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  • 1
    Electronic Resource
    Electronic Resource
    Thermal tolerance and acclimation response of larvae of the sub-Antarctic beetle Hydromedion sparsutum (Coleoptera: Perimylopidae) (2000)
    Springer
    Polar biology 23 (2000), S. 77-84 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydromedion sparsutum is a locally abundant herbivorous beetle on the sub-Antarctic island of South Georgia, often living in close association with the tussock grass Parodiochloa flabellata. Over a 4-day period in mid-summer when the air temperature varied from 0 to 20°C, the temperature in the leaf litter 5–10 cm deep at the base of tussock plants (the microhabitat of H. sparsutum) was consistently within the range of 5–7.5°C. Experiments were carried out to assess the ability of H. sparsutum larvae collected from this thermally stable environment to acclimate when maintained at lower (0°C) and higher (15°C) temperatures. The mean supercooling points (freezing temperature) of larvae collected in January and acclimated at 0°C for 3 and 6 weeks and 15°C for 3 weeks were all within the range of −2.6 to −4.6°C. Larvae in all treatment groups were freeze tolerant. Acclimation at 0°C significantly increased survival in a 15-min exposure at −8°C (from 27 to 96%) and −10°C (from 0 to 63%) compared with the field-fresh and 15°C-treated larvae. Similarly, survival of 0°C-acclimated larvae in a 72-h exposure at −6°C increased from 20 to 83%. Extending the acclimation period at 0°C to 6 weeks did not produce any further increase in cold tolerance. The concentrations of glucose and trehalose in larval body fluids increased significantly with low temperature acclimation. Larvae maintained at 15°C for 3 weeks (none survived for 6 weeks) were less able to survive 1-h exposures between 30 and 35°C than the 0°C-treated samples. Whilst vegetation and snow cover are an effective buffer against low winter temperatures in many polar insects, the inability of H. sparsutum larvae to acclimate or survive at 15°C suggests that protection against high summer temperatures is equally important for this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050011
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  • 2
    Electronic Resource
    Electronic Resource
    Feeding in the two phytophagous beetles Hydromedion sparsutum and Perimylops antarcticus from South Georgia (1989)
    Springer
    Polar biology 10 (1989), S. 141-143 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The consumption of fresh plant materials by adults and larvae of Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) was estimated from the production of faecal pellets and amount of excreted plant remnants as dry weight. Adults and larvae of Hydromedion consumed large quantities of grasses, including the alien Poa annua, but smaller amounts of the indigenous great burnet, Acaena magellanica. Both stages of Perimylops consumed much smaller quantities of grasses and Acaena. Different species of mosses were eaten in both species, and appeared to be a major source of food for Perimylops in addition to microphytes on rocks. The consumption of mosses and microphytes reflects the adaptation of Perimylops to living in habitats at higher altitudes (e.g. above 200 m), where other plants are scarce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239159
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  • 3
    Electronic Resource
    Electronic Resource
    Respiratory metabolism of Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) from South Georgia (1989)
    Springer
    Polar biology 10 (1989), S. 135-139 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Metabolic rates were studied in adults and larvae of the two phytophagous beetles Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) indigenous to the Sub-Antarctic island of South Georgia. From the regression lines for log10 metabolic rate on temperature no difference in oxygen consumption was found between adults and larvae of Hydromedion or adults of Perimylops from lower sites near sea level and upper sites at about 200 m. Elevated rates of metabolism, however, was found in larvae of Perimylops from upper sites. The slopes of the regression lines of corresponding upper and lower sites adults or larvae were similar in all cases. The metabolic rates were of the same level in adults of both species and in the larvae, but generally higher in adults than in larvae. The activation energies, calculated from Arrhenius plots, varied from 6.7 to 13.6 kcal.mol−1 in larvae and from 10.7 to 11.3 kcal.mol−1 in adults. The low values may be interpreted as an expression of cold adapted metabolism. Compared with published data on phytophagous beetles, the metabolic rates of the two species from South Georgia are comparable to two alpine species, but lower than the rates of an Arctic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239158
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  • 4
    Electronic Resource
    Electronic Resource
