Journal articles: 'Arctium – physiologie'

1

Block, W., N. R. Webb, S. Coulson, I. D. Hodkinson, and M. R. Worland. "Thermal adaptation in the Arctic collembolan Onychiurus arcticus (Tullberg)." Journal of Insect Physiology 40, no. 8 (August 1994): 715–22. http://dx.doi.org/10.1016/0022-1910(94)90099-x.

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Dubatolov, V. V., and K. W. Philip. "Review of the northern Holarctic Arctia caja complex (Lepidoptera: Noctuidae: Arctiinae)." Canadian Entomologist 145, no. 2 (February 27, 2013): 147–54. http://dx.doi.org/10.4039/tce.2013.13.

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AbstractArctia olschwangi Dubatolov, formerly known only from Arctic Siberia, Russia, is recorded from northern Alaska, United States of America. Distinguishing characters between northern populations of Arctia brachyptera Troubridge and Lafontaine, Arctia caja (Linnaeus), A. olschwangi Dubatolov, and Arctia opulenta (Edwards) are discussed. Arctia brachyptera Troubridge and Lafontaine is hypothesised to be a subspecies of A. olschwangi Dubatolov but more specimens need to be examined before this taxonomic change is made.

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Behan-Pelletier, Valerie M. "CERATOZETIDAE OF THE WESTERN NORTH AMERICAN ARCTIC." Canadian Entomologist 117, no. 11 (November 1985): 1287–366. http://dx.doi.org/10.4039/ent1171287-11.

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AbstractThe Ceratozetidae of arctic western North America, represented by 12 species in 9 genera, are discussed. A new genus, Cyrtozetes, and species, Cyrtozetes denaliensis, are proposed, and Trichoribates copperminensis Hammer, T. polaris Hammer, Svalbardia paludicola Thor, Iugoribates gracilis Sellnick, Diapterobates notatus (Thorell) both adults and immatures, D. variabilis Hammer, Sphaerozetes arcticus Hammer, Fuscozetes sellnicki Hammer, Melanozetes longisetosus Hammer, and Ceratozetes spitsbergensis Thor and C. parvulus Sellnick are redescribed. Immatures of T. polaris, S. paludicola, F. sellnicki, and M. longisetosus are described. Distribution records of Ceratozetes gracilis (Michael) in the western North American arctic are listed. The new combination, Cyrtozetes shiranensis (Aoki and Fujikawa), is proposed.

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Anonymous, A. "2nd International Arctic Ungulate Conference." Rangifer 16, no. 2 (January 1, 1996): 49. http://dx.doi.org/10.7557/2.16.2.1196.

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The 2nd International Arctic Ungulate Conference was held 13-17 August 1995 on the University of Alaska Fairbanks campus. The Institute of Arctic Biology and the Alaska Cooperative Fish and Wildlife Research Unit were responsible for organizing the conference with assistance from biologists with state and federal agencies and commercial organizations. David R. Klein was chair of the conference organizing committee. Over 200 people attended the conference, coming from 10 different countries. The United States, Canada, and Norway had the largest representation. The conference included invited lectures; panel discussions, and about 125 contributed papers. There were five technical sessions on Physiology and Body Condition; Habitat Relationships; Population Dynamics and Management; Behavior, Genetics and Evolution; and Reindeer and Muskox Husbandry. Three panel sessions discussed Comparative caribou management strategies; Management of introduced, reestablished, and expanding muskox populations; and Health risks in translocation of arctic ungulates. Invited lectures focused on the physiology and population dynamics of arctic ungulates; contaminants in food chains of arctic ungulates and lessons learned from the Chernobyl accident; and ecosystem level relationships of the Porcupine Caribou Herd.

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Holmstrup, M., and L. Sømme. "Dehydration and cold hardiness in the Arctic Collembolan Onychiurus arcticus Tullberg 1876." Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 168, no. 3 (April 7, 1998): 197–203. http://dx.doi.org/10.1007/s003600050137.

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Worland, M. R., G. Grubor-Lajsic, and P. O. Montiel. "Partial desiccation induced by sub-zero temperatures as a component of the survival strategy of the Arctic collembolan Onychiurus arcticus (Tullberg)." Journal of Insect Physiology 44, no. 3-4 (March 1998): 211–19. http://dx.doi.org/10.1016/s0022-1910(97)00166-2.

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PURAĆ, JELENA, DAVID W. POND, GORDANA GRUBOR-LAJŠIĆ, DANIJELA KOJIĆ, DUŠKO P. BLAGOJEVIĆ, MICHAEL ROGER WORLAND, and MELODY S. CLARK. "Cold hardening induces transfer of fatty acids between polar and nonpolar lipid pools in the Arctic collembollan Megaphorura arctica." Physiological Entomology 36, no. 2 (January 18, 2011): 135–40. http://dx.doi.org/10.1111/j.1365-3032.2010.00772.x.

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Scheiber, Isabella B. R., Brigitte M. Weiß, Margje E. de Jong, Anna Braun, Nico W. van den Brink, Maarten J. J. E. Loonen, Eva Millesi, and Jan Komdeur. "Stress behaviour and physiology of developing Arctic barnacle goslings ( Branta leucopsis ) is affected by legacy trace contaminants." Proceedings of the Royal Society B: Biological Sciences 285, no. 1893 (December 12, 2018): 20181866. http://dx.doi.org/10.1098/rspb.2018.1866.

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Natural populations are persistently exposed to environmental pollution, which may adversely impact animal physiology and behaviour and even compromise survival. Responding appropriately to any stressor ultimately might tip the scales for survival, as mistimed behaviour and inadequate physiological responses may be detrimental. Yet effects of legacy contamination on immediate physiological and behavioural stress coping abilities during acute stress are virtually unknown. Here, we assessed these effects in barnacle goslings ( Branta leucopsis ) at a historical coal mine site in the Arctic. For three weeks we led human-imprinted goslings, collected from nests in unpolluted areas, to feed in an abandoned coal mining area, where they were exposed to trace metals. As control we led their siblings to feed on clean grounds. After submitting both groups to three well-established stress tests (group isolation, individual isolation, on-back restraint), control goslings behaved calmer and excreted lower levels of corticosterone metabolites. Thus, legacy contamination may decisively change stress physiology and behaviour in long-lived vertebrates exposed at a young age.

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Nilssen, K. J., O. A. Gulseth, M. Iversen, and R. Kjol. "Summer osmoregulatory capacity of the world's northernmost living salmonid." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 272, no. 3 (March 1, 1997): R743—R749. http://dx.doi.org/10.1152/ajpregu.1997.272.3.r743.

