Rapid thermal responses and thermal tolerance in adult codling moth Cydia pomonella (Lepidoptera: Tortricidae)

In order to preserve key activities or improve survival, insects facing variable and unfavourable thermal environments may employ physiological adjustments on a daily basis. Here, we investigate the survival of laboratory-reared adult Cydia pomonella at high or low temperatures and their responses to pre-treatments at sub-lethal temperatures over short time-scales. We also determined critical thermal limits (CTLs) of activity of C. pomonella and the effect of different rates of cooling or heating on CTLs to complement the survival assays. Temperature and duration of exposure significantly affected adult C. pomonella survival with more extreme temperatures and/or longer durations proving to be more lethal. Lethal temperatures, explored between −20 °C to −5 °C and 32 °C to 47 °C over 0.5, 1, 2, 3 and 4 h exposures, for 50% of the population of adult C. pomonella were −12 °C for 2 h and 44 °C for 2 h. Investigation of rapid thermal responses (i.e. hardening) found limited low temperature responses but more pronounced high temperature responses. For example, C. pomonella pre-treated for 2 h at 5 °C improved survival at −9 °C for 2 h from 50% to 90% (p < 0.001). At high temperatures, pre-treatment at 37 °C for 1 h markedly improved survival at 43 °C for 2 h from 20% to 90% (p < 0.0001). We also examined cross-tolerance of thermal stressors. Here, low temperature pre-treatments did not improve high temperature survival, while high temperature pre-treatment (37 °C for 1 h) significantly improved low temperature survival (−9 °C for 2 h). Inducible cross-tolerance implicates a heat shock protein response. Critical thermal minima (CTmin) were not significantly affected by cooling at rates of 0.06, 0.12 and 0.25 °C min⁻¹ (CTmin range: 0.3-1.3 °C). By contrast, critical thermal maxima (CTmax) were significantly affected by heating at these rates and ranged from 42.5 to 44.9 °C. In sum, these results suggest pronounced plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low temperature responses. We discuss these results in the context of local agroecosystem microclimate recordings. These responses are significant to pest control programmes presently underway and have implications for understanding the evolution of thermal tolerance in these and other insects.     

Cold tolerance of the overwintering larval instars of light brown apple moth Epiphyas postvittana

The light brown apple moth, Epiphyas postvittana, a leafroller native to southeastern Australia was discovered in California in 2006. The highly polyphagous nature of this pest adds to the importance of being able to predict the potential distribution of this invader across the North American continent. The spread of ectothermic species that lack winter diapause, such as E. postvittana, can be limited by their ability to tolerate cold temperature extremes. In this study we examined the cold hardiness of 4th to 6th instar E. postvittana, the only life stages known to overwinter in California, through a combination of supercooling point (SCP) and mortality at low temperatures. Our results showed that the mean SCP for E. postvittana ranged from −14.1 °C for 6th instars to −16.0 °C for 4th instars. Lethal time leading to 50% mortality (LT₅₀) for the three instars combined were 2.5 h at −10.5 °C, 41 h at −6.5 °C and 198 h at −0.9 °C. At 3 °C, the LT₅₀ of 4th instars was significantly lower at 775 h than that for 5th and 6th instars combined at 1029 h. The cold hardiness characteristics of later-instar E. postvittana larvae were comparable to those of pink bollworm, Pectinophora gossypiella, a diapausing invasive with a geographic distribution restricted to southern California. Slightly greater cold hardiness is shown by the indigenous non-diapausing leafroller Argyrotaenia franciscana, which is restricted to the Pacific Coast of North America. We therefore conclude that the moderate cold hardiness of E. postvittana will substantially limit its spread into northern temperate regions of North America.     

