Surface ultrastructure of gills in relation to the feeding ecology of an angler catfish Chaca chaca (Siluriformes,Chacidae)

Surface ultrastructure of the gills of the angler catfish Chaca chaca was investigated to unravel the adaptive modifications associated with the feeding ecology of the fish. The fish is often found in mud or in soft substrates where they remain buried both for protection and to feed. Gill rakers present on the gill arch in most fish species are absent in this fish. The absence of gill rakers are associated with the feeding habit of the fish and is considered to facilitate the swallowing of captured prey smoothly without any hindrance. Highly corrugated surface of the gill arch and gill filaments could be associated to retain water/mucus to prevent dessicassion of the fish. Papillae like epithelial protuberances each bearing a taste bud at its summit toward the pharyngeal side of the gill arch is associated with the sorting of the food. Large number of mucous goblet cells on the gill arch epithelium are considered to secret copious mucus to lubricate the prey for easy swallowing. In C. chaca the gill septa between gill filaments are reduced. This could enhance the flexibility and permit the free movement of the gill filaments. Extensive secondary lamellae and infrequent mucous goblet cells on secondary lamellae are associated to increase the surface area to enhance efficiency of gaseous exchange.     

Morphological studies on the gills of the European hake (Merluccius merluccius,Linnaeus, 1758)

The current work gives concern to study the morphology of the Merluccius merluccius gills by using gross morphology, scanning electron microscopy (SEM), and light microscopy. The findings of the present study revealed that the gill system consisted of four pairs of gill arches which carry the gill filaments on the convex border and gill rakers on the concave border of them. SEM results revealed that the rakers and the spines distribution on the first gill arch differed from that of the other three gill arches on the lateral and medial surfaces. On the surface the gill filaments, there were longitudinal ridges that carried pores of chloride cells and mucous cells. The histological examination revealed that, the gill arch composed of hyaline cartilage that presented in the form of cups. Each cup consisted of central cartilagenous core and peripheral cartilagenous matrix. The gill filaments composed of cartilaginous bar of peripheral cartilaginous matrix and central cartilaginous core extended from the gill arches and covered by an epithelial layers with a few mucous cells permeate it, and chloride cells were straggly in the interlamellar epithelium. Each gill filament carried several leaves like secondary lamellae on both sides of it. The epithelium, which lined the secondary lamellae, composed of epithelial pavement cells, some mucous cells, and pillar cells.     

Morphological investigation of the gills of the dusky grouper Epinephelus marginatus (Lowe 1834) using gross anatomy and scanning electron microscopy

The current study has designed to investigate the morphological characteristics of the gills of the dusky grouper (Epinephelus marginatus) by gross morphology, scanning electron microscopy, and morphometric analysis. The study was carried out on 10 fresh fish. The fish has four-gill arches on each side. The lengths of the first-, second-, third-, and fourth-gill arches were 5.27, 4.2, 3.2, and 2.8 cm. The gill arches carried a longitudinal band, the bases of the gill filaments, and gill rakers that varied from rectangular to circular shapes. Each gill arch had two main lateral and medial rows and two accessory rows of gill rakers in an alternative manner with each other. The dusky grouper fish had long rakers, whereas the longest one was the lateral rakers of the first arch, which were 467 and 1271.9 μm in width and length. Three types of spines appeared on the gill arches and rakers. The long spine had detected on the apex of the short rakers. Each gill arch carried on its ventral side two rows of gill filaments. The long filaments were at the middle of the gill arch, while the short ones were at the rostral end of the gill arch. The study has demonstrated the taste buds, mucous, chloride cells, and significant features of the epithelial covering of the gill arches and rakers. The morphology of the gills of the dusky grouper indicates the adaptation to their marine environment.     

