昆虫耐寒性研究

昆虫是变温动物,气候变化是造成种群季节消长的基本原因之一。尤其在不良的低温环境中,昆虫耐寒力的高低是其种群存在与发展的种要前提,昆虫对低温的适应能力及其机理也因而成为昆虫生态学和生物进化研究中的一个深受重视的问题,本文论述了与耐寒性直接相关的过冷却点昆虫的抗寒对策,明确了昆虫耐寒性的一些基本概念,一方面从环境影响昆虫的角度对耐寒性的一般规律,如季节性变化,地理变异快速冷驯化的作用等做了简要的概念括,另一方面阐述了昆虫适应环境的生理生化机制,包括低分子量的抗冻物质的产生,冰核剂的作用及抗冻蛋白的功能等做了简要的概括,另一方面简单述了昆虫适应环境的生理生化机制,包括低分子量的抗冻物质的产生,冰核剂的作用及抗冻蛋白的功能等。强调昆虫与环境相互作用过程中的生态生理适应,并指出昆虫耐寒性应当与生活史中别的因素联系起来,这样才能对耐寒性有一个更加全面的理解。     

Tolerance to multiple climate stressors: a case study of Douglas‐fir drought and cold hardiness

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Factors affecting the cold hardiness of the peach-potato aphid Myzus persicae

Supercooling point studies were used to investigate the factors influencing the cold hardiness of the peach-potato aphid Myzus persicae, a freezing-susceptible insect. Overwintering adults lost cold hardiness as winter progressed, with a variable proportion showing a marked reduction in supercooling ability. Cold hardiness increased in spring so that all individuals demonstrated extensive supercooling ability typical of aphids reared in the laboratory at 20°C with a long photoperiod; these levels of cold hardiness were maintained in the field during summer and early autumn. First instar nymphs demonstrated considerable cold hardiness all year. Surface moisture caused inoculative freezing in some first instar nymphs and adults when supercooled, but the majority were unaffected. In the laboratory, adults starved for 7 days at 5°C showed distinct losses of supercooling potential equivalent to those observed in the field during mid to late winter. No loss of cold hardiness was found in first instar nymphs starved under the same conditions. The results demonstrate that the cold hardiness characteristics of M. persicae are atypical of those observed in other freezing-susceptible insects and it is suggested that continued feeding during mild winter conditions allows maintenance of cold hardiness particularly in adult aphids, and provides a possible explanation for the successful anholocyclic overwintering of M. persicae during such winters.     

Cold adaptation strategy in insects inhabiting central Yakutia

Cold hardiness in 20 insect species living in extremely cold climate of Yakutia has been investigated for the first time. It was shown that the Yakutian insects prefer to use the strategy of freeze tolerance according to which they produce special substances initiating the freezing of hemolymph at high subzero temperatures. The presence of ice-nucleating agents in the haemolymph of insects belonging to the phylogenetic group of Lepidopteran was shown. We postulate that Pieris rapae may shift between the different cold hardiness strategies when they move from moderately cold regions to a more severe environment.     

Impact of climate change on cold hardiness of Douglas‐fir (Pseudotsuga menziesii): environmental and genetic considerations

