SEM study on the dorsal lingual surface of the lesser dog-faced fruit bat, Cynopterus brachyotis.

The dorsal lingual surface of the lesser dog-faced fruit bat was examined by scanning electron microscopy (SEM). Filiform (Fi), fungiform (Fu) and vallate papillae (V) were observed. The Fi papillae were distributed over the entire dorsal surface of the tongue. The Fi papillae notably differed in morphology by their location on the tongue and could be classified into 5 types: 1) crown-like papillae, 2) giant trifid papillae, 3) scale-like papillae, 4) small conical papillae, and 5) large conical papillae. The Fu papillae were present rounded bodies on the anterior 2/3 of the tongue. The lesser dog-faced fruit bat showed the triangular arrangement of the three V, with the apex of the triangle directed posteriorly.     

SEM study on the dorsal lingual surface of the large flying fox,Pteropus vampyrus

The dorsal lingual surface of the large flying foxes were examined by scanning electron microscopy. Filiform, fungiform and vallate papillae were observed. The filiform papillae were distributed over the entire dorsal surface of the tongue. The filiform papillae notably differed in morphology by their location on the tongue and could be classified into 6 types: 1) scale-like, 2) giant trifid, 3) small crown-like, 4) large crown-like, 5) long conical and 6) short conical papillae. The fungiform papillae were present rounded bodies on the anterior 2/3 of the tongue. The large flying foxes showed the triangular arrangement of the three vallate papillae, with the apex of the triangle directed posteriorly. These findings indicate that the tongue of the large flying bat is similar to that of the lesser dog-faced fruit bat.     

SEM study on the dorsal lingual surface of Microtus montebelli

The dorsal lingual surface of Microtus montebelli was examined by scanning electron microscopy (SEM). The filiform papillae were distributed over the entire dorsal surface of the tongue. The filiform papillae notably differed in morphology by their location on the tongue and could be classified into 4 types: 1) simple conical papillae, 2) true filiform papillae, 3) giant conical papillae, and 4) saw-like papillae. The fugiform papillae were present rounded bodies scattered over the anterior dorsal surface of the tongue. A vallate papilla was located at the middle end of the lingual body. The surface of the radix zone was smooth and without lingual papillae.     

Morphology of the lingual papillae in the raccoon dog and fox

The dorsal lingual surfaces of the raccoon dogs (Nyctereutes procyonoides) and fox (Vulpes vulpes japonica) were examined by scanning electron microscopical (SEM) observations. The distribution and type of the lingual papillae found in the raccoon dog were similar to those in the fox. Filiform, fungiform, foliate and vallate papillae were observed. The filiform papillae were distributed over the entire dosal surface of the tongue. Each filiform papilla on the apical surface of the tongue had several pointed processes. The filiform papillae of the lingual body consisted of a main papilla and some secondary papillae. The fungiform papillae were present rounded bodies, and more densely distributed on the lingual apex. The foliate papillae were seen on the dorsolateral aspect of the tongue. The vallate papillae were located on both sides of the posterior end of the lingual body. Each papilla was surrounded by groove and crescent pad. On the periphery of the papillae, large conical papillae were observed.     

Scanning electron microscopy study of the tongue and lingual papillae of the California sea lion (Zalophus californianus californianus)

We observed the three-dimensional structures on the external surface and the connective tissue cores (CTCs) of the California sea lion (Zalophus californianus californianus), after exfoliation of the epithelium of the lingual papillae (filiform, fungiform, and vallate papillae), using scanning electron microscopy (SEM) and conventional light microscopy. Macroscopically, the tongue was V-shaped and its apex was rounded. At the posterior area of the tongue, five vallate papillae were arranged in a V shape. In the epithelium, numerous taste buds were distributed on the top of the vallate papillae. On the dorsal surface from the apex to the boundary between the anterior and posterior tongue, filiform papillae were densely distributed. The CTCs of the filiform papillae consisted of a main protrusion (primary core) and many small cores (secondary cores). From the apex to the anterior one-third of the tongue, dome-like fungiform papillae were densely distributed, whereas fewer were located at the posterior two-thirds of the tongue. Several taste buds were found in the epithelium on the fungiform papillae. The size of the filiform papillae gradually increased from the apex to the boundary between the anterior and posterior tongue. At the lingual radix, the conical papillae, which were bigger than any filiform papillae, were densely distributed. The morphological characteristics of the tongue of the California sea lion appear to have been transformed to adapt to an aquatic environment; however, they possess some structures similar to those of land mammals.     

