bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Fine Structure of the Stalk of the Pentacrinoid Larva of a Feather Star, Comanthus japonica (Echinodermata: Crinoidea)
Authors: Grimmer John C. , Holland Nicholas D. , Kubota Hiroshi 
Published: April 2010

AbstractThe stalk of the pentacrinoid larva of a feather star (Comanthus japonica) is described for the first time by transmission electron microscopy. One end of the stalk bears the calyx and the other end is cemented to the substrate by attachment cement consisting of a meshwork of 5 nm filaments. The stalk is supported by a scries of skeletal ossicles pierced by a central canal: short intercolumnal ligaments connect adjacent skeletal ossicles and central through‐going ligaments run the length of the central canal. At the end of the stalk nearest the calyx, the chambered organ and the closely associated axial organ are histologically similar to those of adult crinoids. Presumed neurosecretory neurons are associated with the intercolumnal ligaments, and the following kinds of nerves run down the central canal: (1) a large stalk nerve in each of the five interradii; (2) smaller coelomic nerves in each of the five radii in association with the epithelium of tubular aboral extensions of the chambered organ; (3) a very small nerve associated with the aboral extension of the axial organ in the stalk axis. This axial organ extension is surrounded by a haemal channel. Because of the small size of the stalk, none of the nerves or the haemal channel were described in previous light microscopic studies. The discussion gives special attention to the controversial motility of the pentacrinoid stalk.
Coelomocytes of Nephtys coeca (Annelida, Polychaeta)
Authors: Mattisson Artur 
Published: April 2010

AbstractCoelomocytes of Nephtys coeca were studied by transmission electron microscopy. The majority of the coelomocytes were found to be structurally identical with the muscle cells of the body wall. Animals kept under unfavourable conditions tended to have an increased number of coelomocytes and a decreased thickness of the body wall. The muscular coelomocytes, probably released from the body wall, showed various degrees of decomposition, indicating a process of autophagy.
On the Caudal Heart of Myxine (Myxinoidea:Cyclostomata)
Authors: Satchell Geoffrey H. 
Published: April 2010

AbstractThe anatomy of the caudal heart of Myxine glutinosa is reviewed and a hypothesis of its mode of action is outlined. It is a double‐action force pump in which each stroke produces two results, the filling of one chamber and the emptying of the other. This hypothesis is supported by records of blood pressures (a) in the caudal vein, which show elevations of pressure as the left and right chambers are alternately emptied, and (b) in the subcutaneous sinuses, which show alternating reductions of pressure corresponding to the aspiration phases of the left and right sides. The caudal heart shows a diminishing sequence of bursts of activity following each bout of swimming; blood continues to flow slowly through the resting caudal heart. The conclusion is drawn that it is an auxillary venous pump, and it is compared with the lymph heart in the tail of teleost fish.
Observations on the Extracellular Spaces and Intercellular Junctions in Diphyllobothrium dendriticum (Cestoda)
Authors: Lindroos Paula 
Published: April 2010

AbstractExtracellular spaces and intercellular junctions were studied in adult Diphyllobothrium dendriticum after lanthanum nitrate infiltration. The parasitic tapeworms absorb nutrients across the whole body surface, the syncytial tegument. The results indicate that the distribution of nutrients can occur both in the extracellular stroma and in the intracellular compartment, through intercellular junctions of the gap junction‐type. The fibrous basal lamina of the tegument forms a large extracellular compartment communicating through narrow interstices in the subtegument with extracellular lacunae in the parenchyma. Intercellular junctions of the gap junction‐type frequently occur between the tegument cell bodies, as well as between tegument and parenchymal cells. According to the function of these cells in nutrient uptake and storage, metabolic coupling seemed the most likely mission for these junctions. Thus it can be concluded that the extracellular spaces and the intercellular junctions create the possibilities for an efficient distribution of nutrients in this tapeworm.
Dynamics of Oogenesis in a Lower Vertebrate, the Toad Bufo bufo
Authors: Jørgensen C. Barker 
Published: April 2010