The success of conifers over much of the world's terrestrial surface is largely attributable to their tolerance to cold stress (i.e., cold hardiness). Due to an increase in climate variability, climate change may reduce conifer cold hardiness, which in turn could impact ecosystem functioning and productivity in conifer‐dominated forests. The expression of cold hardiness is a product of environmental cues (E), genetic differentiation (G), and their interaction (G × E), although few studies have considered all components together. To better understand and manage for the impacts of climate change on conifer cold hardiness, we conducted a common garden experiment replicated in three test environments (cool, moderate, and warm) using 35 populations of coast Douglas‐fir (Pseudotsuga menziesii var. menziesii) to test the hypotheses: (i) cool‐temperature cues in fall are necessary to trigger cold hardening, (ii) there is large genetic variation among populations in cold hardiness that can be predicted from seed‐source climate variables, (iii) observed differences among populations in cold hardiness in situ are dependent on effective environmental cues, and (iv) movement of seed sources from warmer to cooler climates will increase risk to cold injury. During fall 2012, we visually assessed cold damage of bud, needle, and stem tissues following artificial freeze tests. Cool‐temperature cues (e.g., degree hours below 2 °C) at the test sites were associated with cold hardening, which were minimal at the moderate test site owing to mild fall temperatures. Populations differed 3‐fold in cold hardiness, with winter minimum temperatures and fall frost dates as strong seed‐source climate predictors of cold hardiness, and with summer temperatures and aridity as secondary predictors. Seed‐source movement resulted in only modest increases in cold damage. Our findings indicate that increased fall temperatures delay cold hardening, warmer/drier summers confer a degree of cold hardiness, and seed‐source movement from warmer to cooler climates may be a viable option for adapting coniferous forest to future climate.     

Local adaptations to frost in marginal and central populations of the dominant forest tree Fagus sylvatica L. as affected by temperature and extreme drought in common garden experiments

Local adaptations to environmental conditions are of high ecological importance as they determine distribution ranges and likely affect species responses to climate change. Increased environmental stress (warming, extreme drought) due to climate change in combination with decreased genetic mixing due to isolation may lead to stronger local adaptations of geographically marginal than central populations. We experimentally observed local adaptations of three marginal and four central populations of Fagus sylvatica L., the dominant native forest tree, to frost over winter and in spring (late frost). We determined frost hardiness of buds and roots by the relative electrolyte leakage in two common garden experiments. The experiment at the cold site included a continuous warming treatment; the experiment at the warm site included a preceding summer drought manipulation. In both experiments, we found evidence for local adaptation to frost, with stronger signs of local adaptation in marginal populations. Winter frost killed many of the potted individuals at the cold site, with higher survival in the warming treatment and in those populations originating from colder environments. However, we found no difference in winter frost tolerance of buds among populations, implying that bud survival was not the main cue for mortality. Bud late frost tolerance in April differed between populations at the warm site, mainly because of phenological differences in bud break. Increased spring frost tolerance of plants which had experienced drought stress in the preceding summer could also be explained by shifts in phenology. Stronger local adaptations to climate in geographically marginal than central populations imply the potential for adaptation to climate at range edges. In times of climate change, however, it needs to be tested whether locally adapted populations at range margins can successfully adapt further to changing conditions.     

Cold tolerance of the montane Sierra leaf beetle,Chrysomela aeneicollis

Small ectothermic animals living at high altitude in temperate latitudes are vulnerable to lethal cold throughout the year. Here we investigated the cold tolerance of the leaf beetle Chrysomela aeneicollis living at high elevation in California’s Sierra Nevada mountains. These insects spend over half their life cycle overwintering, and may therefore be vulnerable to winter cold, and prior studies have demonstrated that survival is reduced by exposure to summertime cold. We identify overwintering microhabitat of this insect, describe cold tolerance strategies in all life stages, and use microclimate data to determine the importance of snow cover and microhabitat buffering for overwinter survival. Cold tolerance varies among life history stages and is typically correlated with microhabitat temperature: cold hardiness is lowest in chill-susceptible larvae, and highest in freeze-tolerant adults. Hemolymph osmolality is higher in quiescent (overwintering) than summer adults, primarily, but not exclusively, due to elevated hemolymph glycerol. In nature, adult beetles overwinter primarily in leaf litter and suffer high mortality if early, unseasonable cold prevents them from entering this refuge. These data suggest that cold tolerance is tightly linked to life stage. Thus, population persistence of montane insects may become problematic as climate becomes more unpredictable and climate change uncouples the phenology of cold tolerance and development from the timing of extreme cold events.     

