Life-cycle variation in the aphid Sitobion avenae: costs and benefits of male production

Abstract 1. Patterns of male production and life-cycle variation were investigated in the aphid Sitobion avenae . Seventy-seven field-collected clones were subjected to a 14 °C short day-length regime to assess their reproductive modes, and three clones were used to study life-cycle inheritance. A further analysis assessed the cost of male production.
2. In comparison with those from East Anglia, there were more holocyclic and intermediate clones found in Scottish populations, and they produced significantly more mating females. In total, 44% of clones were androcyclic.
3. The inheritance of life cycle showed a greater level of complexity than could be achieved by previously suggested monohybrid inheritance mechanisms.
4. Holocyclic and intermediate clones produced a higher proportion of males than did androcyclic clones. Inter-clonal differences were reflected in the pattern of male production in the reproductive sequence.
5. A significant cost was associated with male production in terms of a reduction in both fecundity and total offspring biomass.
6. Winged females rarely gave birth to males but the pattern of mating female production differed between holocyclic and intermediate clones.
7. Patterns of male and mating female production by the different types of clone may be related to different advantages and disadvantages of dispersal and inbreeding.
8. Recent models of aphid overwintering could be enhanced by consideration of issues raised in this study, such as the cost of male production, the inheritance of life cycle, and the patterns of sexual morph production.     

Cold hardiness of the overwintering black carpenter ant

Abstract Cold hardiness was investigated in overwintering field nests of the black carpenter ant Camponotus pennsylvanicus (De Geer) in the Commonwealth of Virginia. No active nest thermoregulation was observed: temperatures of galleries, worker bodies, worker clusters, and larval clusters were within 3°C of ambient temperature. Nest temperatures generally fluctuated less rapidly and severely than did ambient temperature; thus, the nest afforded protection from potentially fatal sudden temperature drops. Glycerol, the only polyol cryoprotectant detected, was found in all castes and larvae. Supercooling points were low and ranged from ? 17°C in major workers to ?22°C in larvae. A second heat release peak, occurring around ? 8°C, was seen in all adults, but it was not observed in larvae. This higher temperature peak in adults probably represents the freezing of the gut contents, as adults were found to overwinter with the crop full or partially full. Larvae did not overwinter with liquid food in the gut.     

重阳木锦斑蛾越冬幼虫的耐寒性变化

【目的】重阳木锦斑蛾Histia rhodope是为害重阳木Bischofia polycarpa的重要害虫之一。本研究旨在了解重阳木锦斑蛾幼虫的抗寒能力,并为探讨抗寒机理提供理论基础。【方法】在越冬期的不同阶段(2017年11月7日、2017年12月7日、2018年1月5日、2018年2月4日和2018年3月5日)分别采集室外重阳木锦斑蛾越冬幼虫,对其体重、过冷却点、结冰点、含水量、脂肪、总糖和总蛋白质含量进行测定。【结果】重阳木锦斑蛾幼虫的过冷却点在越冬期不同月份有显著差异,与环境温度呈显著正相关(P<0.05),最低值出现在1月份,为-15.26℃,最高值出现在3月份,为-13.30℃;结冰点变化趋势与过冷却点一致;体重和脂肪含量在越冬期间逐渐下降,与过冷却点无相关性(P>0.05);过冷却能力随着虫体游离水含量的升高而降低,随其降低而升高,而结合水含量的变化趋势恰好相反;总糖含量在11月最高,为14.95 μg/mg,显著高于3月份的5.07 μg/mg;总蛋白质含量在越冬期间呈先升高后降低的趋势,在1月份含量最高,为23.66 μg/mg,显著高于11月份的含量(16.69 μg/mg)。【结论】重阳木锦斑蛾幼虫的耐寒性在越冬期间随气温的降低逐渐增强,随气温的回升又逐渐减弱;蛋白质可能是该虫重要的耐寒物质。     

麦长管蚜脱巴克纳氏共生菌的分子验证

蚜虫脱共生效果的鉴定对蚜虫-巴克纳氏菌共生体系的研究至关重要.采用光学显微镜观察及特异性PCR扩增技术,对麦长管蚜(Sitobion aoenae)脱巴克纳氏共生菌的效果进行了研究.结果表明:用利福平处理5 d和10 d后的麦长管蚜,PCR检测发现有巴克纳氏菌(Buchnera)特异性扩增条带,说明共生菌仍然存在;在利福平处理 15 d后,PCR检测没有发现特异性扩增条带,说明麦长管蚜胞内共生细菌的核酸已经被降解;光学显微镜观察与PCR检测结果相一致.     

