Attract Virgin Females Research Articles

Sex pheromones: Made with a little help from my (bacterial) friends

Males of the olive fruit fly Bactrocera dorsalis team up with Bacillus bacteria in their rectal glands to synthesize 2,3,5-trimethylpyrazine (TMP) and 2,3,5,6-tetramethylpyrazine (TTMP) from glucose and threonine. The bacterially produced TMP and TTMP are utilized as sex pheromones to attract virgin females.

Evidence for Long-range Mate Attraction Mediated By a Male-produced Sex Pheromone in Paysandisia archon (Lepidoptera: Castniidae)

Paysandisia archon (Lepidoptera: Castniidae) is a pest on palms in Europe. The moth was introduced about twenty years ago, when infected palms were imported from South America. In P. archon, little is known about mate location and the putative activity of the male-produced sex pheromone. The aim of this study was, therefore, to study olfactory responses of P. archon to conspecifics, with and without visual cues, in a wind tunnel and in the field. Results showed that the virgin males exhibiting the scratching behavior, whether they were visible or not, attracted virgin females at long range. Females approached the males, and some landed close to them. In P. archon, the mate location is thus mediated by a long-range pheromone released by males during the scratching behavior. Our findings are providing new insights into the chemical ecology and mate location in P. archon and may serve to further develop efficiency in handling the pest.

Enantioselective synthesis and determination of the absolute configuration of the male sex pheromone of the parasitoid wasp Urolepis rufipes.

Males of the parasitoid wasp Urolepis rufipes use 2,6-dimethyl-7-octene-1,6-diol as a sex pheromone to attract virgin females. Herein, we determine the absolute configuration of the pheromone to be (2S,6S)-2,6-dimethyl-7-octene-1,6-diol (2S,6S-6) and present a stereoselective synthesis of the natural enantiomer of this new linalool derivative. In addition, we show that female wasps respond to the natural 2S,6S-6 stereoisomer while 2R,6S-6 is behaviorally inactive.

Male Sex Pheromone of the Parasitoid Wasp Urolepis rufipes Demonstrates Biosynthetic Switch Between Fatty Acid and Isoprenoid Metabolism Within the Nasonia Group

Sex pheromones play a crucial role in the mate finding process of insects. The information has to be encoded in a species specific manner to avoid fitness costs due tocourtship by or even mismating with closely related species. Hence, sex pheromones typically diversify when new species evolve. Pheromones of closely related species typically vary in their chemical composition, but the compounds they use are often biosynthetically related. The biosynthetic pathways of insect pheromones are variations of conserved pathways that lead to primary and secondary metabolites. A switch from one pathway to another, particularly in species that use the same type of pheromone glands, is the exception. Here we use chemical analyses and behavioral bioassays to examine the male sex pheromone of the parasitoid wasp Urolepis rufipes. The genus Urolepis is most closely related to Nasonia and Trichomalopsis, forming the so-called “Nasonia group”. All Nasonia species and T. sarcophagae, the only Trichomalopsis species studied so far, produce fatty acid-derived hydroxylactones in their rectal vesicle. The pheromones are deposited on the ground and other substrates and attract virgin females. We show that males of U. rufipes produce a sex pheromone in the same gland and use it in the same manner as the other species of the Nasonia group. Structure elucidation and stable isotope labelling experiments revealed, however, that the U. rufipes pheromone is 2,6-dimethyl-7-octene-1,6-diol, a monoterpenoid derived from the mevalonate pathway. This suggests a biosynthetic switch between the fatty acid and isoprenoid metabolism in the Nasonia group.

Functional characterisation of two Δ12-desaturases demonstrates targeted production of linoleic acid as pheromone precursor in Nasonia.