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Anadromous Arctic charr (Salvelinus alpinus L.) were caught on their way to and from the sea with the use of a fish trap placed in the Dieset watercourse located on the Spitsbergen Island (79 degrees 10' Northern latitude) within the high-Arctic Svalbard archipelago. When subjected to a seawater challenge test (34 parts/thousand at 4-5 degrees C), charr on their way to the sea showed only minor and temporary changes in blood plasma osmolality and Na+ and Mg2+ concentrations. The seawater tests also revealed good hypoosmoregulatory capacity for Arctic charr returning from the marine environment 4 wk later. A progressive decrease in seawater tolerance was first documented 7-11 days after their return to the freshwater habitat. Thus the Svalbard charr, being the northernmost anadromous salmonid and probably a direct descendant from the first Salvelinus immigrants to freshwater systems, undergoes a preparatory increase of hypoosmoregulatory capacity (smoltification) before entering the oceanic water bodies. Furthermore, the termination of their short annual seawater stay is probably elicited by factors controlling body systems other than osmoregulation.

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Ma, Yi Long, Xiongwei Zhu, Patricia M. Rivera, Øivind Tøien, Brian M. Barnes, Joseph C. LaManna, Mark A. Smith, and Kelly L. Drew. "Absence of cellular stress in brain after hypoxia induced by arousal from hibernation in Arctic ground squirrels." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 289, no. 5 (November 2005): R1297—R1306. http://dx.doi.org/10.1152/ajpregu.00260.2005.

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Although hypoxia tolerance in heterothermic mammals is well established, it is unclear whether the adaptive significance stems from hypoxia or other cellular challenge associated with euthermy, hibernation, or arousal. In the present study, blood gases, hemoglobin O2 saturation (So2), and indexes of cellular and physiological stress were measured during hibernation and euthermy and after arousal thermogenesis. Results show that arterial O2 tension (PaO2) and So2 are severely diminished during arousal and that hypoxia-inducible factor (HIF)-1α accumulates in brain. Despite evidence of hypoxia, neither cellular nor oxidative stress, as indicated by inducible nitric oxide synthase (iNOS) levels and oxidative modification of biomolecules, was observed during late arousal from hibernation. Compared with rats, hibernating Arctic ground squirrels ( Spermophilus parryii) are well oxygenated with no evidence of cellular stress, inflammatory response, neuronal pathology, or oxidative modification following the period of high metabolic demand necessary for arousal. In contrast, euthermic Arctic ground squirrels experience mild, chronic hypoxia with low So2 and accumulation of HIF-1α and iNOS and demonstrate the greatest degree of cellular stress in brain. These results suggest that Arctic ground squirrels experience and tolerate endogenous hypoxia during euthermy and arousal.

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Wiseman, Matthew S. "Unlocking the ‘Eskimo Secret’: Defence Science in the Cold War Canadian Arctic, 1947–1954." Journal of the Canadian Historical Association 26, no. 1 (August 8, 2016): 191–223. http://dx.doi.org/10.7202/1037202ar.

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Between 1947 and 1954, medical scientists in Canada received support from federal and independent agencies to conduct a series of comparative biochemical studies on Inuit and white “test subjects.” Originally conceived from a racialized intrigue in defining the vascular characteristics of cold tolerance, the Canadian defence establishment absorbed the research with the intent to apply the findings to military service work in the North. Potentially unlocking the “Eskimo” secret to cold-weather acclimatization meant scientists could devise a screening process for selecting male white bodies for Arctic service. The research took place within the edifice of colonial science, but unlike wider postwar perceptions of the Indigenous body, this article presents the concept of biological appropriation to explore the perceived value of Inuit physiology to northern defence. Interpreting experiential research on Inuit as distinct from cultural assimilation provides a broader interpretation of postwar Arctic policy, and helps discern an understudied yet important episode of the Cold War sciences in Canada.

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Quinn, Nicole L., Colin R. McGowan, Glenn A. Cooper, Ben F. Koop, and William S. Davidson. "Identification of genes associated with heat tolerance in Arctic charr exposed to acute thermal stress." Physiological Genomics 43, no. 11 (June 2011): 685–96. http://dx.doi.org/10.1152/physiolgenomics.00008.2011.

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Arctic charr is an especially attractive aquaculture species given that it features the desirable tissue traits of other salmonids and is bred and grown at inland freshwater tank farms year round. It is of interest to develop upper temperature tolerant (UTT) strains of Arctic charr to increase the robustness of the species in the face of climate change and to enable production in more southern regions. We used a genomics approach that takes advantage of the well-studied Atlantic salmon genome to identify genes that are associated with UTT in Arctic charr. Specifically, we conducted an acute temperature trial to identify temperature tolerant and intolerant Arctic charr individuals, which were subject to microarray and qPCR analysis to identify candidate UTT genes. These were compared with genes annotated in a quantitative trait locus (QTL) region that was previously identified as associated with UTT in rainbow trout and Arctic charr and that we sequenced in Atlantic salmon. Our results suggest that small heat shock proteins as well as HSP-90 genes are associated with UTT. Furthermore, hemoglobin expression was significantly downregulated in tolerant compared with intolerant fish. Finally, QTL analysis and expression profiling identified COUP-TFII as a candidate UTT gene, although its specific role is unclear given the identification of two transcripts, which appear to have different expression patterns. Our results highlight the importance of using more than one approach to identify candidate genes, particularly when examining a complicated trait such as UTT in a highly complex genome for which there is no reference genome.

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Stevenson, Timothy J., Khrystyne N. Duddleston, and C. Loren Buck. "Effects of Season and Host Physiological State on the Diversity, Density, and Activity of the Arctic Ground Squirrel Cecal Microbiota." Applied and Environmental Microbiology 80, no. 18 (July 7, 2014): 5611–22. http://dx.doi.org/10.1128/aem.01537-14.

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ABSTRACTWe examined the seasonal changes of the cecal microbiota of captive arctic ground squirrels (Urocitellus parryii) by measuring microbial diversity and composition, total bacterial density and viability, and short-chain fatty acid concentrations at four sample periods (summer, torpor, interbout arousal, and posthibernation). Abundance ofFirmicuteswas lower, whereas abundances ofBacteroidetes,Verrucomicrobia, andProteobacteriawere higher during torpor and interbout arousal than in summer. Bacterial densities and percentages of live bacteria were significantly higher in summer than during torpor and interbout arousal. Likewise, total short-chain fatty acid concentrations were significantly greater during summer than during torpor and interbout arousal. Concentrations of individual short-chain fatty acids varied across sample periods, with butyrate concentrations higher and acetate concentrations lower during summer than at all other sample periods. Characteristics of the gut community posthibernation were more similar to those during torpor and interbout arousal than to those during summer. However, higher abundances of the generaBacteroidesandAkkermansiaoccurred during posthibernation than during interbout arousal and torpor. Collectively, our results clearly demonstrate that seasonal changes in physiology associated with hibernation and activity affect the gut microbial community in the arctic ground squirrel. Importantly, similarities between the gut microbiota of arctic ground squirrels and thirteen-lined ground squirrels suggest the potential for a core microbiota during hibernation.

