Cold tolerance of the maize orange leafhopper,Cicadulina bipunctata

Cicadulina bipunctata was originally distributed in tropical and subtropical regions of the Old World. This leafhopper recently expanded its distribution area to southern parts of temperate Japan. In this study, factors affecting the overwintering ability of C. bipunctata were examined. A series of laboratory experiments revealed that cold acclimation at 15 °C for 7 days enhanced the cold tolerance of C. bipunctata to the same level as an overwintering population, adult females were more tolerant of cold temperature than adult males, and survival of acclimated adult females was highly dependent on temperature from −5 to 5 °C and exposure duration to the temperature. The temperature of crystallization of adult females was approximately −19 °C but temperatures in southern temperate Japan rarely dropped below −10 °C in the winter, indicating that overwintering C. bipunctata adults in temperate Japan are not killed by freezing injury but by indirect chilling injury caused by long-term exposure to moderately low temperatures. An overwintering generation of C. bipunctata had extremely low overwinter survival (<1%) in temperate Japan; however, based on winter temperature ranges, there are additional areas amenable to expansion of C. bipunctata in temperate Japan.     

Characterization and evaluation of hydrophobically modified chitosan scaffolds: Towards design of enzyme immobilized flow-through electrodes

Chitosan scaffolds were fabricated by application of thermally induced phase separation from aqueous solutions of unmodified chitosan and hydrophobically modified chitosan polymer. The final pore structure, in terms of diameter and geometry, were correlated to freezing temperature and freezing time for both the unmodified and hydrophobically modified chitosan polymer. Results showed that the resulting pore structure is strongly dependent upon the freezing temperature and less dependant upon the freezing time. For scaffolds produced from unmodified chitosan, the pore size decreased as expected with decreasing freezing temperature from ?5 °C to ?10 °C. However, an inconsistency in this trend was observed as the freezing temperature was decreased to ?20 °C. Combined analysis of pore size distribution and average pore diameter suggested that the freezing process was mainly mass transfer dominated at ?5 °C and ?10 °C, but principally heat transfer dominated at ?20 °C. In comparison, the scaffolds produced from hydrophobically modified chitosan (butyl-chitosan) followed the expected trend of decreasing mean pore diameter with decreased freezing temperatures throughout the entire temperature range. The scaffolds produced from the unmodified chitosan were more stable and rigid, and possessed average pore diameters that were generally smaller than those fabricated from the hydrophobically modified chitosan. The generally larger pores in the butyl-modified chitosan scaffolds might be explained by increased phase separation rates due to the introduced hydrophobicity of the chitosan polymer. Among the scaffolds fabricated from the butyl-modified chitosan, those produced at ?20 °C yielded the most uniform pore structure, the smallest average pore diameters, and the least temporal broadening of pore size distribution.     

Similar metabolic rate-temperature relationships after acclimation at constant and fluctuating temperatures in caterpillars of a sub-Antarctic moth

Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate – temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0–10 °C, 5–15 °C, and 10–20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3–14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q₁₀ of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5–15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic.     

Impact of fluctuating temperatures on development of the koinobiont endoparasitoid Venturia canescens

The effect of temperature on the biology of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. Herein we studied the influence of fluctuating temperatures on biological parameters of V. canescens. Parasitized fifth-instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were reared individually in incubators at six fluctuating temperature regimes (15–19.5 °C with a mean of 17.6 °C, 17.5–22.5 °C with a mean of 19.8 °C, 20–30 °C with a mean of 22.7 °C, 22.5–27.5 °C with a mean of 25 °C, 25.5-32.5 °C with a mean of 28.3 °C and 28.5–33 °C with a mean of 30 °C) until emergence and death of V. canescens adults. Developmental time from parasitism to adult eclosion, adult longevity and survival were recorded at each fluctuating temperature regime. In principle, developmental time decreased with an increase of the mean temperature of the fluctuating temperature regime. Upper and lower threshold temperatures for total development were estimated at 34.9 and 6.7 °C, respectively. Optimum temperature for development and thermal constant were 28.6 °C and 526.3 degree days, respectively. Adult longevity was also affected by fluctuating temperature, as it was significantly reduced at the highest mean temperature (7.0 days at 30 °C) compared to the lowest one (29.4 days at 17.6 °C). Survival was low at all tested fluctuating temperatures, apart from mean fluctuating temperature of 25 °C (37%). Understanding the thermal biology of V. canescens under more natural conditions is of critical importance in applied contexts. Thus, predictions of biological responses to fluctuating temperatures may be used in population forecasting models which potentially influence decision-making in IPM programs.     