四种类型杀虫剂对麦长管蚜的温度效应及其与主要解毒酶的关系

为了明确杀虫剂毒力受温度的影响及其程度,本文测定了4大类8种药剂在10～25℃下对麦长管蚜的毒力;并测定了麦长管蚜Sitobion avenae(Fabricius)在不同温度下2个解毒酶和1个靶标酶的活性差异。结果表明,高效氯氰菊酯对麦长管蚜表现不规则负温度系数,啶虫脒表现不规则正温度系数,高效氟氯氰菊酯对麦长管蚜的毒力不受温度影响,其他药剂(辛硫磷、毒死蜱、灭多威、丁硫克百威、吡虫啉)均表现为明显的正温度系数效应,以有机磷类杀虫剂表现最为明显,毒死蜱温度系数高达57.70。酶活性实验表明:麦长管蚜在高温下GST活性增强,羧酸酯酶和乙酰胆碱酯酶活性降低。它们的变化规律表明:GST活性与负温度系数密切相关,正温度系数与羧酸酯酶活性和靶标酶乙酰胆碱酯酶活性有关。     

稻水象甲越冬成虫的耐寒力测定

测定了浙江乐清 (北纬 2 8 1 4°,东经 1 2 0 94°)稻水象甲LissorhoptrusoryzophilusKuschel越冬成虫的耐寒力 ,从 1 1月下旬至 3月下旬平均过冷却点温度为 -1 5 3～ -2 1 2℃ ,结冰点温度为 -1 4 0～ -1 8 6℃。结合发生地气温条件 ,讨论了该地冬春季低温对该虫越冬群存活的影响。     

麦长管蚜烟碱型乙酰胆碱受体基因的克隆和序列分析

昆虫烟碱型乙酰胆碱受体(nicotinic acetylcholine receptor, nAChR)是杀虫剂的重要作用靶标之一。本研究利用简并引物PCR和半巢式PCR技术从麦长管蚜Sitobion avenae (Fabricius)中克隆nAChR基因,成功地获得了5个α型nAChR亚基的cDNA片段。根据5个α亚基片段设计特异引物,结合快速扩增cDNA末端(RACE)技术,成功克隆了5个α型亚基的全长,并发现α5亚基有两种存在形式,它们仅在胞外区有一段175 bp的片段有差异。序列分析发现,这些基因均具有nAChR基因家族的典型特征,并与已报道的其他昆虫的烟碱型乙酰胆碱受体的相应亚基具有很高的同源性。该研究为进一步利用基因表达技术研究昆虫nAChR的天然亚基组成,以及分析麦长管蚜对新烟碱类杀虫剂的靶标抗性,奠定了基础。     

Aphid colony turn‐over influences the spatial distribution of the grain aphid Sitobion avenae over the wheat growing season

1 Temporary habitats are characterized by the appearance and disappearance of patches in which resources are available for a limited period only. Organisms living in those environments usually exhibit adaptive traits, such as a high ability to find and exploit new patches. Among them are phytophagous insects, such as crop pests living in agroecosystems. Understanding how phytophagous insects invade a new patch is of great agricultural importance. 2 Here, we investigated how aphids colonize a wheat field by studying the spatial and temporal dynamics of their populations at large (field) and fine (group of host plants) scales. 3 The sampling design consisted of counting and locating aphid colonies within 30 0.25 m² squares randomly spaced in a 1.5‐ha winter wheat field over 2 months. All colonies were precisely located within the squares and their composition in terms of morphs was determined. 4 We show that: (i) immigration of winged aphids was a major factor driving the aphid population dynamics during a large part of the season and (ii) within the field, populations established late in the growing season. Aggregated, populations of aphids became progressively homogeneously distributed at the field scale. At the scale of a 0.25 m² square, infested plants were clustered in randomly distributed small patches, and aphid colonies experienced high extinction rates, suggesting failure in population establishment. 5 Because immigration may considerably influence both population dynamics and spatial distribution, our study suggests that future predictive models should give a greater weight to spring immigrants.     

Methods of hatching the eggs and rearing the fundatrices of the English grain aphid, Sitobion avenae

Several methods for hatching the eggs and rearing individuals of the first generation (fundatrices) of Sitobion avenae were investigated. The most successful methods were incubation of the eggs on grass seedlings at 2°C and rearing the fundatrices on grass seedlings (overall survival 66%) and incubation of the eggs in plastic boxes at 2°C and rearing the fundatrices on wheat seedlings (overall survival 62%).

