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  • Articles  (1,026)
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  • Articles  (1,026)
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  • 1
    Publication Date: 2018-03-14
    Description: The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
    Published by Springer
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  • 2
    Publication Date: 2018-03-14
    Description: Pacific salmon ( Oncorhynchus spp. ) populations near their northern range extent in the Arctic-Yukon-Kuskokwim region of Alaska have undergone major changes in population trajectory and illuminated the lack of basic information on juvenile ecology. This study fills information gaps on the early life history of chum salmon at northern latitudes. Energy allocation was examined in the context of distribution, feeding intensity, and diet during a critical life history period for a single cohort of juvenile chum salmon ( O. keta ) as they transition from freshwater to saltwater in Kuskokwim Bay from mid-May to early June. Juvenile chum salmon were primarily captured in the river mouth and plume. Energy density (kJ g −1 dry mass) was related to fork length, timing (day-of-year), and capture location in a general additive model. The smallest fish had slightly higher energy densities, but the change in energy density with fish size was minimal and consistent with allocating energy toward somatic growth rather than lipid storage. Fish captured earlier had higher energy density, likely reflecting the presence of residual yolk lipids during early migration. Fish captured in the river mouth and plume had higher energy densities. Feeding intensity was highest among small fish captured later within the river plume. Diet was dominated by surface prey (insects and calanoid copepods) rather than epibenthic harpacticoid copepods as commonly observed. These results provide the first data on energy allocation of juvenile chum salmon during a critical life history phase and suggest that somatic growth is prioritized over storing lipid at saltwater entry.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 3
    Publication Date: 2018-03-14
    Description: The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye and Lauren E. Culler. Erroneously, the article was published in Polar Biology , Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
    Published by Springer
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  • 4
    Publication Date: 2018-03-09
    Description: The phylum Nemertea is an important component of the benthic ecosystems of the Southern Ocean, but its biodiversity is still relatively poorly known in Antarctic waters. There are few common and well-known nemertean species occurring in the shallow Antarctic waters, and these include the congeneric Antarctonemertes valida (Bürger, 1893) and Antarctonemertes riesgoae Taboada et al., 2013, two relatively small brooding hoplonemerteans whose females lay eggs inside cocoons. A third Antarctic member of the genus, Antarctonemertes belgica (Bürger, 1904), was reported only in the original description. Here we document the existence of a fourth Antarctic member of the genus Antarctonemertes originally described as Tetrastemma unilineatum Joubin, 1910. Our phylogenetic analysis resulted into the placement of the new Antarctonemertes in a robustly supported clade –Antarctic Antarctonemertes – containing the other two congeneric Antarctic species ( A.   valida and A.   riesgoae ), and pairwise COI molecular distances between the three species ranged from 5.2 to 6.2% ( p distance). The analysis of 104 COI sequences of the three species showed star-like haplotype networks, as in other studies on Antarctic invertebrates. Antarctonemertes unilineata comb. nov. is similar in shape to its Antarctic congeneric relatives and its most prominent morphological character is a dorsal mid-longitudinal band present along the body. We also document the presence of a cocoon built by females of A.   unilineata comb. nov., a character shared with its Antarctic congeners analysed here. Although the four Antarctic Antarctonemertes species appear to overlap their distribution, A.   riesgoae , A.   valida and A. belgica appear in sympatry in the West Antarctic shores while A.   unilineata comb. nov. has been mainly found in the East Antarctic shores and sub-Antarctic Islands.
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    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 5
    Publication Date: 2018-03-09
    Description: Porifera dominate vast areas of the Antarctic shelves and are successfully colonized by bacteria. Quorum sensing (QS) is a cell-to-cell communication system based on bacterial population density that, enabling the coordination of group-based behaviour, plays a critical role in the successful colonization of higher organisms, also driving the formation of biofilm for adhesion to surfaces. In this study, the production of N -Acyl homoserine lactones (AHLs), signal molecules involved in the QS mechanism, was examined for 211 Antarctic sponge-associated Gram-negative bacteria. AHL production was screened by using three different AHL biodetection systems, i.e. Agrobacterium tumefaciens pZLR4, Chromobacterium violaceum CV026 and Pseudomonas putida pKR-C12 with optimal sensitivity to moderate-chain (C8–C12), short-chain (C4–C8) and long-chain (≥ C14) AHLs, respectively. 57.8% of tested isolates activated at least one of the monitor systems used and belonged mainly to bacterial genera that are known to be involved in surface colonization by biofilm production. A thin-layer chromatographic assay based on the A. tumefaciens reporter system was utilized to determine the AHL profiles of five selected positive isolates. Visible spots on thin-layer chromatography (TLC) plates were produced by Roseobacter sp. TB60 and Psychrobacter sp. TB67 (both from the sponge, Anoxycalyx joubini ). The former probably produced N -(3-oxohexanoyl)-L-homoserine lactone (similar to the standard 3-oxo-C6-HSL), whereas the isolate TB67 produced molecules that were similar to the standard N -butanoyl-homoserine lactone (C4-HSL). The obtained results demonstrated that AHL-based signalling may play a key role in sponge–bacteria interactions also in the Antarctic environment.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 6
    Publication Date: 2018-03-07
