Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cold Climate”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed2004

Latitudinal variation in habitat specificity of ameronothrid mites (Oribatida).

Ameronothroid mites, including Ameronothridae, Fortuyniidae and Selenoribatidae, are unique among the Oribatida through having a global distribution from the tropics to the poles, and occupying a diversity of habitats including terrestrial, marine and freshwater. Their ecological diversification is of considerable interest from both the perspective of evolution over geological timescales, and the detail of the underlying processes. Given their widespread global distribution, it seems likely that historical global events (tectonic and climatic) have played a fundamental role in their ecological diversification. Previous studies of sub-Antarctic island arthropods have generated considerable circumstantial evidence in support of glaciation being a primary factor influencing ecological patterns: lower habitat specificity and weaker interspecific interactions are associated with more recent (postglacial) vegetated terrestrial biotopes, as compared to the older epilithic and littoral biotopes (which are assumed to have been present, albeit reduced in extent, during Neogene glacial maxima). Here, we use ameronothrid mites as a case study to examine the extent to which the above island scenario generalizes globally across latitudes affected by glaciation. We show that, unlike congeners or even conspecifics at lower latitudes in each hemisphere which are restricted to marine environments, the species found at higher latitudes (especially Alaskozetes antarcticus, Ameronothrus dubinini, Ameronothrus lineatus, and Halozetes belgicae) show greater affinity for terrestrial environments. They show a transition or expansion of habitat use (from marine-influenced to terrestrial habitats) implicit with a lower degree of habitat specificity, in relation to increasing latitude. We contend that the terrestrial environment at higher latitudes in both hemispheres has been colonized by these ameronothrid mite species following the various glaciation events, facilitated by a lack of competition experienced in their low diversity communities, in a manner which represents a larger scale demonstration of the processes described on sub-Antarctic islands.

Animals↗
PubMed1997

Sleeping problems at 78 degrees north: the Svalbard Study.

The aim of this study, was to compare the prevalence of sleeping problems in two ethnically different populations living under the same extreme arctic climate. A total of 453 Norwegians (319 males and 134 females) were compared with 450 Russians (317 males and 133 females), all aged 18 years or older, living on Svalbard, the northernmost regular settlement in the world. Among Russians, 81% of the male subjects and 77% of the female subjects reported sleeping problems lasting for at least 2 weeks. The corresponding figures for the Norwegians were 22% (for males) and 25% (for females). Among Russians, sleeping problems decreased with increasing age, but no such age trend was found in Norwegians. Whereas sleeping problems among Norwegians were approximately equally frequent throughout the year, the Russians reported more problems during the polar night. 'Problems falling asleep', 'not feeling rested in the morning' and 'walking up several times during the night' were the most frequent types of sleeping problems in both groups. Depression, shift work, loneliness, ability to concentrate, alcohol consumption and quality of life were associated with sleeping problems in Norwegian subjects, whereas depression, shift work, ability to concentrate, and worry were associated with sleeping problems in Russians. The prevalence of sleeping problems was nearly fourfold higher among Russian subjects than among Norwegians living on Svalbard. As the Russians were recruited from a lower latitude than the Norwegians, we postulate that their problems should be interpreted in terms of inadequate acclimatization after migration to the north.

Adult↗
PubMed2002

Survival mechanisms in Antarctic lakes.

In Antarctic lakes, organisms are confronted by continuous low temperatures as well as a poor light climate and nutrient limitation. Such extreme environments support truncated food webs with no fish, few metazoans and a dominance of microbial plankton. The key to success lies in entering the short Antarctic summer with actively growing populations. In many cases, the most successful organisms continue to function throughout the year. The few crustacean zooplankton remain active in the winter months, surviving on endogenous energy reserves and, in some cases, continuing development. Among the Protozoa, mixotrophy is an important nutritional strategy. In the extreme lakes of the McMurdo Dry Valleys, planktonic cryptophytes are forced to sustain a mixotrophic strategy and cannot survive by photosynthesis alone. The dependence on ingesting bacteria varies seasonally and with depth in the water column. In the Vestfold Hills, Pyramimonas, which dominates the plankton of some of the saline lakes, also resorts to mixotrophy, but does become entirely photosynthetic at mid-summer. Mixotrophic ciliates are also common and the entirely photosynthetic ciliate Mesodinium rubrum has a widespread distribution in the saline lakes of the Vestfold Hills, where it attains high concentrations. Bacteria continue to grow all year, showing cycles that appear to be related to the availability of dissolved organic carbon. In saline lakes, bacteria experience sub-zero temperatures for long periods of the year and have developed biochemical adaptations that include anti-freeze proteins, changes in the concentrations of polyunsaturated fatty acids in their membranes and suites of low-temperature enzymes.

