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  • 1
    Electronic Resource
    Electronic Resource
    Assimilation of Labelled Glucose from Seawater by Marine Nematodes (1969)
    [s.l.] : Nature Publishing Group
    Nature 224 (1969), S. 720-721 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Longitudinal section of P. vulgare, showing the labelling of the intestinal epithelium. Scale: 40 microns. Fig. 2. Longitudinal section of P. vulgare, showing the labelling of the hypodermal cords (arrows). Scale: 40 microns. Fig. 3. Transverse section of P. vulgare, showing the labelling ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/224720a0
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Fine structure of the cerebral organs in hoplonemerteans (Nemertini), with a discussion of their function (1987)
    Springer
    Zoomorphology 107 (1987), S. 145-159 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The fine structure of the cerebral organs is described in three species of monostiliferous hoplonemerteans. Amphiporus lactifloreus, Paranemertes peregrina and Tetrastemma candidum. There are two distinct groups of sensory cells in the cerebral organs of all three species. The ultrastructure of the sensory elements in these species is consistent with a chemoreceptive function of the dendrites. Incurrent and excurrent channels of the canal are postulated, based on the fine structure of the ciliary axonemes. Flow through the canal is such that each of the two groups of dendrites is downstream from a group of glandular cell outlets and upstream from a group of vesicular cells. It is suggested that the glandular, sensory and vesicular cells form a functional unit in which glandular cells secrete a coating material over the dendrites and vesicular cells actively remove this coating by endocytosis. Vesicular material is also found in glandular cells, where it probably arises in situ through crinophagy. There is no ultrastructural evidence that vesicular material is transferred to the vascular system. Small fibres containing dense vesicles are present among the ciliated cells and may represent an efferent nerve supply controlling the rate of flow through the canal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312308
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Peristaltic constrictions in fertilized barnacle eggs (Pollicipes polymerus) (1973)
    Springer
    Cellular and molecular life sciences 29 (1973), S. 1533-1535 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Résumés La vitesse et l'amplitude des resserrements péristaltiques dans les œufs fertilisés de balane (Pollicipes polymerus) dépend de l'âge de l'embryon et de la position du resserrement dans celui-ci. Les resserrements péristaltiques sont probablement réglés par des microfilaments et non par des microtubules et il se peut que la synthèse de protéine soit nécessaire, mais la phosphorylation oxydative ne l'est pas. Le rapport possible entre les resserrements et les événements morphogénétiques des œufs fertilisés est discuté.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01943901
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  • 6
    Electronic Resource
    Electronic Resource
    Heavy metal accumulation in tissue/organs of a sea cucumber, Holothuria leucospilota (1997)
    Springer
    Hydrobiologia 352 (1997), S. 17-23 
    Details
    ISSN: 1573-5117
    Keywords: Zinc accumulation ; sea cucumber ; longitudinalmuscle ; respiratory tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Holothuria leucospilota Brandt, the large black sea cucumber, is a non-selective deposit feeder, and is commonly found in the bottom of shallow waters in Hong Kong, where the sediments are often polluted with heavy metals. This study was designed to test the possibility of heavy metal accumulation by the sea cucumber at two sites in Hong Kong. Atomic absorption spectrophotometer was used to measure Cu and Zn concentrations in various tissue/organs of the animal as well as in the sediments. The result indicated that H. leucospilota accumulated zinc in the longitudinal muscle bands (97.27–98.07 ppm in dry weight) and in the respiratory tree (83.92–89.64 ppm in dry weight). Copper concentrations in these two organs were much lower than that of zinc. After the animals were kept in the aquarium without sediment for40 days, zinc concentration of the longitudinal muscle and respiratory tree decreased by 48% and 39%respectively whereas copper concentration remained unchanged. The concentrations of zinc and copper in the sediment at the two sites differed significantly but the metal level in the animals from the two sites were similar, suggesting that this sea cucumber was not an ideal bioindicator of heavy metal pollution in the sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003028601518
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  • 7
    Electronic Resource
    Electronic Resource
    The fine structure of the polymorphic spermatozoa of Fusitriton oregonensis (Mollusca: Gastropoda), with notes on the cytochemistry of the internal secretions (1982)
    Springer
    Cell & tissue research 227 (1982), S. 235-255 
    Details
    ISSN: 1432-0878
