Morphological specializations of the buccal cavity in relation to the food and feeding habit of a carp Cirrhinus mrigala: A scanning electron microscopic investigation

The buccal cavity of an herbivorous fish, Cirrhinus mrigala, was investigated by scanning electron microscopy to determine its surface ultrastructure. The buccal cavity shows significant adaptive modifications in relation to food and feeding ecology of the fish. The buccal cavity of the fish is of modest size and limited capacity, which is considered an adaptation with respect to the small‐sized food items primarily consumed by the fish that could be accommodated in a small space. Modification of surface epithelial cells, on the upper jaw, into characteristic structures—the unculi—is considered an adaptation to browse or scrap, to grasp food materials, e.g., algal felts, and to protect the epithelial surface against abrasions, likely to occur during their characteristic feeding behavior. Differentiation of the highly specialized lamellar organ on the anterior region of the palate could be an adaptation playing a significant role in the selection, retention, and sorting out of palatable food particles from the unpalatable items ingested by the fish. The filamentous epithelial projections and the lingulate epithelial projections on the palatal organ in the posterior region of the palate are considered to serve a critical function in final selection, handling, maneuvering, and propelling the food particles toward the esophagus. The abundance of different categories of taste buds in the buccal cavity suggests that gustation is well developed and the fish is highly responsive in the evaluation and the selection of the preferred palatable food items. The secretions of mucous cells in the buccal cavity are associated with multiple functions—particle entrapment, lubrication of the buccal epithelium and food particles to assist smooth passage of food, and to protect the epithelium from possible abrasion. These morphological characteristics ensure efficient working of the buccal cavity in the assessment of the quality and palatability of ingested food, their retention and transport toward the esophagus. Such an adaptation may be essential in conducting the function most basic to the survival of the individuals and species—feeding. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Comparative pharmacology of feeding in molluscs

1. This paper reviews the role of transmitters in identified neurons of gastropod molluscs in generating and modulating fictive feeding. 2. In Lymnaea and Helisoma the 3 phase rhythm is generated by sets of interneurons which use acetylcholine for the N1 (protraction) phase, glutamate for the N2 (rasp) phase interneurons. The N3 interneurons are likely to use several different transmitters, of which one is octopamine. 3. In all the species examined, serotonin (5-HT) is released from giant cerebral cells. Other amines, including dopamine and octopamine, are present in the buccal ganglia and all these amines activate or enhance feeding. 4. Nitric oxide (NO), mostly originating from sensory processes, can also activate fictive feeding, but (at least in Lymnaea) may also be released centrally from buccal (B2) and cerebral neurons (CGC). 5. The central pattern generator for feeding is also modulated by peptides including APGWamide, SCP(B) and FMRFamide. 6. There is increasing evidence that most of these transmitters/modulators act on feeding neurons through second messenger systems--allowing them to act as longer-lasting neuromodulators of the feeding network. 7. Many of the transmitters are used in similar ways by each of the gastropods examined so far, so that their function in the CNS seems to have been conserved through evolution.     

The distribution and function of mucous cells and their secretions in the alimentary tract of Arrhamphus sclerolepis krefftii

The mucosa of the mouth, pharynx, oesophagus and rectum of Arrhamphus sclerolepis krefftii contain saccular mucous cells and the lining of the intestinal mucosa contains goblet mucous cells. Saccular mucous cells in the buccal epithelium are present in relatively low densities and contain acidic and neutral glycoprotein-secreting cells in an approximately 1:1 ratio. The saccular mucous cells in the mucosa of the pharynx, oesophagus and rectum are abundant and contain acidic glycoprotein which consists principally of sialomucin with traces of sulphomucin distributed around the periphery of the mucous vacuoles. Goblet cells in the intestinal mucosa contain neutral glycoprotein. Mechanically digested plant material within the lumen of the gut is bound by a sheath of acidic glycoprotein which is in contact with the intestinal mucosa. From these observations and with information on the known properties of acidic glycoproteins, a novel mechanism for the involvement of mucus in the extraction of nutrients from plant material mechanically digested by fish is proposed.     