Morphological specializations of the epidermis of an angler catfish Chaca chaca (Siluriformes,Chacidae) in relation to its ecological niche: A scanning electron microscopic investigation

The present work was undertaken with the aim to deduce morphological adaptations in skin of an angler catfish Chaca chaca by means of scanning electron microscopy. The fish is nocturnal, bottom dwelling, sluggish, ambush predator, lives in sand, mud, or soft substrates often buried and camouflaged for protection and to feed. The surface of the epidermis is covered with polygonal epithelial cells, each having surface relief of microridges forming intricate patterns. In between epithelial cells irregularly distributed mucous cell openings, randomly distributed epidermal specialized structures, taste buds, and neuromasts are discernible. The epidermal specialized structures are keratinized. These are either irregularly the rounded elevated plaque like or the cone shaped structures. The superficial keratinized cells could frequently be discernible exfoliated at the surface. At intervals, characteristic epidermal projections could be observed. Surface of these projections at intervals is differentiated into short stumpy protuberances, each bearing a taste bud at its summit. Further, near the basal portion of these epidermal projections, conical, or rounded plaque like epidermal specialized structures are also discernible. The surface sculpture of the skin of Chaca chaca is associated with the structural and functional significance and physiological adaptations of the epidermis with respect to its ecological niche.     

Light and transmission electron microscopy study of the peripheral olfactory organ of the guppy, Poecilia reticulata (Teleostei, Poecilidae)

A study of the peripheral olfactory organ, with special attention to the olfactory epithelium, has been carried out in the guppy (Poecilia reticulata). Guppy is well known to have a vision-based sexual behavior. The olfactory chamber caudally opens directly in an accessory nasal sac, which is bent medially and gives rise to two recesses that can be considered secondary accessory nasal sacs, antero-medial and postero-medial, respectively. The sensory epithelium, which lines only the medial wall of the nasal cavity, is basically flat rising in a very low lamella only in the posterior part. The olfactory receptors are not evenly distributed in the olfactory mucosa, but aggregate in shallow folds separated by epithelial cells with evident microridges. Ciliated olfactory sensory neurons and microvillous olfactory sensory neurons are clearly identified by transmission electron microscopy (TEM). Scarce crypt olfactory neurons are found throughout the sensory folds. The nasal sacs indicates the capacity to regulate the flow of odorant molecules over the sensory epithelium, possibly through a pump-like mechanism associated with gill ventilation. The organization of the olfactory organ in guppy is simple and reminds what is found in early posthatching stages of fish which at the adult state have a well developed olfactory organ. This simple organization supports the idea that the guppy rely on olfaction less than other fish species provided with more extended olfactory receptorial surface.     

Healing of cutaneous wounds in a freshwater teleost, Labeo rohita: scanning electron microscopical investigation

In this study, healing of cutaneous wounds in Labeo rohita using scanning electron microscope is reported. Wound area could be divided into three regions. Immediately after infliction of wound, edges retract exposing underlying tissues in wound gap (Region I). Simultaneously, at region close to wound edge (Region II), mucous goblet cell openings are observed with copious mucous secretions. Within 1 h, Region I gets covered by mucous secretions, and epidermis at edges starts migrating. Opposing fronts gradually advance and by 4-6 h come in contact to epithelialize wound gap. Zone of contact of fronts is demarcated by epidermal ridge, which is relatively prominent at 8 h. It gradually diminishes and is not distinguished at 24 h and afterward. At 1-4 h, microridges on epithelial cell surfaces appear irregularly arranged, widely spaced, short with abrupt ends at Region I; relatively extensive at Region II; and similar to those in controls at region surrounding Region II (Region III). At 12 h and afterward, microridges appear similar to those in controls at Regions I and II. At 1-2 h, isolated swollen epithelial cells, often in process of detachment and exfoliation at surface, are observed at Regions I and II. Such cells are infrequent at 8 h and afterward. Region I covered by migrated epidermis appears trough like at 4 h to 2 days, level of which gradually rises and at Day 4, surface of epidermis appears at a level similar to that at Regions II and III. Changes have been associated with the imbalance of osmotic homeostasis due to disruption of barrier between internal and external environment of skin.     