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Bailey, Allison, Peter Thor, Howard I. Browman, David M. Fields, Jeffrey Runge, Alexander Vermont, Reidun Bjelland, et al. "Early life stages of the Arctic copepod Calanus glacialis are unaffected by increased seawater pCO2." ICES Journal of Marine Science 74, no. 4 (April 28, 2016): 996–1004. http://dx.doi.org/10.1093/icesjms/fsw066.

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As the world's oceans continue to absorb anthropogenic CO2 from the atmosphere, the carbonate chemistry of seawater will change. This process, termed ocean acidification, may affect the physiology of marine organisms. Arctic seas are expected to experience the greatest decreases in pH in the future, as changing sea ice dynamics and naturally cold, brackish water, will accelerate ocean acidification. In this study, we investigated the effect of increased pCO2 on the early developmental stages of the key Arctic copepod Calanus glacialis. Eggs from wild-caught C. glacialis females from Svalbard, Norway (80°N), were cultured for 2 months to copepodite stage C1 in 2°C seawater under four pCO2 treatments (320, 530, 800, and 1700 μatm). Developmental rate, dry weight, and carbon and nitrogen mass were measured every other day throughout the experiment, and oxygen consumption rate was measured at stages N3, N6, and C1. All endpoints were unaffected by pCO2 levels projected for the year 2300. These results indicate that naupliar development in wild populations of C. glacialis is unlikely to be detrimentally affected in a future high CO2 ocean.

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Shipp, J. L. "COMPARISON OF SILHOUETTE, STICKY, AND SUCTION TRAPS WITH AND WITHOUT DRY-ICE BAIT FOR SAMPLING BLACK FLIES (DIPTERA: SIMULIIDAE) IN CENTRAL ALBERTA." Canadian Entomologist 117, no. 1 (January 1985): 113–17. http://dx.doi.org/10.4039/ent117113-1.

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AbstractIn 1982 and 1983, silhouette traps, sticky traps, and suction traps with and without dry-ice bait were evaluated for sampling populations of black flies that are pests of cattle in central Alberta. The dry-ice-baited silhouette trap was the most effective. The black-fly species collected were Simulium arcticum, S. aureum, S. decorum, S. meridionale, S. tuberosum, S. venustum, S. verecundum, S. vernum, and S. vittatum. Approximately 80% of the black flies collected each year were S. arcticum, the primary pest species of cattle in Alberta.

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Noren, Shawn R. "Postnatal development of diving physiology: implications of anthropogenic disturbance for immature marine mammals." Journal of Experimental Biology 223, no. 17 (September 1, 2020): jeb227736. http://dx.doi.org/10.1242/jeb.227736.

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ABSTRACTMarine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving mechanisms to prolong aerobically supported dives to great depths, while typically avoiding (or tolerating) hypoxia, hypercarbia, acidosis and decompression sickness (DCS). Over the last few decades, research has revealed that diving physiology is underdeveloped at birth. Here, I review the postnatal development of the body's oxygen stores, cardiorespiratory system and other attributes of diving physiology for pinnipeds and cetaceans to assess how physiological immaturity makes young marine mammals vulnerable to disturbance. Generally, the duration required for body oxygen stores to mature varies across species in accordance with the maternal dependency period, which can be over 2 years long in some species. However, some Arctic and deep-diving species achieve mature oxygen stores comparatively early in life (prior to weaning). Accelerated development in these species supports survival during prolonged hypoxic periods when calves accompany their mothers under sea ice and to the bathypelagic zone, respectively. Studies on oxygen utilization patterns and heart rates while diving are limited, but the data indicate that immature marine mammals have a limited capacity to regulate heart rate (and hence oxygen utilization) during breath-hold. Underdeveloped diving physiology, in combination with small body size, limits diving and swimming performance. This makes immature marine mammals particularly vulnerable to mortality during periods of food limitation, habitat alterations associated with global climate change, fishery interactions and other anthropogenic disturbances, such as exposure to sonar.

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Milano, Stefania, Gernot Nehrke, Alan D. Wanamaker Jr., Irene Ballesta-Artero, Thomas Brey, and Bernd R. Schöne. "The effects of environment on Arctica islandica shell formation and architecture." Biogeosciences 14, no. 6 (March 27, 2017): 1577–91. http://dx.doi.org/10.5194/bg-14-1577-2017.

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Abstract. Mollusks record valuable information in their hard parts that reflect ambient environmental conditions. For this reason, shells can serve as excellent archives to reconstruct past climate and environmental variability. However, animal physiology and biomineralization, which are often poorly understood, can make the decoding of environmental signals a challenging task. Many of the routinely used shell-based proxies are sensitive to multiple different environmental and physiological variables. Therefore, the identification and interpretation of individual environmental signals (e.g., water temperature) often is particularly difficult. Additional proxies not influenced by multiple environmental variables or animal physiology would be a great asset in the field of paleoclimatology. The aim of this study is to investigate the potential use of structural properties of Arctica islandica shells as an environmental proxy. A total of 11 specimens were analyzed to study if changes of the microstructural organization of this marine bivalve are related to environmental conditions. In order to limit the interference of multiple parameters, the samples were cultured under controlled conditions. Three specimens presented here were grown at two different water temperatures (10 and 15 °C) for multiple weeks and exposed only to ambient food conditions. An additional eight specimens were reared under three different dietary regimes. Shell material was analyzed with two techniques; (1) confocal Raman microscopy (CRM) was used to quantify changes of the orientation of microstructural units and pigment distribution, and (2) scanning electron microscopy (SEM) was used to detect changes in microstructural organization. Our results indicate that A. islandica microstructure is not sensitive to changes in the food source and, likely, shell pigment are not altered by diet. However, seawater temperature had a statistically significant effect on the orientation of the biomineral. Although additional work is required, the results presented here suggest that the crystallographic orientation of biomineral units of A. islandica may serve as an alternative and independent proxy for seawater temperature.

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Høye, Toke T., and Derek S. Sikes. "Arctic entomology in the 21st century." Canadian Entomologist 145, no. 2 (March 22, 2013): 125–30. http://dx.doi.org/10.4039/tce.2013.14.