Regulation of diurnal filter feeding by a novel gill structure in Amblypharyngodon melettinus (Teleostei,Cyprinidae)

A unique gill structure, apparently associated with filter feeding on phytoplankton and suspended microdetritus, has been found in Amblypharyngodon melettinus, an abundant small Cyprinidae of Sri Lanka. The gill lamellae, the site of gas exchange, are bordered by a double row of fine appendices which are spread over the interlamellar gaps during daytime, but folded up at night. A respiratory function of the appendices can be excluded. The changing position of appendices correlates with the diurnal pattern of feeding (day) and swimming (night). The mechanism for movement of the appendices consists of hinge-like joints formed from the basement membranes of pavement cells, driven by variation in lamellar blood pressure. Food collection is based on both an efficient hydrosol filter produced by dense populations of clavate mucous cells of the buccopharyngeal epithelia and the lamellar appendices which cause a slower and more turbulent water current in the buccopharyngeal cavity. This may ensure the proper contact of food particles with the sticky mucous surface before they leave the buccopharyngeal cavity. The uniqueness of this structure is that the filter can be switched off during periodically occurring periods of high oxygen demand (high swimming activity at night) probably benefiting the process of respiration.     

Feeding and territorial behavior of Paralvinella sulfincola, a polychaete worm at deep-sea hydrothermal vents of the Northeast Pacific Ocean

Behavioral adaptations to the severe nature and high faunal densities of hydrothermal vent habitats have received little attention from researchers. In this study, video and digital still imagery were analyzed to document the feeding and general behavior of the polychaete Paralvinella sulfincola at deep-sea vents on the Juan de Fuca ridge (North-East Pacific). This worm lives in mucous tubes on the actively growing portions of sulphide mineral chimneys and is considered to be the pioneering macrofaunal species in this habitat. We identified 6 recurrent behavior patterns, including antagonistic territoriality between neighboring conspecifics. The latter likely explains the regular spatial distribution of P. sulfincola populations on the substratum they colonize, and the observed confinement of feeding and exploration activities to a definable territory around the tube opening. Territory size, territorial overlap and density were significantly related to body weight, further supporting the importance of size and aggressive encounters in the maintenance of the worm's feeding area. During feeding, P. sulfincola uses its buccal tentacles to gather particles from the substratum using two different capture modes: seizing single macro-particles and aggregation of small particles.     

The mechanism of ultraplanktonic entrapment in anuran larvae

Tadpoles of several different genera were fed graded suspensions of uniform polystyrene particles to determine the lower size limit of particles that could be ingested. Certain tadpoles can extract suspended particles as small as 0.126 μ in diameter from the water. In terms of particle size, this is an efficiency comparable to the best mechanical sieves that can currently be produced by man. A mechanism for ultrasplanktonic entrapment is proposed on the basis of scanning electron micrographs of the secretory ridges in the branchial food traps of Rana catesbeiana before and after feeding. Xenopus tadpoles in yeast suspensions modify their clearance and buccal pumping rates in response to varying food concentrations. This may be an adaptation for maintaining a constant input of food mass to the tissues that extract the food from the water. Variability in the lower size limit of filterable particles among tadpoles of different genera correlates with the availability of suspended matter in the microhabitat where these tadpoles may be found.     

Drilling in the dorid species Vayssierea cf. elegans (Gastropoda: Nudibranchia): Functional and comparative morphological aspects

The drilling mode of feeding is known from two clades of Gastropoda: Caenogastropoda and Heterobranchia. However, the level of convergence and parallelism or homology among these two lineages is unclear. The morphology of the buccal complex is well studied for drilling caenogastropods, but poorly known for drilling nudibranchs. It is also unclear whether the drilling feeding mechanism is similar between inside gastropods. Accordingly, a comparison between the feeding mechanisms of drilling nudibranchs and caenogastropods can help to understand the evolutional trends inside gastropods. In this study, we redescribe the morphology of the buccal complex of drilling dorid nudibranch Vayssierea cf. elegans, and compare it to that of previous investigations on this species and closely related dorid species. We describe the feeding mechanism of this species based on the obtained morphological and literature data and compare it to the feeding mechanisms described for drilling caenogastropods. The feeding apparatus of Vayssierea cf. elegans corresponds to the general morphology of the dorid buccal complex; that is, it has a similar arrangement of the buccal musculature and pattern of radular morphology. However, there are also adaptations to the drilling feeding mode similar to those found in Caenogastropoda: that is, specialized dissolving glands and lateral teeth with elongated pointed cusps; and even Sacoglossa: the specialized muscle for sucking. The feeding process of Vayssierea cf. elegans includes the same two stages as those described for drilling caenogastropods: (a) the boring stage, which is provided by mechanical and chemical activity, and (b) the swallowing stage.     

