bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural study of the Central Nervous System of Endemic Geocentrophora(Prorhynchida, Platyhelminthes) from Lake Baikal
Authors: Böckerman Inger , Reuter Maria , Timoshkin Oleg 
Published: April 2010

AbstractThe ultrastructure of the central nervous system of four species of the Geocentrophoragroup (Prorhynchida, Lecithoepitheliata) has been studied with Geocentrophora waginias a model organism. This is the first ultrastructural study of the nervous system in flatworms of the endemic Geocentrophoragroup from Lake Baikal.The neurons are characterized by invaginations of the plasma membrane with extracellular material (ECM) extending deep into the neuronal cytoplasm. Two types of neuron are distinguished on the basis of the character of the cytoplasm and the content of neuronal vesicles. Several more vesicle types are observed in the nerve processes in the neuropile.The following kinds of neuronal release sites are distinguished: single synapses, shared synapses, nonsynaptic release sites characterized by omega profiles and neuromuscular contacts. Special features of the synapses in the species of Geocentrophoraare pronounced local thickenings of the presynaptic membrane connected to paramembraneous densities. The ECM‐filled invaginations and the local presynaptic thickenings are features that distinguish the neurons of Geocentrophoraspp. from previously described turbellarian neurons.
The Cytoskeletal Proteins Actin and Tubulin in the Spermatozoa of Four Decapod Crabs (Crustacea, Decapoda)
Authors: Tudge C. C. , Justine J.‐L. 
Published: April 2010

AbstractThe mature spermatozoa of four species of European decapod crabs (Clibanarius erythropus, Maja squinado, Cancer pagurusand Potamon fluviatile)have been investigated using indirect immuno‐fluorescence techniques for the presence of the cytoskeletal proteins actin and tubulin. Indirect immunofluorescence labelling with monoclonal anti‐actin antibody and three different monoclonal anti‐tubulin antibodies indicate that actin is present in the spermatozoa of all four species, but tubulins are restricted to the two species with microtubular arms, Clibanariusand Maja.The pattern of actin fluorescence varies between the spermatozoa of the four species, with Majaand Cancershowing intense fluorescence in the acrosome vesicle and in elements of the sperm cell involved in the acrosome reaction. The spermatozoon of each species is described ultrastructurally using transmission electron microscopy and correlations made between observed patterns of fluorescence and the cellular components described. No obvious filamentous actin (F‐actin) is visible in the electron micrographs of the spermatozoa of any of the species. In most cases the fluorescence is sufficiently specific to indicate in which region of the mature sperm cell the actin and tubulin occurs. Actin is acrosomal in Maja, Cancerand Potamonbut appears to be cytoplasmic in Clibanarius, while the tubulins appear only to be present in the cytoplasm of Clibanarius, Majaand Cancer.
Muscle Fiber Types in the Pectoralis of the White Pelican, a Soaring Bird
Authors: Rosser Benjamin W. C. , Waldbillig Donna M. , Wick Macdonald , Bandman Everett 
Published: April 2010

AbstractThe pectoralis muscle (M. pectoralis) of many premier soaring birds contains a smaller, accessory, deep belly in addition to the much larger superficial belly found in all flying birds. Here we describe the muscle fiber types in both the superficial and deep bellies of the pectoralis of one such adept soaring species, the white pelican (Pelecanus erythrorhynchos).Histochemical techniques are used to demonstrate both nicotinamide adenine dinucleotide (reduced) and myofibrillar adenosine triphosphatase activities within the muscle fibers. Immunocytochemical methods employing several monoclonal antibodies, each directed against a different myosin heavy chain epitope of the chicken, are also used to characterize the fibers. While the superficial belly of the muscle consists entirely of fast‐twitch oxidative‐glycolytic fibers, the deep belly is composed exclusively of slow fibers. These slow fibers are labelled by two different antibodies specific for chicken slow myosin. We suggest that the fibers of the superficial belly are best suited to flapping flight, and that the fibers of the deep belly would be recruited only during soaring flight. Furthermore, we hypothesize that the deep belly found in the pectoralis of soaring species probably evolved from a deep neuromuscular compartment of the superficial belly.
Copulatory Mechanics in the Funnel‐web Spiders Histopona torpidaand Textrix denticulata(Agelenidae, Araneae)
Authors: Huber Bernhard A. 
Published: April 2010