Cold hardiness in summer and winter diapause and post-diapause pupae of the cabbage armyworm, Mamestra brassicae L. under temperature acclimation

Cold hardiness and biochemical changes were investigated in winter and summer pupae of the cabbage armyworm Mamestra brassicae at the diapause and post-diapause stages under temperature acclimation. Diapause pupae were successively acclimated to 25, 20 and then 10 degrees C (warm-acclimated group). Pupae at the diapause and post-diapause stages were successively acclimated to 5, 0, -5 and then -10 degrees C (cold-acclimated groups). Supercooling point values in winter and summer pupae remained constant regardless of the diapause stages and acclimated temperatures. Warm-acclimated pupae at the diapause stage did not survive the subzero temperature exposure, whereas, cold-acclimated pupae achieved cold hardiness to various degrees. Winter pupae were more cold hardy than summer pupae, and pupae at the post-diapause stage were more cold hardy than those at the diapause stage. Trehalose contents in winter pupae rose under cold acclimation. Summer pupae accumulated far lower trehalose contents than winter pupae, with the maximal level occurring in winter pupae at the post-diapause stage. Glycogen content remained at a high level in diapause pupae after warm acclimation, whereas it decreased after cold acclimation. Alanine, the main free amino acid in haemolymph after cold acclimation, increased at lower temperatures in both diapause and post-diapause pupae, but the increase was greater in the diapause pupae. These results suggest that cold hardiness is more fully developed in winter pupae than in summer pupae, and cold acclimation provides higher cold hardiness in winter pupae at the post-diapause stage than at the diapause stage.     

Climatic variability and the evolution of insect freeze tolerance

Insects may survive subzero temperatures by two general strategies: Freeze-tolerant insects withstand the formation of internal ice, while freeze-avoiding insects die upon freezing. While it is widely recognized that these represent alternative strategies to survive low temperatures, and mechanistic understanding of the physical and molecular process of cold tolerance are becoming well elucidated, the reasons why one strategy or the other is adopted remain unclear. Freeze avoidance is clearly basal within the arthropod lineages, and it seems that freeze tolerance has evolved convergently at least six times among the insects (in the Blattaria, Orthoptera, Coleoptera, Hymenoptera, Diptera and Lepidoptera). Of the pterygote insect species whose cold-tolerance strategy has been reported in the literature, 29% (69 of 241 species studied) of those in the Northern Hemisphere, whereas 85 % (11 of 13 species) in the Southern Hemisphere exhibit freeze tolerance. A randomization test indicates that this predominance of freeze tolerance in the Southern Hemisphere is too great to be due to chance, and there is no evidence of a recent publication bias in favour of new reports of freeze-tolerant species. We conclude from this that the specific nature of cold insect habitats in the Southern Hemisphere, which are characterized by oceanic influence and climate variability must lead to strong selection in favour of freeze tolerance in this hemisphere. We envisage two main scenarios where it would prove advantageous for insects to be freeze tolerant. In the first, characteristic of cold continental habitats of the Northern Hemisphere, freeze tolerance allows insects to survive very low temperatures for long periods of time, and to avoid desiccation. These responses tend to be strongly seasonal, and insects in these habitats are only freeze tolerant for the overwintering period. By contrast, in mild and unpredictable environments, characteristic of habitats influenced by the Southern Ocean, freeze tolerance allows insects which habitually have ice nucleators in their guts to survive summer cold snaps, and to take advantage of mild winter periods without the need for extensive seasonal cold hardening. Thus, we conclude that the climates of the two hemispheres have led to the parallel evolution of freeze tolerance for very different reasons, and that this hemispheric difference is symptomatic of many wide-scale disparities in Northern and Southern ecological processes.     

昆虫的耐寒性及其影响因素

昆虫是变温动物,种群的繁衍面临如何安全度过漫长而寒冷的冬季的挑战.为了安全越冬,昆虫必须适应冬季的低温,增强耐寒能力是昆虫的一种重要的季节适应机制.近年来,关于昆虫耐寒性的研究不断开展,研究内容涉及影响耐寒性的因素、耐寒性的机制等方面.影响昆虫耐寒性的因素包括环境因素,如气候的季节变化、纬度或海拔的差异等,以及昆虫自身的发育阶段、滞育发生等.     

