Light and scanning electron microscopic study of the structure of the ostrich (Strutio camelus) tongue

The ostrich's tongue is situated in the posterior part of the oropharyngeal cavity and its length is only about a quarter of the beak cavity. The triangular shortened tongue has retained the usual division into the apex, the body and the root. There are no conical papillae between the body and the root of the tongue, and the presence of the flat fold with lateral processes sliding over the tongue root in the posterior part of the lingual body is a unique morphological feature. All lingual mucosa covers non-keratinised stratified epithelium, and the lamina propria of the mucosa is filled with mucous glands whose round or semilunar openings are found on both the dorsal and ventral surface of the tongue. The complex glands found in the lingual body are composed of alveoli and/or tubules. Moreover, simple tubular glands seen in the posterior part of the tongue root are an exception. Numerous observations have shown that the ostrich's tongue is a modified structure, though not a rudimentary one, whose main function is to produce the secretion moisturising the beak cavity surface and the ingested semidry plant food in this savannah species.     

Light and scanning electron microscopic study of the tongue in the cormorant Phalacrocorax carbo (Phalacrocoracidae, Aves)

The tongue of the cormorant Phalacrocorax carbo is a small, immobile structure with a length of 1.4 cm, situated in the middle part of the elongated lower bill. The uniquely shaped tongue resembles a mushroom, with a short base and an elongated dorsal part with sharpened anterior and posterior tips. A median crest can be observed on the surface of the tongue. Examination by light and scanning electron microscopy revealed that the whole tongue is formed by a dense connective tissue with many bundles of elastic fibers. The lingual mucosa is covered by a multilayered keratinized epithelium. The thickest, horny layer of the lingual epithelium was observed on the surface of the median crest and on the posterior tip of the tongue. Lingual glands are absent in cormorants. The framework of the tongue is composed of a hyoid cartilage incorporated into the base. The localization and structure of the tongue in the cormorant show that it is a rudimentary organ and that the lingual body, usually well-developed in birds, is conserved.     

A scanning electron microscopic study of the dorsal surface of the human tongue

To study the dorsal surface of the human tongue using a scanning electron microscopy (SEM), tissue specimens were taken from the anterior part of the tongues of 15 individuals aged from 21- to 28-years-old. The formalin-fixed samples were processed routinely for SEM. With SEM the surface of the normal tongue mucosa was shown to be rather evenly covered by filiform papillae, with some fungiform papillae scattered among them. Filiform papillae consisted of two parts: the body and hairs. The mucosal surface of the body was smooth; the squamous epithelial cells were polygonal, and their boundaries were prominent. On the surface of the superficial epithelial cells were parallel or branching microplicae. Each filiform papilla had 6-10 hairs, which were scaled and covered by an extensive plaque of microorganism. The upper surface of the fungiform papillae was smooth; only a few desquamating cells were seen. The superficial cells had a pitted appearance and cell boundaries overlapped. Taste pores, up to 3 pores in a single papilla, were found on the upper surface. Desquamation was more pronounced on the base of the fungiform papillae than on the upper surface. In almost all fungiform papillae some hairs protruded from the base. Parallel microplicae were found on the surface of the superficial cells of the base. The structure and function of the human tongue, as well as the microplicae of its superficial cells, are compared to those of various species of animals.     

Pulmonary aspergillosis outbreak in Rhea americana in Southern Brazil

Commercial raising of rheas is currently in expansion in the south of Brazil, and many diseases previously restricted to other avian species are currently emerging on rhea farms, especially as a result of careless management of these animals. The objective of the present article is to report a pulmonary aspergillosis outbreak that occurred in great rhea (Rhea americana) in the south of Brazil. About 50 birds aged 30 to 60 days died suddenly and one of them was submitted to autopsy which revealed the presence of white caseous nodules 0.5 mm in diameter occupying 95% of the lung area. One lung was sent to the Federal University of Santa Maria for histopathological and mycological analyses. Histopathological analysis revealed multifocal areas with necrosis and inflammatory infiltrates and the presence of fungal hyphae, giant cells and fibrous tissue proliferation at the periphery. Aspergillus fumigatus was recovered as pure culture from all culture media. This appears to be the first report of aspergillosis among great rhea in Brazil and the second in the world.     