Rising temperatures may increase growth rates and microcystin production in tropical Microcystis species

Rising temperatures (1.4–6 °C) due to climate change have been predicted to increase cyanobacterial bloom occurrences in temperate water bodies; however, the impacts of warming on tropical cyanobacterial blooms are unknown. We examined the effects of four different temperatures on the growth rates and microcystin (MC) production of five tropical Microcystis isolates (M. ichthyoblabe (two strains), M. viridis, M. flos-aquae, and M. aeruginosa). The temperature treatments are based on current temperature range in Singapore's reservoirs (27 °C and 30 °C), as well as projected mean (33 °C) and maximum temperatures (36 °C) based on tropical climate change estimates of +6 °C in air temperature. Increasing temperatures did not significantly affect the maximum growth rates of most Microcystis strains. Higher growth rates were only observed in one M. ichthyoblabe strain at 33 °C and M. flos-aquae at 30 °C where both were isolated from the same reservoir. MC-RR and MC-LR were produced in varying amounts by all four species of Microcystis. Raised temperatures of 33 °C were found to boost total MC cell quota for three Microcystis strains although further increase to 36 °C led to a sharp decrease in total MC cell quota for all five Microcystis strains. Increasing temperature also led to higher MC-LR:MC-RR cell quota ratios in M. ichthyoblabe. Our study suggests that higher mean water temperatures resulting from climate change will generally not influence growth rates of Microcystis spp. in Singapore except for increases in M. ichthyoblabe strains. However, toxin cell quota may increase under moderate warming scenarios depending on the species.     

Effect of initial freezing temperature on the semen characteristics of frozen-thawed ram spermatozoa in a semi-arid tropical environment

Ram spermatozoa are sensitive to extreme changes in temperature during the freeze-thaw process. The degree of damage depends on a combined effect of various factors including initial freezing temperature. The present study was conducted to observe the effect of initial freezing temperature on post-thawing motility of ram spermatozoa of native and crossbred rams maintained in a semi-arid tropical environment. Good quality semen obtained from native Malpura and crossbred Bharat Merino rams were pooled within breed and diluted at a rate of 1000 million spermatozoa per milliliter in TEST—yolk–glycerol extender. Diluted semen samples were loaded in 0.25 ml straws and cooled to −25, −75 or −125 °C freezing temperature at the rate of −25 °C/min under controlled conditions before plunging into liquid nitrogen for storage. The thawing of straws was performed at 50 °C in a water bath for 10 s and motility characteristics of the frozen-thawed spermatozoa were assessed by a computer-assisted spermatozoa analysis technique. Initial freezing temperature significantly affected the post-thawing motility of sperm in both the breeds. The post-thawing % motility and rapid motile spermatozoa were significantly higher at initial freezing temperature of −125 °C and lower at −25 or −75 °C. The percentage medium motile sperm were similar at all three initial freezing temperatures. The percentage of slow motile and linearity of sperm varied (P<0.01) between the different freezing temperatures. The curvilinear velocity, average path velocity and straight line velocity of spermatozoa were higher (P<0.01) at −125 °C than −25 or −75 °C. Although the lateral head displacement of spermatozoa did not vary significantly between the different initial freezing temperatures, the stroke frequency was significantly lower at −25 °C than −75 or −125 °C. Except for % linearity, the average path velocity and straight line velocity, other spermatozoa characteristics were not significantly different between breeds. The interaction between freezing temperature and breed was significant only for the % motility and linearity of the spermatozoa. The study indicates that initial freezing temperature has a significant effect on spermatozoa motility and velocity following post-thawing. The best motile spermatozoa following thawing were achieved at −125 °C freezing temperature.     