Scanning electron microscope investigation on the process of healing of skin wounds in Cirrhinus mrigala

Present scanning electron microscope study, reports healing of excised skin wounds in Cirrhinus mrigala. Healing process of wounds, inflicted on head skin, using biopsy punch was observed at intervals—0 hour (h), 1, 2, 4, 6, 12 h, 1 day (d) 2 and 4 d. Accumulation of mucus in wound region within 1h after infliction of wound has been considered an immediate measure to provide protection to injured skin from microbial invasion and other external environmental hazards. On infliction of wound, mobilization of epithelial cells at wound edge is associated with disturbance of coaptive relationship of epithelial cells till original coaptive stability is reached. At 6–12 h appearance of epidermal ridge in region of contact of migrating fronts is due to piling up of epithelial cells. This is associated with cessation of migration of epithelial cells and their simultaneous continual arrival in the region. Speedy epithelialization of skin wounds in C. mrigala like in other fishes, compared to that of mammals and other higher vertebrates, is possibly facilitated owing to surrounding wet external environment. Microridges in initial stages of wound healing appear fragmented without particular orientation. Further, epithelial cells in epithelium in wound region and in region adjacent to wound elongate. These changes are associated with the stretching of epithelial cells indicating their streaming and migration, toward wound. Presence of superficial neuromasts, smallest functional units of lateral line system, a hydrodynamic sensory system, has been associated with important functional significance in fish.     

Fine structural aspects of secretion and extrinsic innervation in the olfactory mucosa.

The mucus at the surface of the olfactory mucosa constitutes the milieu in which perireceptor events associated with olfactory transduction occur. In this review, the ultrastructure of olfactory mucus and of the secretory cells that synthesize and secrete olfactory mucus in the vertebrate olfactory mucosa is described. Bowman's glands are present in the olfactory mucosa of all vertebrates except fish. They consist of acini, which may contain mucous or serous cells or both, and ducts that traverse the olfactory epithelium to deliver secretions to the epithelial surface. Sustentacular cells are present in the olfactory epithelium of all vertebrates. In fish, amphibia, reptiles, and birds, they are secretory; in mammals, they generally are considered to be "non-secretory," although they may participate in the regulation of the mucous composition through micropinocytotic secretion and uptake. Goblet cells occur in the olfactory epithelium of fish and secrete a mucous product. Secretion from Bowman's glands and vasomotor activity in the olfactory mucosa are regulated by neural elements extrinsic to the primary olfactory neurons. Nerve fibers described in early anatomical studies and characterized by immunohistochemical studies contain a variety of neuroactive peptides and have several targets within the olfactory mucosa. Ultrastructural studies of nerve terminals in the olfactory mucosa have demonstrated the presence of adrenergic, cholinergic and peptidergic input to glands, blood vessels, and melanocytes in the lamina propria and of peptidergic terminals in the olfactory epithelium. The neural origins of the extrinsic nerve fibers and terminals are the trigeminal, terminal, and autonomic systems.     

Ultrastructural characteristics of the lung of <i>Melanophryniscus stelzneri stelzneri</i> (Weyenberg, 1875) (Anura,Bufonidae)

The lung of the toad, Melanophryniscus stelzneri stelzneri was studied using scanning and transmission electron microscopy. In M.s.stelzneri the parenchyma forms a polygonal network arrangement, therefore the parenchyma is edicular. These spaces are delimited by the interconnection of third order septa which are covered by respiratory epithelium. Small patches of ciliated epithelium without goblet cells appear irregularly distributed on the septa. The respiratory epithelium consists of one type of pneumocyte, which shows characteristics of both type I and type II alveolar cells of higher vertebrates. The pneumocytes are irregular in shape and possess attenuated cytoplasmic processes, which spread around the capillaries to form the outer layer of the air-blood barrier. These cells contain different types of cytoplasmic bodies: electron dense bodies, multivesicular bodies and lamellar bodies. Dense bodies are probably the precursors of lamellar bodies and the multivesicular bodies are incorporated into the latter. Neuroepithelial bodies appear randomly distributed over the septa. These bodies are separated from the lumen of the lung by thin cytoplasmic processes of neighbouring pneumocytes. The air-blood barrier consists of three layers: epithelium, interstitial space and endothelium.
The relatively simple pulmonary structure of M.s.stelzneri is due to a lower degree of partitioning of the pulmonary lumen in comparison to the lung of other bufonid anurans, could be correlated with a well developed cutaneous and buccopharingeal respiration. The testing of this hypothesis awaits further studies.     