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AbstractResearch interest in the Arctic is accelerating because of observed and anticipated dramatic climate change and its impacts on societies and ecosystems. Arthropods form a major part of the terrestrial species diversity in the Arctic, and are particularly sensitive to changes in the abiotic environment. Hence, increased research activity on Arctic arthropods would help towards conservation of Arctic biodiversity as well as in understanding the role of Arctic arthropods in ecosystem functioning. In this introduction to the special issue on Arctic entomology in the 21st century, we identify trophic interactions, biodiversity assessments, and taxonomic revisions as three important research fields in Arctic entomology. We also point to ways in which Arctic entomology could take advantage of recent developments in other research fields and we place the contributions to the special issue in a broader context. Arthropods form ideal model organisms in global change studies and there is a particular need for entomological studies from the dramatically changing Arctic. It is our hope that the papers within this special issue will be a valuable source of inspiration and may stimulate novel insights and achievements in Arctic entomology during the 21st century.

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Shipp, J. L. "DIAPAUSE INDUCTION OF EGGS OF SIMULIUM ARCTICUM MALLOCH (IIS-10.11) (DIPTERA: SIMULIIDAE)." Canadian Entomologist 119, no. 5 (May 1987): 497–99. http://dx.doi.org/10.4039/ent119497-5.

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The Simulium arcticum Malloch sibling (IIS-10.11), which breeds in the Athabasca River (Procunier et al. 1984), is a major pest of cattle in central Alberta (Haufe and Croome 1980). Insecticide treatment of the river is the primary control method with the number of applications per season having increased from one to two treatments since 1978. The timing and number of applications per season are determined from information on larval instar and abundance, which is obtained from an extensive larval monitoring program that is conducted annually from late April to mid-September. Prediction of embryonic development and hatching rates of S. arcticum (IIS-10.11) eggs and when eggs enter diapause would provide for more accurate determination of the timing and number of treatments required each season.

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Cutts, C. J., C. E. Adams, and A. Campbell. "Stability of physiological and behavioural determinants of performance in Arctic char (Salvelinus alpinus)." Canadian Journal of Fisheries and Aquatic Sciences 58, no. 5 (May 1, 2001): 961–68. http://dx.doi.org/10.1139/f01-050.

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The physiological and behavioural mechanisms that confer behavioural dominance are poorly understood. Although recent studies have shown a link between metabolism and dominance, these studies relied on single measurements of both, and assumed that inter-individual variation of physiology and behaviour were repeatable over time. This paper demonstrates that standard metabolic rate is a repeatable trait in Arctic char (Salvelinus alpinus L.) and that relative differences between individuals are consistent across a range of environmental conditions. Furthermore, there were positive associations between metabolic rate, aggression, and competitive ability that were also repeatable over time. However, there was no relationship between competitive ability (measured as feeding attempts) and subsequent growth. This may be due to an energetic cost of dominance: high rates of food capture were only attainable through high rates of effort. This, in addition to elevated aggression, was thought to exert an energetic cost that could not be fully offset by the increased food intake.

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Summers, Natalie, Geir Johnsen, Aksel Mogstad, Håvard Løvås, Glaucia Fragoso, and Jørgen Berge. "Underwater Hyperspectral Imaging of Arctic Macroalgal Habitats during the Polar Night Using a Novel Mini-ROV-UHI Portable System." Remote Sensing 14, no. 6 (March 9, 2022): 1325. http://dx.doi.org/10.3390/rs14061325.

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We describe an Underwater Hyperspectral Imager (UHI) deployed on an instrument-carrying platform consisting of two interconnected mini-ROVs (Remotely Operated Vehicle) for the mapping and monitoring of Arctic macroalgal habitats in Kongsfjorden (Svalbard) during the Polar Night. The mini-ROV-UHI system is easy to transport, assemble and deploy from shore, even under the dark, icy and cold conditions of the Arctic Polar Night. The system can be operated by two persons, keeping the operational costs low. In vivo hyperspectral reflectance of collected specimens of brown, red and green macroalgae was measured with a spectrometer in the lab to provide a spectral library for supervised pigment group classification based on UHI photomosaics. The in situ UHI-photomosaics provided detailed information of the areal coverage of the seafloor substrate (16%), as well as brown (51% habitat cover), red (18%), and green (14%) macroalgae, with spatial resolution in the range of cm and spectral resolution of 2 nm. The collected specimens from the mapped area were also used for species identification and health state evaluation. This innovative UHI sampling method provides significant information about macroalgal distribution and physiology, and due to its flexibility in terms of deployment, it is applicable to a variety of environments.

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Robinson, Clare H. "Cold adaptation in Arctic and Antarctic fungi." New Phytologist 151, no. 2 (August 2001): 341–53. http://dx.doi.org/10.1046/j.1469-8137.2001.00177.x.

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Sørensen, Jesper Givskov, and Martin Holmstrup. "Cryoprotective dehydration is widespread in Arctic springtails." Journal of Insect Physiology 57, no. 8 (August 2011): 1147–53. http://dx.doi.org/10.1016/j.jinsphys.2011.03.001.

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Quinn, Nicole L., Colin R. McGowan, Glenn A. Cooper, Ben F. Koop, and William S. Davidson. "Ribosomal genes and heat shock proteins as putative markers for chronic, sublethal heat stress in Arctic charr: applications for aquaculture and wild fish." Physiological Genomics 43, no. 18 (September 2011): 1056–64. http://dx.doi.org/10.1152/physiolgenomics.00090.2011.

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Arctic charr thrive at high densities and can live in freshwater year round, making this species especially suitable for inland, closed containment aquaculture. However, it is a cold-water salmonid, which both limits where the species can be farmed and places wild populations at particular risk to climate change. Previously, we identified genes associated with tolerance and intolerance to acute, lethal temperature stress in Arctic charr. However, there remained a need to examine the genes involved in the stress response to more realistic temperatures that could be experienced during a summer heat wave in grow-out tanks that are not artificially cooled, or under natural conditions. Here, we exposed Arctic charr to sublethal heat stress of 15–18°C for 72 h, and gill tissues extracted before, during (i.e., at 72 h), immediately after cooling and after 72 h of recovery at ambient temperature (6°C) were used for gene expression profiling by microarray and qPCR analyses. The results revealed an expected pattern for heat shock protein expression, which was highest during heat exposure, with significantly reduced expression (approaching control levels) quickly thereafter. We also found that the expression of numerous ribosomal proteins was significantly elevated immediately and 72 h after cooling, suggesting that the gill tissues were undergoing ribosome biogenesis while recovering from damage caused by heat stress. We suggest that these are candidate gene targets for the future development of genetic markers for broodstock development or for monitoring temperature stress and recovery in wild or cultured conditions.