Acclimatization↗
PubMedDate not supplied

Selection of overwintering microhabitats used by the arctic woollybear caterpillar, Gynaephora groenlandica.

In extreme environments such as the High Arctic, climatic conditions challenge physiological tolerance of insects resulting in prolonged dormancy and extended life cycles. Therefore, the selection of suitable microhabitats for overwintering is crucial. At two field sites on Ellesmere Island, we located hibernacula (silk overwintering structures) used by the Arctic woollybear caterpillar, Gynaephora groenlandica (Wöcke) (Lepidoptera: Lymantriidae) during their 11 month dormancy. All hibernacula found were anchored to the base of rocks and were not associated with vegetation. Rocks may function to absorb solar radiation and re-radiate heat, accelerating localized snowmelt, thus allowing caterpillars to emerge as early as possible in spring to begin foraging. Temperatures experienced by G. groenlandica in hibernacula throughout the winter were well within their physiological tolerance range. During late summer aestivation, hibernaculum temperatures were similar to, but more stable than, nearby soil surface temperatures. Lower maximum daily hibernaculum temperatures during the warmest month (July) may reduce metabolic rates and provide some energy savings. Since hibernacula were not randomly distributed around rocks, this suggests that G. groenlandica key in on some feature of the hibernaculum site. The northeast orientation of hibernacula at Eastwind Lake corresponds to the leeward side of rocks. Therefore wind patterns may be important in hibernaculum site selection. Other potential cues that may guide selection of hibernacula sites remain unclear: no seasonal changes in preference for light or soil moisture were observed between active and dormant caterpillars, and thermotaxis could not be distinguished from thigmotaxis.

Animals↗
PubMed2006

Assessment of thermal stratification within stream pools as a mechanism to provide refugia for native trout in hot, arid rangelands.

Native trout species, such as the redband trout (Oncorhynchus mykiss), occupy thermally harsh stream habitats in hot, arid rangeland basins of the western United States. Declines in the distribution and abundance of these species has generated interest in understanding how these cold water species survive in these systems, as well as in identifying opportunities to restore these species to their former ranges. The purpose of this study was to assess the potential for thermal stratification to provide thermal refuge for redband trout in stream pools characterized by warm intermittent flow conditions on arid rangelands. We studied vertical thermal stratification in two pools during three summers on Boles Creek located on the Modoc Plateau in extreme northeastern California. Water and air temperature data were collected on a 0.5 h time step from 15-Jun through 15-Sep during 1996, 1997, and 2000 using commercial temperature data-loggers. Water temperature was measured at the top (0.3 m below pool surface) and bottom (0.3 m above pool substrates) of each pool. Vertical thermal stratification occurred within these pools creating conditions as much as 7.6 C cooler and consistently more constant at the bottom of pools compared to pool surface waters. Thermal stratification was dependent upon air temperature with the magnitude of stratification increasing as air temperature increased. The magnitude of thermal stratification varied significantly from year to year, likely reflecting variation in annual weather conditions. The thermal regime in the study pools was often near the upper lethal limit reported for redband trout, but temperatures at the bottom of these pools did offer refuge from lethal temperatures realized near the pool surface. Temperatures at pool bottom were consistently above optimal levels published for redbands.

Acclimatization↗
PubMed2003

Recent changes in the North Atlantic.

It has long been recognized that the Atlantic meridional overturning circulation (MOC) is potentially sensitive to greenhouse-gas and other climate forcing, and that changes in the MOC have the potential to cause abrupt climate change. However, the mechanisms remain poorly understood and our ability to detect these changes remains incomplete. Four main (interrelated) types of ocean change in particular are associated in the literature with greenhouse-gas forcing. These are: a slowing of MOC overturning rate; changes in northern seas which might effect a change in Atlantic overturning, including changes in the freshwater flux from the Arctic, and changes in the transport and/or hydrographic character of the northern overflows which ventilate the deep Atlantic; a change in the trans-ocean gradients of steric height (both zonal and meridional) which might accompany a change in the MOC; and an intensification of the global water cycle. Though as yet we have no direct measure of the freshwater flux passing from the Arctic to the Atlantic either via the Canadian Arctic Archipelago or along the East Greenland Shelf, and no direct measure yet of the Atlantic overturning rate, we examine a wide range of time-series from the existing hydrographic record for oceanic evidence of the other anticipated responses. Large amplitude and sustained changes are found (or indicated by proxy) over the past three to four decades in the southward transport of fresh waters along the Labrador shelf and slope, in the hydrography of the deep dense overflows from Nordic seas, in the transport of the eastern overflow through Faroe Bank Channel, and in the global hydrologic cycle. Though the type and scale of changes in ocean salinity are consistent with an amplification of the water cycle, we find no convincing evidence of any significant, concerted slowdown in the Atlantic overturning circulation.