Gustatory ultrastructures of an amphihaline migratory fish hilsa Tenualosa ilisha

This study was conducted with the tongue samples of different life stages of hilsa, that is, adult Marine hilsa, adult Riverine hilsa, and Riverine juvenile hilsa, respectively. Three types of taste buds (Types I, II, and III based on their elevation from the epithelium at different levels) of the tongue, which may be to ensure full utilization of the gustatory ability of the fish were rocorded. Presence of specific taste buds indicate that the fish hilsa dwells in turbid waters with a possible preference toward diatom like planktonic food source. Enhanced expression of taste receptors (T1R1 and T1R3) and associated stimulatory G‐proteins subunits on tongue also indicate occurrence of amino acid like substances that guided sensory cues for feeding by this fish. A firm regularity or stringency of the free surface of the epithelial cells may be attributed to compactly arranged microridges. These structures protect against physical abrasions potentially caused during food manoeuvring and swallowing. In our present observations, the surface architectures of the tongue of hilsa are discussed within the background of migratory adaptation of the species in the context of feeding and habitat preferences.     

The microstructure of buccal cavity and alimentary canal of Siganus rivulatus: Scanning electron microscope study

The microstructure of the oral cavity and alimentary canal of herbivorous fish Siganus rivulatus collected from the Red Sea were investigated by using scanning electron microscope (SEM). The results showed that S. rivulatus has three types of teeth, tri‐cusped, bi‐cusped, and papilliform. A taste bud (Type I) was recorded in the oropharyngeal cavity. Characteristic styles of microridges on the cell's surface inside the buccal cavity were recorded. Also, the distribution of the mucous cells in the lining of the mouth cavity, alimentary canal was observed. Mucosal folds along the distinct parts of alimentary canal, showed characteristic pattern which was complex in the intestinal mucosa. The results concluded that there are characteristic microstructures according to feeding habitat compared with other bony fishes.     

Microscopic study of certain age-related structural changes of maxillary sinus lining epithelium in albino rats

Mucociliary clearance is essential to maintain the defense function of the maxillary sinus; however, no literatures described the age changes in its lining epithelium. Therefore, the current work sought to describe the morphological postnatal age-related changes of maxillary sinus lining epithelium in rats using light, transmission, and scanning electron microscopes. Eighteen albino rats were divided into six groups according to their ages: 2-week-old, 1-month-old, 2-month-old, 3-month-old, adults, and senile rats. One-month-old-rats' group was the first to have recognizable maxillary sinus cavities that were lined by either single flat cellular layer or two distinct epithelial layers. These cells were devoid of microvilli and cilia, none of them showed evidence of differentiation into identifiable cell types. In 2- and 3-month-old rats, the mucosa of maxillary sinus started to be lined with pseudostratified epithelium with apparent increase in both microvilli and cilia. The first indication of goblet cell differentiation was observed in 3-month-old-rats. In the adult rats, the sinuses became completely lined by mature respiratory epithelium. However, in senile rats the epithelium exhibited polyps with clumped cilia and some areas of stratification and desquamation. Goblet cells were scanty and degenerating. The impaired mucociliary components (epithelium, cilia, and goblet cells' mucus) found in young and old ages of the current work might be correlated to human to explain predisposition of rhino-sinusitis in these age groups.     