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Résumé L'éclosion des oeufs de S. avenae peut être induite par le transfert à 10°C ou 12°C, après une incubation de 75–120 jours à 2°C. Le pourcentage le plus élevé d'éclosions a été obtenu quand les oeufs avaient incubé pendant 100 à 110 jours à 2°C (67% at 71.5% respectivement) dans des petites boîtes de plastique, ou pendant 100 jours à 2°C sur des pousses de graminées (73.5%). Si les oeufs sont pondus sur blé, la plante ne peut pas tolérer la période d'incubation, mais cet obstacle peut être surmonté en obligeant les ovipares à pondre leurs oeufs sur de pousses de graminées, comme Poa annua, hôte convenable pour les fondatrices. Les ovipares peuvent aussi pondre sans difficultés sur autre chose que des végétaux, et des récipients peuvent ètre mis à incuber sans contenir du matériel végétal.

     

Molecular-genetic evidence of aphid pathogen Pandora kondoiensis infection in Sitobion avenae collected in Denmark

Entomophthoralean-specific primers were used to estimate the occurrence of entomophthoralean species in the cereal aphid Sitobion avenae in Denmark. Sequencing documented for the first time the presence of Pandora kondoiensis in Denmark. Specific primers were designed and P. kondoiensis was identified on 12% of infested straws sampled in 2012.     

The effect of reducing growth in winter wheat on the population dynamics of the grain aphid Sitobion avenae (F.)

1 The effect of reducing the growth of winter wheat on population size and development of the grain aphid Sitobion avenae was studied. 2 Automatic, mobile, crop shading devices, which reduced radiation comparable to levels found on a cloudy day, whilst minimizing other climatic changes, were used to reduce crop growth. Shading was applied between either GS 31 and 39 (1st node detectable → flag leaf ligule just visible) or GS 39 and 55 (flag leaf just visible → 50% of inflorescence emerged). 3 Sitobion avenae populations were initiated at GS 55 and highest populations were subsequently observed on plants shaded between GS 31 and 39. 4 Individual aphids confined within clip cages were observed to measure development from birth to adult moult, adult lifespan and fecundity. Results indicated that adult lifespan was shortest on plants shaded between GS31 and 39, whilst there were no differences in development time or fecundity. 5 Possible explanations for these observations are discussed.     

越冬期不同阶段二点委夜蛾越冬幼虫耐寒性变化

【目的】二点委夜蛾Athetis lepigone (Moschler)是我国夏玉米苗期的新害虫,随着耕作制度的改变,二点委夜蛾的发生危害区域和面积逐渐扩大。本研究探讨二点委夜蛾的抗寒能力,为揭示抗寒机理提供理论基础。【方法】分别在越冬期的3个不同阶段,即越冬初期（2012年11月7日）、越冬期（2012年1月20日）和越冬末期（2013年3月5日）,对二点委夜蛾老熟幼虫的体重、过冷却点（supercooling point, SCP）、结冰点（freezing point, FP）、含水量、脂肪和糖原含量进行测定。【结果】过冷却点在这3个时期有显著差异,最低值（-23.16±0.38℃）出现在1月份,最高值（-16.24±1.24℃）出现在越冬初期,结冰点变化趋势与过冷却点一致。通过定量检测发现,虫体鲜重与过冷却点无相关性（r=0.17, P=0.12）;脂肪含量在越冬初期含量最高,而在越冬末期最低;糖原含量在越冬期含量最低;自由水的含量随着过冷却能力升高而降低,随其降低而升高,而结合水含量恰好相反。【结论】二点委夜蛾的抗寒性在越冬期不同阶段出现明显的变化,即随着冬季低温的到来,其抗寒能力逐渐增强,冬季过后又随气温的回升,其抗寒力逐渐减弱。     

The major carotenoid pigments of the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae)

The economically important grain aphid, Sitobion avenae (F.) shows colour polymorphism, with brown and green forms predominating. Colour is determined both genetically and in response to environmental factors, including nutrition. The biological significance of the colour polymorphism is unknown, although seasonal changes occur in the frequency of colour morphs in the field, whilst the brown morph may have adaptive significance in terms of hymenopterous endoparasitism. The ground colour of aphids is produced by haemolymph pigments, aphins (glucosides) and carotenoids. The latter may be under the synthetic control of intracellular endosymbiotic bacteria. In this study, the major carotenoid pigments of a brown and a green clone of S. avenae were examined using thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC), and their absorbance spectra recorded. Using TLC, the brown clone produced five bands of different R_f, ranging from yellow, to orange-pink to pink in colour. In contrast, the green clone gave only a single yellow band of higher R_f than any of the bands of brown aphids. Following separation of carotenoids by HPLC, brown aphids gave seven peaks and green aphids five. Comparison of absorbance maxima with known published values for carotenoids provides strong evidence for the identification of four of the carotenoid pigments from brown aphids (RB-4, 3,4-didehydrolycopene; RB-5, torulene; RB-6; lycopene; RB-7, γ-carotene) and one from green aphids (RG-2, α-carotene). The other carotenoids remain unidentified. The biosynthesis and possible biological relevance of the various pigments of S. avenae are briefly discussed.     