Genetic studies of mutations at two loci of Drosophila melanogaster which cause a wide variety of homeotic transformations

Summary The ash-1 locus is in the proximal region of the left arm of the third chromosome of Drosophila melanogaster and the ash-2 locus is in the distal region of the right arm of the third chromosome. Mutations at either locus can cause homeotic transformations of the antenna to leg, proboscis to leg and/or antenna, dorsal prothorax to wing, first and third leg to second leg, haltere to wing, and genitalia to leg and/or antenna. Mutations at the ash-1 locus cause, in addition, transformations of the posterior wing and second leg to anterior wing and second leg, respectively. A similar spectrum of transformations is caused by mutations at yet another third chromosome locus, trithorax. One extraordinary aspect of mutations at all three of these loci is that they cause such a wide variety of transformations. For mutations at both of the loci that we have studied the expression of the homeotic phenotype is both disc-autonomous (as shown by injecting mutant discs into metamorphosing larvae) and cell autonomous (as shown by somatic recombination analysis). The original mutations which identified these two loci, although lethal, manifest variable expressivity and incomplete penetrance of the homeotic phenotype suggesting that they are hypomorphic. The phenotype of double mutants which were synthesized by combining different pairs of those original mutations manifest for two of the four pairs a greater degree of expressivity and slightly more penetrance of the homeotic transformations. This mutual enhancement suggests that the products of both loci interact in the same process. A third double mutant expresses a discless phenotype.Additional alleles have been recovered at both the ash-1 and the ash-2 loci. Some of these alleles as homozygotes or transheterozygotes express the wide range of transformations revealed first by double mutants. One of the alleles at the ash-1 locus when homozygous and several transheterozygous pairs can cause either the homeotic transformation of discs or the absence of those discs. The fact that these two defects, absence of specific discs and homeotic transformations of those same discs can be caused by mutations within a single gene suggests that the activity of the product of this gene is essential for normal imaginal disc cell proliferation. Loss of that activity leads to the absence of discs, whereas, reduction of that activity leads to homeotic transformations.     

Upper thermal limits of aquatic macroinvertebrates: Comparing critical thermal maxima with 96-LT50 values

Water temperature is an important abiotic driver of aquatic ecosystems. It influences many aspects of an organism's existence including its metabolic, growth and feeding rates; fecundity; emergence; behaviour and ultimately survival. This study determined the upper thermal limits of a range of aquatic macroinvertebrates from rivers in the south-western Cape, South Africa, using two methods: the critical thermal method (CTM) and the LT₅₀ method, which is equivalent to the incipient lethal temperature (ILT) technique. The relationship between the two methods was examined with the intention of establishing if the simpler CTM could be used for future testing of thermal sensitivity thereby allowing for extrapolation of longer duration thermal stress. Of the ten species examined, Aphanicerca capensis, Paramelita nigroculus, Chimarra ambulans, Castanophlebia sp. and Afronurus barnardi were all thermally sensitive and had distinct thermal endpoints making them excellent test organisms. There was a significant positive linear relationship between the estimated incipient lethal upper temperature (ILUT) and critical thermal maximum (CTmax), which facilitates future experimental work based on CTM. Future evaluation of hourly in situ stream temperatures to identify periods of exceedance of these 96 h LT₅₀s, in addition to experimental 10 day LT₅₀s, will enable comparison of laboratory data with field conditions, and ultimately the derivation of target water temperature thresholds for management purposes.     

Behavioral thermoregulation of largemouth bass,Micropterus salmoides,and bluegill,Lepomis macrochirus,in a nuclear reactor cooling reservoir

Synopsis Behavioral responses which allow largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus, to survive under unusually high temperature conditions were examined. Distribution of fish was ascertained by angling. Body temperatures of 4 fish were obtained using radio transmitters. Temperatures of other fish were measured after fish were captured by angling. Both species were restricted in range by lethal water temperatures and therefore inhabited a greater portion of a thermally altered reservoir in winter than in summer. Under unheated conditions (during reactor shutdown), bass occupied shallow areas with an abundance of submerged logs and stumps, a deep area with springs, and a cove where the effluent canal entered the reservoir. Commencement of reactor operation resulted in an increase in water temperature to more than 50°C in summer. Bass and bluegill retreated to three refuges and remained there until the reactor shut down and the reservoir cooled. In the refuges, bass experienced a wide variety of temperatures, but adults generally avoided temperatures above 31°C. Large adult bass (>40 cm) occupied particular positions in a refuge cove, medium size bass (15–40 cm) swam in the open water, and small bass (相似文献   

