Differential electroantennogram response of females and males of two parasitoid species to host-related green leaf volatiles and inducible compounds

Parasitoids employ different types of host-related volatile signals for foraging and host-location. Host-related volatile signals can be plant-based, originate from the herbivore host or produced from an interaction between herbivores and their plant host. In order to investigate potential sex- and species-related differences in the antennal response of parasitoids to different host-related volatiles, we compared the electroantennogram (EAG) responses of both sexes of the specialist parasitoid, Microplitis croceipes (Cresson), and the generalist, Cotesia marginiventris (Cresson), to varying doses of selected plant-based host-related volatiles: two green leaf volatiles (cis-3-hexenol and hexanal) and three inducible compounds (cis-3-hexenyl acetate, linalool, and (E,E)-alpha-farnesene). Mating had no significant effect on EAG response. Females of both species showed significantly greater EAG responses than conspecific males to green leaf volatiles, which are released immediately after initiation of herbivore feeding damage. In contrast, males showed greater responses than conspecific females to inducible compounds released much later after initial damage. Cotesia marginiventris females and males showed greater EAG responses than counterpart M. croceipes to the tested compounds at various doses, suggesting that the generalist parasitoid shows greater antennal sensitivity than the specialist to the tested host-plant volatiles. These results are discussed in relation to the possible roles of green leaf volatiles and inducible compounds in the ecology of female and male parasitoids.     

松墨天牛成虫对幼虫虫粪挥发性物质的触角电位反应及林间驱避试验

为了研制松墨天牛Monochamus alternatus Hope驱避剂,本文利用触角电位技术和田间试验的方法研究了松墨天牛雌雄成虫对幼虫虫粪挥发性物质的触角电位反应及幼虫虫粪己烷提取物、合成化合物混合物的林间驱避作用。结果表明：α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯和长叶烯均能引起松墨天牛雌雄成虫一定的触角电生理反应,而4-甲基-2,6-二叔丁基苯酚不能引起松墨天牛雌雄成虫的触角电生理反应。林间驱避试验结果说明,幼虫虫粪的己烷提取物处理过的树干上的刻槽数明显少于对照树干上的刻槽数,二者具有极显著差异;有合成化合物的混合物存在的诱捕器诱捕到的雌虫数（平均值3.80±1.02）与对照诱捕到的雌虫数（平均值16.80±1.16）差异极显著。结果显示α-蒎烯、β-蒎烯、3-蒈烯、柠檬烯、长叶烯和4-甲基-2,6-二叔丁基苯酚的混合物对松墨天牛雌虫具有驱避作用,有望开发出一类新的驱避剂。     

马尾松枝条挥发性组分的鉴定及松墨天牛对其触角电生理反应

为研究松墨天牛Monochamus alternatus Hope取食期引诱剂,利用气相色谱-质谱(GC-MS)联用技术并与标样核对分析了马尾松(Pinus massoniana Lamb.)枝条挥发性气味的化学组成。结果表明,马尾松1年生、2年生、3年生枝条气味均由8种萜烯类物质组成,但各组分相对含量不同。经方差分析,α-蒎烯、莰烯、β-蒎烯、柠檬烯、萜品油烯、β-石竹烯在3种枝条中的相对百分含量的差异均达到极显著水平。1年生枝条中α-蒎烯、莰烯和萜品油烯的相对含量最小,分别为20.81%、0.43%和4.74%,而β-蒎烯、月桂烯和柠檬烯的相对含量最高,分别为12.37%、4.33%和4.53%。鉴定的化合物对松墨天牛雌雄成虫的触角电生理反应的实验,结果表明,松墨天牛雌雄成虫对α-蒎烯的反应最强,对β-石竹烯的反应最弱。     

Electroantennogram responses of the carrot fly, Psila rosae, to volatile plant components

