OLFACTORY RESPONSES OF COTTON BOLLWORM,HELICOVERPA ARMIGERA TO SEX PHEROMONE AND PLANT VOLATILE COMPONENTS*

Abstract Electroantennograms (EAGs) were recorded from unmated, laboratory-reared male and female Helicover pa armigera (Lepidoptera:Noctuidae) adults to two sex pheromone components and a range of plant volatile components, some of which are known volatiles from leaves and fruits. The female-produced sex pheromone was not detected by other female moths. The sex pheromone components to which male moths responded previously show to possess biological activity. As for plant volatile components, a large degree of EAG response uniformity between male and female moth was observed. The greatest EAG responses of all plant volatiles tested were elicited by monoenic C-6 alcohol and aldehyde. They are constituents of the “general green-leaf odor” that emanates from most plants. The potential adaptive benefit of selective perception to sex pheromone and green-leaf volatile components is discussed.     

High resolution measurement of atmospheric carbon dioxide concentration changes by the labial palp organ of the moth Heliothis armigera (Lepidoptera: Noctuidae)

Summary In recordings of single unit action potentials, the responses of CO₂-receptors in the labial palp organ of the moth Heliothis armigera to modulation of CO₂-density around a background of 350 ppm were investigated. Modulation of CO₂-density by square wave changes in concentration at constant barometric pressure evokes modulation of the spike rate. Modulation of CO₂-density by square wave changes in barometric pressure at constant CO₂-concentration evokes responses similar to those evoked by concentration modulation. For modulation depths of less than 1.5%, the output modulation depth is linearly related to the input; at higher modulation depths the gain decreases progressively.Using sinusoidal pressure modulation, the frequency dependence of both gain and output noise was determined over a range of 0.05 to 12.8 Hz. With increasing frequency the gain progressively increases at a rate of 2.4 dB/octave up to a maximum of 63 at 3 Hz; at higher frequencies, it decreases rapidly. The threshold sensitivity of the receptors, using input noise amplitude density as a criterion, is broadly tuned, with a minimum of 1 % contrast Hz^-0.5 between 0.3 and 3 Hz. Using these figures, it is concluded that the sensory organ is capable of detecting fluctuations in CO₂-density of 0.14% or 0.5 ppm. The results are related to the fluctuations in CO₂-density which occur in a natural environment.     

Antennal responses of Cydia pomonella (L.) exposed to surfaces treated with methoxyfenozide

Electroantennogram (EAG) measurements were recorded from the antennae of male and female codling moth, Cydia pomonella L., to determine whether adult moths exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide experience a decline in their antennal reception and thus olfactory sensitivity. Such a phenomenon would offer a possible mechanism for the previously reported decreased responsiveness from moths treated with methoxyfenozide to pheromone‐ and plant volatile‐based monitoring lures. Mean EAG data revealed that the antennae from methoxyfenozide‐treated male moths appear to be just as sensitive to various doses of synthetic codlemone as the antennae from the control and surfactant‐treated moths, but they appeared to be less sensitive to the pheromone component 12OH (collected from female effluvia) than the control male antennae. Mean male EAG responses to the pheromone components E8,E10‐12Al and codlemone collected from methoxyfenozide‐treated females were significantly less than the responses towards those two pheromone components collected from the control and surfactant‐treated females. Female moth exposure to methoxyfenozide did not negatively impact the sensitivity of female antennae to the plant volatile pear ester, but it did towards the apple volatile butyl hexanoate. Data from this study show that adult C. pomonella exposure to methoxyfenozide‐treated surfaces does appear to negatively impact, in a minor way, the (i) olfactory sensitivity (or detection) of male antennae towards some components of the female sex pheromone, (ii) the female antennal sensitivity towards a key apple volatile and (iii) the attractiveness of female pheromone effluvia.     

