Browsing Artikler, rapporter og annet (arktisk og marin biologi) by Author
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Browsing Artikler, rapporter og annet (arktisk og marin biologi) by Author
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Jørgensen, Marte Holten; Ehrich, Dorothee; Schmickl, Roswitha; Koch, Marcus A.; Brysting, Anne Krag (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Effects of polyploidisation on gene flow between natural populations are little known. Central European diploid and tetraploid populations of Arabidopsis arenosa and A. lyrata are here used to study interspecific and interploidal gene flow, using a combination of nuclear and plastid markers. Ploidal levels were confirmed by flow cytometry. Network analyses clearly separated diploids according to species. Tetraploids and diploids were highly intermingled within species, and some tetraploids intermingled with the other species, as well. Isolation with migration analyses suggested interspecific introgression from tetraploid A. arenosa to tetraploid A. lyrata and vice versa, and some interploidal gene flow, which was unidirectional from diploid to tetraploid in A. arenosa and bidirectional in A. lyrata. Interspecific genetic isolation at diploid level combined with introgression at tetraploid level indicates that polyploidy may buffer against negative consequences of interspecific hybridisation. The role of introgression in polyploid systems may, however, differ between plant species, and even within the small genus Arabidopsis, we find very different evolutionary fates when it comes to introgression. URI: http://hdl.handle.net/10037/3878 File(s) in this item: 1
article.pdf (3.034Mb) -
Kekäläinen, Jukka; Figenschou, Lars; Janhunen, Matti; Kortet, Raine; Peuhkuri, Nina; Rudolfsen, Geir (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The ability of captive breeding programs to maintain genetic diversity and fitness has often been questioned. Recent studies suggest that fitness loss can be extremely rapid in various traits, but it is poorly known how captive breeding affects sperm quality and thus male fertility. We studied the potential effects of hatchery-induced selection on traits indicative of semen quality, in four generations of captive bred Arctic charr Salvelinus alpinus L. We found that the number of motile sperm cells decreased, but that the swimming velocity of the sperm increased over generations. The independent effects of inbreeding and hatchery selection on semen traits could not be separated, but since in small captive broodstocks, both of them often act together, the present results should indicate real changes of semen traits in such situations. Taken together, the present data suggest that the fitness loss in some semen traits (number of motile sperm) can be extremely rapid, but selection on other, closely related traits (swimming velocity) may delay or counteract the overall deterioration of male fertilizing ability during captivity. URI: http://hdl.handle.net/10037/4790 File(s) in this item: 1
article.pdf (196.1Kb) -
Kekäläinen, Jukka; Rudolfsen, Geir; Figenschou, Lars; Janhunen, Matti; Peuhkuri, Nina; Tamper, Nina; Kortet, Raine (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)[+][-]
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Killengreen, Siw Turid; Jensvoll, Ingrid; Henden, John-André; Hamel, Sandra; Ims, Rolf Anker; Mørk, Torill; Sarre, Arne Petter; Ørjebu, Alfred; Bye, Åshild; Knutsen, Kjartan (Research report; Forskningsrapport, 2012)[+][-]
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Klemetsen, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
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Knutsen, Kjartan; Ims, Rolf Anker; Mørk, T.; Killengreen, Siw Turid; Langeland, K.; Yoccoz, Nigel Gilles; Henden, John-André; Ravolainen, Virve (Research report; Forskningsrapport, 2006)[+][-]
Description: Faglig årsrapport for 2006 til DN. URI: http://hdl.handle.net/10037/2521 File(s) in this item: 1
report.pdf (302.8Kb) -
Krause, Kirsten; Oetke, Svenja; Krupinska, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: Changes in the developmental or metabolic state of plastids can trigger profound changes in the transcript profiles of nuclear genes. Many nuclear transcription factors were shown to be controlled by signals generated in the organelles. In addition to the many different compounds for which an involvement in retrograde signaling is discussed, accumulating evidence suggests a role for proteins in plastid-to-nucleus communication. These proteins might be sequestered in the plastids before they act as transcriptional regulators in the nucleus. Indeed, several proteins exhibiting a dual localization in the plastids and the nucleus are promising candidates for such a direct signal transduction involving regulatory protein storage in the plastids. Among such proteins, the nuclear transcription factor WHIRLY1 stands out as being the only protein for which an export from plastids and translocation to the nucleus has been experimentally demonstrated. Other proteins, however, strongly support the notion that this pathway might be more common than currently believed. URI: http://hdl.handle.net/10037/5000 File(s) in this item: 1