Role of IGFBPs in the morphogenesis of lingual papillae

The expression of insulin-like growth factor binding proteins (IGFBPs) during the morphogenesis of lingual papillae of mice was examined by in situ hybridization. Among seven mouse IGFBPs, IGFBP-1, -6, and -7 mRNAs were not expressed in the tongue tissue. At E12, though no papillae have formed yet, IGFBP-2, -4, and -5 were expressed in the entire tongue epithelium. At E14, fungiform papillae appeared in the anterior region and circumvallate papillae were distinguished in the posterior region. Strong expression of IGFBP-5 was observed in the apical region of both fungiform and circumvallate papillae. At this stage, the epithelial elevation of filiform papillae was not clear; but IGFBP-5 was expressed in the apex. At E15, foliate papillae were distinguished and IGFBP-5 was expressed in the dorsal epithelium of ridges. In filiform papillae, IGFBP-3 was expressed in the core of the connective tissue. At E17, the expression of IGFBP-5 disappeared from the apical region of fungiform, filiform, foliate, and circumvallate papillae, whereas that of IGFBP-2 remained. This finding suggests that IGFBP-5 and -2 function to cause evagination of the epithelium into a raised structure. In the epithelium of trenches of foliate and circumvallate papillae, strong expression of IGFBP-4 was observed at E15 and E17. As previously suggested from a study on postnatal mice (Suzuki et al. J Comp Neurol 2005;482:74-84), IGFBP-4 acts in the epithelial invagination to form the trenches, grooves, or furrows of lingual papillae during development.     

SEM studies on the connective tissue cores of the lingual papillae of the northern goshawk (Accipiter gentilis)

The lingual papillae and their connective tissue cores (CTCs) of the northern goshawk were examined by scanning electron microscopy (SEM). The length of the tongue was approximately 2.5 cm. The median groove divided the body of the tongue into symmetrical parts. At a point approximately 2/3 of the length, there were large conical papillae between the body and the root of the tongue, the apices of which were pointed towards the posterior part of the tongue. Under the light microscopy, the filiform papillae of the dorsal surface in the lingual body showed the desquamate cells of non-keratinized epithelium. There were openings of the lingual glands on the anterior part and root of the tongue. The lingual papillae and their CTCs of the northern goshawk had a structure similar to those of the white tailed eagle and black kite.     

Morphology of the dorsal lingual papillae in the bush dog (Speothos venaticus)

The dorsal lingual surface of a bush dog (Speothos venaticus) was examined by scanning electron microscopy (SEM). The tongue was about 7 cm in length. Filiform, fungiform and vallate papillae were found. The filiform papillae were distributed over the entire dorsal surface of the tongue. Each filiform papillae on the apical surface of the tongue had several conical processes, in the midportion were larger than those on the apex in size. In the region of the vallate papillae, the filiform papillae had not the conical processes and more larger than those on the midportion of the tongue. The fungiform papillae were present rounded bodies and more densely distributed on the tip of the lingual apex. There were 5 vallate papillae on both sides. The vallate papillae were located on both sides of the posterior end of the lingual body. Each papilla was surrounded by a groove and a crescent pad. In the dorsal surfaces of the papillae, small conical papillae were observed.     