Electroantennogram and behavioural responses of the gypsy moth to enantiomers of disparlure and its trans analogues

The attractive power of both enantiomers of disparlure and its trans analog was tested electrophysiologically (electroantennogram = EAG) and behaviourally (whole organism response). EAG responses correlated very well with the behaviourally determined effectiveness sequence: cis(+)-disparlure was the most effective substance; the authentic racemic disparlure came second; cis(?)-disparlure inhibited the activity of cis(+)-disparlure; and trans enantiomers were not significantly different from the control. These results allow us to conclude that cis(+)-disparlure is the natural sex pheromone of the gypsy moth, and that the male antennae have a chiral receptor system in the antenna for the reception of the sex pheromone.     

小地老虎雄蛾对雌蛾性信息的EAG反应

利用触角电位记录（EAG）技术,测定了小地老虎Agrotis ypsilon (Rottemberg) 雄蛾对性信息素标准化合物Z7-12：Ac（A）、Z9-14：Ac（B）、Z11-16：Ac（C）、Z5-10：Ac（D）和Z8-12：Ac（E）的EAG反应。结果表明：这些标准化合物均能引起EAG反应,其中组分A（Z7-12：Ac）引起的反应最强,为5.65 mV,组分B（Z9-14：Ac）和C（Z11-16：Ac）居中; 组分D（Z5-10：Ac）的EAG反应值最小,为2.50 mV。二元混合物、三元混合物、四元混合物和全组分的EAG反应较高,其EAG反应值均显著高于单组分的反应值。三元混合物ABC的反应值最高,与5头雌蛾腺体的正己烷浸提液的EAG值相当。在使用剂量为0.01 ng～100 μg反应内,小地老虎雄蛾触角对性信息素各组分及其混合物的剂量反应曲线大致呈“S”形。从不同日龄雄蛾对标准化合物的反应中,发现在羽化后第3天达到最高值,之后则随日龄增加EAG反应降低。     

棉铃虫Helicverpa armigera对性外激素和植物气味物质的嗅觉反应(英文)

本文用EAG技术研究棉铃虫对性外激素和植物气味物质的嗅觉反应。供试的气味物质有棉铃虫性外激素的二种主要组分和36种与棉铃虫寄主植物有关的植物气味物质。试验结果表明：1）只有棉铃虫雄蛾对性外激素组分产生反应,二种性外激素的组分中,Z-11-16：AL能引起较强的EAG反应。2）对植物气味物质,雌雄棉铃虫之间的嗅觉反应没有明显的差异。棉铃虫对性外激素和植物气味组分的嗅觉感受过程是一个有选择性的感受过程：不同种类的气味物质能引起不同的EAG反应。只有棉铃虫雄蛾才对性外激素组分起反应,在二种性外激素组分中：主要组分：Z-11-16：AL引起的EAG反应最高,高于大多数植物气味物质。次要组分Z-9-16：AL引起的EAG反应很弱。雌、雄棉铃虫对植物气味组分的嗅觉反应的选择性表现出一致的规律：对苯甲醛和绿叶气味物质的反应最高。单萜类中的萜烯衍生物（萜类醇、醛、酯等）的触角电位反应次之。棉铃虫对大多数的供试化合物的EAG反应都很小。最后,作者讨论了性外激素和植物气味物质对棉铃虫行为的作用。     

植物气味化合物对棉铃虫产卵及田间诱蛾的影响

利用触角电位技术（EAG）研究棉铃虫Helicoverpa armigera对17种植物气味物质的嗅觉反应,实验结果表明：棉铃虫雄蛾、雌蛾对所试各种植物气味物质均无明显的嗅觉反应差异,不同种类的气味物质能引起不同的EAG反应。对其中的几种植物气味物质进行了引诱产卵实验及田间诱蛾实验,结果表明：某些寄主植物的挥发性次生物质显示出较好的引诱产卵活性,且对棉铃虫性诱剂具有增效和协同作用。田间实验数据显示,增加了植物气味物质的棉铃虫性诱剂与单一的棉铃虫性诱剂相比差异显著。     

Electroantennogram responses of Plutella xylostella (L.), to sex pheromone components and host plant volatile semiochemicals