AbstractThe patterns of production and growth of oocytes were studied in female toads brought into the laboratory after hibernation and kept at 20°C. The oogenic state of the ovaries was determined from the number and size frequency distribution of the oocytes, and change in oogenic state was followed by comparing ovarian biopsies with the ovaries at autopsy one month later. New oocytes grew within one month to sizes up to 0.16 mm or more in diameter, and were integrated in the existing pool of small oocytes. Production of new oocytes continued for more than one month, perhaps 2–3 months, to increase the pool of oocytes by about 50%. An episode of oogenesis sensu stricto is followed by a resting period, probably lasting for about 1–2 years. Oogenesis was not coordinated with ovulation or recruitment of oocytes to vitellogenic growth and it occurred also in the ovaries of sexually immature toads. Exogenous gonadotropin (hCG) and/or fasting for one month of toads in a good nutritional condition did not affect oogenesis, but no oogenic episodes were observed in the ovaries of starving toads that were depleted of energy reserves. It is concluded that oogenesis and growth of oocytes constitute a dynamic system that is only inadequately described by the widely accepted linear, sequential model of production of eggs in amphibians and teleosts.
The Sense Organs and Ventral Ganglion of Sagitta (Chaetognatha)
Authors: Bone Quentin , Pulsford Ann 
Published: April 2010

AbstractThis paper describes some features of the chaetognath nervous system from ultrastructural observations and observations on material stained with specific techniques for nervous tissue, and from records of the activity of the locomotor muscles and ventral ganglion. Sensory cells grouped on the ventral surface of the head bear ciliary processes (some with multiple tubules), and are probably in connexion with the central nervous system by their own axons, unlike the sensory cells of the hair fan vibration receptors of head and body. The ventral ganglion is motor to the locomotor muscles of the body, and controls the rhythmic locomotor activity of the animal. Electrical events associated with contraction of these muscles are compound non‐overshooting spike‐like potentials. The ventral ganglion contains several large nerve fibres constant in position and connexions in different individuals. Some of these arise from cells in the ganglia of the head, and pass to the ventral ganglion, others from cells within the ventral ganglion, and probably supply the ciliary hair fan receptors of the body, whilst the motor axons issuing from the ventral ganglion are smaller in diameter. The ganglion is arranged on a ladder‐like plan, and axons of the lateral cell bodies cross the central neuropil transversely before they contribute to the longitudinal tracts or pass out in the radial nerves. Synapses in the neuropil contain 30–40 nm electron lucent vesicles; the transmitter is unknown, but is unlikely to be either acetylcholine or l‐glutamate. Occasional larger electron dense vesicles up to 70 nm in diameter are also found within nerve fibres of the neuropil. It is concluded that the arrangement of the peripheral nervous system is unlike that of several groups which have been suggested as related to chaetognaths.
Larval Attachment by Eversion of the Internal Sac in the Marine Bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea): A Muscle‐Mediated Morphogenetic Movement
Authors: Reed Christopher G. 
Published: April 2010

AbstractThe larval morphology and settlement of the vesicularioid ctenostome bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy in an attempt to elucidate the mechanism of attachment to the substratum at the onset of metamorphosis. The oral epithelium in the free‐swimming larva is infolded to form a glandular internal sac at the oral pole. The internal sac is not specialized into distinct regions, but consists of a uniform, simple columnar epithelium filled with secretory granules. The hemispherical internal sac is underlain by a cup‐shaped layer of undifferentiated cells that constitutes the polypide rudiment. The cupiform layer of undifferentiated cells is in turn embraced by a network of muscle fibers called the rete muscularis. At the onset of metamorphosis, the larva constricts oro‐laterally and the internal sac is everted against the substratum. As the sac everts, the glandular cells secrete an adhesive that is wafted up over the metamorphosing larva by the reversed beating of the coronal cilia. At the same time, the cupiform layer of undifferentiated cells flattens in the plane of the oro‐lateral constriction and doubles in thickness. The cells of the cupiform layer undergo a corresponding transformation from short columnar cells to flask‐shaped cells that bulge into the glandular cells of the internal sac. The narrow ends of the flask‐shaped cells abut the strongly contracted muscle fibers of the rete muscularis. It is hypothesized that the contraction of the muscle fibers of the rete muscularis is responsible for the change in shape of the undifferentiated cells and, consequently, for the eversion of the internal sac. On the basis of this study and a review of the literature, it is concluded that attachment to the substratum at the onset of metamorphosis typically is effected by the eversion of an internal sac in larvae of the ctenostome superfamily Vesicularioidea.
Cypris Settlement, Kentrogon Formation and Host Invasion in the Parasitic Barnacle Lernaeodiscus porcellanae (Müller) (Crustacea: Cirripedia: Rhizocephala)
Authors: Høeg Jens T. 
Published: April 2010