article.pdf (323.4Kb) -
Krause, Kirsten; Herrmann, Ullrich; Fuss, Janina; Miao, Ying; Krupinska, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)[+][-]
Abstract: Whirly proteins belong to a small family of proteins with a characteristic secondary structure and a conserved DNA binding domain that is found mainly in angiosperms. At least one member of the Whirly protein family, Whirly1, is dually targeted to the nucleus and to the chloroplasts and it was shown that apart from its initially described function as a transcriptional regulator of nuclear disease resistance genes, this protein comprises many more functions. It seems to fulfil roles in nuclear telomere homeostasis and possibly chloroplast rRNA metabolism as well as chloroplast intron splicing. A homologous protein with a mitochondrial presequence, Whirly2, in contrast, is presumably involved in the replication of the mitochondrial genome and in mitochondrial gene expression. In addition, it seems to affect the expression of a small subset of nuclear genes. Both Whirly proteins show an antagonistic effect on leaf senescence. Although direct evidence for a nuclear localisation of Whirly2 has yet to be obtained, we hypothesise that all members of the Whirly family are intriguing candidates for organelle-to-nucleus crosstalk with an intricate interaction between each other. URI: http://hdl.handle.net/10037/4156 File(s) in this item: 1
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Krause, Kirsten; Funk, Helena T.; Berg, Sabine; Krupinska, Karin; Maier, Uwe G. (Journal article; Tidsskriftartikkel; Peer reviewed, 22-Aug-2007)[+][-]
Abstract: Background: The holoparasitic plant genus Cuscuta comprises species with photosynthetic capacity and functional chloroplasts as well as achlorophyllous and intermediate forms with restricted photosynthetic activity and degenerated chloroplasts. Previous data indicated significant differences with respect to the plastid genome coding capacity in different Cuscuta species that could correlate with their photosynthetic activity. In order to shed light on the molecular changes accompanying the parasitic lifestyle, we sequenced the plastid chromosomes of the two species Cuscuta reflexa and Cuscuta gronovii. Both species are capable of performing photosynthesis, albeit with varying efficiencies. Together with the plastid genome of Epifagus virginiana, an achlorophyllous parasitic plant whose plastid genome has been sequenced, these species represent a series of progression towards total dependency on the host plant, ranging from reduced levels of photosynthesis in C. reflexa to a restricted photosynthetic activity and degenerated chloroplasts in C. gronovii to an achlorophyllous state in E. virginiana. Results: The newly sequenced plastid genomes of C. reflexa and C. gronovii reveal that the chromosome structures are generally very similar to that of non-parasitic plants, although a number of species-specific insertions, deletions (indels) and sequence inversions were identified. However, we observed a gradual adaptation of the plastid genome to the different degrees of parasitism. The changes are particularly evident in C. gronovii and include (a) the parallel losses of genes for the subunits of the plastid-encoded RNA polymerase and the corresponding promoters from the plastid genome, (b) the first documented loss of the gene for a putative splicing factor, MatK, from the plastid genome and (c) a significant reduction of RNA editing. Conclusion: Overall, the comparative genomic analysis of plastid DNA from parasitic plants indicates a bias towards a simplification of the plastid gene expression machinery as a consequence of an increasing dependency on the host plant. A tentative assignment of the successive events in the adaptation of the plastid genomes to parasitism can be inferred from the current data set. This includes (1) a loss of non-coding regions in photosynthetic Cuscuta species that has resulted in a condensation of the plastid genome, (2) the simplification of plastid gene expression in species with largely impaired photosynthetic capacity and (3) the deletion of a significant part of the genetic information, including the information for the photosynthetic apparatus, in non-photosynthetic parasitic plants. URI: http://hdl.handle.net/10037/1252 File(s) in this item: 1