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious insect pest of cruciferous crops worldwide. Attract-and-kill strategies to manage the DBM based on insect pheromone and plant volatile semiochemicals have been explored and partially applied in the field. However, little is known about whether the attractant effects of insect pheromone and host plant volatile semiochemicals on insects are affected by insect age or volatile concentrations. Therefore, we examined the electroantennogram (EAG) responses of both DBM males and females varying in age and body size to a range of concentrations of seven host plant volatiles and two main female sex pheromone components. Our results showed that DBM age had no influence on EAG responses to trans-2-Hexenal, trans-2-Hexenol, Heptanal, cis-3-Hexen-1-ol and Z11-16:Ald and significantly influenced the EAG responses to Z11-16:Ac and three isothiocyanates. Age and sex had interaction effects on EAG responses of DBMs to some tested semiochemicals. DBM females had significantly stronger responses than males to all tested plant volatiles, and values were enhanced with increasing concentrations. Moreover, the degree of enhancement of EAG responses in females was larger than that in males for trans-2-Hexenal, trans-2-Hexenol, cis-3-Hexen-1-ol, 2-Phenylethyl isothiocyanate and Methyl isothiocyanate treatments. Body size seemed to have no influence on EAG responses. Our results might provide a theoretical basis for optimizing attract-and-kill strategies for insect pests.     

Elevated CO2 levels and herbivore damage alter host plant preferences

Interactions between the moth Spodoptera littoralis and two of its host plants, alfalfa (Medicago sativa) and cotton (Gossypium hirsutum) were examined, using plants grown under ambient (350 ppm) and elevated (700 ppm) CO₂ conditions. To determine strength and effects of herbivore‐induced responses assays were performed with both undamaged (control) and herbivore damaged plants. CO₂ and damage effects on larval host plant preferences were determined through dual‐choice bioassays. In addition, larvae were reared from hatching to pupation on experimental foliage to examine effects on larval growth and development. When undamaged plants were used S. littoralis larvae in consumed more cotton than alfalfa, and CO₂ enrichment caused a reduction in the preference for cotton. With damaged plants larvae consumed equal amounts of the two plant species (ambient CO₂ conditions), but CO₂ enrichment strongly shifted preferences towards cotton, which was then consumed three times more than alfalfa. Complementary assays showed that elevated CO₂ levels had no effect on the herbivore‐induced responses of cotton, whereas those of alfalfa were significantly increased. Larval growth was highest for larvae fed undamaged cotton irrespectively of CO₂ level, and lowest for larvae on damaged alfalfa from the high CO₂ treatment. Development time increased on damaged cotton irrespectively of CO₂ treatment, and on damaged alfalfa in the elevated CO₂ treatment. These results demonstrate that elevated CO₂ levels can cause insect herbivores to alter host plant preferences, and that effects on herbivore‐induced responses may be a key mechanism behind these processes. Furthermore, since the insects were shown to avoid foliage that reduced their physiological performance, our data suggest that behavioural host plant shifts result in partial escape from negative consequences of feeding on high CO₂ foliage. Thus, CO₂ enrichment can alter both physiology and behaviour of important insect herbivores, which in turn may to impact plant biodiversity.     

小地老虎化学感受蛋白AipsCSP8的表达及配体结合特性分析

【目的】本研究旨在解析小地老虎Agrotis ipsilon化学感受蛋白AipsCSP8的表达谱及配体结合特征。【方法】利用qRT-PCR方法测定了AipsCSP8在小地老虎成虫头、胸、腹、足、翅、性腺(附腺)、触角、喙和下唇须以及雌雄虫羽化前后触角中的表达水平。体外重组表达AipsCSP8蛋白,通过荧光竞争结合实验测定重组蛋白AipsCSP8对24种性信息素、22种植物挥发物和10种化学农药的结合特性。【结果】qRT-PCR检测结果显示,AipsCSP8在小地老虎雄成虫的足和下唇须中表达量最高,在附腺和触角中的表达量次之;在雌成虫的触角中表达量最高,在足、性腺、下唇须中的表达量次之。另外,雄、雌虫触角中AipsCSP8表达量分别在成虫羽化前1 d和羽化当天达到顶峰。荧光竞争结合实验结果表明,重组蛋白AipsCSP8对植物挥发物邻苯二甲酸-丁酯(解离常数Ki=14.6 μmol/L)、苯乙醛(Ki=17.2 μmol/L)以及化学农药阿维菌素(Ki=12.9 μmol/L)均有较强的结合能力。【结论】化学感受蛋白AipsCSP8可能参与小地老虎嗅觉行为及味觉识别,并可能在小地老虎感受化学农药的过程中发挥作用。     