Light and scanning electron microscopic study of cerebellar cortex of teleost fishes

Summary The teleostean cerebellar cortex has been studied with respect to its cytoarchitectonic arrangement and intracortical neuronal circuits. Samples of fish cerebellum were fixed either by immersion or vascular perfusion in 5% glutaraldehyde solution and processed for light and scanning electron microscopy. The cerebellar cortex shows four distinct layers: granular; fibrous stratum; Purkinje cell; and molecular layers. In the granular layer, mossy and climbing fiber glomeruli were characterized. The mossy glomerular region appeared as polygonal, round or ovoid clews formed by the convergence of up to 17 dendritic profiles upon a thick mossy fiber branch. The en passant nature of mossy fiber-granule cell dendrite synaptic relationship was clearly appreciated. The climbing fibers showed tendril and glomerular collaterals. The latter form thin, elongated glomeruli. Remnants of a neuroglial envelope were observed in the mossy fiber glomeruli but are apparently absent from the climbing fiber glomeruli. The beaded-shape Golgi cell axonal ramifications were observed participating in the formation of both glomerular types. Velate protoplasmic astrocytes and oligodendrocytes were also identified. The fibrous stratum appeared to be formed by compact bundles of thick and thin myelinated axons, running horizontally beneath the Purkinje cell layer and apparently belonging to ascending climbing fibers and descending Purkinje cell axons. At the Purkinje cell layer a selective removal of Bergmann glial cells was observed allowing the visualization of the pericellular basket and the pinceaux. Climbing fiber stems and their tendril collaterals were seen on their way to the molecular layer ascending parallel to the Purkinje dendritic ramifications. Stellate neuron processes were found passing through the fan-like arborescence of Purkinje cell dendrites.     

Ontogeny of feeding and drinking in the greater rhea (Rhea americana)

Feeding and drinking movements of the greater rhea chick are analyzed. Feeding consists of five movements in the following sequence: orientation, pecking thrust, head lift, forward head jerk and swallow. Drinking is less complex, consisting of a downward movement followed by an upward movement. Adult movements are basically similar; there is a slight trend toward increased variability and decreased energy expenditure. Feeding movements are observed prior to feeding initiation. Drinking movements are first performed during initial water contact. Experience with food and water plays a major role in the development of response efficiency.     

The Complete Mitochondrial Genome of Rhea americana and Early Avian Divergences

The complete mitochondrial DNA, mtDNA, molecule of the greater rhea, Rhea americana, was sequenced. The size of the molecule is 16,710 nucleotides. The organization of the molecule conforms with that described for the chicken and the ostrich. It has been shown previously that relative to other vertebrates the NADH3 gene of the ostrich has an insertion of one nucleotide in position 174 of the gene. The same observation was made in the rhea and in the newly sequenced NADH3 gene of the emu, Dromaius novaehollandiae. Comparison with the NADH3 gene of the chicken and the rook suggests that the inserted nucleotide may be deleted by RNA editing. The divergence between the two struthioniform species, the ostrich and the rhea, was molecularly dated at ≈51 million years before present, MYBP. This dating is more recent than commonly acknowledged. Phylogenetic analysis of the complete cytochrome b genes of seven avian orders placed the Passeriformes basal in the avian tree with the Struthioniformes among the remaining Neognathae. These findings challenge the commonly accepted notion that the most basal avian divergence is that between the Palaeognathae and Neognathae. Received: 13 October 1997 / Accepted: 17 January 1998     

Gross anatomical features of the tongue, lingual skeleton and laryngeal mound of Rhea americana (Palaeognathae, Aves): morpho-functional considerations

The tongue body of Rhea americana is triangular and partially pigmented with each caudo-lateral margin displaying a round, sub-divided lingual papilla. The tongue root is a smooth, non-pigmented tract of mucosa. The tongue body is supported by the paraglossum and distal half of the rostral projection of the basihyal (RPB), and the tongue root by the proximal half of the RPB, body of the basihyal and proximal ceratobranchials. An urohyal is absent; however, peculiar to R. americana, the caudal margin of the cricoid body displays a median projection, which may represent the remnant of the urohyal incorporated into the cricoid. The laryngeal mound is less elevated, the arytenoid cartilages are smaller than in other ratites, and the caudal margin displays pharyngeal papillae that vary in shape and number. The unique morphology of the lingual skeleton and its positioning within the tongue of R. americana, the rostral insertion of the M. ceratoglossus, the absence of the urohyal (enhanced ventroflexion) and the caudal positioning and mobile attachment of the ensheathed basihyal to the paraglossum would appear to allow independent movement of the tongue body relative to the hyobranchial apparatus. Additionally, the deeply indented base and rostral oval opening in the paraglossum limits the length of cartilage present in the midline of the tongue body. This may allow the tongue the necessary flexibility for the lingual papillae to clean the choana. The cleaning action of the tongue would occur simultaneously with the previously described role of this organ and associated structures during feeding. Thus, the so-called reduced, ancestral tongue of R. americana may be structurally and functionally more complex than previously believed.     