Arctic Regions↗
PubMed2000

Antarctic medicine.

Explore the source record for details and available documents.

Adaptation, Physiological↗
PubMedDate not supplied

Neandertal cold adaptation: physiological and energetic factors.

European Neandertals employed a complex set of physiological cold defenses, homologous to those seen in contemporary humans and nonhuman primates. While Neandertal morphological patterns, such as foreshortened extremities and low relative surface-area, may have explained some of the variance in cold resistance, it is suggested the adaptive package was strongly dependent on a rich array of physiological defenses. A summary of the environmental cold conditions in which the Neandertals lived is presented, and a comparative ethnographic model from Tierra del Fuego is used. Muscle and subcutaneous fat are excellent "passive" insulators. Neandertals were quite muscular, but it is unlikely that they could maintain enough superficial body fat to offer much cold protection. A major, high-energy metabolic adaptation facilitated by modest amounts of highly thermogenic brown adipose tissue (BAT) is proposed. In addition, Neandertals would have been protected by general mammalian cold defenses based on systemic vasoconstriction and intensified by acclimatization, aerobic fitness, and localized cold--induced vasodilation. However, these defenses are energetically expensive. Based on contemporary data from circumpolar peoples, it is estimated that Neandertals required 3,360 to 4,480 kcal per day to support strenuous winter foraging and cold resistance costs. Several specific genetic cold adaptations are also proposed--heat shock protein (actually, stress shock protein), an ACP*1 locus somatic growth factor, and a specialized calcium metabolism not as yet understood.

Acclimatization↗
PubMedDate not supplied

Basal metabolic rate in the Yakut (Sakha) of Siberia.

Human indigenous circumpolar populations have elevated basal metabolic rates (BMRs) relative to predicted values; this metabolic elevation has been postulated to be a physiological adaptation to chronic and severe cold stress. The present study examines BMR in the Yakut, an indigenous high-latitude population from the Sakha Republic of Russia to determine (1) whether the Yakut show evidence of an elevated BMR, (2) if the Yakut display evidence of age-related changes in BMR, and (3) whether lifestyle differences influence BMR. BMR was measured during the late summer in 75 women and 50 men (ages 18-56 years) from the Siberian village of Berdygestiakh. Measured BMR (+/- SEM) of the entire sample was significantly elevated (+6.5%) compared to predictions based on body mass (6,623.7 +/- 94.9 vs. 6,218.2 +/- 84.7 kJ/day; P < 0.001). Additionally, measured BMR for the entire sample was significantly higher than predictions based on fat-free mass (+20.8%) and surface area (+8.9%). Males and females both showed significant elevations relative to all three standards. The elevated BMR of the Yakut does not appear to be attributable to extreme levels of protein, since the Yakut consume a mixed diet with a substantial proportion of carbohydrates. No significant age-related changes in BMR were found when controlled for body composition. No significant relationship was found between lifestyle variables and BMR, suggesting the possibility of a genetic or developmental mechanism. This study provides additional evidence of metabolic elevation in indigenous circumpolar groups and has important implications for estimating the nutritional requirements of these populations.

Acclimatization↗
PubMed1992

Macrostructure differences of polar fox and dog lungs.

The lungs of the polar fox and dog have the typical form and lobular structure characteristic of beasts of prey. Both display secondary fusion of the cranial and middle lobes in the left lung, but this is more extensive in the fox. A consistent relationship between the beast body mass and the mass and volume of the lungs is present. The relative weight of dog lungs independent of body size (weight index) is 1.7 times that of the polar fox. In the latter the parenchyma is much more subdivided than in the dog. There are 23 segments per lung pair in the polar fox, compared to 19 in the dog. Although these are of unequal size throughout the lungs of both species, corresponding segments in the fox are about half as large as those in the dog. The greater segmentation of polar fox lungs may be of assistance in restricting the spread of inflammatory processes.

Acclimatization↗