological features of the Egyptian Ossimi sheep tongue: New scanning electron microscopic insights into its papillary system adaptations to Egyptian ecological conditions

The current study aims to illustrate the gross and scanning electron microscopic characterizations and ultrastructural adaptation of the lingual papillary system of Egyptian Ossimi sheep to Egyptian ecological conditions. The tongue had three regions: the apex (with a slightly bifurcated tip), the body (subdivided into rostral and caudal parts) and the root (subdivided into rostral papillary and caudal non-papillary parts). Torus linguae had two parts: the triangular rostral part (the caudal part of the body) and the quadrilateral wide part (the rostral part of the root). The lingual papillary system had mechanical (filiform, conical and lentiform) and gustatory (fungiform and circumvallate) types. Filiform papillae were heavily scattered on the dorsal surface of the apex, the rostral part of the body and the ventral surface of the papillary region of the tip. Filiform papillae had five subtypes (ventral and dorsal processed, triangular, leaf-like and triangular-processed papillae), while the conical papillae had three subtypes: two lingual (small, large) and one paralingual (elongated pointed), and the fungiform had two subtypes: the high-density ovoid (on the ventral surface of the tip) and round papillae (on the dorsal surface) that possessed a high number of taste pores, not previously described. They ranged from 5 to 10 for ovoid and 25 to 25 for round papillae. Each circumvallate papilla had an ovoid bulb (with 2-5 taste pores) encircled by an annular groove and two pads (i.e. not described previously). The papillary system's regional divergence was specialized for their harsh and semi-harsh diet.

Bat flies: source of supplement nutrients for an endemic Malagasy fruit bat

Among frugivorous vertebrates, the nutritional composition of consumed fruits often needs supplementing by other food types, such as leaves, pollen or invertebrates, to meet dietary requirements. The endemic Malagasy fruit bat, Rousettus madagascariensis (Pteropodidae), actively feeds on their dipteran fly ectoparasites, principally of the family Nycteribiidae and Streblidae, during grooming activities. Since bat flies take blood meals from their hosts, the consumption of these flies by bats might represent a mechanism of recycling and reducing the loss of important nutritional components, such as minerals or proteins and fatty acids. The contribution of these ectoparasites to the diet of R. madagascariensis is 4–10% of the daily protein requirements. This is an important proportion for a species considered to be exclusively frugivorous.

Lingual papillary system of the Egyptian mouse-tailed bat (Rhinopoma hardwickii): New insights to its feeding strategies using scanning electron microscope, and immunohistochemical analysis of keratin

The current investigation described the ultrastructural and histological features of the lingual papillary system in 14 adult Rhinopoma hardwickii using scanning electron and light microscopy, and immunohistochemical staining of keratin. Three types of lingual papillae were recognized; one filiform mechanical and two gustatory (fungiform and circumvallate) of three directions: posterior, posteromedian, and median. Five filiform papillae subtypes were observed in four regions. The lingual tip had numerous giant filiform papillae. The lingual root was divided into two regions, an anterior papillary and a posterior non-papillary region that had only three circumvallate papillae in a triangular pattern. Histologically, the papillae exhibited detached thick keratin that spread over the dorsal epithelial surface. The dorsal surface of the root had stratified keratinized circumvallate papillae. Concerning the pan-cytokeratin (CK) antibody staining, moderate CK expression was observed in the superficial corneal layer of the apical lingual mucosa. While the superficial corneal cell layer in both body and root exhibited increasing of CK antibody. Morphometrically, there was a significantly increased, region-specific number of triangular, pointed filiform papillae, which were relatively increased in length and width. However, the round conical blunt filiform papillae and fungiform papillae were sparse. We concluded that our results showed distinguished adaptations in the lingual structure and its different papillae established on the nutritional and energetic demand of this bat species. This lingual adaptation is summarized in number, position, taste buds, direction, ultrastructural features, and histological that concerned with its ability in eating during the night flight.