Optical and scanning electron microscopy observation of the mucosa of human fetal tongue

The structural features of the human foetal tongue have been studied in foetuses from 8th to 20th week of pregnancy. The characteristics of the developing papillae as well as of epithelial and mesenchymal layers have been pointed out. An early differentiation of the mesenchymal tissue has been observed, concerning phenomena of cellular condensation and reticular fibers organization both in superficial and deep layers. The hypothesis of the existence of straight interactions between epithelium and mesenchyme also in the developing human tongue mucosa has been suggested. Also the observations at SEM demonstrate that from the 8th to the 20th week the epithelial surface of the tongue reaches a stable structural pattern. From 11th week a characteristic cellular polymorphism occurs: cells with microvilli that diminish progressively, ciliated cells that disappear almost completely at the 20th week and cells whose free surface show microplicae, definitive stage of the tongue cell evolution.     

Rhinosporidium seeberi: Light,phase contrast,fluorescent and scanning electron microscopic study

Phase contrast microscopic study indicated the multilayered structure of the sporangial wall of R. seeberi while the scanning electronmicroscopic study revealed a trilaminated wall compared to a thick double walled light microscopic structure. The scanning electronmicroscopy revealed the spores of varying sizes which were found either discretely or in groups interconnected and seen attached to the inner aspect of the sporangial wall. Autofluorescence of sporangia and spores was observed under microscope. Acridine orange staining revealed the presence of DNA materials in the spore and sporangia.     

Development of the chemo- and mechanoreceptors of the tongue in mature-born animals (scanning electron microscopy)

Scanning electron microscopy was used to study developmental changes in the chemo- and mechanosensory apparatus of the tongue in guinea-pigs, goats and sheep during the 1st to the 10th postnatal week. The maturation of the chemosensitive postnatal formation of the mechanosensitive papillae was shown.     

Light and scanning electron microscopy of the ecdysis of Haemonchus contortus infective larvae

During the second ecdysis of ruminant trichostrongyles, a region of the second molt cuticle is digested by a 44-kDa Zn-metalloprotease. We have examined this digestion process by light and scanning electron microscopy (SEM). The substrate region of the cuticle appeared, during the ecdysis process, as an indented ring at the 20th cuticular annulus coincident with the anterior terminus of the lateral alae. Continued digestion of the cuticle resulted in holes in the ring region that expanded until they became continuous and separation occurred between the anterior and posterior portions of the cuticle. Mechanical movements of the L3 forced aside the cuticle cap that generally remained attached on one side to the posterior portion as the larva escaped from the sheath. The site of secretion of the 44-kDa ecdysing enzyme causing cuticle digestion was not clear from morphological observations; however, existing evidence strongly points to the release of enzyme from the esophageal (pharyngeal) glands through the mouth.     

Seasonal Changes in Plasma Levels of Sex Hormones in the Greater Rhea (Rhea americana), a South American Ratite with a Complex Mating System

Seasonal rhythm in sex hormones has been extensively studied in birds, as well as its relationship with the type of mating system. The Greater Rhea (Rhea americana), a South American ratite species, reproduces seasonally and has a complex mating system: female-defense polygyny and sequential polyandry. The present study aimed at analyzing the endocrine basis of reproduction in this species and its relationship with its mating system. We used HPLC and electrochemiluminescence techniques to identify and measure plasma testosterone and estradiol levels. Annual oscillations in sex hormones, testosterone and estradiol, in adult males and females were observed. Lower levels of these hormones were exhibited during the non reproductive season (February to July), whereas their maximum values were reached in September for males and November-December for females. These fluctuations reflect the seasonal changes in gonadal function. By contrast, no significant sex hormones oscillations were observed in juvenile males and females (negative control of seasonal changes). Greater rheas maintain high testosterone and estradiol levels throughout the reproductive period. The high testosterone levels during incubation and chick rearing did not inhibit parental behavior in males, which appears not to conform to the “Challenge Hypothesis”. In females, the high estradiol levels throughout the reproductive season would be needed to sustain their long egg-laying period.     

