张家界山区角倍蚜两虫态过冷却点比较及人工植藓保蚜越冬技术

为了解张家界地区所产角倍蚜Schlechtendalia chinensis(Bell)秋迁蚜及越冬若蚜的耐寒性及两虫态间在耐寒性方面的差异,应用过冷却点测定仪,抽样测定了上述两虫态个体的过冷却点和体液结冰点,结果表明:秋迁角倍蚜过冷却点和体液结冰点的平均值、最低值和最高值分别依次为-13.32±0.77,-15.69,-11.12℃和-13.00±0.72,-14.54,-10.80℃;而无翅若蚜过冷却点和体液结冰点的平均值、最低值和最高值分别依次为-18.95±0.82,-20.24,-17.02℃和-18.70±0.82,-20.07,-16.95℃。方差分析表明,越冬若蚜的过冷却点和体液结冰点都明显低于秋迁蚜的过冷却点和体液结冰点,进而推测,越冬若蚜的耐寒能力要显著强于秋迁蚜的耐寒能力。试验还表明,张家界地区角倍蚜的次生寄主苔藓(侧枝匐灯藓Plagiomnium maximoiczii)通过人工植藓可在小型聚酯瓶(polyester bottle)内正常生长,接种后的秋迁蚜可顺利生产若蚜,若蚜也能顺利产织蜡球进而度过寒冷的冬天直至下一年春迁蚜产生。     

Low temperature tolerance and starvation ability of the oak processionary moth: implications in a context of increasing epidemics

• 1 We investigated how modifications in winter and spring temperature conditions may affect the survival of a spring‐hatching Lepidoptera, the oak processionary moth Thaumetopoea processionea.
• 2 Supercooling and chilling injury experiments indicate that eggs are especially cold hardy at the start of the winter period, although this ability is reduced later in the season. In the spring, young larvae are sufficiently cold hardy to ensure no direct mortality as a result of late frosts.
• 3 A comparison of phenological models shows that neonate larvae may await the unfolding of new oak leaves for relatively long periods (e.g. 1–30 days). Under both low (4°C after 5 days at 16°C) and high temperature experimental scenarios (constant 16°C), the majority of neonate larvae can survive starvation for more than 2 weeks.
• 4 Larvae may also suffer from food depletion once their development has been initiated (e.g. during cold springs) if the threshold temperature for feeding is not reached for several consecutive days, or in the case of late frosts affecting foliage availability. When temperature is reduced to 4°C, developing larvae become inactive and do not feed anymore; their starvation survival capability is reduced to approximately 2 weeks (cold spring hypothesis). At 16°C, developing larvae that are deprived of food can only survive for 10 days (late frost hypothesis).
• 5 We conclude that, in the oak processionary moth, neonate larvae are relatively well adapted to early hatching relative to budburst, ensuring them the highest foliage quality for development. In some years, however, phenological asynchrony or cold spring conditions may affect the persistence of populations at the limits of the species' range.

     

Supercooling capacity of Eurasian and North American populations of parasitoids of the Russian wheat aphid, >Diuraphis noxia

Supercooling points were estimated for seven populations of >Aphelinus albipodus, five populations of >Aphelinus asychis, and four populations of >Diaeretiella rapae to assess whether their supercooling points were sufficiently low to provide the potential for overwintering survival in colder temperate climatic areas. Test individuals from all 16 of the parasitoid populations were collected originally from mummies of the Russian wheat aphid, >Diuraphis noxia. Mummies containing parasitoid pupae were maintained for 1 wk under three different temperature conditions (treatments): at room temperature (24.8 ± 0.2 °C), 1 wk at 0 °C, and 1 wk –5 °C, and the supercooling points across treatments, and within and among species were compared. Statistical differences in supercooling points were found among populations of >A. albipodus for each treatment, and for >A. asychis when maintained for 1 wk at room temperature. No differences in supercooling points were found among populations of >D. rapae mummies maintained under the three temperature treatments. The lowest supercooling points obtained for the three parasitoid species maintained at room temperature were the >A. albipodus population from Montana (–31.68 °C), the >A. asychis population from Greece (–32.04 °C), and the >D. rapaepopulation from the Caucasus (–33.12 °C). Preconditioning the parasitoid mummies to cold had no effect on the supercooling points for >A. albipodus, and in some cases unexpectedly increased the supercooling points for >A. asychisand >D. rapae. In comparing the overall mean supercooling points of the three parasitoid species, no differences were found within species (among temperature treatments), nor among species (within temperature treatments). It was concluded that observed differences in supercooling points of only a few degrees Centigrade among parasitoid populations and species would not be expected to cause differences in their overwintering success, especially given the expected variability in temperatures within and among overwintering sites.     

