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  • 1
    Electronic Resource
    Electronic Resource
    Fine structure of the larval eyes of Rostanga pulchra (Mollusca, Opisthobranchia, Nudibranchia) (1983)
    Springer
    Zoomorphology 102 (1983), S. 1-10 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The eyes of Rostanga pulchra larvae develop immediately behind the velar lobes approximately 20 days after hatching. Each is a pigmented cup with a lens occupying the concavity of the cup. The eye is composed of a single corneal cell, 7 sensory cells and 8 pigment cells. Sensory cells are of the rhabdomeric type and bear microvilli as their receptive surface. The eye connects to the inner dorsal region of the optic ganglion through a nerve that consists of axons arising from the 7 sensory cells. The optic ganglion, in turn, joins the lateral region of the cerebral ganglion. The possible functions of the eye are discussed in relation to larval behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310729
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  • 2
    Electronic Resource
    Electronic Resource
    Spermiogenesis in Polyplacophora, with special reference to acrosome formation (Mollusca) (1990)
    Springer
    Zoomorphology 109 (1990), S. 179-188 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The present study examines spermiogenesis, and in particular the formation of the acrosome, in ten species of chitons belonging to four families. This study emphasizes the formation of the acrosome but brings to light several other structures that have received little or no mention in previous studies. The process of spermiogenesis is essentially similar in each species, although Chaetopleura exhibits some significant differences. In early spermiogenesis the Golgi body secretes numerous small pro-acrosomal vesicles that gradually migrate into the apical cytoplasm. The chromatin condenses from granules into fibres which become twisted within the nucleus. A small bundle of chromatin fibres projects from the main nuclear mass into the anterior filament; this coincides with the appearance of a developing manchette of microtubules around the nucleus that originates from the two centrioles. Radiating from the distal centriole is the centriolar satellite complex, which is attached to the plasma membrane by the annulus. The distal centriole produces the flagellum posteriorly and it exits eccentrically through a ring of folded membrane that houses the annulus. Extending from the annulus on one side of the flagellum, in all but one species, is a dense fibrous body that has not been previously reported. The proximal centriole lies perpendicular to the end of the distal centriole and is attached to it by fibro-granular material. Pro-acrosomal vesicles migrate anteriorly through the cytoplasm and move into the anterior filament to one side of the expanding nucleus. Eventually these vesicles migrate all the way to the tip of the sperm, where they fuse to form one of two granules in the acrosome. In mature sperm the nucleus is bullet-shaped with a long anterior filament and contains dense chromatin with occasional lacunae. The mitochondria vary in both number and position in the mature sperm of different species. Both centrioles are housed eccentrically in a posterior indentation of the nucleus, where the membranes are modified. The elongate flagellum tapers to a long filamentous end-piece that roughly corresponds to the anterior filament and may be important in sperm locomotion for hydrodynamic reasons. An acrosome is present in all ten species and stained positively for acid phosphatase in three species that were tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312469
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  • 3
    Electronic Resource
    Electronic Resource
    Fine structure of the larval rhinophores of the nudibranch, Rostanga pulchra, with emphasis on the sensory receptor cells (1982)
    Springer
    Cell & tissue research 225 (1982), S. 235-248 
    Details
    ISSN: 1432-0878
    Keywords: Rhinophore ; Larva ; Nudibranch ; Sensory cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The rhinophores of the veliger larva of Rostanga pulchra are located in the intravelar field near the base of the velar lobes. Each rhinophore is a cylindrical structure, tapering distally, and covered with a dense meshwork of microvilli. A conspicuous row of ciliary tufts runs along each side of the rhinophore and several stiffer tufts, composed of fewer cilia, are positioned around the tip or at the base. The rhinophoral epithelium consists of supporting cells, ciliated cells (giving rise to the ciliary rows), dendritic terminals (giving rise to the tufts around the apex), and sinuses containing occasional amebocytes. The lumen of the rhinophore is occupied by the rhinophoral ganglion and muscle cells that are oriented in two perpendicular planes. Cell bodies of the dendritic endings are located within the rhinophoral ganglion, which in turn joins into the optic and cerebral ganglia. Rhinophoral ganglionic neurons do not synapse with each other, but numerous neuromuscular synapses are found in the lumen of the rhinophore. Morphological evidence suggests that the dendritic endings are chemoreceptors and the ciliated cells are possibly mechanoreceptors but are not functional at this stage in development. The functional role of the rhinophores is discussed in relation to larval behavior at settlement and metamorphosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214678