ABSTRACT. Electroantennogram (EAG) responses of male and female carrot flies, Psila rosae F. (Diptera: Psilidae), were recorded to thirty-six volatile plant constituents. The most distinct EAG responses were obtained to: (1) the general green leaf volatiles 1-hexanol, trans-2-hexen-1-ol and cis-3-hexen-1-ol, their isomers cis-2-hexen-1-ol and trans-3-hexen-1-ol, the alcohol 1-heptanol, the ester cis-3-hexenyl acetate and the leaf aldehydes hexanal and trans-2-hexenal, and (2) from four compounds associated with the umbelliferous host plants of this insect, namely trans-methyl-iso-eugenol, β-caryophyllene, linalool and trans-2-nonenal. Higher responses were elicited by the leaf aldehydes than by the corresponding alcohols. Although the absolute amplitude of the female response was over twice that of the male, there were no differences between the relative responses to the compounds tested in both sexes, with the exception of a much higher response to the leaf aldehydes in the male. The shape of the EAG evoked by the various compounds was consistently different, with the slowest recovery being recorded for trans-methyl-iso-eugenol. While the antennal olfactory receptors of the carrot fly are sensitive to the closely related general green leaf volatiles, they are most specifically tuned to the aldehyde component of this green odour complex. In addition, the ability of this insect to discriminate between different plants may be augmented by the perception of a group of more host specific volatiles. The conformity of the responses of males and females to the compounds tested may indicate that host plant volatiles plays an additional role as an aggregation cue for both sexes.     

Electroantennogram responses of a parasitic wasp, Microplitis croceipes, to host-related volatile and anthropogenic compounds

The parasitic wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) showed its own characteristic electroantennogram (EAG) response profiles to 13 host‐related (cis‐3‐hexenol, α‐pinene (R)‐(+)‐limonene (S)‐(–)‐limonene, trans‐β‐ocimene (±)‐linalool, (–)‐trans‐caryophyllene, α‐humulene, nerolidol, trans‐nerolidol, cis‐nerolidol, methyl jasmonate and indole) and four anthropogenic (2‐diisopropylaminoethanol, 2,2′‐thiodiethanol, 2‐methyl‐5‐nitroaniline and cyclohexanone) volatile compounds. These profiles were similar between males and females except for 2‐diisopropylaminoethanol, which elicited significantly larger EAG responses in males. Among the compounds tested, cis‐3‐hexenol, linalool and cyclohexanone elicited the largest EAG responses. EAG responses were not influenced by the age of wasps between 1 and 13 days after emergence. EAG responses were dose‐dependent, and highly EAG‐active compounds elicited significant EAG responses with less than 10 μg of the compounds at source. Quantification of compounds released from an odour cartridge indicates that release rate is highly dependent on the chemical nature of stimuli, showing up to 10 000‐fold differences in the amount released between different compounds when the same amount was loaded in the odour cartridge. Wasps having undergone a behavioural training regime to be attracted to either cyclohexanone or methyl jasmonate did not show any differences in EAG responses from those of untrained wasps.     

Electrophysiological and behavioural responses of Scyphophorus acupunctatus (Col., Curculionidae) to Agave tequilana volatiles

Abstract:  The weevil Scyphophorus acupunctatus Gyllenhal (Col., Curculionidae) is the most important insect pest of cultivated agaves in Mexico. The objective of this study was to search for potential attractants for this weevil species from the freshly cut fleshy leaves of healthy Agave tequilana Weber var. Blue plants. Combined gas chromatography-electroantennography (GC-EAD) analysis of A. tequilana volatile extracts showed that seven peaks elicited antennal responses from males and females. Five of these peaks were identified by gas chromatography-mass spectrometry (GC-MS) as o -xylene, α -pinene, 3-carene, γ -terpinene and linalool. Electroantennogram (EAG) records of both sexes to 1-, 10- and 100- μ g-stimulus load of these five compounds showed that there was a dose effect on the EAG responses for linalool, 3-carene and α -pinene, but not for γ -terpinene and o -xylene. There were no sexual differences between male and female EAG responses to any of the compounds tested. Y-tube olfactometer bioassays of the compounds showed that males and females were attracted to α -pinene, 3-carene, γ -terpinene and/or linalool at doses of 1 and 10  μ g, while weevils were repelled by linalool at a dose of 100  μ g.     