Development response of Spodoptera exigua to eight constant temperatures: Linear and nonlinear modeling

Temperature-dependent development of Spodoptera exigua (Hübner) were evaluated at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34 and 36 °C with a variation of 0.5 °C on sugar beet leaves. No development occurred at 12 °C and 36 °C. Total developmental time varied from 120.50 days at 15 °C to 14.50 days at 33 °C. As temperature increased from 15 °C to 33 °C, developmental rate (1/developmental time) of S. exigua increased but declined at 34 °C. The lower temperature threshold (T_min) was estimated to be 12.98 °C and 12.45 °C, and the thermal constant (K) was 294.99 DD and 311.76 DD, using the traditional and Ikemoto–Takai linear models, respectively. The slopes of the Ikemoto–Takai linear model for different immature stages were different, violating the assumption of rate isomorphy. Data were fitted to three nonlinear models to predict the developmental rate and estimate the critical temperatures. The T_min values estimated by Lactin-2 (12.90 °C) and SSI (13.35 °C) were higher than the value estimated by Briere-2 (8.67 °C). The estimated fastest development temperatures (T_fast) by the Briere-2, Lactin-2 and SSI models for overall immature stages development of S. exigua were 33.4 °C, 33.9 °C and 32.4 °C, respectively. The intrinsic optimum temperature (T_Φ) estimated from the SSI model was 28.5 °C, in which the probability of enzyme being in its native state is maximal. The upper temperature threshold (T_max) values estimated by these three nonlinear models varied from 34.00 °C to 34.69 °C. These findings on thermal requirements can be used to predict the occurrence, number of generations and population dynamics of S. exigua.     

The effect of acclimation temperature on thermal activity thresholds in polar terrestrial invertebrates

In the Maritime Antarctic and High Arctic, soil microhabitat temperatures throughout the year typically range between ?10 and +5 °C. However, on occasion, they can exceed 20 °C, and these instances are likely to increase and intensify as a result of climate warming. Remaining active under both cool and warm conditions is therefore important for polar terrestrial invertebrates if they are to forage, reproduce and maximise their fitness. In the current study, lower and upper thermal activity thresholds were investigated in the polar Collembola, Megaphorura arctica and Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus. Specifically, the effect of acclimation on these traits was explored. Sub-zero activity was exhibited in all three species, at temperatures as low as ?4.6 °C in A. antarcticus. At high temperatures, all three species had capacity for activity above 30 °C and were most active at 25 °C. This indicates a comparable spread of temperatures across which activity can occur to that seen in temperate and tropical species, but with the activity window shifted towards lower temperatures. In all three species following one month acclimation at ?2 °C, chill coma (=the temperature at which movement and activity cease) and the critical thermal minimum (=low temperature at which coordination is no longer shown) occurred at lower temperatures than for individuals maintained at +4 °C (except for the CTmin of M. arctica). Individuals acclimated at +9 °C conversely showed little change in their chill coma or CTmin. A similar trend was demonstrated for the heat coma and critical thermal maximum (CTmax) of all species. Following one month at ?2 °C, the heat coma and CTmax were reduced as compared with +4 °C reared individuals, whereas the heat coma and CTmax of individuals acclimated at +9 °C showed little adjustment. The data obtained suggest these invertebrates are able to take maximum advantage of the short growing season and have some capacity, in spite of limited plasticity at high temperatures, to cope with climate change.     