Peptide secretion in the cutaneous glands of South American tree frog Phyllomedusa bicolor: an ultrastructural study

The development of the dermal glands of the arboreal frog Phyllomedusa bicolor was investigated by immunocytochemistry and electron microscopy. The 3 types of glands (mucous, lipid and serous) differed in size and secretory activity. The mucous and serous glands were apparent in the tadpole skin, whereas the lipid glands developed later in ontogenesis. The peptide antibiotics dermaseptins and the D-amino acid-containing peptide opioids dermorphins and deltorphins are abundant in the skin secretions of P. bicolor. Although these peptides differ in their structure and activity they are derived from precursors that have very similar preproregions. We used an antibody to the common preproregion of preprodermaseptins and preprodeltorphins and immunofluorescence analysis to show that only the serous glands are specifically involved in the biosynthesis and secretion of dermaseptins and deltorphins. Scanning and transmission electron microscopy revealed that the serous glands of P bicolor have morphological features, especially the secretory granules, which differ from those of the glands in Xenopus laevis skin.     

Role of the giant serotonin-containing cell of the cerebral ganglion in the edible snail in organizing its food-acquiring behavior

By adding dopamine or serotonin to a bath with snail's isolated nervous system and by intracellular activation of giant cerebral serotonergic cells it was established in neurophysiological experiments that, in spite of activating effect of serotonin on buccal motorneurones, dopamine is the transmitter triggering feeding movements of the buccal mass and feeding pattern in buccal motorneurones. This conclusion is confirmed by behavioural experiments in which an experimental group was injected by neruotoxin 5,6-dihydroxytryptamine selectively impairing serotonergic neurones. The consumatory phase of feeding (triggered by dopamine) did not change in treated animals, while the appetitive phase was significantly impaired. It was noted that the giant metacerebral cell was activated during burst activity in buccal motoneurones. The conclusion is made that giant serotonergic cerebral cells only modulate but do not trigger the feeding behaviour in the snail Helix lucorum.     

Non-respiratory podia of clypeasteroids (Echinodermata,Echinoides): II. Diversity

Summary There are five major types of non-respiratory podia in the Order Clypeasteroida: accessory, barrel-tipped, food groove, large food groove, and buccal. The anatomy of each type is intimately related to its function in the feeding mechanism of clypeasteroids. Accessory podia are found aborally and orally in some species, only aborally and ambitally in others. Accessory podia are largely sensory and manipulatory, but can be locomotory in the small fibulariids and juvenile sand dollars. Barrel-tipped podia have expanded disk muscles and connective tissue, and are usually found in two sizes, large and small. In species that have them they are usually restricted to the oral surface. These podia collect food and pass it towards the food grooves in the manner of a bucket brigade. Food groove podia are found only in species with food grooves. These podia are small, with reduced tip musculature and expanded secretory tissue for coating food with mucus. They transport food down the food grooves to the mouth. Large food groove podia are simply large versions of ordinary food groove podia. They help move the clumped food into the mouth area towards the buccals, and are found only in the Clypeasteridae and some scutellines. Buccal podia lack tip musculature, but possess tip support fibres and a single type of small secretory cell. They are sensory, and capable of manipulating particles into the mouth. Buccals are present in all families except the Clypeasteridae. Juvenile Echinarachnius less than 3 mm in diameter have only respiratory, accessory and buccal podia. Food groove and barrel-tipped podia start to differentiate from the accessories as the juvenile approaches a diameter of 4 to 5 mm. Clypeasteroid podial diversity increases the efficiency of the food collecting mechanism. The anatomy and distribution of podia on the oral surface of scutellines supports the fact that this surface is the prime food collecting area in all true sand dollars. The podia (not miliary spines) are the major source of mucus used during the feeding process and are the primary feeding appendages.     