Ontogeny of electroantennogram responses in the moth, Manduca sexta

The antennae of the moth, Manduca sexta, and the sensilla and sensory neurons they contain, develop during metamorphosis from pupa to adult. To determine when, during their development, antennae become capable of generating electrical responses to various stimuli, we recorded the electroantennogram (EAG), believed to be the summed extracellular record of receptor potentials, from developing and mature antennae. Antennae from male and female moths are similarly responsive to trans-2-hexenal, while only males respond to Manduca sex pheromone; these two odorants presumably stimulate separate receptors. Mechanical stimulation also elicits and EAG response. EAG responses to olfactory and mechanical stimuli are detectable several days before eclosion but not until the neurons are morphologically and biochemically quite mature. Responses increase in magnitude until the end of metamorphosis and then change little during the first 3 days after emergence of the adult. Responses to different stimuli do not develop synchronously.     

Isolation of sex pheromone mimic of the American cockroach by monitoring with male/female ratio in electroantennogram

The electroantennogram (EAG) technique was applied as a monitoring tool to isolate germacrene-D, a sex pheromone mimic of the American cockroach. Large values of the male/female ratio, and its index derived from EAG responses of adult males and females to a standard, indicated significant amounts of germacrene-D in plant fractions. Monitoring with behavioural assays and gas chromatographic analysis during the isolation confirmed that the EAG technique using the male/female index was a good indicator in the isolation of sexually active components.     

Sexual dimorphism of adult labial palps of the peach fruit moth Carposina sasakii Matsumura (Lepidoptera: Carposinidae) with notes on their sensilla

The labial palps and their sensilla of the peach fruit moth Carposina sasakii Matsumura, a serious pest of pome fruits in eastern Asia, were investigated using light microscopy and scanning and transmission electron microscopy. The labial palps are three‐segmented and exhibit distinct sexual dimorphism in length: much longer in the female than in the male. Four types of sensilla were found on the labial palps: campaniform, squamiform, chaetic and flattened sensilla. The campaniform sensilla are present on the first segment alone. The squamiform sensilla are located on all the three segments. The chaetic sensilla are mainly present on the third segment. The flattened sensilla are grooved with wall pores and situated in a labial palp‐pit organ, which is located at the apex of the distal segment of the labial palp. The sexual dimorphism of the labial palp and the labial palp‐pit organ was briefly discussed.     

The circadian rhythm of flight activity of Spodoptera exigua males in response to sex pheromone

In many moths, male attraction to the blend of synthetic sex pheromone releasing continuously in the field shows an apparent circadian rhythm similar to that of locomotion activity. In this study, the daily rhythms of electroantennography (EAG) and behavioral responses to sex pheromone, and the daily rhythms of locomotion activity were measured in male beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). The peaks of males trapped by light and sex pheromone were all during the latter part of the night in the field. However, there was no significant variation among time intervals in the EAG responses of male antennae to sex pheromone stimuli. The principal period of locomotion activity under L15:D9 (LD) continued to occur during the scotophase and the subjective scotophase in the day of constant darkness (DD1) and the second of two consecutive days of constant darkness (DD2). The majority of males contacted the sex pheromone source in a wind tunnel during the latter part of the scotophase under LD and the subjective scotophase for DD1 and DD2. There were significant associations between the rhythm of the behavioral response to sex pheromone and locomotion activity. These results suggested that the male's behavioral response to sex pheromone in the beet armyworm could be observed only until locomotion activity of the male occurred at the end of the dark period, despite sex pheromone being released continuously from synthetic pheromone‐baited traps in the field.     