    Body water content and desiccation resistance in some arthropods from subantarctic South Georgia (1990)
    Springer
    Polar biology 10 (1990), S. 581-588 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The body water content and resistance to desiccation were studied in two perimylopid beetles, Perimylops antarcticus and Hydromedion sparsutum, a chironomid midge, Eretmoptera murphyi, and two spiders, Notiomaso australis and Perimaso grytvikensis from the subantarctic island of South Georgia. Comparisons were made between different species, different life stages and, where possible, between a high and a low altitude. Perimylops is abundant at higher elevations and in more exposed habitats (fellfields). This may be accounted for by its feeding behaviour, high body water content (relative to Hydromedion) and low rate of water loss under desiccating conditions, particularly in the larval stages. Hydromedion is more abundant at the lower collection site. It is a more robust beetle than Perimylops and its feeding preference is for plants such as grasses and Acaena. Nevertheless, at the upper site adult Hydromedion are able to withstand desiccation to an even greater degree than Perimylops. Water loss rates for both beetles are significantly higher than those reported for related beetles from arid and semi-arid regions. The ability to regulate water loss is not as apparent in the polar perimylopids Perimylops and Hydromedion as in related species from other xeric habitats. These two species, in fact, resemble more closely carabid beetles in xeric habitats in rates of water loss under controlled conditions. Increased temperatures elevate the rate of water loss significantly. South Georgia spiders have a similar rate of water loss to several species of spiders that have been studied in the temperate zone. Eretmoptera is restricted to moist conditions and cannot survive desiccating conditions even for brief periods. It has the highest body water content (78% of fresh weight) of all of the South Georgian arthropods studied. Among the spiders, sufficient information could be obtained only for Notiomaso. This species is much less resistant to desiccation than the perimylopid beetles, and it has a relatively high body water content. It is quite numerous in the lower, warmer habitats where its insect prey is more abundant and diverse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239369
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of experimental temperature elevation on high-arctic soil microarthropod populations (1996)
    Springer
    Polar biology 16 (1996), S. 147-153 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  An experiment was conducted to measure the effects of summer warming on the total population densities of soil-dwelling microarthropods in the high Arctic and to compare these results with those from natural between-year and between-site variations. Small polythene tents were used to elevate summer temperatures over 3 years on polar semi-desert and tundra heath in West Spitsbergen, Svalbard, Norway. Soil cores were taken at regular intervals from tented and untented (control) plots and heat extracted for mites (Acarina: Oribatida) and springtails (Collembola). Species present were similar at both sites, but at the start of the experiment total springtail populations were greater at the polar semi-desert whilst oribatid mite densities were equal at both sites. No significant effect of temperature elevation on oribatid mite populations emerged, even after 3 years. By contrast, springtail numbers were significantly lower on tented versus control plots at the polar semi-desert at the end of year 3, but not so at the tundra heath. Collembola numbers declined at both sites during the warm dry midsummers of 1992/1993 and this was most marked at the better drained polar semi-desert site. Over the equivalent period total oribatid mite populations, while relatively more stable, increased significantly at the polar semi-desert as a result of an increase in the number of juveniles. Results are interpreted in the context of the ecophysiological adaptations of oribatid mites and springtails to soil temperature and moisture. The resulting survival characteristics are considered in relation to the temperature and moisture characteristics of the two sites. The experiment demonstrated that year to year variation in climate, interacting with physical differences between sites, produced an equal or greater effect on microarthropod numbers at any one site than the 8–10% increase in “heat availability” (day degrees above zero) resulting from the summer tent treatment. The limitations of the use of tents to elevate soil temperatures are discussed. Comparisons are made with microarthropod population data from other polar and alpine sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050039
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of experimental temperature elevation on high-arctic soil microarthropod populations (1996)
    Springer