AbstractThe functional morphology of the copulatory organs of Histopona torpida(C. L. Koch, 1834) and Textrix denticulata(Olivier, 1789), investigated by semi‐thin serial sectioning after freeze‐fixation of the animals in copula, is described. In H. torpida, the long embolus runs through a precisely defined course in the membraneous genital pouch of the female vulva. The patellar apophysis locks the pedipalp in the female epigastric furrow. In T. denticulatathis is accomplished by the retrolateral tibial apophysis that gets hold at the female scape. In both species the conductor has a locking as well as a guiding function for the embolus. A comparison with previously investigated agelenids shows a surprising diversity in the function of the retrolateral tibial apophysis.
Atypical Chordoid Structures in the Aristotle's Lantern of Regular Echinoids
Authors: Bonasoro Francesco , Carnevali M. Daniela Candia 
Published: April 2010

AbstractRegular sea–urchins, as a rule, prepare and process their food as pellets in their buccal cavity before ingesting them. This is obtained through the synergistic interaction of the five teeth with five fleshy protuberances (paradental tongues) which extend into the oral cavity and work like tongues. Each of these structures consists of two anatomically distinct parts: the outer component is a deep pouch of the terminal tract of the pharynx and shows a histological organization similar to that usually shown by the pharyngeal wall itself. The deeper component (paradental axis) is represented by a supporting rod and shows a peculiar histological structure, which consists of glycogen containing vesiculate cells mixed to slim muscle fibres and held together by a thin fibrillar stroma. The paradental axes are very problematic structures in terms of comparative anatomy and phylogenetic aspects. Their microscopic and submicroscopic organization is unusual for an echinoderm and recalls that of different types of chordoid organs commonly found in other invertebrates (Protostomata and Deuterostomata).
The Olfactory Organ of the Hardhead Sea Catfish, Arius felis (L.): Gross Morphology and Fine Structure
Authors: Zeiske Eckart , Theisen Birgit , Breucker Haide 
Published: April 2010

AbstractThe olfactory organ of the hardhead sea catfish, Arius felis(L.), was investigated morphologically by means of light and electron microscopy (SEM, TEM). The two rather large nostrils of each side lie close together, surrounded by upstanding margins. The olfactory rosette consists of a midline raphe with two rows of lamellae. The sensory epithelium on the lamellae is almost continuous and contains receptor cells of both the ciliated and the microvillous type. Ciliated non–sensory cells are scattered throughout the sensory epithelium. Accessory ventilation sacs are lacking. The shape, position and size of the nostrils indicate that forward motion of the fish creates the water current through the olfactory organ (kolymbosmates). The scattered non–sensory cilia may aid in ventilation. The olfactory organ of A. felisdiffers from that of the other marine catfish, Plotosus lineatus, and from those of freshwater catfishes. The morphological differences are discussed with respect to species–specific behavioural activities.
Structure and Innervation of the Inner Ear Sensory Organs in an Otophysine Fish, the Upside–down Catfish (Synodontis nigriventrisDavid)
Authors: Jensen Jan Chr. 
Published: April 2010

AbstractAll the sensory epithelia of the inner ear in the upside–down catfish (Synodontis nigriventrisDavid) were examined by light microscopy. The morphology of the membranous labyrinth and the orientation of the hair cells is similar to what has been found in other otophysine fishes. The sensory cells are of variable size both inter– and intraepithelially; particularly the macula sacculi is equipped with heterogeneous receptors. Regional differences in the hair cell density are presented for all the otolith organs plus the papilla neglecta. Nerve stainings reveal regional differentiation. The central areas are innervated by stout and stubbly nerve endings intermingled with a few thin nerve fibres while the peripheral parts are reached exclusively by thin axons. In the anterior region of the macula sacculi are found unique cup–shaped axon terminations which surround the basal parts of a single or a few sensory cells. The number and diameter range of the myelinated nerve fibres as well as the hair cell/axon ratio are presented. Electron microscopy demonstrates the presence of unmyelinated axons in all inner ear nerve ramuli.
Immunocytochemical Distribution of 5‐HT (Serotonin) in the Nervous System of the Gastrotrich Turbanella cornuta
Authors: Joffe Boris I. , Wikgren Marianne 
Published: April 2010

