bluuebunny/crossref_metadata_2025 huggingface dataset:
The ontogeny of shell secretion in Terebratalia transversa (brachiopoda, articulata) I. Development of the mantle
Authors: Stricker Stephen A. , Reed Christopher G.
Published: February 2005

The morphology of the mantle in free‐swimming and metamorphosing larvae of the articulate brachipod Terebratalia transversa has been examined by scanning and transmission electron microscopy. The mantle begins to form approximately 2 days after fertilization and subsequently develops into a skirtlike lobe that encircles the middle region of the larval body. A simple epithelium covers both the outer surface of the mantle lobe and the inner side situated next to the pedicle lobe of the larva. During metamorphosis, the mantle lobe is everted over the anterior end of the larva. Thus, the epithelium covering the outer part of the mantle lobe in the larva subsequently becomes the inner epithelium of the juvenile mantle. Similarly, the inner epithelium of the larval mantle lobe represents the future outer epithelium of the juvenile mantle. In free‐swimming larvae, the prospective outer mantle epithelium contains two types of cells, called “lobate” and “vesicular” cells. Lobate cells initially deposit a thin layer of amorphous material, and vesicular cells produce ovoid multigranular bodies. Following settlement at about 5 days postfertilization, the vesicular cells secrete an electron‐dense sheet that constitutes the basal layer of the developing periostracum. Within several hours to a day thereafter, reversal of the mantle lobe is rapidly effected, apparently by contractions of the pedicle adjustor muscles.
The mechanism of frill erection in the bearded dragon Amphibolurus barbatus with comments on the jacky lizard A. muricatus (Agamidae)
Authors: Throckmorton Gaylord S. , De Bavay John , Chaffey Wayne , Merrotsy Bruce , Noske Susan , Noske Richard
Published: February 2005

Amphibolurus barbatus has a threat display which includes the erection of the gular regions as a frill and may also include wide opening of the mouth to display a yellow mouth lining. Frill erection involves protraction, depression, and lateral expansion of the hyoid apparatus. Electrical stimulation of the hyoid muscles and dissection of the hyoid apparatus were used to examine specializations for producing frill erection. Specializations of the hyoid skeleton include the absence of a ceratobranchial II, presence of a synovial joint between the ceratohyal and body of the hyoid, and combined shortening of the entoglossal process and lengthening of the posterior arches. The only apparent specialization of the hyoid musculature is the anterior displacement of the origin of m. hyomandibularis. All of the hyoid muscles are involved in some way in frill erection and the actions of each muscle is described. The characteristic frill erection in the threat display of Amphibolurus barbatus is possible because of the 1:2 ratio of the anterior and posterior parts of the apparatus and the absence of the ceratobrnchial II.
External features of the developing embryo of the stonefly, Kamimuria tibialis (pictet) (plecoptera, perlidae)
Authors: Kishimoto Tohru , Ando Hiroshi
Published: February 2005

External features of the egg, developing embryo, and first instar nymph of Kamimuria tibialis are described. The embryonic development from the germ disc to the full‐grown embryo is divided into 12 stages. The saclike embryonic rudiment is formed by the bending and folding of the germ disc. The embryo first elongates at the egg surface and then sinks into the yolk due to caudal flexure. In the head, four paired protocerebral lobes differentiate and the fourth lobes are thought to be the rudiments of preantennal ganglia. The columnar serosal cells appear at the posterior pole of the egg and they disappear before katatrepsis. The coniform chloride cells occur at the hind margins of the first nine abdominal segments in the full‐grown embryo and first instar nymph. Amnion formation in K. tibialis is very similar to that of Allonarcys proteus and the Isoptera. It is proposed that the immersed type of growth pattern of embryos is divided into two subtypes in hemimetabolous insects; one is in the Palaeoptera and Paraneoptera, and the other is in the Plecoptera, Orthoptera, Notoptera, Isoptera, Embioptera, and the blattarian, Periplaneta americana.
Scanning electron microscope studies on blastodisc formation in the zebrafish, Brachydanio rerio
Authors: Beams H. W. , Kessel R. G. , Shih C. Y. , Tung H. N.
Published: February 2005

Upon fertilization, the zebrafish egg undergoes marked physiological and structural changes, one of which involves blastodisc formation. Before fertilization, yolk globules are rounded and the endoplasm extends throughout the oocyte. During blastodisc formation, the yolk globules become angular and the endoplasm is restricted to streamers among the yolk globules. The streamers are oriented in an anterior‐posterior axis of the egg. During blastodisc formation the cytoskeleton consists of an extensive array of filamentous structures of variable width in both the cortex as well as within elongate endoplasmic streamers. Although the filamentous components in the cortex and endoplasmic streamers probably include both microfilaments and microtubules, frequently they are somewhat wider than the usual dimensions, and possible reasons for this are suggested. From their arrangement in both the cortex and endoplasm, it seems likely that the components of the cytoskeleton (e.g., microfilaments and microtubules) may provide, through contraction, the major force responsible for the streaming of the endoplasm into the forming blastodisc. It is assumed that the surface tension of the vegetal hemisphere exceeds that of the animal hemisphere, thus forcing, through differential contraction, the endoplasm to flow in the direction of the forming blastodisc. No distinct barrier between the yolk and forming blastodisc was observed. The compressed condition of the larger and many‐sided yolk globules could prevent their movement into the blastodisc. Scanning electron microscopy is limited in the resolution with which it can depict the cytoskeleton, but nonetheless it provides useful information about structural interrelationships.
Synaptic organization of dorsal area of the turtle, Pseudemys scripta elegans
Authors: Weiss Jonathan C. , Ulinski Philip S.
Published: February 2005