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Lecomte, Nicolas; Ahlstrøm, Øystein Jan; Ehrich, Dorothee; Fuglei, Eva; Ims, Rolf Anker; Yoccoz, Nigel (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Tissue-specific stable isotope signatures can provide insights into the trophic ecology of consumers and their roles in food webs. Two parameters are central for making valid inferences based on stable isotopes, isotopic discrimination (difference in isotopic ratio between consumer and its diet) and turnover time (renewal process of molecules in a given tissue usually measured when half of the tissue composition has changed). We investigated simultaneously the effects of age, sex, and diet types on the variation of discrimination and half-life in nitrogen and carbon stable isotopes (δ15N and δ13C, respectively) in five tissues (blood cells, plasma, muscle, liver, nail, and hair) of a top predator, the arctic fox Vulpes lagopus. We fed 40 farmed foxes (equal numbers of adults and yearlings of both sexes) with diet capturing the range of resources used by their wild counterparts. We found that, for a single species, six tissues, and three diet types, the range of discrimination values can be almost as large as what is known at the scale of the whole mammalian or avian class. Discrimination varied depending on sex, age, tissue, and diet types, ranging from 0.3‰ to 5.3‰ (mean = 2.6‰) for δ15N and from 0.2‰ to 2.9‰ (mean = 0.9‰) for δ13C. We also found an impact of population structure on δ15N half-life in blood cells. Varying across individuals, δ15N half-life in plasma (6 to 10 days) was also shorter than for δ13C (14 to 22 days), though δ15N and δ13C half-lives are usually considered as equal. Overall, our multi-factorial experiment revealed that at least six levels of isotopic variations could co-occur in the same population. Our experimental analysis provides a framework for quantifying multiple sources of variation in isotopic discrimination and half-life that needs to be taken into account when designing and analysing ecological field studies. URI: http://hdl.handle.net/10037/4032 File(s) in this item: 1
article.pdf (673.9Kb) -
Lecomte, Nicolas A Francis; Ehrich, Dorothee; Ims, Rolf Anker; Yoccoz, Nigel Gilles (Journal article; Tidsskriftartikkel, 2009)[+][-]
Abstract: To what extent top predators - carnivores at the top of food chains - drive or just respond to ecosystem dynamics is a central, but partially unresolved, question in ecology. In this report, we highlight how different research approaches employed in aquatic and terrestrial ecology may have a bearing on how the role of top predators in ecosystems is perceived. URI: http://hdl.handle.net/10037/4415 File(s) in this item: 1
article.pdf (160.0Kb) -
Lees, J; Nudds, R; Stokkan, Karl-Arne; Folkow, Lars; Codd, J (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)[+][-]
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Li, Fenglin; Zhang, Yiming; Zhong, Zhijian (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: The current study evaluated the glucose-lowering effect of ganoderma lucidum polysaccharides (Gl-PS) in streptozotocin (STZ)-induced diabetic mice. The diabetic mice were randomly divided into four groups (8 mice per group): diabetic control group, low-dose Gl-PS treated group (50 mg/kg, Gl-PS), high-dose Gl-PS treated group (150 mg/kg, Gl-PS) and positive drug control treated group (glibenclamide, 4 mg/kg), with normal mice used as the control group. Body weights, fasting blood glucose (FBG), serum insulin and blood lipid levels of mice were measured. After 28 days of treatment with Gl-PS, body weights and serum insulin levels of the Gl-PS treated groups was significantly higher than that of the diabetic control group , whereas FBG levels was significantly lower. Moreover, total cholesterol (TC), triglyceride (TG) and low density lipoprotein cholesterol (LDL-C) levels of the Gl-PS treated groups had dropped, whereas the high density lipoprotein cholesterol (HDL-C) levels had increased. In addition, according to acute toxicity studies, Gl-PS did not cause behavioral changes and any death of mice. These data suggest that Gl-PS has an antihyperglycemic effect. Furthermore, considering the Gl-PS effects on lipid profile, it may be a potential hypolipidaemic agent, which will be a great advantage in treating diabetic conditions associated with atherosclerosis or hyperlipidemia. URI: http://hdl.handle.net/10037/3937 File(s) in this item: 1