Cell proliferation and apoptosis in gill filaments of the lucinid Codakia orbiculata (Montagu, 1808) (Mollusca: Bivalvia) during bacterial decolonization and recolonization

The shallow-water bivalve Codakia orbiculata which harbors gill-endosymbiotic sulfur-oxidizing γ-proteobacteria can lose and acquire its endosymbionts throughout its life. Long-term starvation and recolonization experiments led to changes in the organization of cells in the lateral zone of gill filaments. This plasticity is linked to the presence or absence of gill-endosymbionts. Herein, we propose that this reorganization can be explained by three hypotheses: (a) a variation in the number of bacteriocytes and granule cells due to proliferation or apoptosis processes, (b) a variation of the volume of these two cell types without modification in the number, and (c) a combination of both number and cell volume variation. To test these hypotheses, we analyzed cell reorganization in terms of proliferation and apoptosis in adults submitted to starvation and returned to the field using catalyzed reporter deposition fluorescence in situ hybridization, immunohistochemistry, and structural analyses. We observed that cell and tissue reorganization in gills filaments is due to a variation in cell relative abundance that maybe associated with a variation in cell apparent volume and depends on the environment. In fact, bacteriocytes mostly multiply in freshly collected and newly recolonized individuals, and excess bacteriocytes are eliminated in later recolonization stages. We highlight that host tissue regeneration in gill filaments of this symbiotic bivalve can occur by both replication of existing cells and division of undifferentiated cells localized in tissular bridges, which might be a tissue-specific multipotent stem cell zone.     

Goblet cell number in the ileum of rats denervated during suckling and weaning.

The enteric nervous system plays a role on the stimulation of secretory cells of intestinal epithelia. We have demonstrated that ablation of ENS stimulates epithelial cell proliferation. As goblet cells are important constituents of the epithelial sheet, it is mandatory to investigate separately this cell type. The myenteric plexus of the ileum of rats in postnatal development was partially removed by the serosal application of benzalkonium chloride (BAC). Three groups of animals were used: those where BAC application was at 13 days and sacrifice was at 15 (13/28-day-old) or 23 days after treatment (13/36-day-old), and those where BAC was applied at 21 days and rats were killed 15 days after treatment (21/36-day-old) . The number of goblet cells in the ileum was estimated in sections stained by periodic acid-Schiff (PAS) histochemistry. In the 13/28 and 21/36 groups, the number of goblet cells was significantly higher after BAC treatment. These results suggest that the myenteric denervation may have an acute effect on the number of goblet cell in suckling and weanling rats, probably through submucous plexus.     

Ultrastructural neurobiology of the olfactory mucosa of the brown trout, Salmo trutta.

This paper describes four investigations of the olfactory mucosa of the brown trout: 1) the ultrastructure of the olfactory mucosa as revealed by scanning (SEM), conventional transmission (TEM), and high voltage (HVEM) electron microscopy; 2) light and electron-microscopic investigations of retrograde transport of the tracer macromolecule horseradish peroxidase (HRP) when applied to the cut olfactory nerve; 3) SEM and TEM investigations of the effects of olfactory nerve transection on cell populations within the olfactory epithelium; and 4) ultrastructural investigations of reversible degeneration of olfactory receptors caused by elevated copper concentrations. The trout olfactory epithelium contains five cell types: ciliated epithelial cells, ciliated olfactory receptor cells, microvillar olfactory receptor cells, supporting cells, and basal cells. The ciliated and microvillar olfactory receptor cells and a small number of basal cells are backfilled by HRP when the tracer is applied to the cut olfactory nerve. When the olfactory nerve is cut, both ciliated and microvillar olfactory receptor cells degenerate within 2 days and are morphologically intact again within 8 days. When wild trout are taken from their native stream and placed in tanks with elevated copper concentrations, ciliated and microvillar cells degenerate. Replacement of these trout into their stream of origin is followed by morphologic restoration of both types of olfactory receptor cells. Ciliated and microvillar receptor cells are primary sensory bipolar neurons whose dendrites make contact with the environment; their axons travel directly to the brain. Consequently, substances can be transported directly from the environment into the brain via these "naked neurons." Since fish cannot escape from the water in which they swim, and since that water may occasionally contain brain-toxic substances, the ability to close off--and later reopen--this anatomic gateway to the brain would confer a tremendous selective advantage upon animals that evolved the "brain-sparing" capacity to do so. Consequently, the unique regenerative powers of vertebrate olfactory receptor neurons may have their evolutionary origin in fishes.     