Insect pheromones are often derived from fatty acid metabolism. Fatty acid desaturases, enzymes introducing double bonds into fatty acids, are crucial for the biosynthesis of these chemical signals. Δ12-desaturases catalyse the biosynthesis of linoleic acid by introducing a second double bond into oleic acid, but have been identified in only a few animal species. Here, we report the functional characterisation of two Δ12-desaturases, Nvit_D12a and Nvit_D12b, from the parasitic wasp Nasonia vitripennis. We demonstrate that Nvit_D12a is expressed in the rectal vesicle of males where they produce a linoleic acid-derived sex pheromone to attract virgin females. 13C-labelling experiments with Urolepis rufipes, a closely related species belonging to the 'Nasonia group', revealed that females, but not males, are able to synthesise linoleic acid. U. rufipes males produce an isoprenoid sex pheromone in the same gland and do not depend on linoleic acid for pheromone production. This suggests that Δ12-desaturases are common in the 'Nasonia group', but acquired a specialised function in chemical communication of those species that use linoleic acid as a pheromone precursor. Phylogenetic analysis suggests that insect Δ12-desaturases have evolved repeatedly from Δ9-desaturases in different insect taxa. Hence, insects have developed a way to produce linoleic acid independent of the omega desaturase subfamily which harbours all of the eukaryotic Δ12-desaturases known so far.

Electrophysiological and behavioural responses of the Eucalyptus weevil, Gonipterus platensis, to host plant volatiles

Gonipterus spp. weevils (Coleoptera, Curculionidae) are pests of Eucalyptus stands in many world regions. Here, we determined the host plant volatiles that might mediate host selection behaviour in G. platensis. Eucalyptus globulus volatile organic compounds were collected by headspace solid-phase microextraction, monolithic material sorption extraction and simultaneous distillation–extraction. Gas chromatography–mass spectrometry/electroantennographic detection (GC–MS/EAD) was used to determine which compounds triggered antennal responses in the insect. Further chemical analysis of the extracted compounds was conducted using gas chromatography–mass spectrometry (GC/MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC/TOFMS). Gonipterus platensis antennal response was elicited by 51 host plant volatiles and was subsequently confirmed for 33 of these compounds using commercial standards. The behavioural response of G. platensis to individual compounds was assessed in a two-arm olfactometer with ten parallel walking chambers, coupled to video tracking and data analysis software. Weevils of known age, sex and mating status were tested. We identified eight kairomones and two allomones. The behavioural responses differed depending on insect sex and mating status. Three compounds attracted virgin females or both sexes: camphene, (+)-α-pinene and 2-phenylethanol and are potential candidates for application in integrated pest management approaches. Furthermore, the two allomones may have potential use for developing push–pull strategies.

Pheromone Communication in Nasonia vitripennis: Abdominal Sex Attractant Mediates Site Fidelity of Releasing Males

Males of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae) use a substrate-borne sex pheromone to attract virgin females. The pheromone is synthesized in the rectal vesicle and deposited via the anus by dabbing movements of the abdominal tip. The chemicals attracting the females are composed of a mixture (4R,5R- and (4R,5 S)-5-hydroxy-4-decanolides (HDL) being synergized by the trace component 4-methylquinazoline (4-MeQ) which is not attractive for females when offered alone. Here we show that male pheromone deposits are not only attractive to virgin females but also for the releasing males themselves. In an olfactometer bioassay, males were strongly attracted by their own pheromone markings but were unable to discriminate between their own markings and those deposited by other males. Polar fractions of pheromone gland extracts containing the HDLs and 4-MeQ were also highly attractive for males. Bioassays using synthetic pheromones in natural doses revealed that combinations of HDL/4-MeQ and 4-MeQ alone attracted males whereas the HDLs alone were behaviorally inactive. Furthermore, males did not discriminate between HDL/4-MeQ and 4-MeQ alone. We conclude that the trace component 4-MeQ mediates site fidelity of N. vitripennis males at sites previously marked with the abdominal sex pheromone. The use of 4-MeQ to stay at and to return to scent-marked patches rather than marking new ones might be a strategy to economize semiochemical use in N. vitripennis males.

Mechanism and Behavioral Context of Male Sex Pheromone Release in Nasonia vitripennis

Males of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae) attract virgin females by releasing a sex pheromone composed of (4R,5R)- and (4R,5S)-5-hydroxy-4-decanolide (HDL). The pheromone is biosynthesized in the rectal vesicle of males. In the present study, we investigated the mechanism and behavioral context of pheromone release, and determined the range of activity and the longevity of the chemical signal. Our data show that the sex pheromone of N. vitripennis is substrate-borne and is deposited on surfaces by dabbing movements of the abdominal tip, a behavior previously described in N. vitripennis males as 'abdomen dipping'. Chemical markings deposited by a single male were highly attractive to virgin females. Chemical analyses revealed the presence of HDL in surface washings of marked areas, and HDL amounts correlated with male marking activity. Pheromone deposition occurred spontaneously without any additional cues being present, but marking intensity increased greatly after copulation or after a single contact with a virgin female. In contrast, marking intensity was not influenced by the presence of host puparia. Male pheromone deposits were perceived by females in a still-air olfactometer at distances of up to 4.5 cm and remained attractive for at least 2 h. The function of the substrate-borne sex pheromone is discussed with respect to the mating system of N. vitripennis.

