bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interspecific, ontogenetic, and life history variation in the tooth morphology of mole salamanders (Amphibia, Urodela, and Ambystomatidae)
Authors: Beneski John T. , Larsen John H. 
Published: February 2005

AbstractAs revealed by scanning electron microscopy, three basic cusp shapes are found on the premaxillary teeth of mole salamanders: disc, cone, and club. In fully metamorphosed adults, tooth crowns are subdivided into labial and lingual cusps. Except for species of Linguaelapsus, the labial cusps of all adult bifid teeth are disc shaped; lingual cusp shape is more variable, but the taxonomic distribution of the various configurations is generally consistent within the subgroups Rhycosiredon, Ambystoma, and Linguaelapsus. The club shape appears to be a derived character state, but the cone and disc shapes may be either primitive or derived. Prior to the start of metamorphosis, all larvae have conical, monocuspid teeth. During metamorphosis these salamanders develop incipient bifid teeth that have the same basic adult pattern of cusp shapes but in which the cusps are smaller and more generalized. Crown morphology in paedomorphic ambystomatids is similar to that of older larvae; as such, paedomorphosis seems to interrupt and retard the ontogenetic sequence of development rather than to introduce (or reintroduce) novel morphologies into the developmental program. In larvae the crown is firmly attached to the tooth base along the putative zone of weakness, but in transformed adults the crown is separated from a pedicel by a narrow zone of fibrous connective tissue. This latter structural arrangement allows unidirectional lingual flexing of the crowns relative to the pedicel and appears to facilitate the process of tooth replacement.
Kinetics of tongue projection in Ambystoma tigrinum: Quantitative kinematics, muscle function, and evolutionary hypotheses
Authors: Reilly Stephen M. , Lauder George V. 
Published: February 2005

AbstractThe projectile tongue of caudate amphibians has been studied from many perspectives, yet a quantitative kinetic model of tongue function has not yet been presented for generalized (nonplethodontid) terrestrial salamanders. The purposes of this paper are to describe quantitatively the kinnematics of the feeding mechanism and to present a kinetic model for the function of the tongue in the ambystomatid salamander Ambystoma tigrinum. Six kinematic variables were quantified from high‐speed films of adult A. tigrinum feeding on land and in the water. Tongue protrusion reaches its maximum during peak gape, while peak tongue height is reached earlier, 15 ms after the mouth starts to open. Tongue kinematics change considerably during feeding in the water, and the tongue is not protruded past the plane of the gape. Electrical stimulation of the major tongue muscles showed that tongue projection in A. tigrinum is the combined result of activity in four muscles: the geniohyoideus, Subarcualis rectus 1, intermandibularis posterior, and interhyoideus. Stimulation of the Subarcualis rectus 1 alone does not cause tongue projection. The kinetic model produced from the kinematic and stimulation data involves both a dorsal vector (the resultant of the Subarcualis rectus 1, intermandibularis posterior, and interhyoideus) and a ventral vector (the geniohyoideus muscle), which sum to produce a resultant anterior vector that directs tongue motion out of the mouth and toward the prey. This model generates numerous testable predictions about tongue function and provides a mechanistic basis for the hypothesis that tongue projection in salamanders evolved from primitive intraoral manipulative action of the hyobranchial apparatus.
Ultrastructure of the basal lamina and its relationship to extracellular matrix of embryos of the starfish Pisaster ochraceus as revealed by anionic dyes
Authors: Crawford B. 
Published: February 2005