Low temperature tolerance,cold hardening and acclimation in tadpoles of the neotropical túngara frog (Engystomops pustulosus)

Many frogs from temperate climates can tolerate low temperatures and increase their thermal tolerance through hardening and acclimation. Most tropical frogs, on the other hand, fail to acclimate to low temperatures. This lack of acclimation ability is potentially due to lack of selection pressure for acclimation because cold weather is less common in the tropics. We tested the generality of this pattern by characterizing the critical temperature minimum (CTMin), hardening, and acclimation responses of túngara frogs (Engystomops pustulosus). These frogs belong to a family with unknown thermal ecology. They are found in a tropical habitat with a highly constant temperature regime. The CTMin of the tadpoles was on average 12.5 °C. Pre-metamorphic tadpoles hardened by 1.18 °C, while metamorphic tadpoles hardened by 0.36 °C. When raised at 21 °C, tadpoles acclimated expanding their cold tolerance by 1.3 °C in relation to larvae raised at 28 °C. These results indicate that the túngara frog has a greatly reduced cold tolerance when compared to species from temperate climates, but it responds to cold temperatures with hardening and acclimation comparable to those of temperate-zone species. Cold tolerance increased with body length but cold hardening was more extensive in pre-metamorphic tadpoles than in metamorphic ones. This study shows that lack of acclimation ability is not general to the physiology of tropical anurans.     

Thermal tolerance and preferred temperature range of juvenile meagre acclimated to four temperatures

The present study reports the temperature tolerance, estimated using dynamic and static methodologies, and preferred temperature range, based on oxygen consumption rate (OCR), of juvenile meagre (Argyrosomus regius) (Asso, 1801) (3.4±0.9 g) after 30 days of acclimation at 18, 22, 26 and 30 °C. Meagre has dynamic and static thermal tolerance zones of 551 °C² and 460 °C², respectively and is a low resistance fish species, with a resistance zone area of 87 °C². The OCR of juvenile meagre at the above acclimation temperatures was 370, 410, 618 and 642 mg h⁻¹ kg⁻¹, respectively, and is significantly different (P<0.0001, n=20). The fact that OCR increases by rising temperatures and gradually decreases after 26 °C indicates that the preferred temperature range of juvenile meagre is between 26 and 30 °C. Our study suggests that meagre is unable to respond to low and high temperature variation in aquaculture facilities or its natural habitats.     

Effect of variable dew temperatures on infection of green foxtail by Pyricularia setariae,Drechslera gigantea,and Exserohilum rostratum

A thermogradient apparatus was used to investigate the effect of variable dew temperatures on infection of green foxtail by the indigenous pathogen Pyricularia setariae (Ps) and the exotic pathogens Drechslera gigantea (Dg), and Exserohilum rostratum (Er) from the southern USA that showed bioherbicide potential against several grassy weeds. This device is capable of creating multiple diurnal temperature cycles, mimicking daily temperature fluctuations that occur under field conditions. Seven temperature regimes, i.e., 15/10 °C, 20/5 °C, 20/15 °C, 25/10 °C, 25/20 °C, 30/15 °C, and 30/25 °C (maximum/minimum), were used with temperature cycling from maximum to minimum and then back up to maximum in a 24 h period. Ps and Dg were much more virulent than Er on green foxtail, resulting in higher levels of disease and weed control. Dg was little affected by the dew temperatures in terms of plant infection and was more efficacious than Ps under cooler dew temperatures (15/10 °C and 20/5 °C), causing twice as much disease. This greater amount of disease coincided with higher conidial germination, appressorial formation and infection-hypha frequency by Dg at the lower temperatures. The efficacy of Ps improved as dew temperature increased, accompanied by a higher percentage of germination and more frequent appressorial production. Dg caused severe disease 2 d after inoculation whereas Ps required 4 d to initiate disease symptoms. These observations suggest that Dg is a superior candidate than Ps for green foxtail control on the Canadian prairies.     