AbstractThe anatomy of the female cypris is very similar to that of cyprids of the Thoracica. There is no development of a preformed kentrogon within the unsettled cypris. Kentrogon formation is completed within 10–20 min after settlement. Elimination of the spent cypris is necessary for successful development. The kentrogon includes a variety of tissues, such as muscles and part of the cement glands. The injection stylet develops in connection with a moult, and it penetrates into the crab gill through the ventral body wall of the kentrogon c. 50 h after settlement. Only a single cell, also recognizable in the unsettled cypris, is injected into the host, while the rest of the kentrogon degenerates after invasion. The speed of kentrogen development and much of the kentrogon anatomy can be interpreted as a defense against host crab grooming. The single invasion cell may either be considered as a stem cell or an egg.
An Ultrastructural Account of Otoplanid Turbellaria Neuroanatomy II. The statocyst design: evolutionary and functional implications
Authors: Ferrero Enrico Antonio , Bedini Celina , Lanfranchi Alberto 
Published: April 2010

AbstractThe statocyst architecture in the three otoplanid species Notocaryoturbella bigermaria Lanfranchi, 1969, Otoplana truncaspina Lanfranchi, 1969 and Parotoplanella heterorhabditica Lanfranchi, 1969 is compared. Common features are: (a) a fibrillar collagen‐like, 0.2 μm thick, investing capsule continuous with the brain capsule; (b) an inner wall made up of six or more flattened and overlapping parietal cells; (c) a statolith forming cell hanging from the dorsal side down in the lumen, with a large statolith containing vacuole; (d) a bilateral pair of spindle shaped accessory cell groups, adjoining the statolith cell and sending projections to the wall—nerve projections run through the capsule; (e) one accessory cell enveloping the other cells of the group has a filament containing cytoplasm, the filaments coverging into a hemidesmosome making contact with a projection coming from a parietal cell; (f) muscles from the longitudinal body musculature inserting onto the capsule externally. The lack of ciliary structures differentiates the turbellarian statocyst from the majority of invertebrate statocysts. The developmental origin, the phylogenetical meaning and the functional and adaptive value of the statocyst in Turbellaria are here commented on.
Balancer Fine Structure of the Pleurodeles Larva
Authors: Fox Harold 
Published: April 2010

AbstractThe paired balancers of larval Pleurodeles waltl, a urodelan species of the Amphibia, were investigated throughout their life span until final degeneration, using electron microscopy. The evidence from cellular ultrastructure illustrates the mucus‐secreting function of these organs, and the outer epithelial cells actively synthesize muco‐proteinaceous substance. An extensive granular endoplasmic reticulum and well developed Golgi complexes participate in the mucus manufacture. The balancer epidermis is also extensively innervated throughout by non‐myelinated neurites, most of them without Schwann cells, a feature which argues strongly in favour of the organ also having a sensory function, whose nature has yet to be determined.
The Alimentary Canal of a Freshwater Copepoda, Macrocyclops albidus, and some Other Cyclopoida
Authors: Defaye Danielle , Such Janine , Dussart Bernard 
Published: April 2010

AbstractStructural and ultrastructural studies on the gut of a freshwater Cyclopoida, Macrocyclops albidus (Crustacea, Copepoda) during its post‐naupliar development show constant morphological and cytological characteristics. The alimentary canal is composed of three parts: oesophagus, gut and rectum. Three zones are described from the gut, which forms the major part of the alimentary canal. The median part, or midgut, is the more interesting, characterized by its vacuolar cells. All cells of the gut have constant features. An hypothesis on the digestive function is given in relation to behavioral observations and histological and biochemical data.
Estimation of Steroids and Steroid Metabolism in a Lower Vertebrate (Lampetra planeri Bloch)
Authors: Seiler Karl , Seiler Ruth , Ackermann Wilfried , Claus Rainer 
Published: April 2010