AbstractThe ultrastructure of the 51/2–6‐day‐old embryonic asteroid basal lamina (BL) was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and after treatment with anionic dyes. Conventional fixation in glutaraldehyde and osmium reveals a BL consisting of a lamina densa separated from the basal cell surface by a lamina lucida. Little or no reticular lamina is present. Material similar in appearance to the basal lamina extends into the blastocoel, forming an extracellular matrix (ECM). Following fixation in the presence of the dye ruthenium red, proteoglycan (PG) granules are visible in the lamina lucida and immediately beneath the lamina densa. The ECM consists of granules of a similar appearance, which are associated with fibers of an intermediate electron density resembling invertebrate collagen. After fixation in the presence of alcian blue under polyanionic conditions, all aspects of the basal lamina and the ECM stain very densely. The use of alcian blue in 0.3 M MgCl2 (monoanionic condition) or in low concentrations reveals a lamina densa consisting of a fine feltwork and tubule‐like structures. A meshwork composed of thick, densely stained and thinner, intermediately stained strands is embedded in the inner aspect (that adjacent to the blastocoel) of the ectodermal lamina densa. Similar elements are present in the endodermal BL, but the dense material is represented by short regions that do not form a meshwork. The dense and intermediate strands of both basal laminae also extend into the blastocoel as ECM. The tubule‐like structures extend from the dense material of the inner meshwork into the lamina densa. They also cross both the lamina densa and lucida to associatee with the basal cell membranes. The fact that the basal cell surfaces are often puckered outward at the points of contact suggests that this configuration might be providing a means whereby forces can be transferred from the ECM through the basal lamina to the cells.
Ultrastructure of the crayfish antennal gland revealed by scanning and transmission electron microscopy combined with ultrasonic microdissection
Authors: Fuller E. G. , Highison G. J. , Brown F. , Bayer C. 
Published: February 2005

AbstractThe antennal gland of the crayfish Pacifasticus leniusculus was studied using standard techniques for scanning electron microscopy as well as newer procedures for ultrasonic microdissection. To clarify relationships in the nephron tubule, transmission electron microscopy was employed.The coelomosac contains elongated cells (podocytes) displaying microvilli and extensive apical blebbing. A smooth basal lamina lines the blood space that furnishes hemolymph to the coelomosac. The labyrinth consists of tall columnar cells displaying apical microvilli, numerous blebs that seem to represent an expansion of apical plasma membrane, and lateral interdigitations. The nephron tubule consists of two distinctly different areas: a proximal region of flattened cells with extensive intercellular fusions, and a distal segment of separate, dome‐shaped cells.Despite many similarities between the crayfish kidney and the vertebrate nephron, there are striking differences. The amount of surface blebbing that occurs in the coelomosac and labyrinth far exceeds that of the vertebrate nephron and may reflect its importance in the function of the crayfish kidney. The cells of the coelomosac are taller than are the vertebrate podocytes and possess less obvious arms and pedicels. In addition, the proximal segment of the nephron tubule is notable for its intercellular fusions, which are not present in the vertebrate nephron. Although the function of the intercellular fusions is unknown, they may play a role in cellular communication or the redistribution of fluids or electrolytes between cells.
Ultrastructure of the spermatozoon of Megaselia scalaris Loew (Diptera:Brachycera:Cyclorrhapha:Phoridea:Phoridae)
Authors: Curtis Sherill K. , Benner David B. , Musil George 
Published: February 2005

AbstractWhen viewed by scanning electron microscopy (SEM), the spermatozoon of the phorid dipteran Megaselia scalaris appears threadlike, lacking distinct head and tail areas. These areas can be observed, however, in appropriately stained material. Measurements of Feulgen‐stained material reveal average lengths of the head, tail, and total cell of 18.7, 128.7, and 147.4 μm, respectively. When tested for sulfhydryl and disulfide groups, the head displays only disulfide groups. Transmission electron microscopy (TEM) reveals 12 different regions: three (1–3) in the head, four (9–12) in the tail, and five (4–8) in a short zone of overlap between the head and tail. Most of the cell lies in regions 9 and 11 of the tail and 3 of the head, accounting for, respectively, 37.3%, 45.7%, and 11.2% of the total length. A tubelike acrosome indents the anterior end of the nucleus. The tail originates asymmetrically in relation to the long axis of the cell as a peglike structure associated with the dorsolateral region of the nucleus. No centriole is visible, and the nucleus has a notched appearance in longitudinal sections. Two mitochondrial derivatives and an axoneme displaying a 9+9+2 microtubule configuration and ATPase activity extend throughout most of the tail. In regions 9 and 10, an asymmetrically arranged accessory body is also present. Features having possible taxonomic utility include the asymmetrically arranged accessory body, the size and shape of the acrosome, and the notched appearance of the nucleus. The present report is apparently the first to describe the spermatozoon of a cyclorrhaphous dipteran which is not a member of the Schizophora.
Coarctation of the stapedial artery: An unusual adaptive response to competing functional demands in the middle ear of some eutherians
Authors: Diamond Michael K. 
Published: February 2005