Estimation of developmental parameters for adult emergence of Gonatocerus morgani,a novel egg parasitoid of the glassy-winged sharpshooter,and development of a degree-day model

The effects of temperature on the development (egg–adult emergence) of Gonatocerus morgani Triapitsyn, a newly-described parasitoid of Homalodisca vitripennis (Germar), were determined at 14.8, 18.7, 23.5, 26.9, 28.7, 30.4, 32.8, and 33.8 °C in the laboratory. Survival rate (percent adult emergence from parasitized host eggs) varied significantly among the experimental temperatures, with the highest (59%) and lowest (0%) occurring at 30.4 and 33.8 °C, respectively. The survival rates (%) were fitted with a polynomial model to describe a temperature-dependent pattern. Developmental rates (1/d) across seven temperatures were fitted with the nonlinear Briere model, which estimated the lower threshold to be 8.06 °C, the optimal temperature to be 29.22 °C, and the upper threshold to be 33.49 °C. A linear model fitted to developmental rates at 14.8–28.7 °C indicated that 189.75 degree-days above the lower threshold of 9.71 °C were required to complete development. A simulation model of G. morgani adult emergence was constructed to predict daily counts over the entire range of constant temperatures by incorporating the survival rate model, the Briere model, and the Weibull model. In outdoor validation, a degree-day model for predicting adult emergence showed ?2 d differences between prediction and observation. Based on the observed temperature requirement, the insect could complete thirteen to sixteen generations per year in southern California, depending on weather and location.     

Thermal tolerance,growth and oxygen consumption of Labeo rohita fry (Hamilton, 1822) acclimated to four temperatures

A 30 day feeding trial was conducted using a freshwater fish, Labeo rohita (rohu), to determine their thermal tolerance, oxygen consumption and optimum temperature for growth. Four hundred and sixteen L. rohita fry (10 days old, 0.385±0.003 g) were equally distributed between four treatments (26, 31, 33 and 36 °C) each with four replicates for 30 days. Highest body weight gain and lowest feed conversion ratio (FCR) was recorded between 31 and 33 °C. The highest specific growth rate was recorded at 31 °C followed by 33 and 26 °C and the lowest was at 36 °C. Thermal tolerance and oxygen consumption studies were carried out after completion of growth study to determine tolerance level and metabolic activity at four different acclimation temperatures. Oxygen consumption rate increased significantly with increasing acclimation temperature. Preferred temperature decided from relationship between acclimation temperature and Q₁₀ values were between 33 and 36 °C, which gives a better understanding of optimum temperature for growth of L. rohita. Critical thermal maxima (CTMax) and critical thermal minima (CTMin) were 42.33±0.07, 44.81±0.07, 45.35±0.06, 45.60±0.03 and 12.00±0.08, 12.46±0.04, 13.80±0.10, 14.43±0.06, respectively, and increased significantly with increasing acclimation temperatures (26, 31, 33 and 36 °C). Survival (%) was similar in all groups indicating that temperature range of 26–36 °C is not fatal to L. rohita fry. The optimum temperature range for growth was 31–33 °C and for Q₁₀ values was 33–36 °C.     

Effects of growth stage and hardening conditions on the association between frost resistance and the expression of the cold-induced protein COR14b in barley

Sowing date, being determinant for growth stage, may play a decisive role in optimising freezing resistance of winter annual plants. In cereal species, in spite of the abundant literature analysing the factors responsible for the acquisition of frost resistance through the cold hardening process, the involvement of the growth stage per se, has been seldom considered, especially at the earlier vegetative phases. In this work the contribution of growth stage in determining resistance to freezing temperature has been analysed in field and growth chamber experiments using winter and spring barley cultivars exposed to different hardening conditions. Field damage was assessed twice during winter on plants sown at three different dates. In the growth chamber experiments several acclimation treatments at 11/7 and/or 3/1 °C (day/night) were simulated. In both field and laboratory experiments the development of cold acclimation was monitored by means of a COR14b specific antibody, since in previous studies the expression of COR14b was found genetically linked to frost resistance. The lowest resistance, found in the youngest plants and in spring cultivars, however, was not always associated with the lowest level of COR14b accumulation. COR14b accumulation correlated with frost resistance at the earlier field sampling date and in plants grown at 11/7 °C. In a following phase of the hardening process (second sampling in field and 4 weeks at 3/1 °C in growth chamber) the accumulation of COR14b was independent of plant stage and genotype, showing no association with freezing resistance. Results suggest that growth stage is crucial for the achievement of maximal resistance in barley, but not for COR14b expression.     