AbstractPregnenolone, androstenedione and testosterone were identified by RIA in tissue homogenates of the pronephric region, the opisthonephros, the gonads and in plasma samples from male and female immature and mature adult brook lampreys. Additionally, hydroxysteroid dehydrogenase activity was determined spectrophotometrically in homogenates from the same tissues of mature and spent adult brook lampreys employing pregnenolone, testosterone or 3β,17β‐dihydroxy‐5β‐androstane as substrates. The steroid levels show differences corresponding to developmental stages, tissues and sex. Remarkable quantities of testosterone were measured in the testicular tissue homogenates, in homogenates obtained from the pronephric region and in the serum.
Sex Difference in the Cloacal Gland in the Hagfish, Eptatretus burgeri, and its Possible Significance in Reproduction
Authors: Tsuneki Kazuhiko , Suzuki A. , Ouji M. 
Published: April 2010

AbstractThe cloacal gland of the hagfish, Eptatretus burgeri, was studied histologically in four seasons. Before the breeding season (spring and summer) the male cloacal gland was larger than the female cloacal gland. The gland was largest in the males with a more mature testis. After the breeding season (autumn and winter) there was no sex difference in the size of the cloacal gland. The cloacal gland consists of mucus and thread cells, as do the lateral slime glands. The sperm may be entangled within slime in the cloacal gland and be shed outside as a slimy sperm mass. Such a slimy sperm mass may play an important role in reproduction of the hagfish.
The Question of a Presupracleithrum in Brachiopterygian Fishes
Authors: Bjerring Hans C. 
Published: April 2010

AbstractThe presupracleithrum is an exoskeletal pectoral bone that occurs in Paleozoic and Mesozoic actinopterygian fishes. It has been equated more than once with an opercular element in brachiopterygian fishes. In recent cladistic analyses, this alleged homology is used to assign brachiopterygians to actinopterygians. However, a comparison of brachiopterygian and actinopterygian crania shows clearly that the former lack a presupracleithrum.
Histochemical Characterization and Distribution of Fiber Types in the Pectoralis Muscle of the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae)
Authors: Rosser Benjamin W. C. , George John C. 
Published: April 2010

AbstractThe muscle fibers of the pectoralis (M. pectoralis pars thoracicus) of a male and a female ostrich (Struthio camelus) and a male and a female emu (Dromaius novaehollandiae) were studied histochemically for succinate dehydrogenase and myofibrillar adenosine triphosphatase. Slow‐tonic (ST), fast‐twitch oxidative‐glycolytic (FOG) and fast‐twitch glycolytic (FG) fibers were approximately equal in number and distribution in the emu pectoralis examined. In the ostriches, both predominantly FG and approximately equal areas, were present. ST fibers were significantly (P ≤ 0.05) larger than the similarly (P ≥ 0.05) sized FG and FOG fibers in the female ostrich and emus. In the male ostrich ST fibers were smaller (P ≤ 0.05) than FG fibers, neither of which were significantly (P ≥ 0.05) different from FOG fibers. The ratites have the greatest percentage and widest distribution of ST fibers found in any avian pectoralis studied to date. This could represent the ancestoral avian pectoralis, neoteny or an effect of flightlessness. ST fibers are used in the maintenance of posture, which is probably the main role of the pectoralis in the emu. The predominantly FG areas of the ostrich are indicative of an additional function, namely, behavioural display. Sexual dimorphism in the ostrich pectoralis is strongly suggested.
On the Fine Structure of the Alimentary Tract of Cephalodiscus gracilis (Pterobranchia, Hemichordata)
Authors: Dilly Peter Noel , Welsch Ulrich , Rehkämper Gerd 
Published: April 2010