AbstractIn primitive eutherians, the stapedial artery is the primary supplier of blood to the nonneural tissues of the head. Beyond a certain body size, the stapedial artery can no longer function as the sole supplier to its original territory because the diameter of its stem is limited by the size of the intercrural foramen of the stapes, which exhibits strong negative allometry. Some eutherians have extended the upper limit that the diameter of the stapedial stem can attain by developing a coarctation (narrowing) at the transcrural portion of the vessel. In the Norway rat (Rattus norvegicus) and the golden hamster (Mesocricetus auratus) the coarctation develops in postnatal life and is evidently caused by a retardation in growth that keeps the diameter of the vessel at infantile dimensions. In the rat, additional reduction in the external diameter is produced by a thinning of the tunica media of the arterial wall. A comfortable gap between the wall of the artery and the sides of the intercrural foramen is maintained that most likely facilitates the attenuation of potentially disruptive low‐frequency vibrations produced by the arterial pressure pulse. The only negative side effect of a coarctation in rat‐sized animals is that resistance to flow is increased and volume flow rate is concomitantly diminished. The coarctation does not create flow disturbances downstream of the constriction. One possible additional benefit of the coarctation is a flattening out of the arterial pressure pulse. It is speculated that the capacity to develop a coarctation once a certain body size is reached is an ancient trait that dates at least as far back as the Early Cretaceous.
Ultrastructure of the attachment cells of the organ of Bellonci in Gammarus setosus (Crustacea, Amphipoda)
Authors: Steele V. J. , Oshel P. E. 
Published: February 2005

AbstractThe structure of the organ of Bellonci indicates that it is a sensory organ able to receive a variety of external stimuli. The suspension of the organ was investigated in the marine amphipod Gammarus setosus by light, scanning, and transmission electron microscopy. The organ is suspended ventrally by a cord whose specialized cuticular attachment is in the roof of a canal under the interantennal angle of the head. The conical end of the cord consists of five epithelial attachment cells sheathed by processes of 21 cells arranged in five tiers inside a basal lamina. The attachment cells end within a knob in the centre of a diaphragm. The cuticular attachment is confined to the knob and consists of endocuticular rods within pits on the surfaces of the attachment cells. Dorsally, the long processes of the attachment cells form a net over the surface of the organ and reunite in the dorsal suspensor, which anchors the organ in the epidermis at the crown of the head. The attachment cells are characterized by extensive hemidesmosomes and dense core granules at both attachment sites and by microtubules that extend through their entire length of up to 1 mm in the adult. The large size, cephalic position, elaborate structure, and suspension of the organ suggest that it is of considerable importance in the sensory capability of aquatic Malacostraca.
Chemical access to the vomeronasal organs of a plethodontid salamander
Authors: Dawley Ellen M. , Bass Andrew H. 
Published: February 2005

AbstractPlethodontid salamanders have unique nasolabial grooves that may function as “capillary tubes” to convey chemicals to the vomeronasal organ when these animals nose‐tap. 3H‐proline was placed at the base of these grooves in Plethodon cinereus, and autoradiography revealed large concentrations of radioactive material in the vomeronasal organs. There was no significant accumulation of radioactive material in the main olfactory epithelium. Salamanders with blocked nasolabial grooves lacked significant accumulation of material in their nasolabial grooves or vomeronasal epithelia, although some salamanders had radioactive material in the posterior portion of their vomeronasal organ that had entered through the internal nares. Anteriorly placed vomeronasal organs situated adjacent to the posterior limits of the nasolabial grooves may insure that nose‐tapping primarily stimulates the vomeronasal sensory epithelium.
Ovarian follicle development during vitellogenesis in the house cricket Acheta domesticus
Authors: Dennis John C. , Bradley James T. 
Published: February 2005

