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  • Artikel  (7)
  • Biologie  (7)
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  • Artikel  (7)
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  • 1
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 207-208 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SIR - Skeletal check-marks are commonly used to assess the age and growth of organisms. They are usually assumed to be formed annually. By using radiocarbon bomb signals to calibrate growth checks in shells of Antarctic brachiopods, we show that they were laid down with a sub-biennial periodicity. ...
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    ISSN: 1438-3888
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The surface deposit feeding speciesPygospio elegans andMacoma balthica are dominant members of many sandy bottom communities of northern boreal regions. The feeding mode of both species and the tube-building ofP. elegans are assumed to affect community structure by interactions with other species. The weight of tubes ofP. elegans varied between 2 and 13 g DW/100 cm2 at the two stations investigated and during the year, which is equivalent to 230–1500 cm of tubes per 100 cm2 of sediment surface. Sediment stability may be affected directly or indirectly by the amount of tubes present.M. balthica shows a linear relation between the maximum size of particles which can be inhaled and animal length. In Kiel Bay, particles〉0.5 mm are out of the range of this species. In summer, the potential feeding area (PFA) of aP. elegans population at one station in Kiel Bay was 1.8 times the available surface area. The PFA of three different populations ofM. balthica in Kiel Bay exceeded the available surface area by factors of 2.6, 2.7, and 3.2. These findings indicate strong intra- and interspecific competition for food. Additionally, the feeding of both species may strongly affect the recruitment of benthic species via pelagic larvae. Experiments are proposed to evaluate the significance of the investigated behavioural aspects for community structure.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Population dynamics of the epizoic bivalve Lissarca notorcadensis living on spines of cidaroid sea urchins in the Weddell Sea were investigated. Total production (somatic & gonad) of the suspension feeding bivalve ranged between 16.5 and 487.4 mg AFDM y−1 per sea urchin. Annual sedimentation rates are not sufficient to maintain the production of the Lissarca sub-populations carried by the sea urchins, and resuspension of organic matter is most likely to be an important food source. The ratio of the number of freshly settled juveniles to the number of embryos brooded is between 0.054 and 0.207 and seems negatively related to the biomass already present, indicating intraspecific competition for space. Interspecific competition for space is caused by the strong preference of L. notorcadensis as well as other epizoa (colonial anthozoans and bryozoans) for the spines located on the aboral hemispere of the sea urchins.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SIR — Poore and Wilson1, and Rex et al.2, give evidence for a distinct decline in species diversity in deep-sea communities from the tropics towards north polar re-gions; and for a less clear trend but high interregional variability in the Southern Hemisphere. Poore and Wilson1 included some ...
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Two species of the echinoid genus Sterechinus were documented from 92 trawl stations and 55 photographic stations in the eastern and southern Weddell Sea between 100 and 1200 m water depth. We found two species occuring along the whole shelf and slope, S. neumayeri being more abundant above 450 m water depth and S. antarcticus dominating the deeper regions. The size-frequency distributions of both species indicate differences in growth, mortality and longevity. First estimates of abundance and biomass of S. neumayeri and S. antarcticus are 0.085 ind/m2 & 0.005 gAFDW/m2 and 0.022 ind/m2 & 0.005 gAFDW/m2, respectively.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Polar biology 17 (1997), S. 465-468 
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Growth marks in calcareous shells or skeleton parts of benthic invertebrates are often assumed to be formed annually and hence are used for ageing purposes. For some Antarctic species this assumption has been validated by tagging experiments or direct monitoring of growth throughout the year. Here we use the record of stable isotope ratios (δ18O and δ13C) deposited in shell carbonate of Laternula elliptica from King George Island to demonstrate that shell growth bands are formed annually in this species.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    ISSN: 1573-5125
    Schlagwort(e): Population dynamics ; mudskipper ; Periophthalmus papilio ; Cross River ; Nigeria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A seminal study was conducted in which the population dynamics (growth, mortality and recruitment) of the mudskipper (Periophthalmus papilio) in the Cross River, Nigeria, was elucidated for the first time using length frequency data and the ELEFAN software. The allometric relationship was: Weight=0.012(Length)2.940, n=415, r2=0.939, P 〈0.0005. The seasonalized Von Bertalanffy growth parameters were L∞=19.39 cm, K=0.51 y−1, C=0.3, and WP=0.4. The instantaneous total mortality coefficient Z was 2.208 y−1 while the instantaneous natural mortality coefficient was 1.341 y−1. The instantaneous fishing mortality coefficient of 0.867 y−1 yielded the expectedly low exploitation rate E of 0.393. Our estimate shows that the species could reach an average maximum life span of about 6 years in the Cross River system. These results are used in quantitative elucidation of the state of exploitation of the population and will serve as input for the proper and scientific management of the fish resource.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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