The development of the tongue in the chick embryo: observation under a scanning electron microscope

The morphological features of the chick embryo tongue from the 8th day of incubation till hatching and during the early post incubation period have been investigated by means of Scanning Electron Microscope. At the SEM, it is possible to observe that already at the 8th day of incubation, the body and the root are separated by a low smooth-surfaced ridge. In the following days this ridge develops, giving rise to the so-called lingual spines, whose significance is still uncertain. As concerns the evolutive pattern of the superficial layer of the epithelium, in the first days of the considered incubation period the cells appear dome-shaped and have microvilli on their apical surface; afterwards they tend to become more flattened, and the microvilli are replaced by a thick net of microplicae. In the last days of incubation and after hatching desquamative phenomena become evident. The above described evolutive process can be regarded as a common feature of the whole dorsal lingual surface; only few regional differences are to be noted, such as the earlier development of the microplicae on the apex and borders of the tongue. In particular, the microplicae observed at the apex of the tongue show a typical aspect and arrangement; they run regularly parallel to each other. On the lingual dorsal surface taste bud-like structures have never been observed.     

Ultrastructure and electrolyte transport of the epithelium of coprodeum,colon and the proctodeal diverticulum of Rhea americana

The structure and function of the lower intestinal tract of Rhea americana were characterized to evaluate the evolutionary relationship to other struthioniform and avian species. In 5 rheas the gross anatomy and the light and transmission electron microscopy were studied in parallel to in vitro electrophysiological measurements of ion transport. The mucosa in the colon was amplified with villi, often branched, and in the coprodeum with folds. In both tissues the epithelium was a monolayer composed of columnar absorptive cells, goblet cells and mitochondria-rich cells. Colon and coprodeum appeared to produce large amounts of mucus. The proctodeal diverticulum was rich in lymphoid tissue arranged into lobuli bursales, and it was concluded that this structure is a modified bursa of Fabricius. The sparse interlobular epithelium of the diverticulum resembled that of colon and coprodeum. Baseline short circuit currents (I_SC) averaged 114.5 ±13.8 µA/cm² in colon, 193.1 ± 30.3 µA/cm² in coprodeum and 60.4 ± 9.1 µA/cm² in the diverticulum. Amiloride sensitive Na⁺-transport amounted to 31, 88 and 38% of the baseline I_SC in these three tissues, respectively. In all tissues, there was also a modest, theophylline activated chloride secretion response, and ouabain, the Na⁺/K⁺-ATPase inhibitor, abolished most of the I_SC. The transepithelial resistance (TER) of the diverticulum was much higher than the other tissues. Upon dissection, urate from ureteral urine was observed in the lower third of the colon and to a lesser extent in the proctodeal diverticulum, indicating retrograde peristalsis of the urine. Thus, unlike the ostrich, there is no sphincter separating colon and coprodeum. On the other hand, a thick mucus layer was seen overlying the mucosa in both colon and coprodeum, as in the ostrich. This may help to prevent osmotic water loss, despite the presence of hyperosmotic urine (up to 800 mOsm) in the lower intestine. Both morphological and electrophysiological data from the rhea support the hypothesis that the rhea lower intestine contributes to post-renal modification of ureteral urine and to the regulation of osmotic balance, as also seen in domestic fowl and other avian species. The proctodeal diverticulum functions mainly as an immune organ, with only limited transport capability.     

Comparative studies of the dorsal surface of the tongue in three mammalian species by scanning electron microscopy

Comparative features of the dorsal tongue epithelia in musk shrews, mongooses and rats were described. The shapes of the filiform papillae were different in each of the species. The distribution pattern of filiform papillae was similar both in the musk shrews and mongoose, in that the form of filiform papillae changed gradually from the lingual apex to the posterior part of the lingual body. By contrast, the different types of filiform papillae were distributed on definite areas of the dorsal lingual surface in the rat. Microridges on the interpapillar surface in the musk shrew and mongoose presented a clear outline, but those of the rat were not so distinct. In all species, the upper surface of filiform papillae did not show any distinct microridges.