Histomorphological, ultrastructural and morphometrical age-related changes of fundic region of New Zealand rabbits (Oryctolagus cuniculus)

This study investigated the histomorphological, ultrastructural and morphometrical postnatal developmental changes in the rabbit fundic region, especially during changing of the feeding intake. Seventy-two New Zealand rabbits (V-Line breed) at the ages of 1, 7, 15, 23, 30 and 60 days were obtained for light and electron microscopy and morphometric studies of the fundic region. The newborn rabbit's fundic wall was thin and organized into mucosa, submucosa, musclosa and serosa, with a significant increase in thickness with ageing. The fundic glands were few at the first week of life, then increased in length and diameter compared to the preceding age with prominent zonation at 23 days. The gastric pits appeared wide and deep at the first week of life then became typically narrow and shallow at the third week. The mucous cells were the main cell types lining the fundic glands in the first week of life. These cells showed remoulding with a marked increase in Periodic Acid-Schiff reactivity with age. Parietal cells were differentiated earlier (on the first day of life) than the chief cells and distributed at the neck and basal zones. Chief cells differentiated at 15 days old at the base of the glands, followed by an increase in the number and activity. Few active enteroendocrine cells were first seen at 15 days old and then widely distributed throughout the glands. Conclusion: Pronounced histomorphological changes in the fundic mucosal layer, especially the surface and glandular epithelium, correlate with the postnatal rabbit-feeding intake changes.

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.

Morphogenesis of the New Zealand white rabbit tongue (Oryctolagus cuniculus)

The current study was designed to describe the prenatal developmental stages of the rabbit tongue. Thirty-five embryos of prenatal ages (E16, E19, E23, E25, E28, and Postnatal) were obtained from New Zealand white (NZW) rabbit. The primordia of the tongue were observed on the foundation as early as day 16 prenatal age (E16). The first primordia of lingual papillae were observed that including the primordia of circumvallate papillae at day 19 prenatal (E19). Thickenings of lingual epithelium developed at 19 day prenatal of embryo. At day 23-25 pc, the presence of primordia of foliate papillae was shown in addition to primordia of the fungiform and filiform papillae were found. The development of the final shape of the tongue is a longstanding process that occurs during the prenatal and postnatal life. The first primordia of gustatory papillae appear, and only later primordia of mechanical papillae are formed. In conclusion, the morphogenesis of the tongue and its lingual papillae discussed its herbivorous nature of feeding.

Age-related ultrastructural characterizations of the teeth of the white grouper (Epinephelus aeneus) in the different three age-stages

This study represents the first attempt to describe ultrastructural features of teeth in different three ages of white grouper (Epinephelus aeneus) grossly and by the aid of the electron microscope. The current study depends on 18 oropharyngeal cavity of E. aeneus from each age-stages. There are common and special characterization between each age. Five teeth bands in the roof (incisive, canine, upper molar, palatine, and vomer), while two bands in the floor (incisive, molar). The apical teeth part resembles the arrowhead that bordered by groove distally. In 5 cm age, small upper incisive teeth had two appearance (straight and curved), and vomer teeth arranged in triangular in only one row (while, in 12 cm fish arranged in two rows and in 15 cm fish arranged in more than two rows), the palatine teeth began rostrally as one row then two rows and terminated by one row, while in other two ages began by two, then three and ended by two rows. There is no canine teeth in lower jaw in all age. In 12 cm fish, the rostral row of lower incisive teeth usually contain small straight teeth, while the posterior row mainly contain large with some medium upper incisive teeth. In 18 cm fish, upper incisive teeth located within two incisive fossa that separated from each other by longitudinal part of T-shaped upper incisive ridge and small incisive teeth had two appearance (straight and curved), and each canined teeth group contain four teeth (while in other two ages each group contain only two canine teeth).