AbstractTo determine the morphological correlates of vitellogenin uptake and distribution, vitellogenic ovarian follicles of Acheta domesticus were examined by light and transmission electron microscopy. Yolk deposition was usually restricted to the terminal follicle of each panoistic ovariole, but if the terminal follicle had completed vitellogenesis and had not yet been ovulated, the penultimate follicle was often vitellogenic. Vitellogenesis occurred only in the ovaries of adults, with follicles representing all stages of vitellogenic development occurring simultaneously within a single ovary. Vitellogenic follicles were 0.75 to >2.0 mm long. The single irregularly shaped nucleus of each follicle cell contained two to three nucleoli. During vitellogenesis the epithelium of individual follicles progressed from columnar to cuboidal to squamous. The distribution of cytoplasmic organelles within individual follicle cells was polarized during early and middle stages of vitellogenesis. Near the end of vitellogenesis, polarity disappeared, the follicular epithelium became squamous, and the frequency of vesicular and multivesicular bodies in the follicle cell cytoplasm increased. A well‐developed capability for follicle cell protein synthesis and secretion throughout vitellogenesis was indicated by abundant rough endoplasmic reticulum and Golgi bodies. Receptor‐mediated endocytotic activity by the follicle cells during all stages of vitellogenesis was suggested by omnipresent coated pits on all surfaces. Septate junctions, gap‐like junctions, and desmosomes all occurred in the lateral membranes, while gap‐like junctions predominated at the oocyte–follicle cell interface. In follicles longer than 1 mm, adjacent follicle cells were separated by intercellular channels that widened to as much as 10 m̈m by the completion of vitellogenesis. The channels contained a flocculent material, and a similar‐appearing material filled the space between the oolemma and follicle cell apical membranes. The oolemma contained a profusion of coated pits throughout vitellogenesis.
Organization of giant interneuron projections in thoracic ganglia of the cockroach Periplaneta americana
Authors: Stubblefield G. Thomas , Comer Christopher M. 
Published: February 2005

AbstractWe have investigated the structural organization of the wind‐sensitive giant interneurons in the thoracic ganglia of adult American cockroaches. These seven bilaterally paired interneurons have long been thought to play a role in directing the wind‐elicited escape response of the animal. Each of the giant interneurons was labeled individually by intracellular injection of cobaltic hexamine chloride. An individual giant interneuron could be reliably identified from animal to animal based on its branching pattern in thoracic ganglia. The axons of the giant interneurons are situated on each side of the nerve cord in two recognizable subgroups. Comparisons of the axonal arbors of the dorsal and ventral subgroups showed that they project into distinct but partly overlapping regions of thoracic ganglia. Three of the giant interneurons were found to have axonal arbors that cross the longitudinal midline of thoracic and abdominal ganglia. Bilateral pairs of these giant interneurons were labeled concomitantly, and many of the individual neurites from these cells appeared to be closely apposed. All these morphological characteristics are discussed in relation to the connectivity and functional significance of the giant interneurons.
Internal anatomy ofHypochthonius rufulus(acari: Oribatida)
Authors: Smrž Jaroslav 
Published: February 2005