AbstractThe U‐shaped alimentary tract of Cephalodiscus is of exclusively epithelial structure; on the basis of fine structural criteria the entire tract can be divided into two large subdivisions: an anterior one with mouth, mouth cavity, pharynx and oesophagus, and a posterior one with stomach and intestine. The anterior subdivision is built up of a relatively uniform, innervated, pseudostratified, ciliated epithelium with mucus cells which are concentrated in the initial parts of the mouth cavity. Cilia and mucus presumably constitute a mechanism transporting food particles into the stomach. In the area of the gill slits specific vacuolated cells occur which may lend rigidity to the walls of the slits. The gastric epithelium consists of prismatic cells characterized by, among others, large inclusion bodies, which may represent digestive vacuoles, small dense rod‐shaped granules and an elaborate system of microridges, at the base of which abundant endocytotic vesicles occur. The dorsal gastric pouch contains cells rich in rough ER and secretory granules, probably containing digestive enzymes. Thus morphological evidence points both to intra‐ and extracellular digestion. The intestinal epithelium resembles that of the stomach, however, it is lower, its organelles are fewer and it bears, beside cilia, mainly microridges, which towards its distal end become sparse. Both in the gastric and intestinal epithelium small granulated cells have been found, which presumably represent endocrine cells.
Insulin‐Like Immunoreactivity in the Neural Ganglion of the Ascidian Ciona intestinalis
Authors: O'Neil G. S. , Falkmer S. , Thorndyke M. C. 
Published: April 2010

AbstractAntisera raised against salmon insulin and bovine insulin were used to assess the distribution of insulin‐like immunoreactive neurons in the neural ganglion of Ciona intestinalis. Cell bodies of two sizes were found in cortical and medullary positions, together with an extensive network of immunoreactive fibres. These observations indicate that an insulin‐like material is an important component of the central nervous system in Ciona and gives weight to the hypothesis that protochordates utilize insulin‐like factors as neurotransmitters or modulators, as do their invertebrate ancestors.
The Nervous System of Early Larval Stages of the Cestode Diphyllobothrium dendriticum
Authors: Wikgren Marianne C. 
Published: April 2010

AbstractThe nervous system (NS) of the coracidium and procercoid larval stages of the pseudophyllidean cestode Diphyllobothrium dendriticum was examined by whole mount immunocytochemistry and electron microscopy. Antisera against the bioamine serotonin and the molluscan cardioexcitatory peptide FMRF‐amide gave a positive immunoreaction in the NS of the procercoid. Ultrastructurally, three types of nervous elements were discerned. Ultrastructural evidence of both aminergic and peptidergic neurons in the coracidium is provided. The NS of these early larval stages is simply organized. The serotonergic part of the NS shows a beginning centralization in the procercoid, while the peptidergic neurons are more peripherally distributed.
In vivo Observations on a Specialized Microvasculature, the Primary and Secondary Vessels in Fishes
Authors: Steffensen J. F. , Lomholt J. P. , Vogel W. O. P. 
Published: April 2010

AbstractMicroscopical observations have been made on the blood circulation of intact, unanaesthetized specimens of the transparent glass catfish. Along the segmental arteries of the trunk, groups of short, curled vessels of capillary dimensions (termed inter‐arterial anastomoses) branch off and reunite to form large so‐called secondary arteries running parallel to the main (primary) arteries. Secondary arteries give rise to capillaries in the median ventral fin membrane. Secondary capilaries are drained via separate secondary veins. When blood passes from primary to secondary arteries via the inter‐arterial anastomoses a pronounced plasma skimming is observed. Hence, blood perfusing the secondary capillaries of the fin membrane contains very few red blood cells.
A Rostral Sensory Mechanism in Oikopleura dioica (Appendicularia)
Authors: Bollner Tomas , Holmberg Kaj , Olsson Ragnar 
Published: April 2010

AbstractThe ventral sense organ, below the mouth, is composed of 30 primary sensory cells situated in a row perpendicular to the long axis of the animal. Each cell carries one long and slender, modified cilium which arises from an apical pocket in the cell. The sensory cells project 15 axons at each side of the pharynx to the brain, which is rostrally paired and terminates in bulb‐like swellings. Each of these bulbs contains four cell bodies, which, according to their fine structure, as well as the synaptic connections with receptor and brain fibers, belong to three different types. It is suggested that the sense organ is a chemosensor and that its remarkable similarity to the vertebrate mechanisms for olfaction makes it probable that the appendicularian Oikopleura dioica possesses a ‘protochordate’ counterpart to the craniate olfactory apparatus.