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Anderson, J. R., and J. A. Shemanchuk. "THE BIOLOGY OF SIMULIUM ARCTICUM MALLOCH IN ALBERTA. PART I. OBLIGATE ANAUTOGENY IN S. ARCTICUM AND OTHER BLACK FLIES (DIPTERA: SIMULIIDAE)." Canadian Entomologist 119, no. 1 (January 1987): 21–27. http://dx.doi.org/10.4039/ent11921-1.

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AbstractThe primary follicles of all 291 laboratory-reared Simulium arcticum Malloch females provided with only sucrose and water did not develop beyond stage II. This was true for flies derived from field-collected eggs, larvae, or pupae, and for laboratory-reared larvae that received either standard, concentrated, or unsupplemented river water diets. Conversely, all 59 females that digested a meal of cattle blood had follicles at stage IV by 85 h and stage V (mature eggs) by 109 h post-engorgement. Simulium arcticum populations from the Athabasca and Crowsnest River were thus characterized by obligate anautogeny and gonotrophic concordance. Most non-blood-fed females were dissected and examined when 4–19 days old. The presence or absence of a meconium, quantity of fat body, and other internal features were compared in young and old non-blood-fed females.

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Albert, Kristian R., Teis N. Mikkelsen, and Helge Ro-Poulsen. "Effects of ambient versus reduced UV-B radiation on high arctic Salix arctica assessed by measurements and calculations of chlorophyll a fluorescence parameters from fluorescence transients." Physiologia Plantarum 124, no. 2 (June 2005): 208–26. http://dx.doi.org/10.1111/j.1399-3054.2005.00502.x.

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Ormseth, O. A., M. Nicolson, M. A. Pelleymounter, and B. B. Boyer. "Leptin inhibits prehibernation hyperphagia and reduces body weight in arctic ground squirrels." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 271, no. 6 (December 1, 1996): R1775—R1779. http://dx.doi.org/10.1152/ajpregu.1996.271.6.r1775.

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The ob gene product leptin is thought to play a physiological role in the fine tuning of a homeostatic mechanism regulating satiety and adiposity. Mouse recombinant leptin was administered to seasonally hyperphagic arctic ground squirrels as a first step in demonstrating the evolutionary conservation of leptin function and the potential involvement of leptin in the seasonal regulation of adiposity in hibernators. Continuous infusion of leptin for 3 wk via miniosmotic pumps resulted in a reduction in food intake and body weight in a manner consistent with its proposed role as a satiety hormone. During the recovery period after leptin administration, squirrels that had received leptin became hyperphagic relative to controls. Percent body fat was estimated at weekly intervals by measuring total body electrical conductivity and decreased after 3 wk of leptin administration. Our observations support the role of leptin as a regulatory hormone involved in the control of satiety, adiposity, and possibly energy expenditure in hibernating mammals.

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Yan, Jun, Brian M. Barnes, Franziska Kohl, and Thomas G. Marr. "Modulation of gene expression in hibernating arctic ground squirrels." Physiological Genomics 32, no. 2 (January 2008): 170–81. http://dx.doi.org/10.1152/physiolgenomics.00075.2007.

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We performed a broadscale screening of differential gene expression using both high-throughput bead-array technology and real-time PCR assay in brown adipose tissue, liver, heart, hypothalamus, and skeletal muscle in hibernating arctic ground squirrels, comparing animals sampled after two durations of steady-state torpor, during two stages of spontaneous arousal episodes, and in animals after they ended hibernation. Significant seasonal and torpor-arousal cycle differences of gene expression were detected in genes involved in glycolysis, fatty acid metabolism, gluconeogenesis, amino acid metabolism, molecular transport, detoxification, cardiac contractility, circadian rhythm, cell growth and apoptosis, muscle dystrophy, and RNA and protein protection. We observed, for the first time, complex modulation of gene expression during multiple stages of torpor-arousal cycles. The mRNA levels of certain metabolic genes drop significantly during the transition from late torpor to early arousal, perhaps due to the rapid turnover of mRNA transcripts resulting from the translational demands during thermogenesis in early arousal, whereas the mRNA levels of genes related to circadian rhythm, cell growth, and apoptosis rise significantly in the early or late arousal phases during torpor-arousal cycle, suggesting the resumption of circadian rhythm and cell cycle during arousal.

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Buck, C. Loren, and Brian M. Barnes. "Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 279, no. 1 (July 1, 2000): R255—R262. http://dx.doi.org/10.1152/ajpregu.2000.279.1.r255.

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Arctic ground squirrels ( Spermophilus parryii) overwinter in hibernaculum conditions that are substantially below freezing. During torpor, captive arctic ground squirrels displayed ambient temperature (Ta)-dependent patterns of core body temperature (Tb), metabolic rate (TMR), and metabolic fuel use, as determined by respiratory quotient (RQ). At Ta 0 to −16°C, Tb remained relatively constant, and TMR rose proportionally with the expanding gradient between Tb and Ta, increasing >15-fold from a minimum of 0.0115 ± 0.0012 ml O2 · g−1 · h−1. At Ta 0–20°C, Tbincreased with Ta; however, TMR did not change significantly from Tb 0 to 12°C, indicating temperature-independent inhibition of metabolic rate. The overall change in TMR from Tb 4 to 20° equates to a Q10 of 2.4, but within this range of Tb, Q10 changed from 1.0 to 14.1. During steady-state torpor at Ta 4 and 8°C, RQ averaged 0.70 ± 0.013, indicating exclusive lipid catabolism. At Ta −16 and 20°C, RQ increased significantly to >0.85, consistent with recruitment of nonlipid fuels. RQ was negatively correlated with maximum torpor bout length. For Ta values <0°C, this relationship supports the hypothesis that availability of nonlipid metabolic fuels limits torpor duration in hibernating mammals; for Ta values >0°C, hypotheses linked to body temperature are supported. Because anterior body temperatures differ from core, overall, the duration torpor can be extended in hibernating mammals may be dependent on brain temperature.

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Wey, Daniela, Johanna Garefelt, Frida M. Fischer, Claudia R. Moreno, and Arne Lowden. "Individual differences in the sleep/wake cycle of Arctic flexitime workers." Chronobiology International 33, no. 10 (September 16, 2016): 1422–32. http://dx.doi.org/10.1080/07420528.2016.1227331.

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Piedade, Gonçalo, Ella Wesdorp, Elena Montenegro-Borbolla, Douwe Maat, and Corina Brussaard. "Influence of Irradiance and Temperature on the Virus MpoV-45T Infecting the Arctic Picophytoplankter Micromonas polaris." Viruses 10, no. 12 (November 29, 2018): 676. http://dx.doi.org/10.3390/v10120676.