article.pdf (218.4Kb) -
Melnychuk, Michael; Chittenden, Cedar Marget; Welch, David; McKinley, Scott (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)[+][-]
Description: This article has been formally corrected to address errors. See http://dx.doi.org/10.1371/journal.pone.0010869 for details URI: http://hdl.handle.net/10037/3016 File(s) in this item: 1
article.pdf (425.7Kb) -
Menu, B; Peruzzi, Stefano; Vergnet, A; Vidal, MO; Chatain, B (Journal article; Tidsskriftartikkel; Peer reviewed, 2005)[+][-]
Abstract: The objective of this study was to develop a rapid and effective method of sexing juvenile sea bass with minimum labour and material.To this end, the gonad squash mount technique was applied along with macroscopic techniques for sexing a large number of experimental fish at the age of 215-275 days post fertilization (p.f.). At this age, 90% of the 3894 fish could be unambiguously sexed by macroscopic examination of their gonads, whereas the remaining proportion was identified using squash mount preparations (10%). The accuracy of the observations was measured up to classical histology procedures. Undifferentiated gonads accounted for 0.1% of the total population only.The application of the squashmount technique holds out the prospect of considerable improvement in the efficiency and rapidity of current sexing techniques in sea bass. URI: http://hdl.handle.net/10037/5088 File(s) in this item: 1
article.pdf (301.2Kb) -
Mikkelsen, Nina; Pedersen, Torstein (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: The invasive red king crab Paralithodes camtschaticus preys on lumpsucker Cyclopterus lumpus eggs. We tested the hypothesis this egg consumption may hamper the recruitment of lumpsucker. Methods applied included field work, laboratory experiments and modelling of egg consumption. Crabs were sampled and feeding behaviour was studied by means of a remotely operated vehicle and SCUBA divers in a field survey carried out in Varanger Fjord, Norway, in 2003. Laboratory experiments were carried out in 2006 to study the digestion of lumpsucker eggs by red king crabs, and a stomach evacuation model was fitted to the experimental data. Using data from the field and laboratory studies, an egg consumption model was used to quantify the amount of lumpsucker eggs consumed by king crabs in Varanger Fjord. The uncertainty in model input data was assessed using a Monte Carlo simulation. Sex or sampling area did not significantly affect egg predation. A total of 7.9% of all crab stomachs contained an average of 20 lumpsucker eggs, but the number of eggs per stomach varied widely. The average time required to evacuate lumpsucker eggs at 6°C in the laboratory experiment was ~10 h. In 2003, king crabs in Varanger Fjord consumed lumpsucker roe equivalent to approximately one-third of commercial catches during the same period. Red king crab predation on lumpsucker eggs may hamper lumpsucker recruitment in northern Norwegian waters. URI: http://hdl.handle.net/10037/5031 File(s) in this item: 1
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Mousavi, Seyed Karim; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)[+][-]
Abstract: Zoobenthos samples were collected over a 12-month period in the profundal zone of the subarctic Fjellfrøsvatn, a lake in northern Norway. Chironomid larvae numerically dominated the profundal zoobenthos and their mean density decreased with increasing depth. Procladius (Holotanypus) sp. A, Mesocricotopus thienemanni, Psectrocladius (Mesopsectrocladius) sp. and Heterotrissocladius subpilosus exhibited the highest densities at the depth of 20 m, whereas H. subpilosus dominated the chironomid assemblage at 30–40 m. At 20-m depth, the chironomid density was highest in June, decreased towards autumn, and was relatively stable during the ice-covered period. The peak density in June was mainly related to a strong seasonal pattern in the density of Heterotrissocladius maeaeri and M. thienemanni. At 30–40-m depth, no significant seasonal variations in total density of chironomid larvae were observed, although the density of H. subpilosus exhibited a significant seasonal peak in winter. Larval instar groups of H. subpilosus were identified from a classification based on head capsule width. The profundal dwelling H. subpilosus were hemivoltine, having predominantly a two-year life cycle. URI: http://hdl.handle.net/10037/4893 File(s) in this item: 1
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Msomphora, Mbachi Ruth (Chapter; Bokkapittel, 06-Jan-2005)[+][-]