Odour quality discrimination for behavioural antagonist compounds in three tortricid species

The antennal and behavioural response of three tortricid species (Lepidoptera: Tortricidae) to their corresponding sex pheromones and known or putative behavioural antagonists was tested by electroantennography and in field trials. The species and their pheromones and known or proposed behavioural antagonist were lightbrown apple moth, Epiphyas postvittana (Walker) [pheromone: 95% (E)‐11‐tetradecenyl acetate (E11‐14Ac) and 5% (E,E)‐9,11‐tetradecadienyl acetate (E9E11‐14Ac); antagonist: (Z)‐11‐tetradecenyl acetate (Z11‐14Ac)], codling moth, Cydia pomonella (L.) [pheromone: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone); antagonist: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate)], and gorse pod moth, Cydia ulicetana (Haworth) [pheromone: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate); putative antagonist: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone)]. In all three species, the antennal response to the antagonists was not significantly different from the antennal response to con‐specific sex pheromone compounds. In the field trapping experiments, significantly fewer males of all three species were attracted to the respective pheromone when blended with the behavioural antagonist compound. However, this response varied between the species, with lightbrown apple moth and codling moth showing stronger responses to the antagonist compounds than gorse pod moth. Both lightbrown apple moth and codling moth males were able to discriminate between pure pheromone and pheromone blended with the antagonist when placed in traps side‐by‐side separated by ca. 10 cm. The presence of the behavioural antagonist not only affected the catch of males of both species within their own traps but also affected the catch in the neighbouring trap that contained con‐specific sex pheromone; the catch of gorse pod moth was not reduced by the presence of codlemone in the neighbouring trap. These results suggest that strong behavioural antagonists such as codlemone acetate for codling moth and Z11‐14Ac for lightbrown apple moth induce their inhibition effect at a substantial distance downwind from the odour source; however, most of those males that were able to overcome this inhibition effect at the early stage of orientation to odour source, were able to discriminate between the pheromone source and the pheromone source admixed with behavioural antagonist. Moderate behavioural antagonists such as codlemone for gorse pod moth did not elicit a discrimination effect.     

Quantitation of the insect electroantennogram: Measurement of sensillar contributions,elimination of background potentials,and relationship to olfactory sensation

A quantitative study of the electroantennogram (EAG) of Trichoplusia ni (Hübner) response to sex pheromone has provided new information about the physiological basis of the EAG and its relationship to behaviour. Procedures were developed that selectively stimulated defined numbers of sensilla and eliminated extraneous olfactory stimuli. The results show that the EAG is linearly proportional to the number of antennal sensilla stimulated and clarify interpretation of the blank response. Studies with calibrated dispensers indicate that the EAG is related to pheromone concentration by a power function frequently associated with quantitative measures of electrophysiological and behavioural responses in other animals. Based on correlations between the EAG, behaviour, and single-neurone responses, a model is presented that interrelates these three parameters as different indicators of a single quantitative process in the central nervous system.     

Electroantennogram and behavioural responses of different forms of the bird cherry-oat aphid,Rhopalosiphum padi,to sex pheromone and a plant volatile