An epoxide hydrolase involved in the biosynthesis of an insect sex attractant and its use to localize the production site

Epoxide hydrolases (EHs) are enzymes occurring in virtually any living organism. They catalyze the hydrolysis of epoxide containing lipids and are involved in crucial mechanisms, such as the detoxification of xenobiotics or the regulation of inflammation and blood pressure. Here, we describe a function of a putative EH gene in the biosynthesis of a sex attractant in the jewel wasp Nasonia vitripennis and use this gene to localize the site of pheromone production. Males of this parasitic wasp release a mixture of (4R,5R)-( threo-) and (4R,5S)-( erythro-)5-hydroxy-4-decanolide (HDL) to attract virgin females. Using a stable isotope labeled precursor, we demonstrated that vernolic acid ( erythro-12,13-epoxy-octadec-9Z-enoic acid) is converted by N. vitripennis males to threo-HDL. This suggested the involvement of an EH in hydrolyzing the fatty acid epoxide under inversion of the stereochemistry into the respective diol, which might be further processed by chain shortening and lactonization to HDL. We cloned a putative N. vitripennis EH gene (Nasvi-EH1) encoding 470 amino acids and localized its transcripts in the male rectal papillae by in situ RT-PCR. Chemical analyses and histological studies confirmed that males synthesize the sex attractant in the rectal vesicle and release it via the anal orifice. Involvement of Nasvi-EH1 in HDL biosynthesis was established by RNAi-mediated gene silencing. Injection of Nasvi-EH1 dsRNA into male abdomens inhibited pheromone biosynthesis by 55% and suppressed the targeted gene transcripts in the rectal vesicle by 95%.

Whole body extract of Mediterranean fruit fly males elicits high attraction in virgin females

AbstractThe search for effective female attractants emanating from the host or body of fruit flies has been an area of intensive research for over three decades. In the present study, bodies of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), were extracted with diethyl ether or methanol and subjected to gas chromatography–mass spectrometry. Analysis revealed substantial qualitative and quantitative differences between males from a laboratory culture and wild males captured alive in an orchard. Most notably, the hydrocarbon sesquiterpene (±)‐α‐copaene, which is known to be involved in the sexual behaviour of the species, was found in substantial amounts in wild males, but was not detected in laboratory males. In laboratory tests, 15 laboratory or wild male equivalents of diethyl ether extracts or combined diethyl ether and methanol extracts, or, to a lesser extent, methanol extracts alone, were found to attract virgin females. In a citrus orchard, traps baited with combined diethyl ether and methanol extracts of wild males attracted significantly more virgin females than traps baited with various doses of pyranone or blends of other compounds identified in the extracts or reported in the literature, such as ethyl acetate, ethyl‐(E)‐3‐octenoate, and 1‐pyrroline. Traps baited with blends of compounds, however, displayed substantial attractiveness compared to control (non‐baited) traps. These results are important for better understanding the mating system of C. capitata as well as for further improving existing monitoring and control systems.

Atypical Secretions of the Male Cephalic Labial Glands in Bumblebees: The Case of Bombus (Rhodobombus) mesomelasGerstaecker (Hymenoptera, Apidae)

In bumblebees, the male secretion of the cephalic labial gland is species-specific. It is highly involved in the nuptial behavior, acting as a sexual attracting pheromone. Therefore, it is also used to accurately identify the species. In contrast to this common scheme, the secretions of Bombus mesomelas are found to be strongly reduced and do not include the most volatile compounds that are present in the secretions of all the other studied bumblebee species. These secretions correspond to cuticular hydrocarbons that can be found in all bumblebee species. This was also the case for another bumblebee species from the same Rhodobombus subgenus: Bombus pomorum. This atypical composition of the male cephalic labial gland secretions seems to indicate that, at least for these two species of Rhodobombus, these secretions are not used to attract virgin females from a long distance, as it is the case for all the other bumblebee species studied.