Habitat temperature and the temporal scaling of cold hardening in the high Arctic collembolan, Hypogastrura tullbergi (Schäffer)

Abstract.  1. Cold tolerance is a fundamental adaptation of insects to high latitudes. Flexibility in the cold hardening process, in turn, provides a useful indicator of the extent to which polar insects can respond to spatial and temporal variability in habitat temperature.
2. A scaling approach was adopted to investigate flexibility in the cold tolerance of the high Arctic collembolan, Hypogastrura tullbergi , over different time-scales. The cold hardiness of animals was compared from diurnal warming and cooling phases in the field, and controlled acclimation and cooling treatments in the laboratory. Plasticity in acclimation responses was examined using three parameters: low temperature survival, cold shock survival, and supercooling points (SCPs).
3. Over time-scales of 24–48 h, both field animals from warm diurnal phases and laboratory cultures from a 'warm' acclimation regime (18 °C) consistently showed greater or equivalent cold hardiness to animals from cool diurnal phases and acclimation regimes (3 °C).
4. No significant evidence was found of low temperature acclimation after either hours or days of low temperature exposure. The cold hardiness of H. tullbergi remained 'seasonal' in character and mortality throughout was indicative of the summer state of acclimatization.
5. These data suggest that H. tullbergi employs an 'all or nothing' cryoprotective strategy, cold hardening at seasonal but not diel-temporal scales.
6. It is hypothesised that rapid cold hardening offers little advantage to these high Arctic arthropods because sub-zero habitat temperatures during the summer on West Spitsbergen are rare and behavioural migration into soil profiles offers sufficient buffering against low summer temperatures.     

Responses of protein phosphatases and cAMP-dependent protein kinase in a freeze-avoiding insect, Epiblema scudderiana

Larvae of the goldenrod gall moth, Epiblema scudderiana, use the freeze avoidance strategy of winter cold hardiness and show multiple metabolic adaptations for subzero survival including accumulation of large amounts of glycerol as a colligative antifreeze. Induction and regulation of cold hardiness adaptations requires the intermediary action of signal transduction enzymes. Changes in the activities of several signaling enzymes including cAMP-dependent protein kinase (PKA), protein phosphatases 1 (PP1), 2A, 2C, and protein tyrosine phosphatases (PTPs) were monitored over the winter and during experimental exposures of larvae to subzero temperatures (-4 degrees C, a temperature that triggers rapid glycerol synthesis, or -20 degrees C, a common midwinter ambient temperature) or anoxia. A strong increase in the amount of active PP1 in the latter part of the winter may be responsible for shutting off glycogenolysis once glycerol levels are maximized. There appears to be a limited role for PKA in overwintering but PP2A and PP2C activities rose when larvae were exposed to -20 degrees C and PTP activities rose significantly over the winter months and also in response to laboratory subzero (-20 degrees C) and anoxia exposures. The strong responses by PTPs suggest that these may be involved in cell cycle and growth arrest during winter diapause.     

Surviving the Cold, Dry Period in Africa: Behavioral Adjustments as an Alternative to Heterothermy in the African Lesser Bushbaby (Galago moholi)

Behavioral and physiological adaptations are common and successful strategies used by small endothermic species to adjust to unfavorable seasons. Physiological adaptations, such as heterothermy, e.g., torpor, are usually thought to be more effective energy-saving strategies than behavioral adjustments. The African lesser bushbaby, Galago moholi, is physiologically capable of torpor but expresses heterothermy only under conditions of extreme energy limitation, suggesting that it has evolved alternative strategies to compensate energetic bottlenecks. We hypothesized that Galago moholi survives the unfavorable winter period, without —or only rarely— employing torpid phases to save energy, by using behavioral thermoregulation. We compared the ecology and behavior of Galago moholi in summer and winter by telemetric tracking and examined food availability by determination of arthropod and gum availability. We found a significant increase in huddling behavior and a significant increase in the use of enclosed and insulated sleeping sites during winter, as well as a reduction in nightly activity. Galago moholi hunted for insects significantly less in winter than in summer, and increased gum intake in winter, when gum showed an increase in energy content. The availability of high-quality food, albeit in low quantities, presumably enables Galago moholi to stay normothermic throughout the cold, dry period and to focus on reproduction activities. We propose that Galago moholi favors ecological and behavioral adjustments over torpor because these are sufficient to meet energy requirements of this species, and their advantages (flexibility, unrestricted activity, and reproduction) outweigh the energetic benefits of heterothermy.     