Morphological characteristics of the tongue and its papillae in the donkey (Equus asinus): a light and scanning electron microscopical study

The morphology of the donkey tongue and its papillae were investigated by macroscopy and by light and scanning electron microscopy in ten adult animals (six males and four females). The spatula-shaped tongues measured about 28 cm in length, 4.5 cm in breadth and 3.5 cm in thickness. Samples from different areas of four tongues were grossly examined and pieces were processed for light and scanning electron microscopy. Filiform papillae were distributed mainly on the dorsum of the tongue, being thin and relatively short at the apex, conical and scaly in the main part (triangular zone) of the body, and thin and longer at the caudal part of the body. Few of them were found on the lateral surfaces. Fungiform papillae appeared scattered mainly on the lateral surfaces. They were mostly rounded (about 1.0 mm in diameter), but lobulated forms were also observed. Filiform and fungiform papillae were both completely devoid of taste buds, indicating a more mechanical function. The vallate papillae were 2-3 in number, located at the most caudal part of the body. They were three to four times as large as the fungiform papillae (about 5.6 mm in diameter) each with a wide circular groove around the central bulbous projection. Secondary grooves originating from the primary one were also demonstrated. The vallate papillae contained many taste buds with taste pores opening deeply into the papillary groove. Fine filiform papillae were demonstrated on the bulb-like part of the vallate papillae. The donkey tongue had sinister and dexter well-developed sets of foliate papillae close to the basis of the palatoglossal arch. They were arranged in the form of numerous leaves separated by deep, variably wide grooves and contained a very large number of taste buds. It is believed that the existence of well developed foliate papillae in donkey may substitute the comparatively few vallate papillae in this species.     

Comparative morphological study on the stereo-structure of the lingual papillae and their connective tissue cores of the American beaver (Castor canadensis)

The lingual papillae and the connective tissue cores (CTC) of the American beaver were examined by light and scanning electron microscopy. The tongue of American beaver was about 9 cm in length, 3.5 cm in width, and has a lingual prominence. Four types of papillae (filiform, fungiform, vallate and foliate papillae) were observed. The filiform papillae can be classified into three types (filiform, large filiform and dorm-like papillae). Filiform papillae distributed on the anterior tongue and posterior of the lingual prominence consisted of a posterior thick main process and several small accessory processes. After removal of the epithelium, the CTCs of the filiform papillae had U-shaped, horseshoe-like primary cores with 10-15 rod-shaped small accessory cores. Large filiform papillae were distributed at the anterior margin of the lingual prominence. Dome-like papillae were distributed at the top of lingual prominence. Fungiform papillae were observed two types. Fungiform papillae, which were distributed at the anterior tongue, were round shaped. Fungiform papillae of the posterior of the lingual prominence were large and surrounded with a papillary groove. At the posterior of the tongue, three vallate papillae were arranged in a triangular pattern. Foliate papillae were on 22 to 25 parallel ridges and grooves.     

Interactions between taste receptors in the frog tongue

Summary Receptors sensitive to stimulation with dilute CaCl₂ solutions and located in different fungiform papillae of the frog tongue are cross-connected via branches of the glossopharyngeal nerve fibers to form chemical sensory units comprising on average about 3 papillae; often one or more papillae were found to be common to different units.The receptor response observed when single papillae were individually stimulated increased, when the strength of the stimulus was raised, at a much lower rate than that obtained by stimulating the whole tongue surface. This proves that the antidromic impulses travelling in the cross-connections linking different papillae result in an evident depression of the receptor response to CaCl₂.The possible functional significance of mutual interaction between the receptors in the frog tongue is discussed.This study was supported by grants from the Consiglio Nazionale delle Ricerche (Impresa di Elettrofisiologia) of Rome, Italy.     

