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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Lung 58 (1924), S. 481-487 
    ISSN: 1432-1750
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 4 (1985), S. 53-59 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two new species of the genus Heterokrohnia, H. longidentata and H. fragilis, are described and compared with the other three known Heterokrohnia species, H. mirabilis Ritter-Záhony 1911; H. bathybia Marumo and Kitou 1966 and H. involucrum Dawson 1968. The species have been found at great depths (1,000 m–2,000 m) near Elephant Island, north of the Antarctic Peninsula.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Comprehensive data are presented on the total lipid contents of five species of notothenioid fish collected during summer 1991 in the Weddell Sea and the Lazarev Sea south of 69°S. The species were selected based on their different modes of life, benthic, benthopelagic and pelagic, to examine how the life style — among other factors — affects the proximate composition of these high-Antarctic fishes. Lipid contents of whole specimens showed an extremely wide range from 3.1 to 67.5% of dry weight (%DW), with corresponding carbon/nitrogen (C/N) ratios between 3.4 and 11.3. Lowest lipid contents were found in the benthic species Bathydraco marri and Dolloidraco longedorsalis with means of 11.0 and 11.9 %DW. The benthopelagic Trematomus lepidorhinus had an intermediate mean lipid content of 20.8 %DW, and the pelagic species Pleuragramma antarcticum and Aethotaxis mitopteryx were richest in lipid with means of 47.0 %DW and 60.8 %DW. There was a pronounced ontogenetic lipid accumulation with increasing size discernible in the lipid-rich species, especially in P. antarcticum. No clear relationship was found between lipid content and sex or maturity in A. mitopteryx and T. lepidorhinus, only the males of B. marri had higher lipid contents than the females. Lipid contents and water contents were inversely correlated. In conclusion, the mode of life of these species was clearly reflected by their lipid contents and lipids seem to have an important function, particularly as buoyancy aids in the pelagic species, which like all notothenioids lack a swim-bladder.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sympagic (=ice-associated) amphipod Gammarus wilkitzkii usually lives attached to the underside of Arctic sea ice. During an expedition to the Greenland Sea in May/June 1997, high numbers of this species were found in pelagic Rectangular Midwater Trawl catches (0–500 m water depth) in an ice-free area, 35–42 km away from the ice edge. The amphipods seemed to have maintained position in the water column for at least 4 days. Mean biomass data (length: 2.9 cm, organic content: 73% dry mass), gut fullness (〉50% in 85% of specimens) and sex ratio (females:males = 1:1.5) of these amphipods were very similar to values for under-ice populations. Due to their relatively high body density (mean: 1.134 g cm−3), the energy demand for swimming was assumed to be high. Measurements of oxygen consumption of swimming and resting amphipods (8.8 and 4.0 J g wet mass−1 day−1, respectively) suggested that, from an energetic point of view, G. wilkitzkii would maintain position in an ice-free water column for the time period.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lipid and fatty acid compositions of five notothenioid fishes from the Antarctic Weddell and Lazarev Seas were investigated in detail with regard to their different modes of life. The pelagic Aethotaxis mitopteryx was the lipid-richest species (mean of 61.4% of dry mass, DM) followed by Pleuragramma antarcticum (37.7%DM). The benthopelagic Trematomus lepidorhinus had an intermediate lipid content of 23.2%DM. The benthic Bathydraco marri (20.8%DM) and Dolloidraco longedorsalis (14.5%DM) belonged to the lipid-poorer species. Triacylglycerols were the major lipid class in all species. Important fatty acids were 16:0, 16:1(n-7), 18:1(n-9), 18:1(n-7), 20:5(n-3) and 22:6(n-3). The enhanced proportions of the long-chain monounsaturated fatty acids, 20:1 and 22:1, in the lipid-rich pelagic fishes clearly reflected the ingestion of the two copepod species, Calanoides acutus and Calanus propinquus, which are the only known Antarctic zooplankters rich in these fatty acids. Although wax esters are the major storage lipid in many prey species, they were absent in all notothenioid fishes studied. Thus, wax esters ingested with prey are probably converted to triacylglycerols via fatty acids or metabolised by the fishes. The enhanced lipid accumulation with increasingly pelagic lifestyle has energetic advantages, especially with regard to improved buoyancy. It is still unknown to what extent these lipids are utilised as energy reserves, since it has been suggested that not only the benthic but also the pelagic Antarctic fishes are rather sluggish, with a low scope for activity and hence low metabolic requirements.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 5 (1986), S. 181-183 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new bathypelagic species of the genus Heterokrohnia, H. longicaudata, is described and separated from the other five previously described Heterokrohnia species, H. mirabilis Ritter-Záhony 1911, H. bathybia Marumo and Kitou 1966, H. involucrum Dawson 1968, H. longidentata Kapp and Hagen 1985 and H. fragilis Kapp and Hagen 1985. The new specimen has been found at great depths (2,350m–1,000m) near Elephant Island, in the atlantic sector north of the Antarctic Peninsula.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 2015-01-29