Morphologic diversity of the minor salivary glands of the rat: fertile ground for studies in gene function and proteomics

In this article the locations and histologic and ultrastructural features of all of the minor salivary glands of the rat are presented; similarities and differences among them are highlighted. These glands are almost as diverse morphologically as the major salivary glands of the rat. The acini of von Ebner's glands are serous; those of the anterior and posterior buccal glands and minor sublingual glands are mucous; and those of the glossopalatal, palatal, and Weber's glands are mucous with serous demilunes. The anterior buccal, minor sublingual and von Ebner's glands have striated and stratified columnar ducts, while only the minor sublingual and von Ebner's glands have intercalated ducts. The glossopalatal, palatal, posterior buccal and Weber's glands have none of these ducts; the tubulo-acini drain abruptly into short terminal ducts composed of stratified squamous epithelium. All of the mucous acini react with an antibody to a mucin (Muc19) of the rat major sublingual gland, but in some of the glands the reaction varies in intensity among the acinar cells. Ultrastructurally, the mucous secretory granules of the anterior buccal, glossopalatal, palatal and Weber's glands are biphasic, while those of the minor sublingual and posterior buccal glands are monophasic. Although there is a considerable body of literature concerning the development, innervation, physiology and proteomics of von Ebner's glands, investigation of the other minor salivary glands of the rat ranges from modest to nearly nonexistent.     

Morphologic diversity of the minor salivary glands of the rat: fertile ground for studies in gene function and proteomics

In this article the locations and histologic and ultrastructural features of all of the minor salivary glands of the rat are presented; similarities and differences among them are highlighted. These glands are almost as diverse morphologically as the major salivary glands of the rat. The acini of von Ebner's glands are serous; those of the anterior and posterior buccal glands and minor sublingual glands are mucous; and those of the glossopalatal, palatal, and Weber's glands are mucous with serous demilunes. The anterior buccal, minor sublingual and von Ebner's glands have striated and stratified columnar ducts, while only the minor sublingual and von Ebner's glands have intercalated ducts. The glossopalatal, palatal, posterior buccal and Weber's glands have none of these ducts; the tubulo-acini drain abruptly into short terminal ducts composed of stratified squamous epithelium. All of the mucous acini react with an antibody to a mucin (Muc19) of the rat major sublingual gland, but in some of the glands the reaction varies in intensity among the acinar cells. Ultrastructurally, the mucous secretory granules of the anterior buccal, glossopalatal, palatal and Weber's glands are biphasic, while those of the minor sublingual and posterior buccal glands are monophasic. Although there is a considerable body of literature concerning the development, innervation, physiology and proteomics of von Ebner's glands, investigation of the other minor salivary glands of the rat ranges from modest to nearly nonexistent.     

Observations on the feeding mechanism, diet and digestive physiology of Histriobdella homari Van Beneden 1858: an aberrant polychaete symbiotic with North American and European lobsters.

1. The aberrant annelid Histriobdella homari (Polychaeta:Eunicida) lives in the branchial chambers of the marine lobsters Homarus americanus and H. vulgaris where it feeds on the rich microflora of bacteria, blue-green algae and related organisms which grow on the inner surface of the branchial chamber, the setae fringing the edges of the carapace, the gill filaments and, especially, the surfaces and setae of the epipodite plates between the gills. H. homari, therefore, is to be regarded as an epizoic microphagous cleaning symbiote of the lobsters. 2. The alimentary canal consists of mouth, buccal cavity, oesophagus, proventriculus, stomach, intestine and anus. The much-modified proboscis lies ventrally below the oesophagus and proventriculus, with its anterior portions protruding into the rear of the buccal cavity. 3. The proboscis consists of two fixed parallel mandibles, a transverse carrier which slides upon the mandibles and to which is attached, posteriorly, a median flexible dorsal rod and, anteriorly, four pairs of movable articulated maxillae, paired external and internal retractor muscles and various tensor, flexor and extensor muscles. 4. Contraction of the retractor muscles withdraws the carrier and maxillae posteriorly, causing bowing of the dorsal rod which is fixed at its posterior end. Relaxation of the muscles allows the rod to straighten and, thus, causes protraction of the carrier and protraction and lateral expansion of the maxillae. Contraction and relaxation of the relaxation of the retractor muscles are supplemented by appropriate changes in the other muscular components of the proboscis. 5. During feeding the serrated anterior ends of the mandibles are applied to the food, the maxillae are fully expanded and then dawn ventro-posteriorly toward the mid-line by contraction of the retractor muscles in the effective movement of the feeding mechanism. This draws the food organisms across the anterior ends of the mandibles, detaching them from the substratum and allowing their ingestion by ciliary action. The first pair of maxillae are also capable of independent action and can be used while the remainder of the proboscis apparatus is held in the protracted position. 6. Detached microorganisms are entangled in a sticky mucous secretion from the salivary glands; other salivary secretions provide a transport medium for the clumped particles and a third set contain C-esterases which initiate digestion. 7. Ingested food is held briefly in the proventriculus, then passed to the stomach where gland cells secrete A- and C-esterases which continue and extend the digestion initiated by the salivary C-esterases. 8. Some soluble products of gastric digestion are taken up by absorptive cells in the stomach wall and their digestion is completed intracellularly by enzymes which include beta-glucuronidase. Others pass into the intestine for absorption and completion of digestion by cells similar to the gastric absorptive cells but which lack beta-glucuronidase...     