Electroantennogram responses of Chrysoperla carnea (Stephens) to volatiles

Electrophysiological responses of adult males and females of C. carnea to commonly occurring plant volatiles were recorded using the electroantennogram technique. Responses to 28 volatiles evaluated indicate that both depolarization and recovery to the baseline were rapid in females compared to males. Normalized EAG responses relative to the standard, trans-caryophyllene reveal significant differences between the chemicals as also between the sexes. The response of males to several of the compounds, particularly the terpenoids was higher than females. The pooled averages to the different classes of chemical compounds reveal greater response for fatty acid derivatives and terpenoids, particularly the oxygenated monoterpenes and the sesquiterpenes. These findings are discussed in relation to volatiles released in the cotton ecosystem.     

Host recognition by a polyphagous lepidopteran (Helicoverpa armigera): primary host plants, host produced volatiles and neurosensory stimulation

Abstract An important question in the host‐finding behaviour of a polyphagous insect is whether the insect recognizes a suite or template of chemicals that are common to many plants? To answer this question, headspace volatiles of a subset of commonly used host plants (pigeon pea, tobacco, cotton and bean) and nonhost plants (lantana and oleander) of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) are screened by gas chromatography (GC) linked to a mated female H. armigera electroantennograph (EAG). In the present study, pigeon pea is postulated to be a primary host plant of the insect, for comparison of the EAG responses across the test plants. EAG responses for pigeon pea volatiles are also compared between females of different physiological status (virgin and mated females) and the sexes. Eight electrophysiologically active compounds in pigeon pea headspace are identified in relatively high concentrations using GC linked to mass spectrometry (GC‐MS). These comprised three green leaf volatiles [(2E)‐hexenal, (3Z)‐hexenylacetate and (3Z)‐hexenyl‐2‐methylbutyrate] and five monoterpenes (α‐pinene, β‐myrcene, limonene, E‐β‐ocimene and linalool). Other tested host plants have a smaller subset of these electrophysiologically active compounds and even the nonhost plants contain some of these compounds, all at relatively lower concentrations than pigeon pea. The physiological status or sex of the moths has no effect on the responses for these identified compounds. The present study demonstrates how some host plants can be primary targets for moths that are searching for hosts whereas the other host plants are incidental or secondary targets.     

Volatile attractants for the common bluebottle, Graphium sarpedon nipponum, from the host, Cinnamomum camphora

Floral scent has been shown to elicit behavioral responses by butterflies which forage for flowers after receiving appropriate signals. In comparison with investigations about the role of floral scent, those of foliar odor are, however, very few. In this study, the foliar volatiles of Cinnamomum camphora (Lauraceae), which had been collected by air entrainment, exhibited activities toward Graphium sarpedon nipponum (Papilionidae) in both electrophysiological and behavioral tests. The volatiles were analyzed by capillary gas chromatography with electro-antennographic detection (GC-EAD). Two electrophysiological active compounds were found which were determined as nonanal and decanal by using gas chromatography-mass spectrometry (GC-MS). Female butterflies generally tend to show a greater EAG response than males to the headspace volatiles and EAG-active aldehydes. Two EAG-active aldehydes were found in attractant tests to be attractive to both sexes of the butterfly when treated individually. Although the difference between the sexes was not significant, the female butterflies' preference tended to be more active than that of the males.     

Physiological state influences the antennal response of Anastrepha obliqua to male and host volatiles

The sexual and host‐related behaviours of the fruit fly Anastrepha obliqua Macquart (Diptera: Tephritidae) are mediated by volatile compounds. However, whether the physiological state of this species affects its antennal and behavioural responses to semiochemicals is unknown. The effects of age, mating status, diet and the topical application of methoprene, a Juvenile hormone analogue (JHA), on the antennal sensitivity of this tephritid fruit fly species to selected male [(Z)‐3‐nonenol] and host fruit volatiles (ethyl benzoate, ethyl hexanoate, ethyl butyrate and trans‐β‐ocimene) are investigated using electroantennography (EAG). Overall, (Z)‐3‐nonenol and ethyl benzoate elicit the highest EAG responses in both sexes. Flies of both sexes aged 1, 5 and 10 days old show higher EAG responses to the tested compounds compared with flies aged 20 days old. Virgin females and males show higher EAG responses to volatile compounds than mated flies. Females and males fed with sugar plus protein show higher antennal responses to volatiles compared with flies fed sugar or protein alone. Flies of both sexes treated with methoprene show higher antennal responses than flies treated with acetone (control). These results suggest that the peripheral olfactory system in A. obliqua is modulated by the physiological state of the flies.     