    Keywords: Sperm polymorphism ; Ultrastructure ; Mollusca ; Prosobranchia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The prosobranch Fusitriton oregonensis exhibits an unusual form of sperm polymorphism. The viable, eupyrene sperm are attached in groups of about fifty to worm-shaped, apyrene, carrier sperm. There is a second apyrene sperm, which is lancet-shaped and has a different internal organization than the carrier, but does not transport eupyrene sperm. The eupyrene sperm are filiform (185 μm long), with a conical acrosome, elongate nucleus and midpiece. They contain large stores of glycogen in the principal piece, together with an unusually high proportion of protein. The latter is due to a complex interconnecting system of fibres that supports the tail internally. A distinct annulus is located, characteristically, at the junction between midpiece and principal piece. The carrier sperm has a core of about 112 axonemes that arise from basal bodies in the anterior end and extend through its entire length of 36 μm. The basal bodies have unstriated rootlets that are embedded in a granular cap. Large membrane-bound “yolk bodies” are arranged along the length of the carrier sperm, on either side of the median axonemal core. Dense bodies, which may be indigestible residues formed from the degeneration of the nucleus, are excreted by exocytosis. Individual carrier sperm are capable of “corkscrew” propulsion, resembling that of spirochaetes. The lancet sperm is three times as long as the carrier. The sixteen or so axonemes, which are arranged peripherally like a cage enclosing the cytoplasm, originate from a dense centriolar plate in the anterior end. The cytoplasm is filled with secretions including small yolk granules, dense bodies (also excreted), clear vesicles, and a membranated granular secretion that resembles mucus. The possible functions of the lancet and carrier sperm are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210883
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  • 8
    Electronic Resource
    Electronic Resource
    On the nurse cell and the spermatozeugma in Littorina sitkana (1977)
    Springer
    Cell & tissue research 179 (1977), S. 347-356 
    Details
    ISSN: 1432-0878
    Keywords: Nurse cell ; Spermatozeugma ; Ultrastructure ; Mollusca ; Littorina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nurse cells develop from diploid cells in the testis. Each cell undergoes a reduction division which leaves the nucleus with half the volume of a normal diploid cell. They send out pseudopodia which form desmosomelike junctions with developing spermatids. The nurse cells detach from the testicular wall, their nuclei degenerate and secretion droplets form in the cytoplasm. The pseudopodia are drawn in as the cytoplasmic secretions swell and the nurse cell becomes spherical. The eupyrene sperm become grouped unilaterally and at this stage are attached to the nurse cell by only the tips of their acrosomes. At maturity the nurse cells with their clumps of attached eupyrene sperm (spermatozeugmata) are released from the testis via ducts into the seminal vesicles, where they are stored prior to copulation. Nurse cells serve similar functions to those of apyrene sperm which are common among the Molluscs. We believe that the nurse cell and apyrene sperm are homologous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221105
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  • 9
    Electronic Resource
    Electronic Resource
    Spermatogenesis of a marine snail, Littorina sitkana (1976)
    Springer
    Cell & tissue research 170 (1976), S. 455-475 
    Details
    ISSN: 1432-0878
    Keywords: Spermatogenesis ; Mollusca, Prosobranchia (Littorina) ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the spermatogonium, spermatocyte and spermatid of a marine snail, Littorina sitkana is described. The ring centriole (annulus) is formed from the distal centriole and it migrates to the base of the mitochondrial region where it lies in a joint-like structure which is formed by an area of invaginated plasma membrane. The distal and proximal centrioles are at first perpendicular to each other but the proximal centriole rotates to a position coaxial with the distal centriole and fuses with it. The peripheral doublet fibers are continuous between the two centrioles but the central fibers originate only in the distal centriole. The acrosome differentiates from the proacrosomal granule which is derived from a Golgi body. Microtubules, present at this stage, may assist acrosomal formation. Chromatin condensation begins with the formation of fibrous strands, then to lamellar plates which become folded and later twisted around the flagellar shaft. In the final stages the lamellae appear in cross section as concentric rings which eventually fuse to form a homogeneously dense nuclear tube.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361704
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  • 10
    Electronic Resource
    Electronic Resource
    Fine structural observations of sperm resorption in the seminal vesicle of a marine snail, Littorina scutulata (Gould, 1849) (1976)
    Springer
    Cell & tissue research 172 (1976), S. 503-515 
    Details
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Spermatozoa ; Phagocytosis ; Mollusca ; Littorina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Waste sperm and spermatozeugmata in the seminal vesicle of Littorina scutulata are phagocytised either by cell buds (large vesicles given off from the epithelial cells) or by the epithelial cells themselves. Cell buds containing sperm, are in turn engulfed by epithelial cells. In both cases, heterophagic vacuoles are formed inside the cell and subsequently the vacuoles are fused with primary lysosomes or lysosomal derivatives to become secondary lysosomes. Throughout this process the sperm are being digested. The second lysosome transforms further to telolysosome and finally to residual body when the sperm is completely digested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220335
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