The dorsal ventricular ridge is a subcortical structure receiving sensory information from the thalamus in reptiles. In the red‐eared turtle, Pseudemys scripta elegans, it contains four cytoarchitectonic areas each characterized by distinct thalamic projections. This is an electron microscopic study of one of these, the dorsal area, which receives its thalamic input from the tectorecipient nucleus rotundus. It contains four concentric zones, internal to the ependymal zone, each of which is distinguished by the distribution of spiny and aspiny neurons.

The ependymal zone of dorsal area contains tanycytes whose tails extend into zones 2 and 4. Synapses, usually with asymmetric junctional complexes and round synaptic vesicles, occur on these processes. Zone 1 neurons have fusiform somata and dendrites that parallel the ventricular surface. Their cytoplasm contains rough endoplasmic reticulum located primarily in Nissl bodies, lipofuchsin granules, multivesicular bodies, extensive arrays of Golgi apparatus, and large numbers of mitochondria. Synapses occur mainly on dendritic spines and shafts of zone 1 neurons and less frequently on somata. The majority have round vesicles and asymmetric junctional complexes. In contrast to those in zone 1, neurons in zones 2 and 4 have large amounts of rough endoplasmic reticulum, giving their cytoplasm an electron‐dense quality. Synapses occur mainly on spines and shafts of zone 2 and 4 neurons. As in zone 1, the majority have round synaptic vesicles and contain asymmetric junctional complexes. Zones 2 and 4 contain clusters of neurons distributed among isolated neurons. The clusters are larger and less frequent in zone 2. Protoplasmic and fibrous glial processes, axon boutons, dendrites, and axon fascicles surround the neuron clusters. Though less numerous, the same structures also occur inside the clusters. Most synapses inside the clusters have round synaptic vesicles, asymmetric junctional complexes, and occur mainly on spines. Some neurons in clusters have somata whose plasma membranes are in direct apposition. In contrast to dorsal ventricular ridge in snakes, no specialized intercellular contacts were seen between somata in clusters.
Fine structure of oviducal epithelium of Xenopus laevis in relation to its role in secreting egg envelopes
Authors: Yoshizaki Norio
Published: February 2005

During passage through the oviduct, the egg of Xenopus laevis acquires the following substances or envelopes: electron‐dense particles in the vitelline coat, the prefertilization layer in and around the vitelline coat, and four layers of jelly. Both gross anatomical observation and light and scanning or transmission electron microscopic observations of various levels of oviduct revealed that the first two are produced in the pars recta 1 and 2 portions, and that jelly layers 1–4 are added in the pars convoluta 1–4 respectively. The relative lengths of these portions were 0–0.044, 0.044–0,055, 0.055–0.52, 0.52–0.70, 0.70–0.87 and 0.87–1.00 from anterior to posterior. Along the whole length of the oviduct, the epithelium was comprised of ciliated cells and various types of secretory cells. Except for the pars recta 1 portion, there were two or three types of secretory cells in each portion of the oviduct, indicating that the structure of each stratum of the egg envelope is formed by an interaction of products from the specific types of secretory cells in each portion of the oviduct.
Light and electron microscopic localization of a monoclonal antibody in neurons in situ in the head region of Hydra
Authors: Yu Shang‐Ming , Westfall Jane A. , Dunne John F.
Published: February 2005

A mouse monoclonal antibody to Hydra attenuata was used to demonstrate immunoreactive product in neurons in situ, in both whole mount and sectioned hypostomes and tentacles of H. oligactis and H. littoralis. Immunoreactive cells were concentrated around the mouth and scattered along the length of the tentacles. In the hypostome, nerve cells sent one or more processes orally and the others aborally but the processes were more distinctly stained in H. oligactis. A thin strand of five to six perihypostomal neurons was present close to the hypostome‐tentacle junction. In the tentacles, neurons with long processes contacted up to five different batteries of nematocysts. Neural processes were associated with nematocyst batteries in three ways: (1) forming a perikaryal loop to encircle a centrally located stenotele, (2) branching at a distance from the perikaryon to contact a variety of nematocysts, and (3) terminal branching by one or more neurons with contacts on one to several nematocysts within a battery. Immunocytochemical localization of neurons in Hydra by light microscopy was correlated for the first time with electron microscopy. Peroxidase‐antiperoxidase (PAP)‐positive sensory cells were concentrated around the mouth opening. PAP‐positive ganglion cells were predominant in the tentacles. Sensory cells were elongate or spindle‐shaped (unipolar), triangular with two oppositely directed processes (bipolar), and multipolar (tripolar or tetrapolar) with one of the processes extending to the epidermal surface. Ganglion cells were either unipolar or bipolar or multipolar, with neurites paralleling the mesoglea and occasionally having processes abut on it.
Scanning electron microscope study of cat and dog enamel structure
Authors: Skobe Ziedonis , Prostak Kenneth S. , Trombly Paul L.
Published: February 2005