Mathematical modeling of Microcystis aeruginosa growth and [D-Leu1] microcystin-LR production in culture media at different temperatures

The effect of temperature (26 °C, 28 °C, 30 °C and 35 °C) on the growth of native CAAT-3-2005 Microcystis aeruginosa and the production of Chlorophyll-a (Chl-a) and Microcystin-LR (MC-LR) were examined through laboratory studies. Kinetic parameters such as specific growth rate (μ), lag phase duration (LPD) and maximum population density (MPD) were determined by fitting the modified Gompertz equation to the M. aeruginosa strain cell count (cells mL⁻¹). A 4.8-fold increase in μ values and a 10.8-fold decrease in the LPD values were found for M. aeruginosa growth when the temperature changed from 15 °C to 35 °C. The activation energy of the specific growth rate (Eμ) and of the adaptation rate (E₁/LPD) were significantly correlated (R² = 0.86). The cardinal temperatures estimated by the modified Ratkowsky model were minimum temperature = 8.58 ± 2.34 °C, maximum temperature = 45.04 ± 1.35 °C and optimum temperature = 33.39 ± 0.55 °C.Maximum MC-LR production decreased 9.5-fold when the temperature was increased from 26 °C to 35 °C. The maximum production values were obtained at 26° C and the maximum depletion rate of intracellular MC-LR was observed at 30–35 °C. The MC-LR cell quota was higher at 26 and 28 °C (83 and 80 fg cell⁻¹, respectively) and the MC-LR Chl-a quota was similar at all the different temperatures (0.5–1.5 fg ng⁻¹).The Gompertz equation and dynamic model were found to be the most appropriate approaches to calculate M. aeruginosa growth and production of MC-LR, respectively. Given that toxin production decreased with increasing temperatures but growth increased, this study demonstrates that growth and toxin production processes are uncoupled in M. aeruginosa. These data and models may be useful to predict M. aeruginosa bloom formation in the environment.     

Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)

The influence of temperatures on the life parameters of the solitary oothecal parasitoid Evania appendigaster, was investigated in the laboratory. Parasitized oothecae of Periplaneta americana were left to develop under seven constant temperatures: 15, 17, 20, 25, 30, 35, and 40 °C. At the end, we found that: (i) E. appendigaster was able to complete development within the temperature range of 17–34 °C; (ii) mean adult longevity decreased as temperature increased, with the temperature of 40 °C being fatal in a matter of hours; (iii) males lived longer than females between 15 and 30 °C; (iv) adult emergence rate was the highest at 25 °C, and (v) no wasps emerged at 15 or 40 °C. Non-emerged oothecae contained either unhatched eggs or dead larvae. We determined the theoretical lower developmental threshold and thermal constant for the complete development as 12.9 °C and 584.8 day-degrees for males, and 13.1 °C and 588.2 day-degrees for females, respectively. A good balance between faster development, maximum adult longevity and good egg viability was obtained between 25–30 °C, and that would be the best temperature range for rearing E. appendigaster.     

