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  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Anatomical and ultrastructural studies of chemical defence in the sponge Dysidea fragilis (1998)
    Springer
    Marine biology 131 (1998), S. 639-645 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine sponge Dysidea fragilis from El Mar Menor, a hypersaline coastal lagoon (Murcia, Spain), contains the furanosesquiterpenoid ent-furodysinin as the major secondary metabolite. D. fragilis emits a defensive white fluid when it is disturbed. Electron micrographs of this fluid revealed intact vesiculated cells together with other amorphous material. Dissociated cells are more rounded in shape but maintain the same ultrastructural features as cells observed in ultra-thin sections of the whole sponge. The defensive secretion is composed mainly of sponge cells with abundant light vesicles. Sometimes these light vesicles appear to open into the intercellular space; this correlates with surface blebs on these cells observed under scanning electron microscopy. The intracellular location of ent-furodysinin was confirmed by Erlich staining. In laboratory assays, we examined the role of ent-furodysinin as a feeding deterrent to generalist fish predators. It was isolated from D. fragilis and incorporated into a carrageenan-based artificial diet. The addition of ent-furodysinin to the artificial diet reduced feeding by the fish Thalassoma pavo. Similarly, fish did not feed on artificial diet above which defensive secretion of D. fragilis had been ejected with a small syringe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050356
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Applying Lagrangian relaxation to the resolution of two‐stage location problems (1999)
    Springer
    Annals of operations research 86 (1999), S. 179-198 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract A family of two‐stage location problems is considered. These problems involve a systemproviding a choice of depots andyor plants, each with an associated location cost, and a setof demand points which must be supplied, in such a way that the total cost is minimized. Byusing Lagrangian relaxation, lower bounds and heuristic solutions are obtained for two kindsof formulation involving two or three indexes for each transportation variable. The goodnessof both formulations is compared by means of a computational study, and the results forseveral instances are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018998500803
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of high temperatures on germination ofPinus halepensis Mill. andP. pinaster Aiton subsp.pinaster seeds in southeast Spain (1995)
    Springer
    Plant ecology 116 (1995), S. 69-72 
    Details
    ISSN: 1573-5052
    Keywords: Germination dynamics ; Heat ; Obligate seeders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seeds ofPinus halepensis andPinus pinaster subsp.pinaster were subjected to four heat treatments (90, 110, 150 and 200 °C) for 1 and 5 min to investigate their tolerances to high temperatures resulting from fires. Another group of seeds of each species were not heated and considered as a control. Information on responses of seeds to high temperatures would help to determine whether or not the species are pyrophytes. Heating for 1 min at all temperatures did not affect the average germination ofPinus halepensis seeds whereas that ofP. pinaster subsp.pinaster seeds was decreased significantly when they were heated to 200 ° C. HoweverP. pinaster seeds were more resistant than that ofP. halepensis when heat treatment was 150 °C for 5 min. Data obtained also indicated that, in general,P. halepensis andP. pinaster subsp.pinaster seed germination is not favoured by a temperature increase than can be reached in soils during a fire. Thus, the species are not pyrophytes but colonizers of burnt sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045279
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    Paper (German National Licenses)
    Fulltext
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