Scanning electron microscopy revealed several similarities as well as significant differences in the enamel structure between cat and dog teeth. Three enamel layers were present in both species; a surface rodless (aprismatic) layer, an outer layer of parallel rods (only at some sites), and an inner layer with prominent Hunter‐Schreger bands. In the inner layer of both carnivores, the diameter of individual rods varied significantly and frequently their course changed abruptly with respect to neighboring rods. In dog teeth the cross‐sectional shape of inner enamel rods was pleomorphic, but hexagonal in outer enamel. In contrast, cat enamel rods were rounded in both inner and outer enamel layers. Hunter‐Schreger bands of cats circumscribed the teeth in relatively straight segments, but these bands showed pronounced waviness in dog teeth. In cats and dogs the surface rodless layer was structurally continuous with subjacent interrod enamel and covered all tooth surfaces with the exception of the cervical areas.

The data show that the structure of inner and outer enamel layers differ between these two carnivore species and that the enamel structure of the cat was most similar to that described in humans. One principal difference between carnivore and human teeth is that the growth lines of carnivores do not terminate at perikymata on the tooth surface.
The morphology and histology of the endocrine pancreas of the Southern Hemisphere lamprey, Geotria australis gray
Authors: Hilliard R. W. , Epple A. , Potter I. C.
Published: February 2005

The location and arrangement of the pancreatic endocrine tissue in larval and adult Geotria australis (Geotriidae) differ markedly from those exhibited by the comparable stages of Northern Hemisphere lampreys (Petromyzontidae). In larval Geotria australis, the main zones of islet proliferation are located laterally between the oesophagus and the inner edge of the two large intestinal diverticula unique to this species rather than dorsal and ventral to the oesophagus. In adult Geotria australis, the islet follicles are closely packed into a single discrete capsule which could be easily removed surgically, rather than into cranial, intermediate, and caudal cords. The differences in the adult can be related to a lack of involvement of the bile duct in islet formation during metamorphosis. While B cells were found in both larval and adult islet follicles, the PI acidophilic cells and argyrophilic cells, which appeared respectively at stages 3 and 4 in metamorphosis, were present in all adult stages.
Fine structure of the micropylar cell and its change during oocyte maturation in the chum salmon, Oncorhynchus keta
Authors: Kobayashi Wataru , Yamamoto Tadashi S.
Published: February 2005

In the ovarian follicle, the micropylar cell (MPC) is distinguished from neighboring granulosa cells by its larger cell size and its thick cytoplasmic process. The micropylar cell body fits into a shallow depression (micropylar vestibule) on the outer surface of the egg envelope; its process extends through the micropylar canal, which extends from the bottom of the vestibule through the full thickness of the zona pellucida interna. At its distal end, the cell process expands into a bulb which fits into an indentation of the ooplasmic surface immediately beneath the inner opening of the micropylar canal. Intermediate and desmosomelike junctions establish an intimate association between MPC process and oocyte. Various kinds of organelles and inclusions in the MPC show a characteristic pattern of cytoplasmic distribution; rough endoplasmic reticulum with markedly dilated cisternae is found exclusively in the main cell body, while microtubules and thin filaments are observed in the cytoplasmic process.

Immediately before or during the breakdown of the germinal vesicle in the intrafollicular oocyte, the cytoplasmic process of the MPC gradually decreases in length and begins to withdraw from the micropylar canal. At the same time, the ooplasmic surface protrudes outward to form a papilla in the canal. The intimate MPC‐oocyte association disappears during formation of the ooplasmic papilla. Hydration of the oocyte apparently occurs at the final stage of maturation and probably participates in papilla formation. Although the MPC undergoes degenerative changes as ovulation draws near, it remains attached to the inner surface of the granulosa cell layer even after its association with the oocyte has completely disappeared.

We speculate that the micropyle develops during fish oogenesis through the combined activity of the MPC and neighboring granulosa cells. It appears that the cell body of the micropylar cell and nearby granulosa cells exert mechanical pressure on the external surface of the growing oocyte and thus participate in formation of the micropylar vestibule. The cytoplasmic process of the MPC evidently forms a passive barrier to deposition of material for the egg envelope in the animal pole, thereby resulting in formation of the micropylar canal.
Development and rudimentation of the peripheral olfactory system in the harbor porpoise Phocoena phocoena (Mammalia: Cetacea)
Authors: Oelschläger Helmut A. , Buhl Eberhard H.
Published: February 2005