ICE NUCLEATION IN SEAWEEDS IN RELATION TO VERTICAL ZONATION1

The ice nucleation temperatures of thallus fragments of different macroalgal species were investigated. The samples were collected from the littoral zone on a rocky shore in Trondheimsfjord, central Norway. Thallus fragments of species growing in the upper parts of the eulittoral zone had lower ice nucleation temperatures than those of species living in the lower eulittoral zone and in the upper sublittoral zone. Samples collected in the winter had lower nucleation temperatures than samples from the same species collected in the summer, which indicates that the seaweeds are removing or inactivating ice nucleators as a part of their cold hardiness strategy.     

ADAPTATIONS OF TERRESTRIAL ARTHROPODS TO THE ALPINE ENVIRONMENT

1. The climate changes drastically above the timberline. Diverse adaptations have been evolved by insects and other terrestrial arthropods to survive the alpine environment. The fitness of each species depends on a combination of different factors in accordance with their special habitats. 2. Morphological adaptations such as reduced body-size, are known from a number of alpine insects, increasing their possibility to find sheltered microhabitats. Selection for reduced body size in Andean Phulia spp. butterflies is probably a result of their rigorous environment. Wing atrophy, which is also known in insects from other extreme environments, is widespread in alpine species. In several terrestrial arthropods the absorption of solar radiation is increased by melanism. Increased pubescence, protecting against the loss of heat, is known in alpine butterflies and bumblebees. 3. Several behavioural adaptations are described. Thermoregulatory behaviour is important in many species to raise their body temperatures. Alpine butterflies orient the dark basis of their wings perpendicular to the rays of the sun. Body temperatures of 30 °C may be required for flight. To increase their activities many alpine terrestrial arthropods seek warmer microhabitats in the vegetation and under rocks. The adaptive advantage of nocturnal activity as observed in several species, may be to maintain the water balance or to avoid predation. 4. Tropical alpine terrestrial arthropods are faced with special problems. The large diel temperature fluctuations require cold-hardiness during the night and tolerance to heat during the day. Many species seek sheltered microhabitats under rocks and in vegetation. 5. Due to low precipitation and high evaporation rates many mountain areas are extremely dry. High resistance to desiccation may be very important to alpine species, and in particular to tropical species. Rates of water loss at low relative humidities are comparable to those of desert arthropods. 6. As an adaptation to the cold alpine summers several species of terrestrial arthropods require more than one year to complete their life-cycles. Special to these species is their adaptation to low temperatures in two or more overwintering stages. In spite of their cold surroundings several species have univoltine life cycles, frequently combined with highly specialized adaptations. Increased metabolic rates as a compensation to low temperatures may be widespread in alpine species, but few data are available. 7. Cold tolerance is of particular importance in temperature alpine species. Winter survival in Collembola and Acari depends on supercooling. Great seasonal variations have been observed in a number of species. Freezing tolerance is also known from alpine insects, e.g. in some species of beetles. At high latitudes alpine species must endure periods of up to eight or nine month at low temperatures during hibernation. Anaerobiosis is known from species that are enclosed in ice, with lactate as the main end product of metabolism.     