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Arctic marine ecosystems are currently undergoing rapid changes in temperature and light availability. Picophytoplankton, such as Micromonas polaris, are predicted to benefit from such changes. However, little is known about how these environmental changes affect the viruses that exert a strong mortality pressure on these small but omnipresent algae. Here we report on one-step infection experiments, combined with measurements of host physiology and viability, with 2 strains of M. polaris and the virus MpoV-45T under 3 light intensities (5, 60 and 160 μmol quanta m−2 s−1), 2 light period regimes (16:8 and 24:0 h light:dark cycle) and 2 temperatures (3 and 7 °C). Our results show that low light intensity (16:8 h light:dark) delayed the decline in photosynthetic efficiency and cell lysis, while decreasing burst size by 46%. In contrast, continuous light (24:0 h light:dark) shortened the latent period by 5 h for all light intensities, and even increased the maximum virus production rate and burst size under low light (by 157 and 69%, respectively). Higher temperature (7 °C vs 3 °C) led to earlier cell lysis and increased burst size (by 19%), except for the low light conditions. These findings demonstrate the ecological importance of light in combination with temperature as a controlling factor for Arctic phytoplankton host and virus dynamics seasonally, even more so in the light of global warming.

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Vonnahme, Tobias R., Martial Leroy, Silke Thoms, Dick van Oevelen, H. Rodger Harvey, Svein Kristiansen, Rolf Gradinger, Ulrike Dietrich, and Christoph Völker. "Modeling silicate–nitrate–ammonium co-limitation of algal growth and the importance of bacterial remineralization based on an experimental Arctic coastal spring bloom culture study." Biogeosciences 18, no. 5 (March 11, 2021): 1719–47. http://dx.doi.org/10.5194/bg-18-1719-2021.

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Abstract. Arctic coastal ecosystems are rapidly changing due to climate warming. This makes modeling their productivity crucially important to better understand future changes. System primary production in these systems is highest during the pronounced spring bloom, typically dominated by diatoms. Eventually the spring blooms terminate due to silicon or nitrogen limitation. Bacteria can play an important role for extending bloom duration and total CO2 fixation through ammonium regeneration. Current ecosystem models often simplify the effects of nutrient co-limitations on algal physiology and cellular ratios and simplify nutrient regeneration. These simplifications may lead to underestimations of primary production. Detailed biochemistry- and cell-based models can represent these dynamics but are difficult to tune in the environment. We performed a cultivation experiment that showed typical spring bloom dynamics, such as extended algal growth via bacterial ammonium remineralization, reduced algal growth and inhibited chlorophyll synthesis under silicate limitation, and gradually reduced nitrogen assimilation and chlorophyll synthesis under nitrogen limitation. We developed a simplified dynamic model to represent these processes. Overall, model complexity in terms of the number of parameters is comparable to the phytoplankton growth and nutrient biogeochemistry formulations in common ecosystem models used in the Arctic while improving the representation of nutrient-co-limitation-related processes. Such model enhancements that now incorporate increased nutrient inputs and higher mineralization rates in a warmer climate will improve future predictions in this vulnerable system.

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Street, Lorna E., and S. Caldararu. "Why are Arctic shrubs becoming more nitrogen limited?" New Phytologist 233, no. 2 (November 25, 2021): 585–87. http://dx.doi.org/10.1111/nph.17841.

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Folk, G. Edgar, Diana L. Thrift, M. Bridget Zimmerman, and Paul C. Reimann. "Mammalian activity – rest rhythms in Arctic continuous daylight." Biological Rhythm Research 37, no. 6 (December 2006): 455–69. http://dx.doi.org/10.1080/09291010600738551.

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35

Kuhnlein, Harriet V. "Benefits and risks of traditional food for Indigenous Peoples: focus on dietary intakes of Arctic men." Canadian Journal of Physiology and Pharmacology 73, no. 6 (June 1, 1995): 765–71. http://dx.doi.org/10.1139/y95-102.

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A variety of community and external pressures on Indigenous Peoples are leading to increased use of food that is available through industrialization and market economies; food in traditional food systems derived from local, natural environments is declining in use. This report focusses on dietary intake of Arctic men. While nutrient density of Arctic traditional food systems is superior to that of the composite of market food consumed in the North, the percentage of men's daily energy derived from market food is more than double that from traditional food in some communities. Older members of communities consume more traditional food than younger members; men consume more traditional food than do women. In addition to providing excellent nutrition and opportunities for physical exercise, Indigenous Peoples identify many sociocultural benefits to the harvest and use of traditional food. Evaluation of environmental accumulation of organochlorines in wildlife animal food species shows that risk of organochlorine consumption is higher in food systems containing sea mammals, and that tolerance levels for some organochlorines may be exceeded.Key words: Indigenous Peoples, traditional food, contaminants, nutrition.

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Airaksinen, S., L. Sistonen, and M. Nikinmaa. "Stress response in cold adapted Arctic charr." Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 124 (August 1999): S103. http://dx.doi.org/10.1016/s1095-6433(99)90408-7.

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Anthony, Susan E., Christopher M. Buddle, Toke T. Høye, Nils Hein, and Brent J. Sinclair. "Thermal acclimation has limited effect on the thermal tolerances of summer-collected Arctic and sub-Arctic wolf spiders." Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 257 (July 2021): 110974. http://dx.doi.org/10.1016/j.cbpa.2021.110974.

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38

Tøien, Ø., K. L. Drew, M. L. Chao, and M. E. Rice. "Ascorbate dynamics and oxygen consumption during arousal from hibernation in Arctic ground squirrels." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, no. 2 (August 1, 2001): R572—R583. http://dx.doi.org/10.1152/ajpregu.2001.281.2.r572.

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During hibernation in Arctic ground squirrels ( Spermophilus parryii), O2 consumption and plasma leukocyte counts decrease by >90%, whereas plasma concentrations of the antioxidant ascorbate increase fourfold. During rewarming, O2 consumption increases profoundly and plasma ascorbate and leukocyte counts return to normal. Here we investigated the dynamic interrelationships among these changes. Plasma ascorbate and uric acid (urate) concentrations were determined by HPLC from blood samples collected at ∼15-min intervals via arterial catheter; leukocyte count and hematocrit were also determined. Body temperature, O2 consumption, and electromyographic activity were recorded continuously. Ascorbate, urate, and glutathione contents in body and brain samples were determined during hibernation and after arousal. During rewarming, the maximum rate of plasma ascorbate decrease occurred at the time of peak O2 consumption and peak plasma urate production. The ascorbate decrease did not correlate with mouth or abdominal temperature; uptake into leukocytes could account for only a small percentage. By contrast, liver and spleen ascorbate levels increased significantly after arousal, which could more than account for ascorbate clearance from plasma. Brain ascorbate levels remained constant. These data suggest that elevated concentrations of ascorbate {[Asc]} in plasma {[Asc]p} provide an antioxidant source that is redistributed to tissues during the metabolic stress that accompanies arousal.