Serial sections of 13 embryos and fetuses of the harbor porpoise from 10 mm crown‐rump length up to 167 mm total length were studied. Unlike the adult animals, ontogenetic stages of 18–27 mm crown‐rump length still show a typical mammalian olfactory bulb. The olfactory bulb primordium is penetrated by olfactory nerve fibers, the latter passing through the cribriform plate. However, the olfactory bulb anlage is gradually reduced in later stages, its placodal component being largely uncoupled from the telencephalon. As a ganglionlike structure, the remains of the placodal component stay in contact with the nasal septum and mucosa via thin bundles of nerve fibers. The ganglion and plexus can be traced within the meninges until the adult stage of the porpoise. There is strong evidence that they represent the material of the terminalis system, which cannot be distinguished from the olfactory system in earlier stages. A vomeronasal organ could not be detected in the embryonal and fetal material investigated.
The intrarenal and pericapsular venous systems of kidneys of the ringed seal, Phoca hispida
Authors: Munkacsi I. M. , Newstead J. D.
Published: February 2005

The kidneys of Phoca hispida are comprised of many closely adherent renculi, each of which is a small kidney, functionally independent of its neighbours except with respect to venous drainage. Venous blood from the rencular parenchyma drains to the periphery through interlobular veins. These interlobular veins empty into a perirencular plexus comprised of subcapsular veins on the free surface of the renculus, interrencular veins on adjoined surfaces, and marginal subcapsular veins lying in the furrows between adjoined renculi. A pericapsular plexus of large veins overlies the marginal subcapsular veins and has frequent connections with them. Blood drains from the pericapsular plexus into large superficial collecting veins that converge over the surface of the kidney toward the divided hilum and connect directly to the paired trunks of the posterior vena cava. There are also connections to other major venous systems of the region.

There is no arcuate venous system, no major vein at the rencular hilum, and no vein of consequence emerging from the renal hilum. Venous outflow is virtually entirely directed to the peripheral plexuses. The venous pattern differs from that of most mammals in which blood drains from the renal parenchyma to arcuate veins and leaves the kidney through a renal vein, or veins, emerging from the hilum.

The walls of veins in the kidney are remarkably thin in comparison to their size. Subcapsular veins up to 0.5 mm wide have walls on the parenchymal side that in places consist only of a thin, fenestrated endothelium and a basal lamina.
The follicle cell‐oocyte interaction in ovarian follicles of the stick insect Bacillus rossius (Rossi): (Insecta: Phasmatodea)
Authors: Mazzini Massimo , Giorgi Franco
Published: February 2005

Developing ovarian follicles of Bacillus rossius have been examined ultrastructurally in an attempt to understand how inception of vitel‐logenesis is controlled. Early vitellogenic follicles are characterized by a thick cuboidal epithelium that is highly interlocked with the oocyte plasma membrane. Gap junctional contacts are present both at the follicle cell/oocyte interface and in between adjacent follicle cells. In addition, microvilli of follicle cells protrude deeply into the cortical ooplasm of these early vitellogenic oocytes. With the onset of vitellogenesis, wide intercellular spaces appear in the follicle cell epithelium and at the follicle cell/oocyte interface. Gap junctions become progressively reduced both on the follicle cell surface and on the oocyte plasma membrane. Microvilli from the two cell types no longer interlock.

From a theoretical standpoint each of the two structural differentiations present at the follicle cell/oocyte interface—gap junctions and follicle cell microvilli—could potentially trigger inception of vitellogenesis. Gap junctions might permit the passage of a regulatory molecule, transferring from follicle cells to oocyte, which would control the assembly of coated pits on the oocyte plasma membrane. Alternatively cell interaction via microvilli might induce the appearance of coated pits, thus creating a membrane focus for vitellogenin receptors. Both possibilities are discussed in relation to current literature.
Development of gap junctions in normal and mutant ovaries of Drosophila melanogaster
Authors: Giorgi F. , Postlethwait J. H.
Published: February 2005

An ovarian follicle of Drosophila consists of an oocyte, 15 nurse cells, and hundreds of follicular epithelial cells. A freeze‐fracture analysis of the surfaces between glutaraldehyde‐fixed ovarian cells showed that all three cell types were interconnected by gap junctions. This is the first report of gap junctions between adjacent nurse cells, between nurse cells and oocytes, and between follicle cells and oocytes in Drosophila. Since we did not observe intramembranous particle clumping into crystalline patterns and since structurally different gap junctions occurred at different times in development and at different cell‐cell interfaces, it is unlikely that fixation artifacts influenced particle distribution in our experiments. A computer‐assisted morphometric analysis showed that the extent, size, and morphology of gap junctions varied with development and that these junctions can cover up to 9% of the cell surfaces. To test the role of gap junctions in follicular maturation, we studied ovaries from flies homozygous for the female sterile mutation fs(2)A17, in which follicles develop normally until yolk deposition commences. During the development of mutant follicles, gap junctions became abnormal before any other morphological aspect of the follicle. These studies show that gap junctions are available to play an important role in coordinating intercellular activities between all three cell types in ovarian follicles of Drosophila.
Formation of the pronephros and pronephric duct rudiment in the Mexican axolotl
Authors: Gillespie Laura L. , Armstrong John B.
Published: February 2005