Role of host volatiles in mate location by the Japanese pine sawyer, Monochamus alternatus hope (Coleoptera: Cerambycidae)

We evaluated the responses of male and female Monochamus alternatus Hope (Coleoptera: Cerambycidae) to various terpenes commonly associated with host trees. Electroantennogram (EAG) tests were conducted with 12 plant volatile compounds and ethanol. Antennae of both sexes were highly sensitive to (R)-(+)-alpha-pinene, (+)-3-carene, (-)-beta-pinene, and terpinolene. Both sexes of M. alternatus were attracted by traps baited with (+)-alpha-pinene, (-)-beta-pinene, (+)-3-carene, or terpinolene. Our results support the first of the three-stage hypothesis posed by Ginzel and Hanks that suggests that location of stressed trees by cerambycids involves three stages: (1) both sexes locate larval hosts by using plant volatiles as kairomones; (2) males produces sex pheromones to attract females after both sexes land on the larval hosts; (3) males and female recognize each other by contract pheromones in their epicuticular wax layer. Males and females showed differences in their EAG responses to several compounds, including (R)-(+)-alpha-pinene, (-)-beta-pinene, myrcene, (+)-3-carene, (R)-(+)-limonene, terpinolene, and trans-caryophyllene. In all cases, males exhibited greater sensitivity than females. In laboratory assays, male M. alternatus showed strong preference for 1% (+)-alpha-pinene and 1% (-)-beta-pinene over other compounds. In field assays, traps baited with (+)-alpha-pinene, (-)-beta-pinene, (+)-3-carene, or terpinolene caught more beetles than control traps. We found strong male bias in beetle catches in baited traps and those captured on the stem of stressed trees despite a strong female bias in emerging beetles in 2004. We hypothesize that male M. alternatus are more responsive than females to plant volatiles and that males have more capacity than females in finding mating locations.     

Role of plant volatiles in host plant location of the leafminer, Liriomyza sativae (Diptera: Agromyzidae)

Abstract The role of plant volatiles in host plant location of the leafminer Liriomyza sativae Blanchard was studied. Four types of antennal sensilla were identified on the funiculus by scanning electron microscopy: trichoid, basiconic, clavate and grooved sensilla. An olfactory pit, containing groups of sensilla, was present on the ventral side of the funiculus. No sexual difference was detected in sensilla diversity and distribution. In behavioural assays, both males and females were attracted by the odour of the bean Phaseolus vulgaris L. They had distinct EAG responses to the bean odour. No significant sexual difference was found in behaviour or EAG responses.
Electroantennograms were recorded from female L. sativae to 14 plant volatile compounds. The most distinct EAG responses were obtained for: (1) the general green leaf volatiles 1-hexanol (E)-2-hexen-1-ol, (E)-3-hexen-1-ol and its isomers, (Z)-3-hexen-1-ol, the acetate (E)-3-hexenylacetate and the aldehyde hexanal; and (2) limonene, a compound associated with tomato, which is a key host plant of this insect. Other volatile compounds associated with host plants, such as α-pinene, myrcene, β-caryophyllene, and eugenol did not elicit responses. The ability of this insect to locate a host plant appears to be augmented by the perception of a combination of host-specific and general green leaf volatiles. A modification of the EAG recording method of Dipteran species was provided.     

Electroantennogram responses of Apanteles obliquae (Hym., Braconidae) to various infochemicals

Abstract:   The electroantennogram recording technique (EAG) was used to study the olfactory sensitivity of Apanteles obliquae (Hym., Braconidae), a gregarious larval endoparasitoid of Spilosoma obliqua (Walker) (Lep., Arctiidae), to 25 general plant volatiles belonging to alcohol, aldehyde and terpenoid groups and also to volatiles from the host and plant–host complex. The EAG data indicated different olfactory sensitivity between the sexes, not only to individual plant volatiles but also to the volatiles from host and plant–host complex. Females were found to be more responsive than males. However the synthetic sex pheromone blend of the host insect elicited similar EAG responses in both sexes. The EAG data of the present study is correlated with the reported behaviour observed in other parasitoids.     

