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  • 1980-1984  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Development, settling behaviour, metamorphosis and pentacrinoid feeding and growth of the feather star Florometra serratissima (1983)
    Springer
    Marine biology 73 (1983), S. 309-323 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryonic development of the northeastern Pacific feather star Florometra serratissima takes place within a ridged fertilization membrane. Cleavage is radial, resulting in a coeloblastula, and gastrulations is by invagination. Cilia are swollen terminally during ciliogenesis whereas fully grown cilia possess several swellings along the length of their shafts. Young doliolaria larvae begin to hatch from the fertilization membranes 35 h after fertilization (9.5° to 11.5°C); by 4 d the doliolaria has acquired ciliated bands, a vestibular invagination and an antero-ventral adhesive pit. The surface of the larva is covered with a delicate glycocalyx supported by microvilli. Larvae swim along a vertical sinusoidal path just below the water surface; they begin to explore the substratum at 4.5 d and settlement begins as early as 4.6 d, but can be delayed for up to 9 more days. Larvae settle gregariously in culture and it is suggested that gregarious settlement plays a role in the formation and maintenance of adult aggregations of F. serratissima. Metamorphosis into a stalked cystidean following settlement is rapid. Major changes at this period include: loss of cilia; withdrawal of ectoderm from the glycocalyx; covering over of the vestibular invagination; and a 90 degree rotation of the vestibule to the former posterior end of the doliolaria. Transformation from cystidean to pentacrinoid includes the opening of the 5 oral plates, the extension of the 15 papillate tube feet and further elongation of the stalk. The pentacrinoid is able to feed on small food particles. Rudiments of all 10 adult arms are present by 4 months; at 6 months the pentacrinoid has an arm span of 6.5 mm but cirri and pinnules are not yet present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392257
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Reproduction and development of Sabella media, a sabellid polychaete with extratubular brooding (1983)
    Springer
    Marine biology 76 (1983), S. 301-309 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Known reproductive patterns in the polychaete family Sabellidae include: (1) broadcasting of gametes, (2) depositing of benthic egg masses, (3) brooding outside the lip of the tube, and (4) brooding within the tube. There is little information for sabellids in the third category; there-fore we have studied the reproductive biology of Sabella (=Demonax) media (Bush), one of the few species known to brood its early developmental stages outside the tube. A total of 32 adults of S. media with egg cocoons were collected from the surfaces of compound ascidians (Aplidium sp. and Didemnum sp.) and from holdfasts of a brown alga (Hedophyllum sessile) at Eagle Cove, San Juan Island, Washington, USA, from June 1981 through June 1982, between tidal levels of 0.0 and 0.6 m. The donutshaped cocoons, each containing over 1 000 eggs, are deposited just outside the tube aperture from April through September. Larval development takes place within the cocoon through the 3-setiger stage, at which time the larvae emerge (about 8 d after egg deposition). The newly hatched larvae are demersal and swim near the bottom of the culture dish for 1 d before settlement. Metamorphosis takes nearly a week, and initial formation of the tube is also gradual. The reproductive patterns within the family Sabellidae are discussed, and the adaptive significance of extratubular brooding considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393033
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Microhabitat-associated variability in survival and growth of subtidal solitary ascidians during the first 21 days after settlement (1984)
    Springer
    Marine biology 81 (1984), S. 61-68 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Newly settled juvenile ascidians were transplanted into shaded and unshaded sites at two subtidal depths to test the hypothesis that photonegative settlement behavior enhances juvenile survival. Silt, filamentous algae and grazing gastropods (Margarites pupillus) were identified as sources of mortality associated primarily with non-cryptic microhabitats. Silt inflicted heavy mortality on all six species tested. Algal overgrowth was important in shallow water, where it increased mortality and depressed growth rates over a 14-d period. Laboratory experiments demonstrated that gastropods can remove juvenile ascidians from the substratum. The sources of post-settlement mortality investigated may help determine distributional patterns of ascidians in the San Juan Islands, Washington, USA, and may also represent selective pressures that maintain negative phototaxis in the behavioral repertoires of ascidian tadpoles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397626
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Morphogenesis of the digestive system during metamorphosis of the nudibranch Doridella steinbergae (Gastropoda): Conversion from phytoplanktivore to carnivore (1981)
    Springer