A field evaluation of different criteria for determiningthe need to treat winter wheat against the grain aphid Sitobion avenae and the rose-grain aphid Metopolophium dirhodum

The economics of control of grain aphid (Sitobion avenae) and rose-grain aphid (Metopolophium dirhodum) were investigated in a series of experiments carried out across England in 1988 and 1989. Sprays of pirimicarb or dimethoate were applied at three growth stages and yield effects measured. Aphid infestations were determined by a range of different methods, to evaluate the value of each for decision making. Aphids overwintered in crops in mild conditions in both seasons, resulting in early population build-up and decline in many cases. Aphicide sprays applied during the booting stage increased average yields by 0.26 t/ha. Profitability of the treatment strategies considered was not greatly enhanced by selective spray application related to aphid assessment at this stage. Delaying decision making to the flowering or grain-filling stages resulted in reduced profitability. A poor correlation between aphid numbers and crop yield response to sprays was found. This was shown to be due to differences in subsequent aphid population development and in aphicide efficacy. Grain quality was affected only by high aphid infestations which caused large yield reductions.     

Migration and genetic structure of the grain aphid (Sitobion avenae) in Britain related to climate and clonal fluctuation as revealed using microsatellites

Genetic structuring of populations reflects the interaction of genetic drift, mutation, migration and selection, with influences from life history. Aphids are interesting in this regard as they have the potential for unusually high levels of dispersal and natural selection, which typically counter each other. In the present study, winged grain aphids Sitobion avenae (F.) were collected in four 12.2-m high suction traps along a north-south transect in Britain in order to eliminate sampling bias from plant hosts (cereals and grasses; Poaceae), it being known that these insects show host adaptation demonstrable using molecular markers. Samples were analysed at four polymorphic microsatellite loci over two consecutive years. Population allele frequencies were similar nationally during the two years, although clonal diversity varied greatly between sites and years. In the first sampling year following a harsh winter, diversity was found to display a latitudinal clinal trend: the proportion of unique clones (genotypes) increased with latitude. However, this pattern was less apparent the following year, after a milder winter. Nonetheless, overall FST analysis showed that there was little spatial genetic structuring in either sampling year. These data support the view that the insect is highly migratory and also support a theoretical model and previous data suggesting that the reproductive mode is clinal in S. avenae. This appears to be because natural selection (reduced reproductive success of asexual genotypes under cold conditions) is sufficiently powerful to overcome the homogenizing effects of strong migration. There was no clear evidence for isolation by distance for the genetic data obtained. The data are compared with similar data from other aphid species and other insects. Only by the collection of such data sets can an accurate picture be built up relating genetic variability to flight behaviour, including migratory ambit in this group of insects since, due to their small size and rapid dilution in the air, other marking approaches are impracticable over large geographical distances.     

上海地区红棕象甲的耐寒性研究

红棕象甲Rhynchophorus ferrugineus (Olivier)是我国危害棕榈科植物的重要入侵害虫, 为探明其越冬抗寒性, 利用过冷却点测定仪测定了红棕象甲上海种群不同虫态的过冷却点, 在低温箱内测定了该虫不同虫态的耐寒性, 然后结合田间越冬模拟试验、气象资料和寄主分布情况, 初步确定了红棕象甲在我国的越冬北界。结果表明： 红棕象甲过冷却点随虫态的发育程度的升高而下降, 卵、1龄幼虫、5龄幼虫、9龄幼虫和成虫的平均过冷却点分别为-5.92, -6.42, -7.19, -7.43和-11.84℃, 过冷却点由高到低的顺序依次为: 卵>幼虫>成虫。在6, 24, 48和72 h 4个时间处理下, 各虫态在低温与存活率之间呈显著或极显著的logistic回归, 半致死温度（Ltemp₅₀）均随处理时间的延长而上升, 不同虫态在处理72 h 后, 卵、1龄幼虫、5龄幼虫、9龄幼虫和成虫之间的Ltemp₅₀分别为1.61, -1.67, -2.39, -2.40和-0.40℃, 各虫态耐寒性由弱到强的顺序依次为: 卵<成虫<幼虫。红棕象甲不同发育阶段的过冷却点与其耐寒性并不完全相关, 幼虫和成虫均可能是该虫的越冬虫态。连续两年的田间模拟越冬试验表明, 在上海地区, 红棕象甲的幼虫和成虫的越冬存活率均在60％以上, 说明红棕象甲在上海地区是可以越冬的。根据这些结果, 结合寄主分布情况, 初步将红棕象甲在我国的越冬北界定于北纬35°附近, 即1月份0℃等温线左右。     

Seasonal changes in supercooling capacity and major cryoprotectants of overwintering Asian longhorned beetle (Anoplophora glabripennis) larvae

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