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds

Two Oedipodinae grasshopper species Oedaleus decorus asiaticus B.-Bienko and Angaracris baraben-sis Pall. (Orthoptera: Acrididae) are important pests on the natural grasslands in Inner Mongolia and often require insecticide treatment during outbreaks[1]. They both prefer overgrazed steppes and xerophytous habi-tats, and have thus been suggested as indicator species for steppe deterioration in typical steppe zones of In-ner Mongolia[2]. The two species have a sympatric distribution and sync…     

Increased EAG responses of tortricid moths after prolonged exposure to plant volatiles: evidence for octopamine-mediated sensitization

As measured by electroantennograms (EAG), both male and female obliquebanded leafrollers, Choristoneura rosaceana (Harris), and redbanded leafrollers, Argyrotaeniavelutinana (Walker), were similarly sensitive to host-related plant volatiles: trans-2-hexenal, benzaldehyde, 1-hexenol, cis-3-hexen-1-ol, geraniol, linalool, (+)-limonene, hexenal and trans-2-hexenol. Females of both species were similarly sensitive to the shared major component of their sex-attractant pheromone ((Z)11-14:Ac). Continuous 60 min pre-exposure of male and female C. rosaceana and A. velutinana to successively higher concentrations of a mixture of the nine plant volatiles in Teflon chambers with continuous air exchange caused a dosage-dependent increase in subsequent responsiveness (sensitization) to green leaf volatiles, as measured by EAGs. In addition, 60 min of pre-exposure of male C. rosaceana to certain individual volatiles ((+)-limonene, geraniol, benzaldehyde) increased EAGs nearly as much as did the mixture of nine volatiles. Pre-exposures to the nine plant-volatile mixture at concentrations achieved by 100 microg and 1 mg loading dosages in 100 microl of mineral oil significantly increased EAG depolarization to pheromone (cross-sensitization) in males but not females of both moth species. Antennae of male C. rosaceana pre-injected with 100 microg of octopamine (OA) without volatile pre-exposure exhibited sensitization nearly identical to that induced by pre-exposing moths to sensitizing concentrations of the plant-volatile mixture. Moreover, injection of the OA antagonist chlorpromazine (CP) blocked sensitization by the plant-volatile pre-exposure. Collectively, these findings suggest that exposures of tortricid moths to certain host-plant related volatiles may modulate subsequent olfactory sensitivity to behaviorally relevant chemical cues and that plant-volatile induced sensitization may be octopamine mediated.     

苹毛丽金龟对植物挥发物成分的触角电位及行为反应

为筛选适宜的苹毛丽金龟Proagopertha lucidula (Faldermann)引诱剂化学物质, 对已报道的金龟子科两性引诱剂单一组分进行了触角电位（EAG）和Y型嗅觉仪中的嗅觉反应测定。结果表明: 在10 μg刺激剂量下测试的11 种植物挥发物中, 只有顺-3-己烯-1-醇、香叶醇、茴香脑和丁香酚有明确的EAG反应值, 其他7种化合物具有弱反应值。剂量反应曲线表明, 具有明确的EAG活性的4种化合物激发的反应强度与化合物的剂量呈正相关。在Y型嗅觉仪中, 顺-3-己烯-1-醇、香叶醇、茴香脑和丁香酚4种化合物在1, 10, 100 μg剂量下的行为反应百分率都显著高于对照溶剂正己烷, 且雌雄之间无显著差异。该研究结果可为开发苹毛丽金龟田间引诱剂奠定基础。     

Olfactory responses of the leafminer Liriomyza sativae (Dipt., Agromyzidae) to the odours of host and non-host plants

Abstract: Electroantennogram (EAG) responses of male and female leafminer Liriomyza sativae Blanchard to 15 species of host and non-host plant odours were recorded. The most distinct EAG responses of both sexes were obtained in the host plants bean and tomato. EAG responses to other host plants, such as cucumber, celery, chrysanthemum, towel gourd and cotton were reduced. Odours of non-host plants, such as Chinese rose, tobacco and morning glory elicited minimal EAG responses. In a behavioural study, both sexes of L. sativae were more attracted by the odours of host plants than of non-host plants. Thus, olfactory cues are important for host plant location by L. sativae . In addition, the combination of strong EAG and behavioural responses for both males and females to specific plant odours suggests that host plant volatiles can be important as aggregation cues for both sexes.     