炭疽杆菌致死因子的克隆与表达

以炭疽杆菌A16R株基因组DNA为模板,PCR扩增出炭疽杆菌致死因子LF基因。构建pET-28(a)/LF表达质粒,并在大肠杆菌中表达。优化表达条件,可溶性目的蛋白表达量约占细菌可溶性总蛋白的10%,表达产物经疏水层析纯化后,目的蛋白约占90%。免疫双扩散及免疫印迹试验检测结果显示,该表达产物与炭疽杆菌诊断血清有特异性反应,具有抗原性。     

蘑菇菌丝体代谢产物对果蝇的致死效应

以果蝇为靶标 ,对 15种蘑菇液体培养产物的毒性进行了检测 ,发现硫磺菌红色变种Laetiporussulphureusvar miniatus和硫磺菌原变种Laetiporussulphureusvar sulphureus液体培养中产生的代谢产物对果蝇具有致死活性。气升式生物反应器 (Airlift/ff)培养条件下 ,硫磺菌红色变种和原变种培养体系的 pH值均连续下降 ,最终都降至 2 2左右。研究发现致死活性产物被分泌到细胞外 ,离子交换树脂柱层析的线性洗脱分离结果表明活性代谢产物呈酸性 ,进一步分析表明草酸是活性代谢物之一 ,而树脂静止交换表明另外一种未知色素也具有致死活性     

Role of residues constituting the 2beta1 strand of domain II in the biological activity of anthrax protective antigen

Anthrax toxin consists of three proteins, protective antigen, lethal factor and oedema factor. A proteolytically activated 63-kDa fragment of protective antigen binds lethal factor/oedema factor and translocates them into the cytosol. Domain II of protective antigen has been implicated in membrane insertion and channel formation. In the present study, alanine substitutions in 14 consecutive residues of the 2beta1 strand that are highly homologous to the putative membrane interacting segment of Clostridium perfringens iota-b toxin were generated and the effect on the biological activity of protective antigen studied. One of the mutants, Pro260Ala, showed considerably reduced toxicity in combination with lethal factor. The mutant also showed decreased membrane insertion and translocation of lethal factor into the cytosol. The data suggest that Pro260 is important for membrane insertion and translocation by protective antigen.     

Measurement of blood clearance time by Limulus G test of Candida-water soluble polysaccharide fraction, CAWS, in mice

The Limulus G test, responsive to beta-1,3-D-glucan, is a well-established method for the detection of invasive fungal infection. We have recently found that Candida albicans released a water-soluble polysaccharide fraction (CAWS) into synthetic medium (Uchiyama et al., FEMS Immunol. Med. Microbiol. 24 (1999) 411-420). CAWS was composed of a mannoprotein-beta-glucan complex and activated Limulus factor G, and thus would be similar to the Limulus active substance in patient's blood. In a preliminary investigation, we have found that CAWS is lethal when administered intravenously in a murine system. In this study, we examined the toxicity and then the fate of CAWS in mice. The lethal toxicity was strain-dependent and strain DBA/2 was the most resistant. The toxicity was, at least in part, reduced by salbutamol sulfate and prednisolone treatment in the sensitive strains. On intravenous administration, the half clearance time (t1/2) was approximately 40 min in mice (DBA/2). On intraperitoneal administration, CAWS appeared in the blood with a peak concentration at 1 h. In order to establish a treatment plan, it is important to demonstrate the onset and the termination of deep-seated mycosis. The Limulus G test is suitable for the above purpose; however, it is necessary to fully understand the fate of beta-1,3-D-glucan in patients' blood.