AbstractThe 5‐HT (serotonin) distribution in the nervous system of the macrodasyoid gastrotrich Turbanella cornuta was studied using immunocytochemical methods. Positive immunoreaction was found in two pairs of neurons. The neurons of one pair had processes which extended peripherally to the surface of the body. Central processes of both pairs entered the brain commissure and proceeded into the longitudinal cords. Unlike other acoelomate worms studied so far, the Platyhelminthes and the Nematoda, in this gastrotrich no 5‐HT positive perikarya or processes were present in the pharynx innervation, and no positive neurons sent processes directly to the nerve cords
Occurrence and Ultrastructure of Collar Cells in the Stomach Gastrodermis of Polypodium hydriforme Ussov (Cnidaria)
Authors: Raikova Ekaterina V. 
Published: April 2010

AbstractThe existence of collar cells lining the stomach gastrodermis in free‐living Polypodium hydriforme and their ultrastructure are described. The collar cells are provided with a collar consisting of 9–10 microvilli which encircles a central flagellum and forms a flagellar pit. At the bottom of the pit around the basal part of the flagellum there is fine crystalline material which extends also in the spaces between the microvilli and keeps them straight. The flagellum has a typical axoneme (9+2), its basal body is located below the apical surface of the collar cell and continues into a striated rootlet. An accessory centriole is situated close to the upper part of the rootlet. The cell nucleus is located in the basal part of the cell. Prominent mitochondria with tubular cristae, Golgi cisternae and fragments of rough endoplasmic reticulum are situated mostly in the basal part of the cytoplasm. Discoidal vesicles are abundant in the apical cytoplasm. The collar cells are connected to each other by septate junctions and interdigitations. The ultrastructure of collar cells described here is discussed in comparison to that of other Cnidarians and in connection with the problem of Polypodium's systematic position.
Ultrastructure of Spermatozoa of the Yellow‐rumped Elephant Shrew Rhynchocyon chrysopygus (Mammalia: Macroscelidea) and the Phylogeny of Elephant Shrews
Authors: Woodall Peter F. , FitzGibbon Clare 
Published: April 2010

AbstractThe spermatozoa of the yellow‐rumped elephant shrew Rhynchocyon chrysopygus have a spatulate head, tapering to a rounded proximal end with a marked narrowing at the equatorial segment. There is a short pointed subacrosome and about 24 gyres of mitochondria were found in the midpiece. The coarse fibres surrounding the axonome show enlargement of numbers 1, 5, 6 and 9. The spermatozoa of all genera of elephant shrews have now been described allowing comparisons among them. R. chrysopygus has the shortest spermatozoon and the fewest number of gyres. The pointed subacrosome is considered an ancestral feature and is shared with Macroscelides. The enlargement of coarse fibres 1, 5, 6 and 9 is found in several groups including members of the archonta and paenungulates, both postulated as being related to elephant shrews.
Microscopical Anatomy of the Cyrtocrinid Cyathidium meteorensis (sive foresti) (Echinodermata, Crinoidea)
Authors: Heinzeller Thomas , Fechter Hubert 
Published: April 2010

AbstractLight microscopy and scanning electron microscopy of three specimens of Cyathidium meteorensis (order Cyrtocrinida) revealed some special morphological features. The brachial articulation is provided with a long tendon at the aboral side; the entire articulation surface, including the areas where ligaments attach is built up by labyrinthic stereom. The calycinal ossicle lacks any internal vestiges of a pentameric composition; vertical planes with changing stereom direction lie irrespectively of radial or interradial planes. Gut, ovary and testis are histologically inconspicuous, and the location of the gonads inside the calyx is quite unusual. Both sexes develop outer gonoducts which probably are functionally adapted madreporic canals. The coelomic system differs from that of other crinoids in that a chambered organ is completely lacking. Simultaneously, the aboral nervous subsystem has no aboral nerve centre and simply terminates aborally in the ring‐shaped commissure. A glandular axial organ is absent, as are typical sacculi. The data are in accordance with two proposals made previously for Holopus rangii, viz., that the animals can feed raptorially, and that cyrtocrinids probably have evolved by loss of aboral calycinal ossicles of ancestors. In part, our observations differ from those in Cyathidium foresti, so we have chosen to use the species name meteorensis which has been considered a synonym of foresti.
Further Ultrastructural Studies on the Encapsulated Larva of Kronborgia isopodicola (Platyhelminthes, Fecampiidae), with Particular Reference to Nuclei
Authors: Williams J. B. 
Published: April 2010