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  • 4
    Electronic Resource
    Electronic Resource
    The fine structure of the newly discovered propodial ganglia of the veliger larva of the nudibranch Onchidoris bilamellata (1989)
    Springer
    Cell & tissue research 256 (1989), S. 17-26 
    Details
    ISSN: 1432-0878
    Keywords: Larval development ; Ganglia, invertebrate ; Onchidoris bilamellata (Mollusca, Nudibranchia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two pairs of ganglia are found in the propodial region of the veliger of Onchidoris bilamellata: the anterolateral pair is located at the foremost corners of the propodium, and the frontal pair is located beside the propodial midline. Both sets of ganglia are positioned below the epidermis, and they are joined to the cerebral ganglia by large, common connectives. Each ganglion possesses sensory cells, nerve cells and sheath cells, and the frontal pair contains a complement of secretory cells. Externally, the propodial ganglia are manifested as sensory fields. The fields of the anterolateral pair are elliptical in shape, and each appears as a band of cilia bordering an unciliated zone. The region devoid of cilia is composed of ordinary epidermal cells, whereas the ciliated portion is comprised of dendritic endings originating from cells in the ganglion. Dendrites arise from one type of sensory cell and pass through the epidermis in bundles. Each dendrite terminates as a single cilium at the epidermal surface. Sensory fields of the frontal ganglia are key-shaped and oppose one another on the anterior end of the foot. Each field appears as a flat, circular, unciliated region which extends into a ciliated groove that runs dorsally toward the mouth. The groove contains the terminals of secretory cells, ciliated sensory cells, and the cell bodies of nonciliated sensory cells. The nonciliated sensory cells, characterized by a microvillous apex, are the dominant cells in the flattened circular zone. The space between the frontal ganglia and the epidermis is bridged by bundles of processes which are similar to those of the anterolateral ganglia. However, these tracts contain collections of the apical processes of secretory cells, the dendrites of ciliated sensory cells, and the axons of nonciliated sensory cells. Morphological and behavioral evidence indicates that the propodial ganglia serve a chemosensory function during settlement and metamorphosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224714
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  • 5
    Electronic Resource
    Electronic Resource
    Fine structure of the doliolaria larva of the feather star Florometra serratissima (Echinodermata: Crinoidea), with special emphasis on the nervous system (1986)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 189 (1986), S. 99-120 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The epidermis of the doliolaria larva of the Florometra serratissima is differentiated into distinct structures including an apical organ, adhesive pit, ganglion, ciliary bands, nerve plexus, and vestibular invagination. All these structures possess unique cell-types, suggesting that they are functionally specialized in the larva, except the vestibular invagination that becomes the postmetamorphic stomodeum. The epidermis also contains yellow cells, amoeboid-like cells, and secretory cells. The enteric sac, hydrocoel, axocoel, and somatocoels have differentiated but are probably not functional in the doliolaria stage. Mesenchymal cells, around the enteric sac and coeloms, appear to be actively secreting the endoskeleton and connective tissue fibers.The nervous system is composed of a nerve plexus, ganglion, and sensory receptor cells in the apical organ. The apical organ is a larval specialization of the anterior end; the ganglion is located in the base of the epidermis at the anterior dorsal end of the larva. The nerve plexus underlies most of the epidermis, although it is more prominent in the anterior region. Here, processes from sensory receptor cells of the apical organ, as well as those from nerve cells, contribute to the plexus. These processes contain one or a combination of organelles including vesicles, vacuoles, microtubules, and mitochondria. The configuration of glyoxylic acid-induced fluorescence, revealing catecholamine activity, correlates to the apical organ, nerve cells, and nerve plexus. Morphological evidence suggests that the nervous system may function in initiation and control of settlement, attachment, and metamorphosis. The crinoid larval nervous system is discussed and compared to that found in other larval echinoderms.