Winged (alate) virginoparae were induced in the laboratory by crowding the bird cherry-oat aphid, Rhopalosiphum padi (L.) under long-day conditions. Males and gynoparae (the winged female form that produces sexual females) were induced by short days. Electroantennogram (EAG) and behavioural responses were investigated in each of the three forms to two aphid sex pheromone components, (-)-(4aS,7S,7aR)-nepetalactol and (+)-(4aS,7S,7aR)-nepetalactone, and benzaldehyde, a volatile which is released by the winter host plant. All three compounds elicited EAG responses with the males showing the highest sensitivity to each compound. Both the nepetalactol and the nepetalactone elicited larger EAG responses in gynoparae than in the winged virginoparae but antennae from virginoparae were more responsive to benzaldehyde. Although the nepetalactone is not a sex pheromone component in R. padi the EAG responses were similar to those evoked by the nepetalactol, the sex pheromone, in all three aphid forms. In a linear-track olfactometer, significantly more male R. padi moved into air containing nepetalactol, nepetalactone or benzaldehyde than into a simultaneous choice of clean air (i.e. attraction) but nepetalactol was more attractive than nepetalactone. Males, however, showed no response to a mixture of nepetalactol and nepetalactone. Gynoparae were attracted only to the nepetalactol but were less sensitive than the males and showed no response to the nepetalactone or benzaldehyde. In contrast, alate virginoparae showed no behavioural responses to any of the compounds. The present study supports the idea that the male R. padi utilise both sex pheromone and benzaldehyde for mate/host-plant location in autumn. It also demonstrates, for the first time, polyphenic differences in the olfactory responses at the peripheral level between the two female forms. Such differences impact on the life-cycle strategy where winged virginoparae move between graminaceous summer host plants while gynoparae move from the summer hosts to the bird cherry, winter host. The latter move appears to be assisted by the sex pheromone released by sexual females, already present on that host, acting as an aggregation pheromone.     

Ultrastructure and potential role of integumentary glandular cells in adult male and female Callosobruchus subinnotatus (Pic) and C. maculatus (Fabricius) (Coleoptera : Bruchidae)

Transmission and scanning electron microscopy methods were used to study the ultrastructure of integumentary glandular cells that may be involved in the production of sex pheromones and other semiochemicals in Callosobruchus subinnotatus and C. maculatus (Coleoptera : Bruchidae). Additionally, we measured electroantennogram (EAG) responses of male and female antennae to solvent extracts and glassadsorbed volatiles from both sexes of C. maculatus in order to localize the source of the putative sex pheromone. Both species have numerous cuticular pores on the abdomen and thorax. These pores open via an epicuticular duct into a single type 3 secretory cell. Solvent extracts of the pygidium from the female elicit the highest EAG responses from male antennae, suggesting this area of the abdomen to be the source of the putative sex pheromone in C. maculatus.     

Environmental conditions terminate reproductive diapause and influence pheromone perception in the long‐lived moth Caloptilia fraxinella

Reproductive diapause enables long‐lived insects to time mating with environmental conditions suitable for offspring development. Plasticity in the perception of pheromones used in sexual communication may enable mate‐finding at the appropriate time of year. The moth Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) undergoes a 9‐month reproductive diapause, during which the male response to pheromone is plastic and is highest during the period of reproductive activity. The mechanisms controlling this pheromone response plasticity are not well‐understood, and the aim of the present study is to determine the main factors involved. In the present study, the impact of temperature, photoperiod, juvenile hormone analogue (JHA) and adult nutrition on diapause termination are tested using electroantennogram (EAG) and behavioural response to pheromone in male C. fraxinella. Eclosion in a state of reproductive diapause occurs in most males; diapause is maintained under short‐day or cool conditions indoors, or under natural conditions outdoors. Exposure to long‐day, warm conditions over a period of 4 weeks causes a small number of males to become behaviourally responsive to pheromone; a larger number of males become behaviourally responsive over a period of 3 months of post‐eclosion. Treatment with a JHA impacts male EAG and the behavioural response to pheromone during the period of reproductive diapause. A carbohydrate food source is not required by reproductively active adult male C. fraxinella to respond to pheromone and express mate location behaviours. The main factors involved in controlling male pheromone response plasticity and the implications of these factors for the C. fraxinella population in its expanded range are discussed.     

Electrophysiological correlates of attraction in Trichoplusia ni

A quantitative comparison was made between pheromone-induced electroantennogram (EAG) potentials and the attraction of male cabbage loopers, Trichoplusia ni. For this comparison, duplicate pheromone dispensers were used in both assays. The slope of the function of evoked EAG potentials was the same as the slope of the function of percentage attraction to different amounts of pheromone, but the EAG was calculated to be about 3 × 10⁴ times less sensitive than the attraction response. Thus, the EAG of T. ni was not a reliable indicator of relative attraction to various batches of synthetic pheromone, and no difference in the evoked EAG was observed between an inhibitor of the behavioural response to the pheromone and the pheromone itself.