In the Mexican axolotl (Ambystoma mexicanum), the pronephros begins to form at the four‐somite stage. It is initially continuous with the posterior‐lateral region of somite 2 and the lateral margin of somites 3 and 4. By the seven‐somite stage, the pronephros has become compacted, and the cells are now morphologically distinct from the somitic cells. At this stage, a mass of loosely connected cells, apparently originating from the lateral mesoderm, is seen below somites 4 and 5. By the eight‐somite stage, these presumptive duct cells have migrated dorsally to the duct path and are found below somites 5–7. By the nine‐somite stage they have begun to migrate caudally.
Functional morphology of the feeding mechanism in aquatic ambystomatid salamanders
Authors: Lauder George V. , Shaffer H. Bradley
Published: February 2005

This study addresses four questions in vertebrate functional morphology through a study of aquatic prey capture in ambystomatid salamanders: (1) How does the feeding mechanism of aquatic salamanders function as a biomechanical system? (2) How similar are the biomechanics of suction feeding in aquatic salamanders and ray‐finned fishes? (3) What quantitative relationship does information extracted from electromyograms of striated muscles bear to kinematic patterns and animal performance? and (4) What are the major structural and functional patterns in the evolution of the lower vertebrate skull?

During prey capture, larval ambystomatid salamanders display a kinematic pattern similar to that of other lower vertebrates, with peak gape occurring prior to both peak hyoid depression and peak cranial elevation. The depressor mandibulae, rectus cervicis, epaxialis, hypaxialis, and branchiohyoideus muscles are all active for 40–60 msec during the strike and overlap considerably in activity. The two divisions of the adductor mandibulae are active in a continuous burst for 110–130 msec, and the intermandibularis posterior and coracomandibularis are active in a double burst pattern. The antagonistic depressor mandibulae and adductor mandibulae internus become active within 0.2 msec of each other, but the two muscles show very different spike and amplitude patterns during their respective activity periods. Coefficients of variation for kinematic and most electromyographic recordings reach a minimum within a 10 msec time period, just after the mouth starts to open.

Pressure within the buccal cavity during the strike reaches a minimum of −25 mmHg, and minimum pressure occurs synchronously with maximum gill bar adduction. The gill bars (bearing gill rakers that interlock with rakers of adjacent arches) clearly function as a resistance within the oral cavity and restrict posterior water influx during mouth opening, creating a unidirectional flow during feeding.

Durations of electromyographic activity alone are poor predictors of kinematic patterns. Analyses of spike amplitude explain an additional fraction of the variance in jaw kinematics, whereas the product of spike number and amplitude is the best statistical predictor of kinematic response variables.

Larval ambystomatid salamanders retain the two primitive biomechanical systems for opening and closing the mouth present in nontetrapod vertebrates: elevation of the head by the epaxialis and depression of the mandible by the hyoid apparatus.
Calcitonin cell population and distribution in the thyroid gland of the rat
Authors: Monsour P. A. , Kruger B. J. , Barnes A.
Published: February 2005

Calcitonin‐containing cells (C cells) were identified in male Wistar white rats using an immunoperoxidase technique. They occupied a central position within the thyroid; very few were found peripherally, inferiorly, and superiorly; and none were present in the isthmus. The number of calcitonin‐containing cells present per gram of body weight increased with age up to 70 days and had declined by 100 days. Determining the true total C‐cell count through the entire thyroid is a very laborious procedure. However, a simple estimate of this total count can be made; the total number of C cells in every tenth section (6 μm) of thyroid was found to be highly correlated with the weight of the animal expressed as an allometric function. A better estimate can be derived from counts of just three sections: the tenth, twentieth, and thirtieth after the section of greatest cross sectional area.
The innervation of some proboscis structures involved in feeding behavior of the blowfly (Calliphora vicina)
Authors: van Mier P. , van der Molen L. , van der Starre H.
Published: February 2005

The microtopology of the motoneurons involved in protraction and retraction of the proboscis of the blowfly (Calliphora vicina) has been studied. In addition, taste input from the labellar hairs was investigated. As a result of this study it appears that protraction movements are controlled by two while retraction movements are guided by three motoneurons on each side. The neurons in each group apear to be in ipsicontralateral communication with each other. The musculi protractores fulcri (MPF) probably contain a proprioceptive cell group which projects to the MPF motoneurons. It is proposed that the proboscis motor system can be modulated by proprioception as well as by chemosensory labellar input. Neurosecretory cells may be involved in adjusting muscle power.
Morphology and histochemistry of the ambiens muscle of the red‐eared turtle Pseudemys scripta
Authors: Hermanson John W. , Lennard Paul R. , Takamoto Richard L.
Published: February 2005

Six fiber types have been described in the ambiens muscle of red‐eared turtles. These include one slow oxidative type, two fast oxidative types, two fast oxidative and glycolytic types, and one fast glycolytic type. Fiber types are non‐randomly distributed throughout cross sections of the muscle. There is a decreasing gradient of oxidative staining and an increasing gradient of glycolytic staining along an axis from the superficial to deep regions of the muscle. The slow oxidative fibers are predominantly located within one or two fascicles of the superficial surface of the muscle. The fast glycolytic fibers are predominant in deep fascicles.