Abstract: Several of the African Great Lakes are distinctive for their very long water residence time >100 years. Incoming nutrients will be retained within the lakes and recovery will be slow even if inputs are reduced. While changes in chemistry and plankton composition of Lake Malawi have not been extreme to date, strong eutrophication is already happening in Lake Victoria, where damage has reduced its biological wealth and human misery may follow (Baskin, 1992). It could be advisable to prevent this happening to Lake Malawi and Tanganyika. Description: This is chapter 21 of the book "Drainage basin nutrient inputs and eutrophication: an integrated approach." URI: http://hdl.handle.net/10037/2387 File(s) in this item: 1
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Muñoz, Lorena; Hausner, Vera Helene (Conference object; Konferansebidrag, 2012)[+][-]
Abstract: The protected area (PA) coverage is used as an indicator of biodiversity protection worldwide. The effectiveness of using PAs as indicators has been questioned due to the diversity of designations included in such measures, especially those PAs established for other purposes than biodiversity protection. Although international standards have been developed by the International Union for Conservation of Nature (IUCN), the policies on the ground have been developed independently of the IUCN categories. This makes the use of IUCN categories dubious measures of biodiversity conservation. A management plan is crucial for effective management of the parks and for guidance on how biodiversity should be prioritized against other goals. We therefore analyzed the aims and the regulations in management plans of alpine PAs in Spain as a first step for evaluating conservation performance. We used content analysis and CAiv to assess how aims and regulations vary in relation to three explanatory factors: IUCN categories, Vegetation Zones and Autonomous Communities. We found the aims of many parks to be vague, without clear indication on how to prioritize biodiversity goals. Furthermore only 50% of them actually have a management plan, which strengthens our argument about unclear guidance of PA management. Although aims could partly be related to IUCN categories, the regulations showed no clear relationship to international policies, which reflects that aims are not necessarily implemented in practice. Devolution to Autonomous Communities could be one explanation for the large variation in management practices among parks. Further studies are needed to evaluate the impact of such policies on biodiversity. URI: http://hdl.handle.net/10037/4954 File(s) in this item: 1
article.pdf (2.076Mb) -
Myers-Smith, Isla; Forbes, Bruce C.; Wilmking, Martin; Hallinger, Martin; Lantz, Trevor; Blok, Daan; Tape, Ken D; Ravolainen, Virve; Macias-Fauria, Marc; Sass-Klaassen, Ute; Levesque, Esther; Boudreau, Stephane; Ropars, Pascale; Hermanutz, Luise; Trant, Andrew; Collier, Laura Siegwart; Weijers, Niels Martin; Rozema, Jelte; Rayback, Shelly A; Schmidt, Niels Martin; Schaepman-Strub, Gabriela; Wipf, Sonja; Rixen, Christian; Menard, Cecile B; Venn, Susanna; Goetz, Scott; Andreu-Hayles, Laia; Elmendorf, Sarah; Welker, Jeffrey; Grogan, Paul; Epstein, Howard E.; Hik, David S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)[+][-]
Abstract: Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ecosystems, and (4) address potential lines of investigation for future research. Satellite observations from around the circumpolar Arctic, showing increased productivity, measured as changes in 'greenness', have coincided with a general rise in high-latitude air temperatures and have been partly attributed to increases in shrub cover. Studies indicate that warming temperatures, changes in snow cover, altered disturbance regimes as a result of permafrost thaw, tundra fires, and anthropogenic activities or changes in herbivory intensity are all contributing to observed changes in shrub abundance. A large-scale increase in shrub cover will change the structure of tundra ecosystems and alter energy fluxes, regional climate, soil–atmosphere exchange of water, carbon and nutrients, and ecological interactions between species. In order to project future rates of shrub expansion and understand the feedbacks to ecosystem and climate processes, future research should investigate the species or trait-specific responses of shrubs to climate change including: (1) the temperature sensitivity of shrub growth, (2) factors controlling the recruitment of new individuals, and (3) the relative influence of the positive and negative feedbacks involved in shrub expansion. URI: http://hdl.handle.net/10037/4051 File(s) in this item: 1
article.pdf (1.712Mb)
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