Buccal Cavity (buccal + cavity)

Distribution by Scientific Domains

Selected Abstracts

Ultrastructural study of the jaw structures in two species of Ampharetidae (Annelida: Polychaeta)

ACTA ZOOLOGICA, Issue 3 2004
Alexander B. Tzetlin
Abstract Two species of jaw bearing Ampharetidae (Adercodon pleijeli (Mackie 1994) and Ampharete sp. B) were investigated in order to describe the microanatomy of the mouth parts and especially jaws of these enigmatic polychaetes. The animals of both studied species have 14,18 mouth tentacles that are about 30 µm in diameter each. In both species, the ventral pharyngeal organ is well developed and situated on the ventral side of the buccal cavity. It is composed of a ventral muscle bulb and investing muscles. The bulb consists of posterior and anterior parts separated by a deep median transversal groove. In both species, the triangular teeth or denticles are arranged in a single transversal row on the surface of the posterior part of the ventral bulb just in front of its posterior edge. There are 36 denticles in Adercodon pleijeli and 50 in Ampharete sp. B. The height of the denticles (6,12 µm) is similar in both species. Each tooth is composed of two main layers. The outer one (dental) is the electron-dense sclerotized layer that covers the tooth. The inner one consists of long microvilli with a collagen matrix between them. The thickness of the dental layer ranges from 0.95 to 0.6 µm. The jaws of the studied worms may play a certain role in scraping off microfouling. The fine structure of the jaws in Ampharetidae is very similar to that of the mandibles of Dorvilleidae, the mandibles and the maxillae of Lumbrineridae, Eunicidae and Onuphidae, and the jaws of other Aciculata. This type of jaw is characterized by unlimited growth and the absence of replacement. The occurrence of jaws in a few smaller Ampharetidae is considered as an apomorphic state. [source]

Risks of cancer among a cohort of 23,935 men and women with osteoporosis

Katherine A. McGlynn
Abstract Low hormone levels among persons with osteoporosis may decrease risk of some cancers. Other osteoporosis risk factors, such as smoking and alcohol consumption, however, may increase risk. As these deleterious factors are more often associated with osteoporosis diagnosed prior to age 70 years, cancer risk may be higher in these younger persons than in the general population. To examine this hypothesis, a cohort study of 23,935 persons with osteoporosis was conducted in Denmark. Patients hospitalized with osteoporosis between 1978 and 1993 were identified in the Danish Inpatient Register. Linkage to the Danish Cancer Registry identified all cancer outcomes through 2003. Standardized incidence ratios (SIR) and 95% confidence intervals (95%CI) were calculated to compare cancer incidence in the cohort with that in the general population. Persons diagnosed prior to age 70 years were at increased cancer risk (women: SIR = 1.11, 95%CI = 1.04,1.19; men: SIR = 1.31, 95%CI = 1.13,1.50) due, in part, to increased risks of cancers of the buccal cavity, esophagus, liver, pancreas and lung. Persons diagnosed at ages 70 and older were at decreased risk (women: SIR = 0.91, 95%CI = 0.87,0.96; men: SIR = 0.89, 0.77,1.01) due, in part, to decreased risks of breast, endometrial, colon, rectal and brain cancers in women and prostate cancer in men. These results suggest that risk factors associated with earlier onset osteoporosis may be associated with increased risk of cancer. Conversely, factors associated with later onset osteoporosis may be related to a decreased risk of cancer. © 2007 Wiley-Liss, Inc. [source]

Differential correlates of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae)

M. Linde
Abstract We explore the correlational patterns of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae) from the western Mediterranean Sea. The premaxilla is less variable, and in spite of the presence of species-specific features, a common structural pattern is easily recognizable in all species (i.e. the ascending and the articular processes are fused in a single branch, as in many percoid fishes). In contrast, tooth shape is more variable, and different structural types can be recognized (e.g. canine-like or incisive). Coupling geometric morphometric and comparative methods we found that the relationship between shape, diet and phylogeny also differs between premaxilla and tooth. Thus, the shape of the premaxilla is significantly correlated with food type, whereas the shape of the teeth is not correlated with diet, and probably reflects the species phylogenetic relationships. Two biological roles, resistance against compressive forces generated in the buccal cavity and the size of the oral gape, would explain the ecomorphological patterns of the premaxilla. The premaxilla and anterior tooth appear to evolve at different rates (mosaic evolution) and represent an example of morphological traits belonging to the same functional unit but following uncoupled evolutionary pathways. [source]

Comparative and functional morphology of the buccal cavity of Diplogastrina (Nematoda) and a first outline of the phylogeny of this taxon*