In contrast to previous reports of histochemically monotypic intrafusal fibers in turtle muscle, ambiens muscle spindles have been observed containing one to eleven intrafusal fibers, including two fiber types. Fiber diameter and area are consistently smaller than observed in most extrafusal fibers. Spindles are predominantly located in superficial and cranial fascicles of the ambiens muscle and are located in regions characterized by extrafusal fibers with high oxidative activity.
The fine structure of the nephronic tubule of the mudskipper Periophthalmus koelreuteri (Pallas)
Authors: Safer A. M. A. , El‐Sayed N. K.
Published: February 2005

Ultrastructural examination of the head kidney of Periophthalmus koelreuteri (Pallas) (Teleostei, Gobiidae) revealed that the nephronic tubule cells are bound by tight junctions and desmosomes with little intercellular space. The first proximal segment (PI) consists of low columnar cells with well developed brush borders, indented nuclei, and numerous apical endocytic vesicles and lysosomes. A second cell type possessing clusters of apical cilia and lacking brush border and lysosomes is occasionally found between PI cells. The second proximal segment (PII) is formed of high columnar cells with brush border, regular spherical nuclei and numerous mitochondria located between well developed infoldings of the basal membrane. Single ciliary structures protrude into the lumen from PI and PII cells. The distal segment is lined by low columnar epithelium with few microvilli, regular spherical nuclei, numerous scattered mitochondria, and microbodies. The collecting tubule cells are cuboidal with few euchromatic nuclei, some mitochondria, and secondary lysosomes.
The pharyngeal jaw apparatus of labrid fishes: A functional morphological perspective
Authors: Liem Karel F. , Sanderson S. Laurie
Published: February 2005

Among the acanthopterygian fishes, the Labridae possess the most highly integrated and specialized pharyngeal jaw apparatus. The integrated feature involves many osteological components and aspects of muscle form, architecture, composition, and function. The upper jaw articulates by means of a true diarthrosis with the pharyngeal process of the parasphenoid, whereas the lower jaw has established physical contact with the cleithrum. Complex muscle fusions have contributed significantly in the development of a double muscle sling operating the lower jaw. The original levator externus 4 fuses with the central head of the obliquus posterior, whereas the original levator posterior combines with the lateral head of the obliquus posterior as well as with the adductor branchialis 5.

During the masticatory cycle, both upper and lower jaws undergo complex movement orbits resulting in shearing and crushing functions. Shearing occurs as the forward moving upper jaw collides with the dorsally held lower jaw. Crushing is effected by an extreme posterodorsal movement of the lower jaw against the retracted upper jaw, thereby establishing full occlusion of the teeth.

The specialized morphological and functional design of the labrid pharyngeal jaw apparatus is similar to that found in cichlids. In sharp contrast to primitive acanthopterygian fishes, the Labridae and Cichlidae exhibit a spectacular morphological diversity that parallels their ecological diversification. Our combined functional and historical analysis has established a correlation between the complex integration of the pharyngeal jaw apparatus and morphological and ecological diversity in the Labridae and Cichlidae.
Ultrastructure of the dental epithelium and odontoblasts during enameloid matrix deposition in cichlid teeth
Authors: Prostak Kenneth , Skobe Ziedonis
Published: February 2005

Teleost enameloid matrix has been proposed to be an ectodermal, mesodermal, or joint ectodermal‐mesodermal product. To determine its origin we examined the ultrastructure of the inner dental epithelium (IDE), odontoblasts, enameloid, and dentin matrices of cichlid tooth buds at the stage of enameloid formation. © Alan R. Liss, Inc.

Columnar IDE cells had apical and basal terminal webs and contained organelles associated with protein synthesis, including elongated secretory granules containing fibrillar material having cross‐striations with 60‐nm periodicity. The morphology of IDE secretory granules was typical of procollagen granules observed in a large variety of ectodermal and mesodermal cells synthesizing collagen. In contrast, the paucity of secretory granules within three odontoblast types indicates that these cells probably do not synthesize enameloid matrix. These observations are consistent with the idea that the bulk of the enameloid matrix is itself an ectodermal collagen synthesized and secreted by IDE cells.
Morphological and fine structural features of the basilar papilla in ambystomatid salamanders (amphibia; caudata)
Authors: White James S.
Published: February 2005

The morphology and fine structure of the basilar recess and basilar papilla were investigated in four species of salamanders from the family Ambystomatidae. The otic relationships of the recess and papilla to the proximal part of the lagena and saccule are described, and new terminology is suggested for the periotic relationships of the basilar recess to a diverticulum of an intracapsular periotic sac. The basilar papilla consists of supporting cells united laterally by gap junctions, capped by microvilli uniformly arranged around a short, central cilium, and hair cells that typically show several synapses with a single afferent nerve fiber, each marked by a rounded synaptic body surrounded by vesicles. In contrast to anuran basilar papillae, efferent nerve terminals were observed in synapse with hair cells and, rarely, upon afferent fibers. The distal half of the ambystomatid papilla contained hair cells capped by tall ciliary bundles, with kinocilia that show swellings near their tips with delicate attachments to adjacent tall stereocilia. A tectorial body covers only this region of the papilla. Hair cells with shorter stereocilia, situated in the proximal half and at the papillar margins, are related only to filamentous extensions of the tectorial body. The ambystomatid basilar recess and papilla are compared to auditory end‐organs in other vertebrates, and it is suggested that a basic distinction can be made between aural neuroepithelia in amniotes versus that in nonamniotic vertebrate ears.
Limb morphology of domestic and wild canids: The influence of development on morphologic change
Authors: Wayne Robert K.
Published: February 2005