AbstractThe internal anatomy of juveniles and adults ofHypochthonius rufulusselected as a model species representing the lower Oribatida was investigated histologically and compared with the published characteristics of higher oribatid internal anatomy. In this species, the cuticle is weak and flexible, consisting of epicuticle and endocuticle on the body, but including an exocuticle between the epicuticle and endocuticle of the legs. Walls of the mesenteron in the digestive tract are of uniform thickness and structure without any regional thickening, and there are no proventricular glands. The hindgut is apparently divided into five parts: colon 1 and 2, rectum 1 and 2, and anal atrium; food bolus exhibits a multilamellar structure in this section. The glandular system is less diversified than in some other oribatids. Tracheae are apparently lacking. Females possess only two relatively large eggs, filling one‐half of opistosoma, and they lack ovipositors. Eggs are present in females during the whole year. Gonad buds appear first in the protonymph stage. Only one male was found among 146 adults studied. No male external organ (aedeagus or penis) is present.
Development of the ethmoidal structures of the endocranium in the anuran Pipa pipa
Authors: Roček Zbyněk , Veselý Milan 
Published: February 2005

AbstractInvestigation of eight developmental stages by means of serial sections and subsequent graphic or wax model reconstructions, as well as by means of cleared‐and‐stained and dissected material, revealed that the ethmoidal endocranium in Pipa pipa consists in early states of a single horizontal ethmoid plate lacking labial cartilages. Later in the course of development, structures comparable with those in other anurans appear, though modified and of reduced size. These adult structures arise from the new cartilaginous tissue located above the former larval ethmoid plate, whereas the latter entirely disappear. This phenomenon can be observed also in P. carvalhoi and in Xenopus laevis; hence, it supposedly occurs in all pipids. On the other hand, in anuran larvae, which develop cornua trabecularum in the ethmoidal region, these persist in adults as part of the nasal septum. Positional and developmental differences suggest that, although the ethmoid plate and the cornua trabecularum arise from the same region of the cranial neural crest, they are not fully corresponding structures. Comparison with adults of other pipid genera confirmed the conclusion of some earlier investigators that P. pipa is the most specialized among pipids.
Morphological differentiation of the müller cell: Golgi and electron microscopy study in the chick retina
Authors: Prada F. A. , Magalhaes M. M. , Coimbra A. , Genis‐Galvez J. M. 
Published: February 2005

AbstractThe sequence of morphological differentiation of Müller cells in the chick retina was investigated in relation to the differentiation of the retinal neurons using the Golgi method. From the beginning of differentiation, the Müller cell develops spurs and lateral processes. Some of these glial processes become transformed into accessory prolongations of the Müller cell. From the 17th or 18th day of incubation, the morphology of the Müller cells is similar to that of the adult retina. On the basis of their inner prolongation, two types of Müller cells were identified. The first type, with diffuse and abundant descending processes, is identical to that described classically. The second type is a cell characterized by sparse and scanty inner ramifications.This report also describes electron microscopic observations of Müller cells and their enwrapping relationship with the axons of the optic nerve fiber layer.
Tectorial structures on the inner ear sensory epithelia of Proteus anguinus (Amphibia, caudata)
Authors: Bulog Boris 
Published: February 2005

AbstractThe tectorial structures of the inner ear of the proteid salamander Proteus anguinus were studied with transmission and scanning electron microscopy in order to analyze the ultrastructure of the otoconial membranes and otoconial masses of the maculae and the tectorial membrane of the papilla amphibiorum. Both otoconial and tectorial membranes consist of two parts: (1) a compact part and (2) a fibrillar part that joins the membrane with the sensory epithelium. Masses of otoconia occupy the lumina above these membranes.There are two types of calcium carbonate crystals in the otoconial masses within the inner ear of Proteus anguinus. The relatively small otoconial mass of the utricular macula occupies an area no greater than the diameter of the sensory epithelium, and it is composed of calcite crystals. On the other hand, the enormous otoconial masses of the saccular macula and the lagenar macula are composed of aragonite crystals. In the sacculus and lagena, globular structures 2–9 m̈m in diameter were discovered on the lower surfaces of the otoconial masses above the sensory epithelia. These globules show a progression from smooth‐surfaced, small globules to large globules with spongelike, rough surfaces. It is hypothesized that these globules are precursors of the aragonite crystals and that calcite crystals develop similarly in the utriculus. The presence of globular precursors in adult animals suggests that the formation of new crystals in the otoconial membranes of the sacculus and lagena of Proteus is a continuous, ongoing process.