Light and scanning electron microscopic study on the lingual papillae and their connective tissue cores of the Cape hyrax Procavia capensis

We examined the epithelial surface and connective tissue cores (CTCs) of each lingual papilla on the Paenungulata, Cape hyrax (Procavia capensis), by scanning electron microscopy and light microscopy. The tongue consisted of a lingual apex, lingual body and lingual root. Filiform, fungiform and foliate papillae were observed on the dorsal surface of the tongue; however, fungiform papillae were quite diminished on the lingual prominence. Moreover, no clearly distinguishable vallate papillae were found on the tongue. Instead of vallate papillae, numerous dome-like large fungiform papillae were arranged in a row just in front of the rather large foliate papillae. Foliate papillae were situated in the one-third postero-lateral margin of the lingual body. The epithelium of filiform papillae was covered by a keratinized layer with kerato-hyaline granules, whereas weak keratinization was observed on the interpapillary epithelium. The external surface of the filiform papillae was conical in shape. CTCs of the filiform papillae were seen as a hood-like core with a semicircular concavity in the anterior portion of each core. Large filiform papillae were distributed on the lingual prominence. The CTCs of large filiform papillae after exfoliation of their epithelium consisted of a concave primary core and were associated with several small protrusions. The surface of fungiform papillae was smooth and dome-like. After removal of the epithelium, CTCs appeared as a flower bud-like primary core and were associated with several protrusions that were arranged on the rim of the primary core. Several taste buds were found on the top of the dorsal part of the epithelium of both fungiform and large fungiform papillae. Well-developed foliate papillae were seen and numerous taste buds could be observed in the lateral wall of the epithelium in a slit-like groove. The morphological characteristics of the tongue of the Cape hyrax had similarities with other Paenungulata such as Sirenia. However, three-dimensional characteristics, especially CTCs of lingual papillae, exhibited multiple similarities with rodents, insectivores and artiodactyls.     

Scanning electron microscopic study on the lingual papillae of the Japanese insectivora

The tongue and lingual papillae of the Japanese Insectivora, the Shinto shrew (Sorex caecuiens saevus), the long-clawed shrew (S. unguiculatus), the dsinezumi shrew (Crocidura dsinezumi dsinezumi) and the Japanese water shrew (Chimarrogale himalyica platycephala), were observed by scanning electron microscope. The tongue of these animals had two vallate papillae. In two species of the Sorex a papilla in the vallate papilla was surrounded by two separated trenches, but in the other species it was surrounded by only a continuous trench and a clear vallum. The fungiform papillae in the Sorex were less developed than those of the other species. In the Sorex and Crocidura, there was no filiform papilla on the lingual apex. These genera, however, have papillary projections in the margin of the lingual apex. The results of this investigation suggest that the Sorex and Crocidura indicate an ancient form of the mammalian tongue. These characters, furthermore, were compared among seven species in six genera added three species observed by Kobayashi et al. (1983) to this study.     

Light and scanning electron microscopic study on the tongue and lingual papillae of the common raccoon, Procyon lotor

We observed the external surface and connective tissue cores (CTCs), after exfoliation of the epithelium of the lingual papillae (filiform, fungiform, foliate and vallate papillae) of the common raccoon (Procyon lotor) using scanning electron microscopy and light microscopy. The tongue was elongated and their two-third width was almost fixed. Numerous filiform papillae were distributed along the anterior two-thirds of the tongue and fungiform papillae were distributed between the filiform papillae. Eight vallate papillae that had a weak circumferential ridge were distributed in a V-shape in the posterior part of the tongue and numerous taste buds were observable in the circumferential furrows of vallate papillae. Weak fold-like foliate papillae were observable at the lateral edge in the posterior part of the tongue and a few salivary duct orifices were observable beneath the foliate papillae. An islet-like structure with numerous taste buds, was observable on the deep part of the salivary duct of foliate papillae. Large conical papillae were distributed at the posterior part and root of the tongue. After removal of epithelium, filiform papillae of CTCs were appeared to be a thumb or cone-like main core and associating several finger-like short accessory cores. These cores were surrounded an oval concavity. The main core was situated behind the concavity and associated with accessory cores. CTCs of fungiform papillae were cylinder-like with numerous vertically running ridges and with a few concavities seen at the top of the cores. CTCs of vallate papillae and their surrounded circumferential ridge were covered with numerous pimple-like protrusions. The lingual papillae of Common raccoon's tongue had morphological feature of carnivore species.     