Biomechanical hypotheses are often invoked to explain the characteristic scaling of limb proportions. Patterns of static allometry and morphologic diversity, however, may also reflect the developmental mechanisms underlying morphologic change. In this study I document the importance of such developmental influences on the evolution of limb morphology in the extremely polymorphic domestic dog and in wild canid species. I use bivariate and discriminant function analyses to compare the limb morphology of adult dogs and wild canid species. I then compare ontogenetic allometry of four dog breeds with static allometry of domestic and wild canids.

Results reveal, first, that there is considerable similarity between dogs and wild canid species; many wolf‐like canids cannot be distinguished from domestic dogs of equivalent size. However, all dogs are consistently separated from fox‐sized, wild canids by subtle but evolutionarily significant differences in olecranon, metapodial, and scapula morphology. Second, in domestic dogs the pattern of static allometry is nearly identical to that of ontogenetic allometry. This finding can be attributed to simple heterochronic alterations of postnatal growth rates. Apparently the diversity of limb proportions among adult domestic dogs and the observed difference between dogs and wild canids are somewhat predetermined, as they directly reflect the diversity of limb proportions evident during development of the domestic dog.
Egg capsules of a parasitic turbellarian flatworm: Ultrastructure of hatching sutures
Authors: Shinn George L. , Cloney Richard A.
Published: February 2005

Egg capsules of Syndisyrinx franciscanus, an intestinal parasite of sea urchins (Strongylocentrotus spp.), consist of a bulb, which contains the embryos, and a stalk‐like filament. The wall of the bulb is about 12 μm thick and is composed of sclerotized proteins. The end of the bulb opposite the attachment of the filament bears a reticulum of hatching sutures. Transmission electron microscopy discloses that hatching sutures traverse the entire thickness of the capsule wall. The inner 9‐10 μm of sutures are a uniform 20 nm in width and contain a trilaminar cementum. The outer 2‐3 μm of sutures are 15 nm to more than 500 nm in width and contain an electron‐lucent cementum. The latter may contain an irregular, median, electron‐dense layer or, more commonly, electron‐dense granules. The outside of some capsules is partially covered by a thin, electron‐dense material.

A previous study showed that sutures in intact capsules of Syndisyrinx franciscanus are not affected by host digestive fluids, but are severely weakened immediately prior to hatching owing to activities of the embryos. The hypothesis that the embryos secrete a hatching enzyme is supported by findings that sutures of intact capsules are not affected by externally applied trypsin, but become weakened when capsules are cut open and then incubated in trypsin. Scanning electron microscopy reveals that the outer parts of sutures often remain intact after hatching. We hypothesize that the ability of sutures to resist enzymatic attack from the outside, but not the inside, results from differences in the chemical properties of the cementums in outer and inner parts of sutures.
Electron microscopy of the dorsomedial cortex in the lizard Psammodromus algirus
Authors: Guirado S. , Dávila J. C. , De La Calle A. , Marín‐Girón F.
Published: February 2005

The cellular populations and the plexiform layers of the dorsomedial cortex of Psammodromus algirus are described at the ultrastructural level. Solitary globous cells are located in the outermost layer of the cortex, the superficial plexiform layer. Double pyramidal cells of the cellular layer show uniform ultrastructural characteristics. Displaced double pyramidal cells, vertical fusiform cells, and globous cells are found in the deep plexiform layer. Two types of dendritic spines are described. Large spines may contain membranous sacs and mitchondira and are located at the upper third of the superifical plexiform layer; small spines do not contain organelles and are located throughout the entire cortex. Two types of axon terminals are widely distributed in both plexiform layers: terminals with only clear vesicles and terminals with both dense‐core and clear vesicles. Terminals with large dense‐core vesicles may be related to peptidergic synapses and are more frequent at the upper levels of the superficial plexiform layer. The neuroglia described in the dorsomedial cortex of Psammodromus are protoplasmatic astrocytes and oligodendrocytes.
Use of a monoclonal antibody to classify neurons isolated from the head region of Hydra
Authors: Yu Shang‐Ming , Westfall Jane A. , Dunne John F.
Published: February 2005