Retinal characterization in the eyes of two bats endemic in the Egyptian fauna, the Egyptian fruit bat (Rousettus aegyptiacus) and insectivorous bat (Pipistrellus kuhlii), using the light microscope and transmission electron microscope

Bats are the only mammals that can fly in the dark without eye usage. This study was conducted to describe the structural and functional adaptations of the retina of two bats very common in the Egyptian fauna having a different lifestyle: the Egyptian fruit bat (Rousettus aegyptiacus) and insectivorous bat (Pipistrellus kuhlii). Seven eyes were collected from adult individuals of each species. Examination of the retina using a light microscope and a transmission electron microscope was carried out. The retina of P. kuhlii was thicker than that of R. aegyptiacus, which had many projections extended from the choroid layer into retina forming papillae. Despite rods being dominant in retinae of both species, cone photoreceptors were encountered in both retinae. The outer plexiform layer of R. aegyptiacus was arranged into islets between the outer nuclear layer produced differences in its thickness. However, the retina of P. kuhlii showed a normal arrangement of retinal structure. The retinal pigment epithelium of both bat species consists of a single layer of the cuboidal cells with a round to oval vesicular nuclei, which showed a lack of pigmentation in R. aegyptiacus and poor pigmentation in the P. kuhlii. In conclusion, our investigation detected many structural and ultrastructural differences between the two bat species. The presence of many projections protruded from the choroid layer of R. aegyptiacus retina is considered the most characteristic difference between the retinae of R. aegyptiacus and P. kuhlii.

Visual adaptability and retinal characterization of the Egyptian fruit bat (Rousettus aegyptiacus, Pteropodidae): New insights into photoreceptors spatial distribution and melanosomal activity

Our study was conducted to characterize the retinal structure of the Egyptian fruit bat, Rousettus aegyptiacus to determine the distribution of photoreceptors and melanosomal populations in various retinal zones. Also, we paid attention to the specific structural and functional adaptations related to their nocturnal habits. We analyzed the retinae of 12 adult male Egyptian fruit bats using morphometrical, histological, ultrastructural, and immunoblotting standard techniques. Histological findings revealed that the retinal cells have variations in geometrical architecture and different retinal thickness together with their corresponding layers bearing specific choroidal papillae projecting towards the inner retina. Immunoblotting and ultrastructure results showed that the microstructure of the retina conforms to that pattern found in mammalian species. The retinal photoreceptors are rod-dominant; alternatively, possess two spectral types of cones: SWS and LW/MWS cones as evidence for the basis for dichromatic vision. In addition, the outer retina showed densely-distributed melanin granules with a significant increase in the number of pigment epithelium cells in the eccentric retina. Furthermore, the asymmetric distribution among the retinal quadrants for the visual pigments of both rods and cones coinciding with neuronal cells such as bipolar and ganglion cells confers instructive information about their visual perception and orientation. In conclusion, our findings indicate that R. aegyptiacus efficiently discriminates colors with complex visual adaptations to mediate increased visual acuity coopted for the nocturnal niches.

Morphological study of the rabbit gustatory lingual papillae during postnatal life by light and scanning electron microscopy

This study aimed to investigate the postnatal morphological features of rabbit's lingual gustatory papillae using histological, histochemical, morphometrical and scanning electron microscopical studies. A total of 48 New Zealand rabbits (1, 7, 15, 23, 30, 60 days postnatal) were used as the material. Tongue consisted of an apex, body and root with three types of gustatory papillae fungiform, vallate and foliate. Rounded to oval fungiform papillae were distributed on lingual apex among filiform papillae. Two foliate papillae on lateroposterior side have parallel folia increased progressively in number (14-20) with age advancement. Two oval vallate papillae on lingual root surrounded by annular grooves. Histologically, the gustatory papillary epithelium was thin at birth then increased in stratification and cornification from third to fourth week. Vallate and foliate grooves were shallow in newborns then grew deeply by desquamation of their lining epithelium which completely opened and connected with lingual excretory ducts at 23 days. Developing serous von Ebner's glands appeared at 23 days and became lobulated form 1-2 months. They gave a negative reaction with Periodic Acid Schiff-Alcian blue stain, while mucous Weber's glands showed Alcian blue positive reaction. Taste buds were firstly seen at 15 days old, increased in number and size and became mature with taste pores from third to fourth week. They distributed dorsally on fungiform and on lateral sides of vallate and foliate. This structural adaptation and maturity of gustatory papillae to meet the functional demands of food ingestion during the transition from suckling to dry matter feeding.