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  • 1
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    Invasive versus native brachyuran crabs in a European rocky intertidal: respiratory performance and energy expenditures (2018)
    SPRINGER
    In:  EPIC3Marine Biology, SPRINGER, 165(54), pp. 1-14, ISSN: 0025-3162
    Details
    Publication Date: 2018-02-27
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
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    Habitat modelling of crabeater seals (Lobodon carcinophaga) in the Weddell Sea using the multivariate approach Maxent (2017)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, 40(5), pp. 961-976, ISSN: 0722-4060
    Details
    Publication Date: 2017-07-11
    Description: The crabeater seal (Lobodon carcinophaga) is the most abundant Antarctic seal and inhabits the circumpolar pack ice zone of the Southern Ocean. Until now, information on important environmental factors affecting its distribution as well as on foraging behaviour is limited. In austral summer 1998, 12 crabeater seals of both sexes and different age classes were equipped with satellite-linked dive recorders at Drescher Inlet (72.85°S, 19.26°E), eastern Weddell Sea. To identify suitable habitat conditions within the Weddell Sea, a maximum entropy (Maxent) modelling approach was implemented. The model revealed that the eastern and southern Weddell Sea is especially suitable for crabeater seals. Distance to the continental shelf break and sea ice concentration were the two most important parameters in modelling species distribution throughout the study period. Model predictions demonstrated that crabeater seals showed a dynamic response to their seasonally changing environment emphasized by the favoured sea ice conditions. Crabeater seals utilized ice-free waters substantially, which is potentially explained by the comparatively low sea ice cover of the Weddell Sea during summer 1998. Diving behaviour was characterized by short (〉90 % = 0–4 min) and shallow (〉90 % = 0–51 m) dives. This pattern reflects the typical summer and autumn foraging behaviour of crabeater seals. Both the distribution and foraging behaviour corresponded well with the life history of the Antarctic krill (Euphausia superba), the preferred prey of crabeater seals. In general, predicted suitable habitat conditions were congruent with probable habitats of krill, which emphasizes the strong dependence on their primary prey.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
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    Respiration physiology and ecosystem impact of European and Asian shore crabs in a temperate European habitat (2017)
    The Crustacean Society
    In:  EPIC3The Crustaxean Society Mid-Year Meeting, Barcelona, Spain, 2017-06-19-2017-06-22Barcelona, Spain, The Crustacean Society
    Details
    Publication Date: 2017-07-24
    Description: Hemigrapsus sanguineus, the Asian shore crab, is a successful invader at the U.S. east coast and the European Atlantic coast, where populations are established from France to Germany. Numerous studies on behavioral aspects and population development are available, however, physiology and energetic impact of the invader on its ecosystem are virtually unknown. We measured respiration rates of H. sanguineus and its native equivalent, the European shore crab C. maenas, from the island of Helgoland, North Sea, Germany. Measurements were conducted at 5, 10, 15 and 20 °C, using a flow-through system. Specific respiration rates were overall similar for both species. Rates increased with temperature and decreased with the mass of the crab. Mass-standardized data revealed that small H. sanguineus showed significantly higher respiration rates at higher temperatures than C. maenas. This difference vanished with increasing crab size. Statistical modelling was used to develop species-specific equations to calculate a crab´s respiration rate in relation to its mass and the ambient temperature. Taking the overall biomass and temperature into account, the population respiration, carbon uptake and the metabolic energy demand, a measure for the population´s ecosystem impact, was calculated. In the Helgoland intertidal, total biomass of H. sanguineus is now about 59% of that of the C. maenas population but the cumulative metabolic energy demand represents already 78% of the value for C. maenas. With still increasing abundances of H. sanguineus and globally rising temperatures, the ecosystem impact of this invader will increase in the future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Physiological response of adult Antarctic krill, Euphausia superba, to long-term starvation (2015)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, ISSN: 0722-4060
    Details
    Publication Date: 2015-03-05
    Description: Adult Euphausia superba survive winter without or with little feeding. It is not exactly known whether the scarcity of food or an internal clock, set by the natural Antarctic light regime, are responsible for non-feeding. Our research questions were therefore the following: (1) How will physiological and biochemical conditions of krill change during long-term starvation at constant light regime? (2) If and how do enzyme activities change during such starvation? (3) What is the influence of food availability versus that of light regime? To answer these questions, adult krill were starved under laboratory conditions for 12 weeks with constant light regime (12:12; dark/light) and the impact on physiological functions was studied. Initial experimental condition of krill resembled the condition of late spring krill in the field with fully active metabolism and low lipid reserves. Metabolic activity and activities of enzymes catabolising lipids decreased after the onset of starvation and remained low throughout, whereas lipid reserves declined and lipid composition changed. Mass and size of krill decreased while the inter-moult period increased. Depletion of storage- and structural metabolites occurred in the order of depot lipids and glycogen reserves after onset of starvation until proteins were almost exclusively used after 6–7 weeks of starvation. Results confirmed various proposed overwintering mechanisms such as metabolic slowdown, slow growth or shrinkage and use of lipid reserves. However, these changes were set in motion by food shortage only, i.e.without the trigger of a changing light regime.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Diet, energy storage and breeding strategy of two ecological equivalents, an invasive and a native shore crab (2017)
    The Crustacean Society
    In:  EPIC3The Crustaxean Society Mid-Year Meeting, Barcelona, Spain, 2017-06-19-2017-06-22Barcelona, Spain, The Crustacean Society
    Details
    Publication Date: 2017-07-24
    Description: The physiology of the successful intertidal invader, the Asian shore crab Hemigrapsus sanguineus, is essentially unknown. It is quite abundant from France to German coasts but information on food preferences, energy storage and breeding strategy are still lacking. Hemigrapsus sanguineus and its native ecological equivalent, the European green crab Carcinus maenas, were collected in April, June, August and October 2016 in the intertidal area of the island of Helgoland, North Sea, Germany. Midgut glands were dissected and in case of ovigerous females, additionally the egg masses were sampled. Lipids were extracted and the fatty acid composition was determined by gas chromatography. The lipid contents of H. sanguineus midgut glands was higher and more variable over the seasons than those of C. maenas (20 - 60% vs. ~20%, respectively). Trophic marker fatty acids revealed a more herbivorous diet of H. sanguineus, whereas C. maenas profiles suggested a wide range from more herbivorous to more carnivorous diets. The fatty acid compositions of eggs and midgut glands formed two separate clusters in H. sanguineus but both tissue types were similar in C. maenas. Hemigrapsus sanguineus stored much more energy than C. maenas and may cope better with longer periods of starvation. The invaders were able to build up and maintain these reserves by utilizing mostly low quality algal food. Further, H. sanguineus is an income breeder, utilizing recently eaten food for reproduction, whereas C. maenas is a capital breeder. The physiological properties suggest that the invader is competitively superior over the native crab.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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