Lipidomic analysis of psychrophilic yeasts cultivated at different temperatures

Analysis of polar lipids from eight psychrophilic yeasts (Cryptococcus victoriae, Cystofilobasidium capitatum, Holtermaniella wattica, Mrakiella aquatica, M. cryoconiti, Rhodotorula lignophila, Kondoa malvinella and Trichosporon aggtelekiense) grown at 4–28 °C by hydrophilic interaction liquid chromatography/high resolution electrospray ionization tandem mass spectrometry determined 17 classes of lipids and identified dozens of molecular species of phospholipids including their regioisomers. Most of the yeasts were able to grow over the whole temperature range, reaching the highest biomass at 4 or 10 °C. On temperature drop to 4 °C, all eight strains showed a significant decrease of MUFA and a simultaneous increase of PUFA such as α-linolenic acid, the content of which in the biomass reached up to 20%. We also found alterations in the proportions of individual phospholipids (PI, PE and PC), the PC/PE-ratio decreasing with decreasing temperature. With increasing temperature the content of PoO-PC rose while that of LL-PC decreased, the drop in the content of LL-PC being nearly 100-fold while the content of PoO-PC increased more than twice.A change in temperature brought about changes in molecular species of PC (molecular species PO-PC versus OP-PC) as well as PE, i.e. PO-PE and OP-PE. The phase transition temperature of PO-PC differs from OP-PC by 7 °C and the difference between PO-PE and OP-PE is some 10 °C; we thus assume that the cell compensates for the adverse temperature effect by changing the fatty acids in the sn-1 and sn-2 positions.     

Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates

The extreme polar environment creates challenges for its resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditions experienced at microhabitat level, few studies have explicitly set out to link field conditions experienced by natural multispecies communities with the more detailed laboratory ecophysiological studies of a small number of ‘representative’ species. This is particularly the case during winter, when snow cover may insulate terrestrial habitats from extreme air temperature fluctuations. Further, climate projections suggest large changes in precipitation will occur in the polar regions, with the greatest changes expected during the winter period and, hence, implications for the insulation of overwintering microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow, Shallow Snow (30 cm) and Deep Snow (120 cm). Air temperatures during the winter period fluctuated frequently between +3 and −24 °C, and the No Snow soil temperatures reflected this variation closely, with the extreme minimum being slightly lower. Under 30 cm of snow, soil temperatures varied less and did not decrease below −12 °C. Those under deep snow were even more stable and did not decline below −2 °C. Despite these striking differences in winter thermal regimes, there were no clear differences in survival of the invertebrate fauna between treatments, including oribatid, prostigmatid and mesostigmatid mites, Araneae, Collembola, Nematocera larvae or Coleoptera. This indicates widespread tolerance, previously undocumented for the Araneae, Nematocera or Coleoptera, of both direct exposure to at least −24 °C and the rapid and large temperature fluctuations. These results suggest that the studied polar soil invertebrate community may be robust to at least one important predicted consequence of projected climate change.     

Thermal tolerance and preference of exploited turbinid snails near their range limit in a global warming hotspot

Predicted global climate change has prompted numerous studies of thermal tolerances of marine species. The upper thermal tolerance is unknown for most marine species, but will determine their vulnerability to ocean warming. Gastropods in the family Turbinidae are widely harvested for human consumption. To investigate the responses of turbinid snails to future conditions we determined critical thermal maxima (CTMax) and preferred temperatures of Turbo militaris and Lunella undulata from the tropical-temperate overlap region of northern New South Wales, on the Australian east coast. CTMax were determined at two warming rates: 1 °C/30 min and 1 °C/12 h. The number of snails that lost attachment to the tank wall was recorded at each temperature increment. At the faster rate, T. militaris had a significantly higher CTMax (34.0 °C) than L. undulata (32.2 °C). At the slower rate the mean of both species was lower and there was no significant difference between them (29.4 °C for T. militaris and 29.6 °C for L. undulata). This is consistent with differences in thermal inertia possibly allowing animals to tolerate short periods at higher temperatures than is possible during longer exposure times, but other mechanisms are not discounted. The thermoregulatory behaviour of the turban snails was determined in a horizontal thermal gradient. Both species actively sought out particular temperatures along the gradient, suggesting that behavioural responses may be important in ameliorating short-term temperature changes. The preferred temperatures of both species were higher at night (24.0 °C and 26.0 °C) than during the day (22.0 °C and 23.9 °C). As the snails approached their preferred temperature, net hourly displacement decreased. Preferred temperatures were within the average seasonal seawater temperature range in this region. However, with future predicted water temperature trends, the species could experience increased periods of thermal stress, possibly exceeding CTMax and potentially leading to range contractions.