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Robinson, Clare H., Philip A. Wookey, and Thomas C. Parker. "Root‐associated fungi and carbon storage in Arctic ecosystems." New Phytologist 226, no. 1 (February 13, 2020): 8–10. http://dx.doi.org/10.1111/nph.16443.

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40

Fan, Rong, Tomoki Morozumi, Trofim C. Maximov, and Atsuko Sugimoto. "Effect of floods on the δ13C values in plant leaves: a study of willows in Northeastern Siberia." PeerJ 6 (September 20, 2018): e5374. http://dx.doi.org/10.7717/peerj.5374.

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Although stable carbon isotopic composition (δ13C) of plants has been widely used to indicate different water regimes in terrestrial ecosystems over the past four decades, the changes in the plant δ13C value under waterlogging have not been sufficiently clarified. With the enhanced global warming in recent years, the increasing frequency and severity of river floods in Arctic regions lead to more waterlogging on willows that are widely distributed in river lowland. To investigate the δ13C changes in plants under different water conditions (including waterlogging), we measured the δ13C values in the leaves of willows with three species,Salix boganidensis,S. glauca, andS. pulchra, and also monitored changes in plant physiology, under several major flooding conditions in Northeastern Siberia. The foliar δ13C values of willows varied, ranging from −31.6 to −25.7‰ under the different hydrological status, which can be explained by: (i) under normal conditions, the foliar δ13C values decrease from dry (far from a river) to wet (along a river bank) areas; (ii) the δ13C values increase in frequently waterlogged areas owing to stomatal closure; and (iii) after prolonged flooding periods, the δ13C values again decrease, probably owing to the effects of not only the closure of stomata but also the reduction of foliar photosynthetic ability under long period of waterlogging. Based on these results, we predict that plant δ13C values are strongly influenced by plant physiological responses to diverse hydrological conditions, particularly the long periods of flooding, as occurs in Arctic regions.

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Daniels, C. J., R. M. Sheward, and A. J. Poulton. "Biogeochemical implications of comparative growth rates of Emiliania huxleyi and Coccolithus species." Biogeosciences Discussions 11, no. 7 (July 10, 2014): 10513–36. http://dx.doi.org/10.5194/bgd-11-10513-2014.

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Abstract. Coccolithophores are a diverse and biogeochemically important group of phytoplankton in terms of the production and export of calcite, yet the comparative physiology and ecology of species other than the ubiquitous Emiliania huxleyi is poorly understood. Despite assumptions that Emiliania huxleyi is a fast growing species, we found it had comparable growth rates (0.16–0.85 d−1) with strains of Coccolithus pelagicus and Coccolithus braarudii when grown under identical temperature and light conditions. A recently isolated Arctic strain of C. pelagicus (RCC4092) exhibited only a 12% slower growth rate, on average, than a recently isolated Arctic strain of E. huxleyi (RCC3533), over a temperature range of 6–12 °C. Established temperate strains of E. huxleyi and C. braarudii (RCC1228 and RCC1198) exhibited a slightly larger difference in growth rates, with E. huxleyi growing 28% faster on average than C. braarudii over a temperature range of 12–19 °C. Coupled with the 30–80 times higher cellular calcite content of C. pelagicus and C. braarudii compared to E. huxleyi, this suggests that Coccolithus species could be major calcite producers in mixed populations. The relative abundance of coccolithophore species is key for determining which species will dominate calcite production in mixed communities growing at similar rates. Field samples from the North Atlantic show that C. pelagicus is in a high enough relative abundance in 69% of samples collected in the spring and summer of 2010 to be a larger source of calcite production than E. huxleyi.

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Boyer, Bert B., Brian M. Barnes, Bradford B. Lowell, and Danica Grujic. "Differential regulation of uncoupling protein gene homologues in multiple tissues of hibernating ground squirrels." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 275, no. 4 (October 1, 1998): R1232—R1238. http://dx.doi.org/10.1152/ajpregu.1998.275.4.r1232.

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Nonshivering thermogenesis in brown adipose tissue (BAT) provides heat through activation of a mitochondrial uncoupling protein (UCP1), which causes futile electron transport cycles without the production of ATP. Recent discovery of two molecular homologues, UCP2, expressed in multiple tissues, and UCP3, expressed in muscle, has resulted in investigation of their roles in thermoregulatory physiology and energy balance. To determine the expression pattern of Ucp homologues in hibernating mammals, we compared relative mRNA levels of Ucp1, -2, and -3 in BAT, white adipose tissue (WAT), and skeletal muscle of arctic ground squirrels ( Spermophilus parryii) hibernating at different ambient and body temperatures, with levels determined in tissues from ground squirrels not in hibernation. Here we report significant increases in mRNA levels for Ucp2 in WAT (1.6-fold) and Ucp3 in skeletal muscle (3-fold) during hibernation. These results indicate the potential for a role of UCP2 and UCP3 in thermal homeostasis during hibernation and indicate that parallel mechanisms and multiple tissues could be important for nonshivering thermoregulation in mammals.

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Vlasova, O. S., F. A. Bichkaeva, T. V. Tretyakova, and N. F. Baranova. "Saturated Fatty Acids and Parameters of Carbohydrate Metabolism in Adolescents of sub-Arctic and Arctic regions." Journal of Evolutionary Biochemistry and Physiology 54, no. 3 (May 2018): 185–91. http://dx.doi.org/10.1134/s0022093018030031.

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44

Barger, Jamie L., Brian M. Barnes, and Bert B. Boyer. "Regulation of UCP1 and UCP3 in arctic ground squirrels and relation with mitochondrial proton leak." Journal of Applied Physiology 101, no. 1 (July 2006): 339–47. http://dx.doi.org/10.1152/japplphysiol.01260.2005.