Scanning electron microscopic and histological studies of the buccal cavity of a phytoplanktivorous small freshwater fish,Amblypharyngodon mola

The electron microscopic and histological studies of the buccal‐cavity of herbivorous fish Mola (Amblypharyngodon mola) were performed. The studies revealed that the architectures of the buccal cavity of A. mola support the herbivory nature of the fish. Both the upper and lower jaws of the fish are rich in mucus glands, unculi, and microridges. The presence of papillae like taste buds in the lower jaw of A. mola indicates the mechanosensory role of the lower jaw during gustation. These features directly support a gustatory feeding behavior associated with filter feeding in this small freshwater fish.     

Light and scanning electron microscopic features of the tongue in cattle egret

Adult individuals of both sexes were sacrificed by decapitation and their tongues were teared out in order to be investigated. Cattle egret's tongue is distinguished into the apex, body, and root regions. A shallow median sulcus is apparently noticed on the dorsal surface of the tongue's body only. Histologically, the tongue mucosa is covered with a thick parakeratinized epithelium. The dorsal epithelia of the apex and body are densely packed with exfoliated superficial cells. However, the dorsal surface showed microridges observed on the surface epithelial cells. In the body region, the gland's outlets are integrated in glandular patches on the top of keratinized folds at both sides of the median sulcus. The ventral surface of the tongue is devoid of any glandular outlets. The egret's tongue is supported by a paraglossum cartilage wrapped up with a fibrous perichondrium and striated muscle fibers. It extends ventrally as paraglossale apex then flattened in the body giving the corpus paraglossale which bifurcates caudally in the root giving paraglossalis caudalis. The tongue exhibits certain features that are unique as an adaptation to food intake, the type of food, lifestyles and bird's habitat with no any sex‐specific differences. Microsc. Res. Tech. 79:595–603, 2016. © 2016 Wiley Periodicals, Inc.     

In vitro confocal imaging of the rabbit cornea

We were able to observe in vitro the fine structure of the rabbit cornea using a laser scanning confocal microscope, especially in the regions between Descemet's membrane and the epithelial basal lamina. We observed submicrometre filaments throughout the stroma with high concentrations adjacent to Descemet's membrane, and found extensive interconnecting processes between stromal keratocytes. There are numerous regions containing nerve plexuses in the stroma. We found a deeply convoluted basal lamina adjacent to the epithelium, and observed regions containing junctions between endothelial cells in fluorescent images of rabbit corneas stained with the actin-specific compound fluorescein phalloidin.     

Biological aspects of the nasal turbinates of the Anatolian shepherd dog captured from Egypt: Using computed tomography,histological, and scanning electron microscopic observations

The current study was designed to describe the nasal turbinates of 15 heads of Anatolian shepherd dogs using the histology and scanning electron microscope. The caudal part of the nasal cavity is almost occupied by the ethmoidal concha that is related to the high dog's smelling. Keratinized stratified squamous epithelial lining of the rostral part of dorsal and ventral concha were interdigitated with the underlying lamina propria, with numerous sebaceous and sweat glands. The pseudostratified squamous epithelium lining of the middle part of the dorsal and ventral conchae had simple seromucous glands. The caudal third of dorsal, ventral, and ethmoidal conchae covered by olfactory epithelium that had three cell types; basal, supporting, and bipolar cells with mucous glands. SEM of the vestibular region shows that the dorsal conchae had a wrinkled surface with microvilli, little olfactory buds, and small sebaceous and sweat glands openings, while the ventral conchae had a lot of filiform-like microvilli. SEM of the respiratory region shows that the dorsal conchae had a little number of seromucous glands and a rosette-shape cilia, while the ventral conchae had numerous cellular cilia that cover all surface. SEM of the fundus region shows that the dorsal conchae had numerous microvilli of ciliated olfactory cells, while the ventral conchae had numerous long microvilli of ciliated olfactory cells. SEM of the ethmoidal nasal conchae shows a dense network of long microvilli of ciliated olfactory cells. We concluded that the morphological features of the dog's nasal turbinates were correlated with their environmental condition.