Insect freeze tolerance: Roles of protein phosphatases and protein kinase A

Freeze-tolerant larvae of the goldenrod gall fly, Eurosta solidaginis Fitch, show multiple metabolic adaptations for subzero survival including the autumn synthesis of high concentrations of polyols. The induction and regulation of cold hardiness adaptations requires the intermediary action of signal transduction enzymes. The present study evaluates changes in the activities of cAMP-dependent protein kinase (PKA), protein phosphatases 1 (PP1), 2A, 2C, and protein tyrosine phosphatases (PTPs) over the course of the winter season and also in insects exposed to -4, -20 degrees C, or anoxic conditions in the laboratory. The increased PKA and decreased PP1 over the winter season and/or at subzero temperature support a regulatory role for these enzymes in cryoprotectant polyol synthesis. PTP activities were also strongly increased under these conditions and may act to antagonize tyrosine kinase mediated cell growth and proliferation responses and, thereby, contribute to hypometabolism and diapause over the winter.     

The long summer: pre-wintering temperatures affect metabolic expenditure and winter survival in a solitary bee

The impact of climate change on insect populations depends on specific life cycle traits and physiological adaptations. The solitary bee Osmia lignaria winters as a pre-emergent adult, and requires a period of cold temperature for winter diapause completion. It is a univoltine species, and diapause induction does not depend on photoperiod. To understand the potential effects of longer summers on O. lignaria populations, we exposed individuals to three treatments simulating early, mid and late winter arrivals, and measured respiration rates, metabolic expenditure, weight loss, fat body depletion, lipid levels and winter mortality. The early-winter treatment disrupted diapause development, but had no apparent negative effects on fitness. In contrast, late-winter bees had a greater energetic expenditure (1.5-fold), weight (1.4-fold) and lipid (2-fold) loss, greater fat body depletion, and a 19% increase in mortality compared to mid-winter bees. We also monitored adult eclosion and arrival of winter temperatures under natural conditions in four years. We found a positive correlation between mean degree-day accumulation during pre-wintering (a measure of asynchrony between adult eclosion and winter arrival) and yearly winter mortality. Individually, bees experiencing greater degree-day accumulations exhibited reduced post-winter longevity. Timing of adult eclosion in O. lignaria is dependent on the duration of the prepupal period, which occurs in mid-summer, is also diapause-mediated, and is longer in populations from southerly latitudes. In a global warming scenario, we expect long summer diapause phenotypes to replace short summer diapause phenotypes, effectively maintaining short pre-wintering periods in spite of delayed winter arrivals.     

抗寒类蛋白与冷驯化诱发昆虫耐寒性研究进展

昆虫是变温动物,温度对其生长发育、基本行为及进化途径都会产生很大的影响,种群的繁衍面临如何安全度过漫长而寒冷的冬季的挑战。通过长时间的进化,昆虫获得一系列完整的耐寒策略。绝大多数的昆虫都是耐寒昆虫,在陆地寒冷温度刺激下,昆虫受抗寒基因的调控,体内产生大量抗寒物质,如海藻糖、甘油、山梨醇、抗冻蛋白、热激蛋白等,提高昆虫的耐寒能力,使其得以在低温寒冷的条件下成功越冬。同样,经过冷驯化后的昆虫能显著提高昆虫的耐寒力。近年来,关于昆虫耐寒性、抗寒类蛋白的研究不断开展,研究内容涉及昆虫的耐寒性、抗寒基因HSPs和AFPs的调控、冷驯化诱导抗寒等方面。本文综述了昆虫耐寒性、主要耐寒策略及冷驯化诱发昆虫耐寒性增强等研究内容。有助于全面认识昆虫耐寒性及其作用机制,为天敌昆虫低温储存和提高生物防治等应用打下坚实的基础。     

常绿木兰科植物的抗寒性研究

连续4个冬季,对16种常绿木兰科植物进行了田间受冻程度观察,用电导法追踪了抗冻崩溃点温度的变化,并调查了这些树种在自然分布区北缘和垂直分布上缘30a内经历的最低气温,发现3者的种间差异相当一致。同时发现各树种的崩溃点温度最低值与它的生态分布北缘和上缘的常年最低气温接近,由此提出了生态分布最低温度的概念。它能较准确地指示植物的最大抗寒能力,从而有可能避免引种和推广工作中的盲目性。 文章还根据上海近100余年的低温资料,对这16个树种在今后越冬和春季萌发时可能受冻的前景做了预测。