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Uncoupling protein (UCP) 1 (UCP1) catalyzes a proton leak in brown adipose tissue (BAT) mitochondria that results in nonshivering thermogenesis (NST), but the extent to which UCP homologs mediate NST in other tissues is controversial. To clarify the role of UCP3 in mediating NST in a hibernating species, we measured Ucp3 expression in skeletal muscle of arctic ground squirrels in one of three activity states (not hibernating, not hibernating and fasted for 48 h, or hibernating) and housed at 5°C or −10°C. We then compared Ucp3 mRNA levels in skeletal muscle with Ucp1 mRNA and UCP1 protein levels in BAT in the same animals. Ucp1 mRNA and UCP1 protein levels were increased on cold exposure and decreased with fasting, with the highest UCP1 levels in thermogenic hibernators. In contrast, Ucp3 mRNA levels were not affected by temperature but were increased 10-fold during fasting and >3-fold during hibernation. UCP3 protein levels were increased nearly fivefold in skeletal muscle mitochondria isolated from fasted squirrels compared with nonhibernators, but proton leak kinetics in the presence of BSA were unchanged. Proton leak in BAT mitochondria also did not differ between fed and fasted animals but did show classical inhibition by the purine nucleotide GDP. Levels of nonesterified fatty acids were highest during hibernation, and tissue temperatures during hibernation were related to Ucp1, but not Ucp3, expression. Taken together, these results do not support a role for UCP3 as a physiologically relevant mediator of NST in muscle.

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Jones, P. J., I. Jacobs, A. Morris, and M. B. Ducharme. "Adequacy of food rations in soldiers during an arctic exercise measured by doubly labeled water." Journal of Applied Physiology 75, no. 4 (October 1, 1993): 1790–97. http://dx.doi.org/10.1152/jappl.1993.75.4.1790.

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To investigate the adequacy of food rations to supply energy needs in cold-temperature environments, caloric expenditure and intake and body composition changes were measured in a group of infantrymen during a 10-day field exercise in the Canadian Arctic. Energy expenditure was measured by the doubly labeled water method (n = 10), and caloric intake was measured by complete food intake records (n = 20). Body composition was determined by isotope dilution (n = 10) and bioelectrical impedence analysis (n = 20) on days 0 and 10. Baseline isotopic enrichment shifts due to geographical relocation were also monitored (n = 5). Mean body weight decreased 0.63 +/- 0.83 (SD) kg over the study period (P < 0.005), although fat-free and fat mass compartment changes were not significant. Baseline isotopic changes were -4.65 +/- 2.54 and -0.48 +/- 0.07 /1000/day for deuterium and 18O, respectively. Mean baseline corrected energy expenditure level was 4,317 +/- 927 kcal/day. Self-reported caloric intakes obtained from food records were 2,633 +/- 499 kcal/day (61.0% of expenditure). Rations packs contained 4,350 kcal/day. Results suggest that 1) food intake was significantly underreported and 2) the energy needs of most subjects were being met by rations and available supplements.

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Solovieva, K. B., I. V. Dolbin, and E. B. Koroleva. "Hemodynamic indicators varying in different flight phases in hypertensive pilots of the Arctic transport aviation." Human Physiology 41, no. 7 (December 2015): 780–84. http://dx.doi.org/10.1134/s0362119715070233.

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Ware, Jasmine V., Karyn D. Rode, Charles T. Robbins, Tanya Leise, Colby R. Weil, and Heiko T. Jansen. "The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears." Journal of Biological Rhythms 35, no. 2 (January 24, 2020): 180–94. http://dx.doi.org/10.1177/0748730419900877.

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Life in the Arctic presents organisms with multiple challenges, including extreme photic conditions, cold temperatures, and annual loss and daily movement of sea ice. Polar bears ( Ursus maritimus) evolved under these unique conditions, where they rely on ice to hunt their main prey, seals. However, very little is known about the dynamics of their daily and seasonal activity patterns. For many organisms, activity is synchronized (entrained) to the earth’s day/night cycle, in part via an endogenous (circadian) timekeeping mechanism. The present study used collar-mounted accelerometer and global positioning system data from 122 female polar bears in the Chukchi and Southern Beaufort Seas collected over an 8-year period to characterize activity patterns over the calendar year and to determine if circadian rhythms are expressed under the constant conditions found in the Arctic. We reveal that the majority of polar bears (80%) exhibited rhythmic activity for the duration of their recordings. Collectively within the rhythmic bear cohort, circadian rhythms were detected during periods of constant daylight (June-August; 24.40 ± 1.39 h, mean ± SD) and constant darkness (23.89 ± 1.72 h). Exclusive of denning periods (November-April), the time of peak activity remained relatively stable (acrophases: ~1200-1400 h) for most of the year, suggesting either entrainment or masking. However, activity patterns shifted during the spring feeding and seal pupping season, as evidenced by an acrophase inversion to ~2400 h in April, followed by highly variable timing of activity across bears in May. Intriguingly, despite the dynamic environmental photoperiodic conditions, unpredictable daily timing of prey availability, and high between-animal variability, the average duration of activity (alpha) remained stable (11.2 ± 2.9 h) for most of the year. Together, these results reveal a high degree of behavioral plasticity in polar bears while also retaining circadian rhythmicity. Whether this degree of plasticity will benefit polar bears faced with a loss of sea ice remains to be determined.

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Oliver, D. R., and M. E. Dillon. "REVIEW OF CRICOTOPUS (DIPTERA: CHIRONOMIDAE) OF THE NEARCTIC ARCTIC ZONE WITH DESCRIPTION OF TWO NEW SPECIES." Canadian Entomologist 120, no. 5 (May 1988): 463–96. http://dx.doi.org/10.4039/ent120463-5.

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AbstractThe genus Cricotopus of the arctic zone of the Nearctic region, represented by 14 species in seven species groups, is reviewed. Descriptive notes on 11 species supplement those given by Hirvenoja (1973), with addition of descriptions of immature stages of C. lestralis (Edwards) and larva of C. tristis Hirvenoja. Two new species names, C. beringensis and C. trilobus, are proposed. New species names synonymies are Chironomus basalis Staeger and Chironomus holmgreni Kieffer with Chironomus tibialis (Meigen) (= C. tibialis). Several undetermined individuals are assigned to the fuscus group. Eleven species are Holarctic in distribution, of which C. bicinctus (Meigen) and C. sylvestris (Fabricius) are circumboreal. Seven species are restricted to the arctic zone, two are wide-ranging in both arctic and temperate zones, and four temperate species barely extend into the arctic zone. Keys to all known life-history stages and some ecological data, primarily of larvae, are given.

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Hoffmann, Matthias H., and Martin Röser. "Taxon recruitment of the arctic flora: an analysis of phylogenies." New Phytologist 182, no. 3 (April 16, 2009): 774–80. http://dx.doi.org/10.1111/j.1469-8137.2009.02782.x.

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Campbell, I. T., D. W. Wilson, R. F. Walker, and K. Griffiths. "The Use of Salivary Steroids to Monitor Circadian Rhythmicity on Expeditions in the Arctic." Chronobiology International 2, no. 1 (January 1985): 55–59. http://dx.doi.org/10.3109/07420528509055542.

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Journal articles on the topic 'Arctium – physiologie'

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