    Marine biology 62 (1981), S. 1-16 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural changes undergone by the digestive system of a phytoplanktotrophic nudibranch larva during metamorphosis into a benthic carnivore are described using histological and electron microscopic techniques. The relative positions of the stomach, digestive gland, and distal end of the intestine are rearranged at metamorphosis by the actions of the larval retractor muscle and the accessory pedal retractor muscle. Although the anus and distal end of the intestine are secondarily displaced to the posterior end of the gastropod, the stomach undergoes further torsional displacement at metamorphosis. The tissues of the larval stomach and distal end of the larval esophagus undergo drastic alteration at metamorphosis. The larval stomach consists of a ciliated vestibule, which receives the openings of the esophagus and left digestive gland, a gastric shield, a style sac, and an intestinal groove. All of these areas, except the vestibule, are destroyed by cell dissociation at metamorphosis. The vestibule becomes the ventral stomach of the benthic stage and the proximal end of the intestine becomes enlarged and muscularized to form the dorsal ‘stomach’ of the benthic stage. The metamorphic changes involving the distal end of the esophagus include the continued development of the radula and oral lip glands, which both appear in rudimentary form during the larval stage, and differentiation of the buccal pump, salivary glands, and oral lips.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396946
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Factors controlling spatial distribution of the sea cucumber Psolus chitonoides: Settling and post-settling behavior (1982)
    Springer
    Marine biology 69 (1982), S. 195-205 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Substratum selection experiments were carried out in situ with larvae of the holothurian Psolus chitonoides Clark in the rocky subtidal of the San Juan Islands, Washington. The experiments indicated, in agreement with laboratory findings, that pentactula larvae settle gregariously, either on the adult, or (when the bivium is obscured by epizooites) by clustering around the margin of the adult sole. Late larvae and early juveniles are strongly photonegative. Following metamorphosis, juveniles migrate from the adults into nearby shaded habitats, where they may take up residence indefinitely. Although adults retain the capacity to move, they relocate only when their living conditions become unsuitable; in most circumstances they are effectively sessile. Small-scale spatial pattern of the adults, which was documented quantitatively on subtidal rock walls, boulders and cobbles, correlates well with microtopographical features. The aggregation observed in the field is primarily due to post-settling migration rather than larval substratum choice at settlement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396899
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Fine structure of the cephalic sensory organ in the larva of the nudibranch Rostanga pulchra (Mollusca, Opisthobranchia, Nudibranchia) (1984)
    Springer
    Zoomorphology 104 (1984), S. 131-139 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cephalic sensory organ in the veliger larva of Rostanga pulchra is situated dorsally between the rhinophores, emerging as a tuft of cilia. This organ is made up of three types of sensory cells, and based on their morphology have been termed ampullary, parampullary and ciliary tuft cells. The cell bodies of the organ originate in the cerebral commissure, and their dendrites pass to the epidermis as three tracts. Dendrites terminate in the epidermis to form a sectorial field. Axons of these cells run into the mass of neurites in the cerebral commissure but no synapses were observed in this area. Morphological evidence suggests that the cephalic sensory organ may function in chemoreception and mechanoreception related to substrate selection at settlement, feeding, or other behaviors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312131
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  • 7
    Electronic Resource
    Electronic Resource
    Fine structural study of the statocysts in the veliger larva of the nudibranch, Rostanga pulchra (1981)
    Springer
    Cell & tissue research 214 (1981), S. 67-80 
    Details
    ISSN: 1432-0878
    Keywords: Statocyst ; Larva ; Nudibranch ; Sensory cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The two statocysts of the veliger larva of Rostanga pulchra are positioned within the base of the foot. They are spherical, fluid-filled capsule that contain a large, calcareous statolith and several smaller concretions. The epithelium of the statocyst is composed of 10 ciliated sensory cells (hair cells) and 11 accessory cells. The latter group stains darkly and includes 2 microvillous cells, 7 supporting cells, and 2 glial cells. The hair cells stain lightly and each gives rise to an axon; two types can be distinguished. The first type, in which a minimum of 3 cilia are randomly positioned on the apical cell membrane, is restricted to the upper portion of the statocyst. The second type, in which 9 to 11 cilia are arranged in a slightly curved row, is found exclusively around the base of the statocyst. Each statocyst is connected dorso-laterally to the ipsilateral cerebral ganglion by a short static nerve, formed by axons arising from the hair cells. Ganglionic neurons synapse with these axons as the static nerve enters the cerebral ganglion. The lumen of the statocyst is continuous with a blind constricted canal located beneath the static nerve. A diagram showing the structure of the statocyst and its association with the nervous system is presented. Possible functions of the statocyst in relation to larval behavior are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235145
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