斑须蝽生物学特性及成虫耐寒性的研究

斑须蝽Dalycoris baccarum(Linnaeus)是多种作物和苗木的重要害虫。在鲁西南一年发生3代，以成虫主要在越冬菜叶夹缝、作物根际、枯枝落叶，树皮及房屋缝隙等处越冬。其越冬成虫结冰点和过冷却点分别为-5．2℃和-8．5℃。冬季极端低温对其越冬成活率有明显影响．第一代发生较轻．第二代发生重。成虫具弱趋光性，第二代上灯量占全年总量的77．56%。     

Aspects of the Cryobiology of the Intertidal Harpacticoid CopepodTigriopus brevicornis(O. F. Müller)

Cold-resistance studies of marine invertebrates have concentrated on intertidal sedentary organisms, which are often subjected to subzero air temperatures in winter. Mobile rock pool inhabitants have been rarely studied because such habitats are thought to buffer environmental variation. However, it is not uncommon for small upper-shore rock pools ( approximately 2 by 1 cm) to become completely frozen. Such supralittoral habitats are subject to extreme physicochemical fluctuations especially in salinity (0 to 300 per thousand) and temperature (-1 to +32degreesC) due to evaporation and dilution. The dominant invertebrate in such habitats is the harpacticoid copepod Tigriopus brevicornis. Aspects of the cryobiology of T. brevicornis were investigated using differential scanning calorimetry (DSC). Thermograms obtained from DSC allowed determinations of freeze-onset (supercooling point, SCP), melt-onset, and melt-peak (melting point, MP) temperatures, together with estimation of the proportion of water freezing in the samples. The effects of acclimation salinity, temperature, starvation, and reproductive state on these cryobiological parameters were investigated. Acclimation to increasing salinity depressed the SCP, with the highest salinity (70 per thousand) producing the lowest SCP, melt-onset, and MP temperatures at -27.5, -15.2, and -9.5degreesC respectively. The highest acclimation temperature (20degreesC) produced the lowest SCP (-23.4degreesC). Starvation significantly increased the SCP, melt-onset, and MP temperatures in comparison to fed individuals acclimated to the same salinity. The presence of eggs or ovaries in individual copepods elevated the SCP compared to nongravid females and males. LT50 studies showed that acclimation to high salinity improved the ability of T. brevicornis to survive in frozen seawater. Seventy parts per thousand acclimated individuals had an LT50 of 64.9 h compared with just 1.4 h for 5 per thousand acclimated individuals in frozen seawater at -5degreesC. The study shows that the cold-resistance capabilities of T. brevicornis can be affected by several different factors, and the link between the osmoconforming nature of this species and its cold resistance is discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press     

Geographic variation in winter freezing susceptibility in the eggs of the European pine sawfly (Neodiprion sertifer)

Abstract 1 The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera, Diprionidae), frequently defoliates Scots pine (Pinus sylvestris L.) forests in northern Europe. It overwinters as an egg. It has been proposed that the high egg mortality caused by low winter temperatures limits the occurrence of outbreaks to the southern part of Fennoscandia. 2 In this study, variation in freezing avoidance by egg supercooling between four Finnish populations (originating between latitudes 60°N and 69°N) of N. sertifer was tested by differential thermal analysis. Offspring of 20 females within each population were selected for the study. The freezing avoidance of parasitized eggs was also examined. 3 The northernmost Inari population was found to be the cold hardiest, and the southernmost (Hanko) was the least hardy population. The within‐population variation between females was greatest in the population from Inari, and the next greatest in the one from Hanko. The inland populations in Eastern Finland had the smallest within‐population variation in freezing avoidance. 4 The high variation in freezing avoidance of eggs will enable N. sertifer to adapt to the predicted climate change and to spread its distribution northwards. This may also change the risk for outbreaks in this area. Parasitized eggs froze at higher temperature than healthy eggs. This observation indicates that N. sertifer may experience reduced egg parasitism in certain winter climate conditions.     