Morphology of the lingual papillae and their connective tissue cores in the cape hyrax

The dorsal lingual surfaces of four adult cape hyraxes (Procavia capensis) were examined by scanning electron microscopy (SEM). Filiform, fungiform and foliate papillae were observed. The lingual body had lingual torus on the posterior third. In the lateral sides of the tongue large fungiform papillae were observed and in the lateral sides of the torus very developmental foliate papillae were observed. Many fungiform papillae were observed in the ventral surface of the lingual apex. No vallate papillae were seen on the dorsal surface. The filiform papilla on the apical surface of the tongue had shovel-shaped papilla. The filiform papilla contained the connective tissue core consisting of some processes. The connective tissue core of the fungiform papillae was floral bud in shape. In the surface of the lingual torus numerous dome-shaped papillae are found. The dome-shaped papilla contained the connective tissue core consisting of a zigzag surface structure and the connective tissue core is surrounded by the processes of various sizes. In the surface of the lingual root numerous openings of the lingual glands were found. Around the glandular openings connective tissue ridges formed circular sheaths. In the lateral sides of the tongue large fungiform papillae were round in shape. The connective tissue core of the fungiform papilla was floral bud in shape. The foliate papillae were seen on the dorsolateral aspect of the tongue and some ridges and grooves were exposed reciprocally. Many small protrusions appeared on the connective tissue core of the ridge of the foliate papilla. These findings suggested that in the structure of the lingual papillae of the cape hyrax there was intermediate type between Rodentia and Artiodactyla.     

Scanning electron microscopic study on the tongue and lingual papillae of the adult Spotted seal, Phoca largha

We observed the external surface and connective tissue cores (CTCs) of the lingual papillae (filiform, fungiform and vallate papillae) of adult Spotted seals (Phoca largha) using SEM and light microscopy. The tongue was V-shaped and its apex was rather rounded. On the dorsal surface from apex to the one-third posterior of the tongue, the lingual mucosa was densely covered by filiform papillae, with a scatted distribution of dome-like fungiform papillae, which have orthokeratinized epithelium. At the posterior part of the tongue, filiform papillae were totally diminished and their epithelium was parakeratinized. Approximately 6-7 vallate papillae were arranged in a V-shape on the posterior of the tongue. After removal of the epithelium, the CTCs of the filiform papillae that were distributed at apex consisted of a primary core and approximately 5-6 rod-shaped small accessory cores. The CTCs of filiform papillae that were distributed at anterior part of the tongue lacked primary protrusions and possessed approximately 10-15 rod shaped small accessory cores that were arranged in a horseshoe manner. The CTCs offungiform papillae had cylindrical primary cores and were fringed with accessory protrusion. In the Vallate papillae, taste buds were only seen at the dorsal epithelium.     

Anatomical and histological structure of the tongue and histochemical characteristics of the lingual salivary glands in the Persian squirrel (<Emphasis Type="Italic">Sciurus anomalus</Emphasis>)

This study was carried out to describe the anatomical, histological and mucinous histochemical characteristics of the tongue in the Persian squirrel. This species is a rodent distributed all over the Middle East and recently has been considered a companion animal. Anatomical observations showed the median sulcus on the apex and absence of a lingual prominence in the body. Light and scanning electron microscopy showed that the filiform papillae cover the entire dorsal surface of the tongue, and their sizes increased approaching the root. The fungiform papillae, which contained 1–4 taste buds, were scattered on the apex, margin, body and root of the tongue. Three vallate papillae were observed on the root, each one surrounded by a groove and crescent pad with taste buds on its lateral walls. The foliate papillae on both margins of the tongue contained several laminae with taste buds. The core of the tongue was composed of lingual glands, skeletal muscles and connective tissues. These glands were confined to the body and root, which were composed of serous cells located anteriorly and mucosal and seromucosal cells placed posteriorly. The mucin histochemistry using the periodic acid-Schiff (PAS), alcian blue (AB) (pH 1.0 and 2.5), PAS–AB (pH 2.5) and aldehyde fuchsin-AB (pH 2.5) techniques showed that the mucosal content included both carboxylated and sulfated acidic mucins with neutral mucins. The results of this study could contribute to the knowledge of the morphological characteristics of the wild animal tongue and provide data for comparison with other rodents.     