The diamond-tip rasp

A new nasal rasp has been developed from tungsten-carbide steel and is available in eight different cutting grits. One-hundred rhinoplasties were completed using a single tungsten-carbide steel rasp without evidence of dulling or loss of cutting effectiveness. Both a conventional stainless steel Fomon rasp and the diamond-tip tungsten-carbide steel rasp were wear tested on an accelerator for comparison. The testing involving the conventional stainless steel rasp was discontinued after the removal of 20 mm of bone. At this time, there was severe loading of the instrument with bony debris and there was an apparently complete lack of cutting ability. The test involving the diamond-tip tungsten-carbide steel rasp was electively discontinued after the removal of 300 mm of bone, at which time there was no evidence of either debris loading or diminished cutting effectiveness. The scanning electron microscope photographs of the two instruments support our conclusions regarding the clinical and laboratory studies.     

Ultrastructure of the Feeding Apparatus of Rhabdodemania minima Chitwood, 1936 (Enoplida: Rhabdodemaniidae)

The feeding apparatus of the marine nematode Rhabdodemania minima Chitwood, 1936 has been examined with light and transmission electron microscopy. The buccal capsule consists of a posterior region with smooth walls bearing three sets of three minute denticles at its posterior end and three large onchia in its mid region; a middle region with grooved walls; and an anterior region with costae and six odontia. The anterior and middle portions of the buccal capsule are enveloped by the cephalic cuticle, whereas the posterior region, which is set off from the middle region by a buccal seam, is partially enveloped by the anterior end of the esophagus. Two subventral esophageal glands open into the lumen of the esophagus. Secretions of each of three paraesophageal glands are conveyed through a duct in each of the three corresponding corners of the buccal wall to an opening between labia. A pair of wing-like thickenings, termed pterons, embraces the duct of each paraesophageal gland in the posterior and middle regions of the buccal capsule. A model of how the buccal capsule operates is proposed and tested. Morphological and functional aspects of the buccal apparatus and cephalic cuticle are compared with those of other taxa of the Enoplida, and their phylogenetic implications are discussed.     

Epithelium of lips and associated structures of the Indian major carp,Catla catla

Structural organization of the epithelium of the lips and associated structures of the Indian major carp,Catla catla, is described. The upper lip is thin and is associated on its dorsal side with a membranous fold of skin and the rostral cap. In contrast, the lower lip is thick and very conspicuous. It is associated on its ventral side with a fold of skin between it and the ventral head skin. The lower lip is divided into a non-projectile portion, a projectile portion and an intermediate groove region. The projectile portion remains folded covering a part of the ventral head skin when the mouth is closed. Their role in relation to the formation of the characteristic feeding tube is discussed. The epithelium of the lips and associated structures is stratified in nature and is composed of the epithelial cells, mucous cells, club cells, lymphocytes and the taste buds. The mucous cells are small, few or even absent and do not appear to secrete profusely at the surfaces of the upper and the lower lips. This suggests that the lips inCatla catla, which feeds on micro-organisms, do not need extra lubrication for protection against abrasion during feeding. In the epithelium at the folds of skin, the voluminous mucous cells secrete profusely and provide extra lubrication to their surface. This reduces the resistance to surface drag during stretching and enables the jaws to protrude with increasing efficiency and swiftness. The club cells are developed additionally to complement the mucous cells in the rostral cap and the upper lip epithelium. Their primary function appears protective in some way, which needs further confirmation. The taste buds, though few in the lower lip, are located in a good number in the upper lip on the characteristic epithelial papillae-like projections, and are projected at the surface. These have been associated with the acute gustatory sense of the fish. The taste buds are absent on the folds of skin where they may not be of much significance.