    Description: Intensive efforts are being made to find new compounds with antimicrobial activity. The search for these novel bio-products in sparsely explored environments may be the key to providing solutions for many emerging problems. Antarctic environments are valuable locations for bioprospecting. In this study, 63 cold-adapted bacterial strains of 6100 different colony morphotypes were isolated from Antarctic seawater samples around South Shetland and Deception islands. Strains were selected based on cold-active antimicrobial production and were grouped into 11 operational taxonomic units by internal spacer region-PCR and amplified ribosomal DNA restriction analysis. Isolates arbitrarily named 2D, 5D, and 6D were closely related to Halomonas titanicae , with 99.8, 98.9, and 96.7% identity according to 16S rDNA sequencing, and 99.7, 99.3, and 98.3% according to gyrB region sequence analysis, respectively. The isolate 18SH was closely related to Candida sake (99.2%) based on sequence analysis of the ITS1–5.8S rDNA–ITS2 and D1/D2 domain of 26S rDNA. Antimicrobials produced by isolates 2D, 5D, and 6D exhibited a low-molecular weight (〈 6000 Da) and stability in wide pH and temperature ranges. When tested against foodborne and phytopathogenic bacteria, selected isolates exhibited a wide spectrum of activity. This work reports the isolation and identification of cold-adapted microorganisms with the ability to produce antimicrobial compounds with potential application in the pharmaceutical or in cold-chain management in the food industry. The current results highlight the potential of the Antarctic environment as a valuable and underexploited source of new antimicrobial molecules with exceptional properties for different biotechnological applications.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 7
    Publication Date: 2018-03-06
    Description: Studies investigating viral ecology have mainly been conducted in temperate marine and freshwater habitats. Fewer reports are available on the often less accessible “extreme environments” such as hot springs. This study investigated prokaryotic- and virus-like particles (VLP) associated to hot springs, themselves situated in cold environments of the Southern Hemisphere (i.e. in the French Southern and Antarctic Lands). This was performed by examining their abundance in hot springs and surrounding temperate seawater using both epifluorescence microscopy (EFM) and flow cytometry (FCM), which was applied for the first time to such ecosystems. On one hand, prokaryotic abundances of 4.0 × 10 5 –2.2 × 10 6  cell mL −1 and 7.0 × 10 4 –2.8 × 10 6  cell mL −1 were measured using EFM and FCM, respectively. The abundances of virus-like particles (VLP), on the other hand, ranged between 9.8 × 10 5 and 7.5 × 10 6 particles mL −1 when using EFM, and between 1.3 × 10 5 and 6.2 × 10 6 particles mL −1 when FCM was applied. A positive correlation was found between VLP and prokaryotic abundances, while the virus-to-prokaryote ratio was generally low and ranged between 0.1 and 6. In parallel, samples and culture supernatants were also visualised using transmission electron microscopy. For this, enrichment cultures were prepared using environmental samples. Both raw sample and enrichment culture—supernatants were analysed for the presence of VLPs. Observations revealed the presence of Caudovirales, membrane vesicles and possibly a new type of virion morphology, associated to members of the order Thermotogales, a thermophilic and anaerobic bacterium.
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    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 8
    Publication Date: 2018-03-06
    Description: Although research on parasitic diseases in Antarctic birds is scarce and the information largely fragmented, an increasing number of studies are currently in progress in this area. The host/parasite relationship is very important for understanding the impact of parasitism on the seabirds’ feeding ecology, especially in those isolated regions where the host is extremely sensitive to new diseases. Penguins are a big favorite for these studies because of their importance as indicators of change in the Antarctic ecosystem. This study aims at adding information on gastrointestinal parasites of the Emperor Penguin Aptenodytes forsteri from Snow Hill colony. Based on a sample of 43 individuals found freshly dead (3 adults and 40 chicks) from predation or starvation, the gastrointestinal helminth community in Emperor penguins was composed of two species of cestodes ( Parorchites zederi and Tetrabothrius sp.) and three species of nematodes ( Stegophorus macronectes, Tetrameres sp. and Contracaecum osculatum ). This is the first record of S. macronectes in the Emperor Penguin. The low parasite richness observed might be related to the stenophagic and pelagic diet of this host.
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    Topics: Biology
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  • 9
    Publication Date: 2018-03-06
    Description: An integrative inventory of the amphipod scavenging fauna (Lysianassoidea), combining morphological identifications with DNA barcoding, is provided here for the Filchner area situated in the south-eastern Weddell Sea. Over 4400 lysianassoids were investigated for species richness and relative abundances, covering 20 different stations and using different sampling devices, including the southernmost baited traps deployed so far (76°S). High species richness was observed: 29 morphospecies of which 5 were new to science. Molecular species delimitation methods were carried out with 109 cytochrome c oxidase I gene (COI) sequences obtained during this study as well as sequences from specimens sampled in other Antarctic regions. These distance-based analyses (trees and the Automatic Barcode Gap Discovery method) indicated the presence of 42 lineages; for 4 species, several (cryptic) lineages were found. More than 96% of the lysianassoids collected with baited traps belonged to the species Orchomenella pinguides s. l. The diversity of the amphipod scavenger guild in this ice-bound ecosystem of the Weddell Sea is discussed in the light of bottom–up selective forces. In this southernmost part of the Weddell Sea, harbouring spawning and nursery grounds for silverfish and icefishes, abundant fish and mammalian food falls are likely to represent the major food for scavengers. Finally, the importance of biodiversity surveys in the context of the establishment of a marine protected area in this region (Weddell Sea MPA) is highlighted and how future studies can contribute to a better understanding the ecological role of scavengers in this system is discussed.
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    Topics: Biology
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  • 10
    Publication Date: 2018-03-06
    Description: The authors regret an error in the published article, where incorrect data was used to produce Figure 2, showing the temporal development of pH over the duration of the experiment. The corrected Fig. 2 shows that the error did not affect the interpretation of nor the conclusions drawn from the present dataset. The original article has been corrected.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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