AbstractDuring development of the encapsulated Kronborgia isopodicola larva, nuclei of the body tissues and differentiating eyes undergo a continuous condensation, the progression of which is described. The brain is composed of a central neuropil and an outer layer of nerve cell perikarya. Neurosecretory cells are located at the sides of the brain. Some neurosecretory cell extensions are interposed between the cerebral neuropil and nerve cell perikarya; others overlie the photoreceptor cell processes of the eyes. The advanced encapsulated larva possesses a frontal complex, consisting of modified epidermis, secretory cells, gland ducts and nerve cell processes. The advanced larva is transparent and diminished in size, advantages possibly due in part to the extraordinary process of comprehensive nuclear condensation during ontogeny. The larva has a uniform epidermal ciliation and, while sharing certain features with trochophore larvae, is not of the trochophore type.
Is Sperm Ultrastructure Useful in Polychaete Systematics? An Example Using 20 Species of the Fabriciinae (Polychaeta: Sabellidae)
Authors: Rouse Greg W. 
Published: April 2010

AbstractThe utility of sperm morphology in the systematics of polychaetes has been questioned in the past. This doubt stems from a problem with methodology, not with sperm morphology. It is argued that sperm characters used in combination with other morphological features have utility at various hierarchical levels. As a test of this proposition males in species from each of the following 10 fabriciin genera: Augeneriella, Fabricia, Fabriciola, Fahricinuda, Manayunkia, Novafabricia, Parafabricia, Pseudofabricia, Pseudofabriciola and an undescribed new Genus A (Fitzhugh et al., in preparation), were examined in order to provide new characters for phylogenetic systematic studies. All species were found to have a dorsal sperm duct running beneath the faecal groove of the thoracic region. No sabellin sabellids or serpulids have this duct. The above Fabriciinae have spermatids developing in large clusters of several hundred cells. Serpulids and sabellins nearly always have sperm developing in tetrads or small groups. Fabriciins studied also have a sperm structure distinct from the Sabellinae and the Serpulidae. Proposed synapomorphies for the members of the Fabriciinae, based on sperm structure, include (1) a thick glycocalyx over the plasma membrane; (2) a distinctive nuclear projection, with an anterior thickening of the nuclear membrane; (3) a thickened. spiraling ridge of nuclear membrane; (4) an extra‐axonemal sheath and (5) a unique sheath of mitochondrial material in the midpiece. Within the sub‐family there were differences among species in sperm structure. This variability involves acrosome morphology; the structure of the sperm nucleus and nuclear projection; the spiral of thickened nuclear membrane; the structure of the extra‐axonemal sheath; the mitochondrial sheath. The monophyly of the Fabriciinae (sensu Fitzhugh, 1991, 1993) is well supported by this analysis. The status of Caobangia is still unresolved and a close examination of this genus is warranted.
Origin and Differentiation of the Inner Follicular Cells during Oogenesis in Molgula pacifica (Urochordata), an Ascidian without Test Cells
Authors: Cloney Richard A. 
Published: April 2010

AbstractIn Molgula pacifica small previtellogenic oocytes are found between cells of the ovarian epithelium. Each oocyte subsequently grows within a compartment of the epithelium known as a primary follicle. The wall of the primary follicle is composed of outer follicular epithelial cells. While growing from about 15–70 μm in diameter, each oocyte gradually recruits a set of about 950 non‐epithelial inner follicular cells. These cells co‐differentiate in sets with each oocyte, but test cells never appear. The first filamentous components of the vitelline coat appear on the surface of an oocyte in places where it is in contact with undifferentiated (stage 2) inner follicular cells. Each fully differentiated inner follicular cell stores adhesive precursors in a large compartment of the endoplasmic reticulum and probably secretes components of the vitelline coat. There is no evidence that the outer follicular epithelial cells transform into inner follicular cells by dedifferentiation as has often been assumed. Inner follicular cells, in stage 1, are nearly identical to hemoblasts. Hemoblasts may form the inner follicular cells, but to do this they would have to cross the outer follicular epithelium and this phenomenon has not yet been seen.
Embryos and Larvae of a Lancelet, Branchiostoma floridae, from Hatching through Metamorphosis: Growth in the Laboratory and External Morphology
Authors: Stokes M. Dale , Holland Nicholas D. 
Published: April 2010