A mouse monoclonal antibody (JD1) to Hydra attenuata using the peroxidase‐antiperoxidase (PAP) method revealed unipolar, bipolar, and multipolar sensory and ganglion cells in the head region of H. littoralis. Neurons isolated from macerated hypostomes and tentacles were classified according to the number of their cytoplasmic processes and the position of the cilium, when present, relative to the perikaryon. PAP‐stained sensory cells had an apical ciliary cone, whereas ganglion cells did not. Neurons with cytoplasmic processes longer than 50 μm stained faintly, whereas those with processes shorter than 50μm in length stained mainly dense brown. Unipolar neurons had an oval, crescent, round, or elliptic perikaryon with a single short axon. The perikaryal shape of bipolar neurons varied from round to tall triangular, short triangular, crescent, oval, or elliptic with two oppositely directed symmetric or asymmetric processes. Asymmetric processes were present in a bipolar sensory cell with a long apical cilium typical of gastrodermal sensory cells. One type of bipolar ganglion cell had a short perikaryal cilium. Another type had neurites longer than 50 μm. We found seven morphological variations of multipolar neurons, including one with an apical knob, two with a short perikaryal cilium, two with cytoplasmic loops near the perikaryon, one with perpendicular processes projecting from the major neurites, and one with a branched process longer than 50 μm opposite a tangled mass of neurites.
Ultrastructure and role of the lobster vas deferens in spermatophore formation: The proximal segment
Authors: Kooda‐Cisco M. , Talbot P.
Published: February 2005

We have examined the anatomy of the vas deferens of the lobster Homarus americanus and have described the structure of the proximal vas deferens (segments one and two). The two tubes of segment one descend from the testes and gradually merge into segment two. The epithelium of segment one has synthetic activity and appears to contribute to the sperm‐supporting matrix by exocytotic release of granules through its apical surface. The epithelium of segment two is also highly synthetic and secretes the primary spermatophore layer and part of the intermediate layer that surround the sperm mass. The trifoil shape of the extruded spermatophore is established through a change in height of some of the cells lining the lumen in segment two. Connective tissue and circular bands of striated muscle surround the epithelium of both segments.
Tympanohyal bone in toothed whales and the formation of the tympano‐periotic complex (Mammalia: Cetacea)
Authors: Oelschläger Helmut A.
Published: February 2005

A tympanohyal bone is reported in dolphins for the first time. The exceptional occurrence of this element in the bottlenose dolphin (Tursiops truncatus) and its location in a furrow of the tympanic can be taken as a vestige of an ancestral conformation indicating that, in cetacean ancestry, uncoupling of the periotic from the mastoid must have taken place laterally and dorsally to attachment of the hyoid arch and the stylomastoid foramen. There is a good correspondence between morphology and topographical relations of structures surrounding the facial canal in toothed whales and terres‐trial mammals (especially perissodactyls and artiodactyls).

During early cetacean evolution, the tympanic had to undergo strong modification because of its functional correlation with the periotic. In precetaceans, the tympanic was probably loosely attached to neighboring skull bones, while at the same time it was suspended from the periotic via the tympanohyal. The earliest known cetaceans obviously lost this indirect osseous suspension but retained the peripheral attachments of the tympanic. In advanced archeocetes, two of these attachments are maintained but have shifted onto the periotic. In modern dolphins, the tympanic is in firm osseous contact exclusively with the periotic (tympano‐periotic complex). Both elements are isolated from the skull acoustically and form a separate mechanical unit specialized for high‐frequency underwater sound perception.
Chiton integument: Development of sensory organs in juvenile Mopalia muscosa
Authors: Leise Esther M.
Published: February 2005

The girdle epidermis of adult Mopalia muscosa secretes several types of structures, including calcareous spicules and innervated hairs. Newly metamorphosed chitons superficially resemble adult animals, but they lack the adult girdle ornaments, shell sculpture, and coloration. The morphogenesis of the adult girdle structures has not been described previously for any species. Juvenile Mopalia muscosa secrete hairs at metamorphosis, but it was not known if these hairs were sensory or if they were retained as the animals grew. I discovered that the hairs of juveniles become the tips of adult hairs. When juvenile hairs are detectable by light microscopy the sensory components already exist, suggesting that they are functional receptor organs. The other girdle ornaments of young juveniles, the primary calcareous spicules, are lost as the animal grows. I also demonstrated that the hairs are not uniquely innervated; the same sensory structures are produced in conjunction with other girdle ornaments on the marginal and ventral faces.
Odontogenesis and amelogenesis in interacting lizard—Quail tissue combinations
Authors: Lemus D. , Coloma L. , Fuenzalida M. , Illanes J. , De La Vega Y. Paz , Ondarza A. , Blanquez M. J.
Published: February 2005

In this study we examined the possible inductive role of the dental papilla from polyphyodont lizard tooth germs. Flank skin sheets of quail ectoderm enzymatically separated from dermal tissue were recombined with lizard tooth papillae and placed on semisolid medium and cultured for 2 days. Subsequently, the recombinants were removed and placed on the chorioallantoic membrane of chick hosts and incubated for 6 days. After this period of 8 days in explant, control tissues differentiated according to their own phenotypes. Lizard dental papilla alone differentiated as fibroblasts. Quail flank skin ectoderm differentiated into epithelial sheets. Intact lizard tooth buds developed into teeth with dentine and incipient enamel. In the best experimental recombinants, advanced and relatively well‐constructed teeth were observed, with clear indications of hard tissue deposition in association with quail epithelium. The results show that mesenchyme of the adult lizard dental papilla and embryonic quail ectoderm of heterotopic origin are capable of carrying out the complex sequence of morphogenetic interactions involved in normal odontogenesis.