    Description: Lipid content, fatty acid composition, and feeding activity of the dominant Antarctic copepods, Calanoides acutus, Calanus propinquus, and Metridia gerlachei, were studied at a quasi-permanent station in the eastern Weddell Sea in December 2003. During 3 weeks of the spring phytoplankton development, total lipid levels of females and copepodite stages V (CVs) of C. acutus were almost doubled. Meanwhile, only a slight increase in total lipid content occurred in M. gerlachei, and no clear trend was observed in lipids of C. propinquus females. The pronounced increase of lipids in C. acutus was due to an accumulation of wax esters. The proportion of wax esters in the lipids of M. gerlachei was clearly lower, while triacylglycerols played a more important role. In C. propinquus, triacylglycerols were the only neutral lipid class. There were no pronounced changes in the feeding activity of M. gerlachei, whereas the feeding activity of C. acutus had rapidly increased with the development of the phytoplankton bloom in December, which explains its rapid lipid accumulation. The combination of gut content and fatty acid trophic marker analyses showed that C. acutus was feeding predominantly on diatoms. The typical diatom fatty acid marker, 16:1(n-7), slightly decreased and the tracer for flagellates, 18:4(n-3), increased in females and CVs of C. acutus. This shift indicates the time, when the significance of flagellates started to increase. The three copepod species exhibited different patterns of lipid accumulation in relation to their trophic niches and different duration of their active phases. The investigations filled a crucial data gap in the seasonal lipid dynamics of dominant calanoid copepods in the Weddell Sea in December and support earlier hypotheses on their energetic adaptations and life cycle strategies.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2019-02-01
    Description: We conducted a year-round mesozooplankton study in the Arctic Kongsfjord from August 1998 until July 1999 to investigate seasonal abundance and vertical as well as stage distributions of the prevalent taxa. It is the first investigation in Kongsfjord that covers the Arctic winter season and provides reasonable estimates also of small-sized copepod species. Abundant smaller copepods comprised Oithona similis, Pseudocalanus minutus, Microcalanus spp., Triconia borealis and Acartia longiremis. Among the larger copepods, Calanus finmarchicus, C. glacialis, C. hyperboreus and Metridia longa dominated. The thecosome pteropod Limacina helicina was also an important component. Abundance maxima occurred in November (988,669 ind. m−2) with one to two orders of magnitude higher numbers as compared to all other months (39,832–200,067 ind. m−2). The summers of 1998 and 1999 were characterized by intrusions of Atlantic water, but the community was not entirely dominated by advected boreal species. During winter, the majority of the mesozooplankton occurred below 100 m. Advection is the most likely reason for the accumulation of zooplankton at depth in winter, but local production may also contribute to high overwintering numbers. Much lower abundances of most species in spring suggest high winter mortality and emphasize the importance of sufficient reproductive success during the previous summer to ensure enough winter survivors as seed stock for the coming reproductive season. This study was conducted prior to the recent warming trend in the Arctic. Therefore, it provides valuable baseline data and allows comparing present and future states of the zooplankton community in Kongsfjord.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 9
    Publication Date: 2016-11-09
    Description: The year-round variation in abundance and stage-specific (vertical) distribution of Pseudocalanus minutus and Oithona similis was studied in the Arctic Kongsfjorden, Svalbard. Maxima of vertically integrated abundance were found in November with 111,297 ind m−2 for P. minutus and 704,633 ind m−2 for O. similis. Minimum abundances comprised 1,088 ind m−2 and 4,483 ind m−2 in June for P. minutus and O. similis, respectively. The congener P. acuspes only occurred in low numbers (15–213 ind m−2), and successful reproduction was debatable. Reproduction of P. minutus took place in May/June, and stage distribution revealed a 1-year life cycle with copepodids CIII, CIV, and CV as the overwintering stages. Oithona similis exhibited two main reproductive peaks in June and August/September, respectively. Moreover, it reproduced more or less continuously throughout the whole year with all stages occurring during the entire sampling period, suggesting two generations per year. Both species migrated towards greater depth in November, but O. similis preferred to stay longer in the upper 100 m as compared to Pseudocalanus. The reproduction of the two species in Kongsfjorden seemed to be linked to phytoplankton dynamics.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2016-11-09
    Description: Seasonal activities of the digestive enzyme trypsin were measured between August 1998 and May 1999 to study different nutritional strategies of the two copepods Pseudocalanus minutus and Oithona similis in the Arctic Kongsfjorden (Svalbard) using a highly sensitive fluorescence technique. Stage-, depth- and season-specific characteristics of digestive activity were reflected in the trypsin activity. P. minutus females and stage V copepodids (C) had highest trypsin activities in spring during reproduction (197.5 and 145.7 nmol min−1 ng C−1, respectively). In summer stages CIII–V and in autumn stages CIV and V had high activities (80–116 nmol min−1 ng C−1) in the shallow layer (〈 100 m) presumably as a consequence of prolonged feeding before descending to overwintering depth. Trypsin activities at depth (〉 100 m) in summer and autumn were low in stages CIII and CIV (29–60 nmol min−1 ng C−1) and in winter in all stages in both layers (20–43 nmol min−1 ng C−1). Based on low trypsin activity, males most likely did not feed. In O. similis, the spring phytoplankton bloom did not significantly affect trypsin activity as compared to the other seasons. O. similis CV and females had high trypsin activities in summer in the deep stratum (304.5 nmol min−1 ng C−1), which was concomitant with reproductive processes and energy storage for overwintering. In autumn, stage CV and female O. similis had significantly higher activities than stage CIV (130–152 versus 78 nmol min−1 ng C−1), which is in accordance with still ongoing developmental and reproductive processes in CVs and females. Comparisons of both species revealed different depth-related responses emphasizing different nutritional preferences: the mainly herbivorous P. minutus is more actively feeding in the shallow layer, where primary production occurs, whereas the omnivorous O. similis is not as much restricted to a certain depth layer, when searching for food. P. minutus had lower levels of trypsin activity during all seasons. In contrast to P. minutus, higher enzyme activities in males of O. similis suggest that they continue to feed and survive after fertilization of females.
    Type: Article , PeerReviewed
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