Morphology of the tongue in a newborn Stejneger's beaked whale (Mesoplodon stejnegeri)

This light and scanning electron microscopic (SEM) study on the tongue of a newborn Stejneger's beaked whale (Mesoplodon stejnegeri) demonstrated a clear difference in its form from than that of other cetacean and adult Stejneger's beaked whales. This newborn Stejneger's beaked whale had a spoon-like shaped tongue. The dorsal surface in the center part of the tongue was flat and did not have papillae, but there were marginal papillae and small papillae on the anterior part of the tongue. In the posterior of the tongue, hillock-shaped papillae with taste buds on the epithelium were observed.     

Morphological characteristics of the tongue and lingual papillae of the large bamboo rat (<Emphasis Type="Italic">Rhizomys sumatrensis</Emphasis>)

The large bamboo rat (Rhizomys sumatrensis) is a fossorial rodent found throughout Indochina that has a distinct habitat dominated by bamboo thickets. In the study reported here, the lingual biology of this rodent is described in detail, based on characteristic features of the tongue and lingual papillae as determined by light and scanning electron microscopy studies. The tongue was found to be elongated with a rounded apex and possessed a median groove and a well-developed intermolar prominence. Three types of the papillae were found on the dorsal lingual surface: filiform, fungiform and vallate papillae. The most abundant papillae were the filiform papillae, the majority of which had a wide base and fork-like processes. Rounded fungiform papillae with one to four taste buds were randomly distributed among the filiform papillae, with a high density found at the anterior tongue, particularly the apex. Two oval vallate papillae were observed on the posterior part of the tongue, surrounded by a circumferential groove into which their numerous gustatory pores opened. The lingual radix had no papillae but contained mucus-secreting Weber’s salivary glands. Structural adaptations of the tongue to meet the functional demands of food ingestion and food manipulation in the oral cavity are also discussed.     

Biological aspects of the tongue morphology of wild-captive WWCPS rats: a histological,histochemical and ultrastructural study

The aim of this study was to characterise the tongue in wild-type rats using several microscopic techniques. Warsaw Wild Captive Pisula Stryjek (WWCPS) rats belong to a lineage of wild-caught rats. The study was carried out on tongues of 15 male and 15 female WWCPS rats. Histological, histochemical and ultrastructural studies were carried out. There were no significant differences between the male and female WWCPS rat tongues. There was a median groove approximately 1 cm long in the apex of the tongue that faded caudally. The intermolar prominence was clearly marked in the distal part of the lingual body. Lingual mechanical papillae located on the surface of the tongue formed four subtypes based on their shape: small filiform papillae, giant filiform papillae, thin elongated filiform papillae and wide filiform papillae. Gustatory papillae formed the second group of papillae and were divided into bud-shaped fungiform papillae, a single vallate papilla surrounded by an incomplete papillary groove and foliate papillae, which were a well-formed and composed of several pairs of folds divided by longitudinal grooves. In the posterior lingual glands (mucoserous and serous), acidic sulphated mucin-secreting cells gave a strong AB pH 2.5 positive reaction, and a positive reaction with the AB pH 1.0 stain for acidic carboxylated mucin. Double AB/PAS staining showed the presence of the majority of mucous cells with predominant of acidic mucins. Positive PAS staining showed the presence of neutral mucin. HDI staining demonstrated a weak positive reaction within Weber’s glands of the WWCPS rat tongue.