AbstractFlorida lancelets were raised in laboratory cultures from the egg to the juvenile stage. At frequent intervals during development, elongation of the embryonic and larval body was measured at room temperature (22.5°C) and at the approximate temperature of the natural environment (30°C). Development was slower at the lower temperature, with metamorphosis commencing during the fifth week as compared to the third week at the higher temperature. Scanning electron microscopy (SEM) was used to describe a frequently sampled series of hatched embryos, pre‐metamorphic larvae, metamorphic larvae, and juveniles. The advent (and sometimes subsequent disappearance) of the following structures was determined from the SEM data: general epidermal ciliation, peroral pit, mouth, primary gill slits, ciliary tuft, external opening of the club‐shaped gland, sense cells, anus, metapleural folds, and preoral cirri. Our SEM did not substantiate the claims of van Wijhe for a transitory larval mouth near the anteriovental end of the larvae. The general epidermal cilation, which is uniformly distributed in the embryos, becomes somewhat reduced in the pre‐metamorphic larvae and then disappears almost entirely during metamorphosis. The epidermis includes two distinct sense cell types (I and II) and possibly a third type (the ventral pit cells, to which an adhesive role has alternatively been attributed). The anus first opens on the right‐hand side and only later migrates across the mid‐ventral line to assume a position on the left‐hand side of the larva; this is contrary to the established view that the anus of the larval lancelets opens on the left‐hand side and remains there.
The Larval Nervous System of Polygordius lacteus Scheinder, 1868 (Polygordiidae, Polychaeta): Immunocytochemical Data
Authors: Hay‐Schmidt Anders 
Published: April 2010

AbstractThe nervous system of the planktotrophic trochophore larva of Polygordius lacteus has been investigated using antibodies to serotonin (5‐HT) and the neuropeptide FMRFamide. The apical ganglion contains three 5‐HT‐ir neurons, many FMRFamide‐ir neurons and a tripartate 5‐HT‐ir and FMRFamide‐ir neuropil. A lateral nerve extends from each side of the apical ganglion across the episphere and the ventral hyposphere, where the two nerves combine to form the paired ventral nerve cord. These nerves have both 5‐HT‐ir and FMRFamide‐ir processes. Three circumferential nerves are associated with the ciliary bands: two prototroch and one metatroch nerve. All contain 5‐HT‐ir and FMRFamide‐ir processes. An oral nerve plexus also contain both 5‐HT‐ir and FMRFamide‐ir processes develops from the metatroch nerve, and an esophageal ring of FMRFamide‐ir processes develops in later larval stages. In young stages the ventral ganglion contains two 5‐HT‐ir and two FMRFamide‐ir perikarya; during development the ventral ganglion grows caudally and adds additional 5‐HR‐ir and FMRFamide‐ir perikarya. These are the only perikarya that could be found along the lateral nerve and ventral nerve cord. The telotroch nerve develops from the ventral nerve cord. The 5‐HT‐ir and FMRFamide‐ir part of the nervous system is strictly bilateral symmetric. and much of the system (i.e. apical ganglion, lateral nerves ventral nerve cord, dorsal nerve and oral plexus) is retained in the adult.
Larval Planktotrophy—A Primitive Trait in the Bilateria?
Authors: Haszprunar Gerhard , Salvini‐Plawen Luitfried v. , Rieger Reinhard M. 
Published: April 2010

AbstractThe concept of Gösta Jägersten of a primary biphasic metazoan life‐cycle, consisting of a planktotrophic larva and a benthic adult, forms the basis for several theories on metazoan phylogeny. In this paper the assumed planktotrophic life‐style of the larva is critically analyzed and reconsidered. It is shown, in particular for the Mollusca, that a biphasic life‐cycle with a lecithotrophic larva is probably the plesiomorphic condition. Character distribution and structural data suggest a parallel evolution of the downstream collecting system used in planktotrophic larvae or filter‐feeding adults of gastropods, bivalves and other spiralian or aschelminth taxa. In the basic metazoans (Parazoa, Placozoa, coelenterates) direct or lecithotrophic development dominates by far. For the acoelomate (Platyhelminthes, Gnathostomulida) and pseudocoelomate taxa direct development is probably the plesiomorphic condition. The structural similarities of the upstream collecting system in tentaculate and deuterostome phyla may also be explained by parallel events of heterochrony out of an ancestor with adult filter‐feeding. The main conclusion of this survey is that larval planktotrophy is likely to be secondary and not a plesiomorphic condition among the Bilateria. Accordingly, theories which are based on the assumed plesiomorphy of larval planktotrophy of the Bilateria, need careful reevaluation.