    Additional Material: 50 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051890202
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  • 6
    Electronic Resource
    Electronic Resource
    Fine structural studies of the nervous system and the apical organ in the planula larva of the sea anemone Anthopleura elegantissima (1979)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 160 (1979), S. 275-297 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The nervous system of the planula larva of Anthopleura elegantissima consists of an apical organ, one type of endodermal receptor cell, two types of ectodermal receptor cells, central neurons and nerve plexus. Both interneural and neuromuscular synapses are found in the nerve plexus.The apical organ is a collection of about 100 long, columnar cells each bearing a long cilium and a collar of about 10 microvilli. The cilia of the apical organ are twisted together to form an apical tuft. The ciliary rootlets of the apical organ cells are extremely long, reaching to the basal processes of the cells adjacent to the mesoglea.All three types of sensory cells are tall and slender in profile and are identified by the presence of one or more of the following features: microtubules, small vesicles, membrane-bound granules and synapses. The interneurons are bipolar cells with somas restricted to the aboral end, adjacent to the apical organ. All synapses observed are polarized or asymmetrical.A diagram including all the elements of the nervous system is presented and the possible functions of the nervous system are discussed in relation to larval behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051600303
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  • 7
    Electronic Resource
    Electronic Resource
    A fine structural study of metamorphosis of the hydrozoan Mitrocomella polydiademata (1983)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 176 (1983), S. 261-287 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This report is a comprehensive fine structural analysis of the morphological changes occurring during metamorphosis of the marine hydrozoan Mitrocomella polydiademata. Five stages are recognized during metamorphosis: planulae just prior to settlement, ball and filiform stages, immature polyps, and primary feeding polyps. Settlement and metamorphosis of cnidarian planulae involve such changes as ciliary arrest, discharge of nematocytes, secretion of glandular cells, differentiation of cells, and changes in cell and body shape.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051760303
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  • 8
    Electronic Resource
    Electronic Resource
    Fertilization in a chiton: Acrosome-mediated sperm-egg fusion (1988)
    New York, NY : Wiley-Blackwell
    Gamete Research 21 (1988), S. 199-212 
    Details
    ISSN: 0148-7280
    Keywords: egg envelopes ; polyspermy ; mollusca ; polyplacophora ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Contrary to the widely accepted view that chiton sperm lack acrosomes and that fertilization in this group occurs via a micropyle, we demonstrate here that fertilization in Tonicella lineata occurs by acrosome-mediated sperm-egg fusion. The acrosome is a small vesicle containing two granules located at the tip of the sperm. The eggs have an elaborate hull (=chorion), which is formed into cupules that remain covered by follicle cells until maturity. When dissected ripe eggs were exposed to sperm in vitro, the sperm were attracted only to open cupules, inside which they swam through one of seven channels to the base where they penetrated the hull. The acrosome fired on contact with, or in, the hull, and during passage through it the apical granule was exhausted while the basal granule was exposed. If sperm contacted follicle cells between the cupules the acrosome did not react. The vitelline layer beneath the hull contains pores arranged in a regular pattern. Embedded in the base of each pore is an egg microvillus. Having penetrated the hull the sperm anterior filament located a pore and fused with the tip of the egg microvillus projecting into it. This created a membranous tube, through which the sperm nucleus was injected into the egg. The egg membrane appeared to be raised up into a small fertilization cone around the penetrating sperm, the vitelline layer became slightly elevated, and some cortical granules were released by exocytosis.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120210302
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