Cold hardiness in the black rice bug, Scotinophara lurida

Abstract.  The mechanisms and strategies for winter survival of the black rice bug Scotinophara lurida are investigated along with the relationship between cold hardiness and diapause. The ability of S. lurida to survive subzero temperatures varies depending on developmental stage, temperature and exposure duration. Mean supercooling point (SCP) varies from –7.6 to –10.7 °C with developmental stage, but is not significantly different between stages examined. The SCP also varies with season, being lowest in January and increasing rapidly in February and remaining almost at the same level (–7.3 to 9.6 °C) until April The osmolality of haemolymph of field-collected S. lurida adults rises dramatically from 53.9 mOsm kg⁻¹ in August to 75.3 mOsm kg⁻¹ in December, and then declines linearly to 57.0 mOsm kg⁻¹ in May. Field-collected S. lurida adults show a peak glucose content in October, glycerol content in November and trehalose content in December. Only trehalose content decreases after the application of the juvenile hormone analogue, fenoxycarb, suggesting that trehalose is a cryoprotectant during diapause. These various physiological and biochemical traits related to cold tolerance in S. lurida may be, at least in part, under the control of juvenile hormone through the reproductive diapause programme.     

Thermal survival limits of young and mature larvae of a cold stenothermal chironomid from the Alps (Diamesinae: Pseudodiamesa branickii [Nowicki, 1873])

The threats posed by climate change make it important to expand knowledge concerning cold and heat tolerance in stenothermal species from habitats potentially threatened by temperature changes. Thermal limits and basal metabolism variations were investigated in Pseudodiamesa branickii (Diptera: Chironomidae) under thermal stress between ‐20 and 37 °C. Supercooling point (SCP), lower (LLTs) and upper lethal temperatures (ULTs), and oxygen consumption rate were measured in overwintering young (1st and 2nd instar) and mature (3rd and 4th instar) larvae from an Alpine glacier‐fed stream. Both young and mature larvae were freezing tolerant (SCPs = ‐7.1 °C and ‐6.4 °C, respectively; LLT₁₀₀ <SCP and > ‐20 °C) and thermotolerant (ULT₅₀ = 31.7 ± 0.4, 32.5 ± 0.3, respectively). However, ontogenetic differences in acute tolerance were observed. The LLT₅₀ calculated for the young larvae (= ‐7.4 °C) was almost equal to their SCP (= ‐7.1 °C) and the overlapping of the proportion of mortality curve with the CPIF curve highlighted that the young larvae are borderline between freezing tolerance and freezing avoidance. Furthermore, a lower ULT₁₀₀ in the young larvae (of ca. 1 °C), suggests that they are less thermotolerant than mature larvae. Finally, young larvae exhibit a higher oxygen consumption rate (mgO₂/gAFDM/h) at any temperature tested and are overall less resistant to oxygen depletion compared to mature larvae at ≥10 °C. These findings suggest that mature larvae enter into a dormant state by lowering their basal metabolism until environmental conditions improve in order to save energy for life cycle completion during stressful conditions.     

Cryo-scanning electron microscopic study on freezing behaviors of tissue cells in dormant buds of larch (Larix kaempferi)

The freezing behavior of dormant buds in larch, especially at the cellular level, was examined by a Cryo-SEM. The dormant buds exhibited typical extraorgan freezing. Extracellular ice crystals accumulated only in basal areas of scales and beneath crown tissues, areas in which only these living cells had thick walls unlike other tissue cells. By slow cooling (5 °C/day) of dormant buds to −50 °C, all living cells in bud tissues exhibited distinct shrinkage without intracellular ice formation detectable by Cryo-SEM. However, the recrystallization experiment of these slowly cooled tissue cells, which was done by further freezing of slowly cooled buds with LN and then rewarming to −20 °C, confirmed that some of the cells in the leaf primordia, shoot primordia and apical meristem, areas in which cells had thin walls and in which no extracellular ice accumulated, lost freezable water with slow cooling to −30 °C, indicating ability of these cells to adapt by extracellular freezing, whereas other cells in these tissues retained freezable water with slow cooling even to −50 °C, indicating adaptation of these cells by deep supercooling. On the other hand, all cells in crown tissues and in basal areas of scales, areas in which cells had thick walls and in which large masses of ice accumulated, had the ability to adapt by extracellular freezing. It is thought that the presence of two types of cells exhibiting different freezing adaptation abilities within a bud tissue is quite unique and may reflect sophisticated freezing adaptation mechanisms in dormant buds.