A. Fürst Von Lieven
The Diplogastrina include about 290 species of free living nematodes. Traditional classifications of this taxon are not based upon hypotheses of phylogenetic relationships. The highly variable structures of the buccal cavity were examined in 21 species using light microscopy and SEM. The function of the stomatal structures was studied with the aid of video recordings of living worms. The morphological data were used to reconstruct a first outline of the phylogenetic relationships of the Dipolgastrina. A rhabditoid gymnostomatal tube which is longer than wide, a short stegostom and a small dorsal tooth as in Pseudodiplogasteroides belong to the stem species pattern of Diplogastrina. Diplogastrina with a ,Rhabditis'-like gymnostomatal tube feed on bacteria and small fungal spores. A short and broad gymnostom as well as a right subventral tooth which forms a functional unit with the dorsal tooth were acquired step by step in the ancestral line leading to Mononchoides and Tylopharynx. The cuticularized cheilostom was divided into six plates connected by pliable regions twice independently within the Diplogastrina. The teeth-bearing posterior part of the buccal capsule can move forewards by pushing apart the plates of the cheilostom so that the teeth can get in contact with food items that are too big to be sucked into the buccal cavity. Diplogastrina with a divided cheilostom can feed not only on bacteria, but also on larger fungal spores, ciliates or other nematodes. Tylopharynx is specialized to rip apart the cell wall of fungal hyphae with the movements of a dorsal and a subventral tooth in order to suck out the contents of the fungus. This shows that the transformation of the buccal cavity in Diplogastrina is linked with an expansion of ecological niches. [source]

The highly specialized secretory epithelium in the buccal cavity of the alkalinity adapted Lake Magadi cichlid, Oreochromis alcalicus grahami (Teleostei: Cichlidae): a scanning and transmission electron microscope study

J. N. Maina
Abstract Oreochromis alcalicus grahami is a small cichlid fish that lives in the hot, highly alkaline, highly saline peripheral lagoons of Lake Magadi, Kenya. The fish faces profound diurnal oscillations of oxygen concentration. During the day, from photosynthetic activity of cyanobacteria (blue-green algae), the water is supersaturated with oxygen but after sunset when photosynthetic activity stops the water is virtually anoxic as a result of bacterial respiration. During the night and after explosive exercise, O. a. grahami characteristically skims the surface of the water with the mouth agape, suggesting that the buccal cavity is used as a gas-exchange organ. Contrary to expectation, however, the buccal cavity was found to be conspicuously non-vascularized: the surface epithelial lining was fundamentally of a mucus secretory type. In addition, certain cells in the deeper layers showed extensive lateral labyrinths similar to the epithelium of the renal tubules. These morphological features respectively indicated roles of secreting a protective film and regulation of ions taken across the epithelial lining of the buccal cavity. The allocation of gas-exchange to the gills and the air-bladder, osmoregulation essentially to the gills, and mucus secretion/protection to the buccal cavity displays an adaptive trade-off process in an elite animal. Effective use of the buccal cavity as a gas-exchanger would entail air-gulping followed by brief retention of it in the cavity to allow oxygen uptake. During such interval, both the gills and the air-bladder would of necessity be rendered temporarily non-functional. Skimming the top layer of water with the mouth open ensures that the gills are passively ventilated with well aerated water and the air-bladder is simultaneously used for gas-exchange, a strategy that should enhance oxygen acquisition, especially at higher ambient temperatures. [source]

Morphogenesis in the Marine Spirotrichous Ciliate Apokeronopsis crassa (Claparčde & Lachmann, 1858) n. comb. (Ciliophora: Stichotrichia), with the Establishment of a New Genus, Apokeronopsis n. g., and Redefinition of the Genus Thigmokeronopsis

ABSTRACT. Morphogenetic events during the division of the marine spirotrichous ciliate, Apokeronopsis crassa (Claparčde & Lachmann 1858) n. comb. were investigated. Compared with members of the well-known genera Thigmokeronopsis, Uroleptopsis, and Pseudokeronopsis, A. crassa has one row of buccal cirri, high number of transverse cirri, clearly separated midventral rows, lacks thigmotactic cirri and a gap in adoral zone, its undulating membranes (UMs) anlage forms one cirrus and marginal rows and dorsal kineties form apokinetally during division. All these characteristics indicate that this organism represents a new taxon at the generic level, and hence a new genus is suggested, Apokeronopsis n. g. It is defined as thus: Pseudokeronopsidae with Pseudokeronopsis -like bicorona of frontal cirri and one marginal row on each side; one row of two or more buccal cirri in ordinary position; two midventral rows distinctly separated, hence of cirri that are not in a typical zig-zag pattern; high number of transverse cirri, caudal cirri absent, and frontoterminal cirri present; thigmotactic cirri absent, many macronuclear nodules fuse into many masses as well as marginal and dorsal kineties form apokinetally during morphogenesis. At the same time, the genus ThigmokeronopsisWicklow, 1981 is redefined, and one new combination, Apokeronopsis antarctica (Petz, 1995) n. comb. is proposed. The morphogenetic events of A. crassa are characterized as follows: (1) In the proter, the adoral zone of membranelles and UMs are completely renewed by the oral primordium. The UM anlage is formed apokinetally on the dorsal wall of the buccal cavity and is hence clearly separated from the frontoventral-transverse (FVT) cirral anlagen in the proter. (2) Frontoventral-transverse cirral anlagen are generated de novo in the outermost region of the cortex to the right of the old UMs. (3) A row of buccal cirri arises from FVT cirral streak I. (4) The marginal rows and dorsal kineties originate de novo in both dividers; no caudal cirri are formed. (5) The last FVT-streak contributes two frontoterminal cirri. (6) The many macronuclear nodules fuse into many masses (about 50 segments) during division, unlike a singular or branched mass as described in other urostylids. [source]