Sex differentiation studies relating to releaser aggregation pheromones of the desert locust,Schistocerca gregaria

Behavioural responses of nymphs and adults in the gregarious phase of the desert locust,Schistocerca gregaria (Forskal) (Orthoptera: Acrididae) were investigated in a single-chamber bioassay system to a choice of two columns of air, one permeated with airborne volatiles emanating from either sex of nymphs or adults and the other untreated. There was no sexual differentiation in the production of or response to nymphal volatiles. Young adults of either sex did not produce a stimulus with significant activity. Of the older adults, only the males produced the aggregation stimulus to which both sexes were equally responsive. Charcoal-trapped volatiles from the two sexes of nymphs and adults evoked similar aggregation responses. Antennae of the older adults showed significantly higher EAG responses than those of fifth instar nymphs to all four volatile collections, of which volatiles from older adult males were the most stimulatory and evoked the highest EAG amplitudes.     

华北大黑鳃金龟对桃树挥发物的电生理反应

【目的】华北大黑鳃金龟Holotrichia oblita是一种分布范围广,寄主种类多的农业害虫。本研究鉴定了桃树顶空挥发物中对华北大黑鳃金龟雌虫具有触角电生理活性的化合物,并探索桃树挥发物活性成分的剂量对华北大黑鳃金龟雌、雄虫触角电生理反应的影响。【方法】采用顶空吸附法收集桃树枝叶挥发物,用气相色谱 触角电位联用技术(GC-EAD)和气相色谱 质谱联用技术(GC-MS)鉴定有电生理活性的桃树挥发物成分,最后用触角电位(electroantennograph, EAG)技术测试这些挥发物在0.01,0.1, 1, 10和100 μg剂量下引起的华北大黑鳃金龟雌、雄成虫EAG反应。【结果】桃树挥发物中能引起华北大黑鳃金龟雌成虫触角电生理反应的成分有7种,包括Z-β-罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯以及2种未知化合物。所测试的对华北大黑鳃金龟雌成虫触角具有电生理活性的5种桃树挥发物成分在各剂量下都能引起雌、雄成虫明显的EAG反应。雌、雄虫对同种物质的EAG反应随着剂量的增加而有增大的趋势,并且雌虫的EAG反应显著高于雄虫。【结论】桃树挥发物中,罗勒烯、顺-3-己烯乙酸酯、顺-3-己烯醇、壬醛、水杨酸甲酯均能引起华北大黑鳃金龟雌、雄成虫的剂量依赖性的触角电生理反应,而且存在显著的性别差异。可利用这些化合物开展行为反应和田间诱集试验,进一步验证其对华北大黑鳃金龟的引诱活性。     

豆野螟成虫触角对植物挥发性和性信息素化合物的触角电位反应

以顺3-己烯乙酸酯为标准化合物,研究了豆野螟雌、雄成虫触角对不同浓度的植物挥发性和性信息素化合物组分的触角电位（EAG）反应.结果表明：豆野螟雌、雄成虫触角对植物挥发性气味具有强烈的EAG反应,但在大部分浓度下,雌、雄虫的反应没有显著差异.在测试的9种植物挥发性化合物中,雌、雄虫对高浓度反-2-己烯醛刺激的相对EAG反应的最大值分别达到250%和260%,且雌、雄虫触角对这种化合物的EAG反应的形状也有很大差异;但对豇豆花气味中的柏木烯和柏木脑没有明显的EAG反应.雌、雄蛾对性信息素都有明显反应,且雌、雄虫的反应存在显著差异,雄虫触角对性信息素化合物主要组分（反10,反12）-十六碳二烯醛的EAG反应的最大值达到250%,远超过雌虫反应的最大值(53%).雌、雄成虫这种神经感觉反应的差异反映了它们在感器结构、功能和行为上的差异.