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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of the integument of a pelagic Crustacean: moult cycle related studies on the Antarctic krill, Euphausia superba (1989)
    Springer
    Marine biology 101 (1989), S. 355-365 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructure of euphausiid integument was examined in relation to the moult cycle and supplemented by investigations of chitinase activity in the integument and content of N-acetyl-β-D-glucosamine in the hemolymph. The Antarctic krill, Euphausia superba was collected in 1983 in Admiralty Bay, King George Island, Antarctica. Some specimens of the Northern krill, Meganyctiphanes norvegica, from the Danish Kattegat served for comparison. As a major aim of the study, the moult staging system developed for living tissue could be verified by ultrastructural findings. Under experimental high production conditions of the Antarctic summer, no period of rest or “intermoult” between post- and premoult was observed in subadult E. superba. Neither was a resting phase seen at the cellular level, the epidermis remained active. The epidermal gland cells did not show any cyclical changes, and the organelles of protein synthesis were generally well developed in all moult stages. In order to follow the physiological course of events, structural and biochemical methods were combined and showed as a result that the last moult stage before ecdysis is characterized by massive cuticular resorption. The epicuticle remained ultrastructurally unchanged before and after ecdysis, even though its permeability should alter at ecdysis. The existence of muscle insertions which connect the old and the new cuticle across the exuvial space suggests an answer to the question why E. superba is hardly impaired in swimming almost up to the time of ecdysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428132
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  • 2
    Electronic Resource
    Electronic Resource
    Colonization behaviour of two enterobacterial strains on cereals (2000)
    Springer
    Biology and fertility of soils 30 (2000), S. 550-557 
    Details
    ISSN: 1432-0789
    Keywords: Key words Bacteria-plant interaction ; Pantoea agglomerans ; Klebsiella pneumoniae ; Double antibody sandwich enzyme linked immunosorbent assay ; Population densities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Two diazotrophic enterobacterial strains, Pantoea agglomerans D5/23 and Klebsiella pneumoniae CC12/12, were observed in sterile and non-sterile hydroponic and soil experiments in order to determine, by means of an immunological detection method (double antibody sandwich enzyme linked immunosorbent assay), their colonization sites, their migration within individuals of different plant species, and their ability to compete with indigenous organisms. To investigate the interaction between bacteria and plants, root and shoot samples were analysed using electron microscopy. Field experiments were performed to determine the growth-promoting abilities of the bacterial strains. In field experiments, inoculation with P. agglomerans led to an increase in the grain yield of different wheat (Triticum aestivum) cultivars. The same strain was also able to colonize the rhizosphere and the phyllosphere of different cereals due to its ability to migrate within the plant. Roots and media were colonized 10–100 times more intensively than shoots, with about 106 cells g–1 root and 104 cells g–1 shoot. We found that P. agglomerans colonized the root and plant-growth medium of wheat to a greater extent than those of rye (Secale cereale) and barley (Hordeum vulgare), whereas the colonization of shoots was higher in rye and barley compared to wheat. Furthermore, while cell numbers of K. pneumoniae in media and roots were 10 times higher than cell numbers of P. agglomerans, only the latter markedly increased root growth. We were able to detect significant differences in colonization numbers between treatments even if the data were not normally or log-normally distributed or the variances were not homogenous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050035
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  • 3
    Electronic Resource
    Electronic Resource
    Diel vertical migrations ofMeganyctiphanes norvegica in the Kattegat: Comparison of net catches and measurements with Acoustic Doppler Current Profilers (1995)
    Springer
    Helgoland marine research 49 (1995), S. 849-866 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diel vertical migration of a stable and well-defined population of Nordic krill,Meganyctiphanes norvegica (Crustacea, Euphausiacea) was investigated during eight days in August 1989, in the Läsö-Deep, East of the Danish island Läsö. Net catches with a multi-net (MOCNESS) and measurements with a moored and a shipboard Acoustic Doppler Current Profiler (ADCP) were compared. Backscattered energy as a measure for biomass gave good correlations to the dry weight ofM. norvegica and smaller zooplankton from net catches. Diel migratory patterns matched well, as determined, parallel with both methods. Migratory vertical velocity was determined with ADCP at 2–3 cm sec−1. The potential for the use of ADCPs for biological investigation is discussed. Vertical migration was dependent on environmental parameters. The krill did not cross a temperature barrier of 14°C, although rich food sources were situated beyond it. Differences in salinity did not play a role. Currents were involved in plankton distribution. Light was an important Zeitgeber (synchronizer) and determined the density of the krill aggregations. Feeding behaviour did not interfere with the light-induced migratory pattern of Nordic krill at the Läsö-Deep.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368407
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    Paper (German National Licenses)
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