    Polar biology 16 (1996), S. 147-153 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An experiment was conducted to measure the effects of summer warming on the total population densities of soil-dwelling microarthropods in the high Arctic and to compare these results with those from natural between-year and between-site variations. Small polythene tents were used to elevate summer temperatures over 3 years on polar semi-desert and tundra heath in West Spitsbergen, Svalbard, Norway. Soil cores were taken at regular intervals from tented and untented (control) plots and heat extracted for mites (Acarina: Oribatida) and springtails (Collembola). Species present were similar at both sites, but at the start of the experiment total springtail populations were greater at the polar semi-desert whilst oribatid mite densities were equal at both sites. No significant effect of temperature elevation on oribatid mite populations emerged, even after 3 years. By contrast, springtail numbers were significantly lower on tented versus control plots at the polar semi-desert at the end of year 3, but not so at the tundra heath. Collembola numbers declined at both sites during the warm dry midsummers of 1992/1993 and this was most marked at the better drained polar semi-desert site. Over the equivalent period total oribatid mite populations, while relatively more stable, increased significantly at the polar semi-desert as a result of an increase in the number of juveniles. Results are interpreted in the context of the ecophysiological adaptations of oribatid mites and springtails to soil temperature and moisture. The resulting survival characteristics are considered in relation to the temperature and moisture characteristics of the two sites. The experiment demonstrated that year to year variation in climate, interacting with physical differences between sites, produced an equal or greater effect on microarthropod numbers at any one site than the 8–10% increase in “heat availability” (day degrees above zero) resulting from the summer tent treatment. The limitations of the use of tents to elevate soil temperatures are discussed. Comparisons are made with microarthropod population data from other polar and alpine sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02390435
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Simulated climate change: the interaction between vegetation type and microhabitat temperatures at Ny Ålesund, Svalbard (1993)
    Springer
    Polar biology 13 (1993), S. 67-70 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small polythene tents were used to simulate the effects of climate warming on two contrasting vegetation types (polar semi-desert and tundra heath) at Ny Ålesund, Spitzbergen, Svalbard. Temperature microclimates are compared within and without tents and between sites with contrasting vegetation types. Summer temperatures were increased by about 5°C in the vegetation mat and by about 2°C in the soil at 3 cm depth. Cumulative day degrees above zero were enhanced by around 35% in the vegetation and by around 9% in the soil. Soil temperatures were greatly influenced by the nature of the overlying vegetation, which at one of the sites appeared to act as an efficient thermal insulator, preventing heat conductance into the soil from above and enhancing thermal contact between the upper soil layer and the cooling permafrost below. The significance of the observed temperature differences for the ecology of the plants and invertebrates is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236585
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Cold acclimation and cryoprotectants in a freeze-tolerant Antarctic nematode, Panagrolaimus davidi (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 321-327 
    Details
    ISSN: 1432-136X
    Keywords: Key words Liquid culture ; Freeze tolerance ; Intracellular freezing ; Trehalose ; Glycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Panagrolaimus davidi is a freeze-tolerant Antarctic nematode which survives extensive intracellular freezing. This paper describes the development of culture techniques which provide clean samples, with a high degree of freeze tolerance and in sufficient quantities for the analysis of potential cryoprotectants. Cultures grown at 20 °C survived a short-term freezing stress but survival declined with the time spent frozen. Acclimation of cultures at 5 °C enhanced the long-term survival of freezing. Starvation, however, reduced the nematode's ability to survive short-term freezing. The principal cryoprotectants detected by gas chromatography were trehalose and glycerol. The levels of trehalose, but not those of glycerol, increased significantly after acclimation. Trehalose may stabilise membranes and protect them against the dehydrating effects of the osmotic stresses resulting from freeze concentration effects but other factors, such as recrystallisation inhibition, may be involved in long-term survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600000106
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    Paper (German National Licenses)
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