A male sex pheromone in a parasitic wasp and control of the behavioral response by the female's mating status

Male insects may increase their chance of successful reproduction by releasing pheromones that attract females or elicit sexual acceptance. In parasitic wasps, male pheromones have been suggested for a few species but no chemicals have been identified so far. Here we report the first identification of a male sex pheromone in parasitic Hymenoptera. In abdomens of male jewel wasps, Nasonia vitripennis Walker, we found a mixture of (4R,5R)- and (4R,5S)-5-hydroxy-4-decanolide (HDL), which was released intermittently and attracted virgin females, but no males, in an olfactometer bioassay. However, only a few minutes after copulation mated females avoided the male-derived pheromone. Neither preference nor avoidance was shown by mated females after 24 h and even after they had been allowed to oviposit for 6 days. Nasonia vitripennis females normally mate only once. Thus, their variable response to the sex attractant depending on the mating status makes sense from an evolutionary perspective. Firstly, it increases the chance of virgins to be inseminated. Secondly, by terminating the response or even avoiding the male pheromone, mated females decrease the probability of encountering males and being disturbed by their courtship activities when searching for new oviposition sites.

A NO-CHOICE WIND TUNNEL OLFACTOMETER SYSTEM FOR EVALUATING THE ATTRACTIVENESS OF PLANT VOLATILES TO ADULT HELICOVERPA ARMIGERA (HÜBNER) (LEPIDOPTERA:NOCTUIDAE)

Abstract A bioassay system to evaluate adult cotton bollworm (CBW), Helicoverpa armigera, behavioral responses to plant volatiles was described. The system was comprised of a no-choice olfactometer, a wind tunnel, and a wind tunnel room. The olfactometer was designed to provide for the testing and evaluation of volatiles from a variety of natural and synthetic sources. The behavioral responses in this system demonstrated that the volatiles of wilted leaves of Pterocarya stenoptera, Toona sinensis and Populus canadensis, the main materials of which poplar bundles were made, only could attract virgin females but not mated females and males. The volatiles emitted from fresh carrot and celery flowers did not exhibit significant attractiveness to both sexes of CBW. 0.1% phenylacetaldehyde showed significant attraction for virgin females and males. The biological significance of attraction of volatiles from these plants for CBW was discussed.

Attraction of a Laboratory Strain of Anastrepha ludens (Diptera: Tephritidae) to the Odor of Fermented Chapote Fruit and to Pheromones in Laboratory Experiments

Odor of fermented yellow chapote ( Sargentia greggii S. Wats.) fruit was 3.6 times more attractive than yeast hydrolysate to hungry, laboratory-strain Mexican fruit flies, Anasttepha ludens (Loew), over short distances (<0.3 m) in laboratory experiments. Starvation for periods of 1–3 d increased responsiveness to chapote odor over the no-starvation level. Age had little effect on responses of flies between 1 and 30 dafter eclosion. However, newly emerged flies did not respond. Chapote odor attracted flies at all times during the 14-h photophase, but responses, especially of males, declined late in the photophase. Response levelsincreased with odor concentration throughout the range of test concentrations. Gamma irradiation reduced responses of females by 25% but did not affect responsesof males. Females were 1.7 times more responsive than males to chapote odor. Male-produced pheromone did not attract virgin females that were 0–7 d old (sexually immature) but attracted virgin females that were 8–37 d old (sexually mature). Odor of fermented chapote and maleproduced pheromone are maximally attractive to different segments of the adult population.

Silence as a Defense against Predatory Bats in Two Species of Calling Insects

Silence as a Defense against Predatory Bats in Two Species of Calling Insects

Female Attraction to Males in Rhagoletis cerasi1 , 3

Experiments conducted in large plastic-screen field enclosures placed over small sweet-cherry trees have shown that Rhagoletis cerasi L . males caged in groups of 150 attract virgin females or females which have not mated recently. This attraction was found to be due to an odor, apparently a pheromone, released by the males. No attraction of males to females, males to males, or females to females could be detected.

Recapture of Virgin Female Caribbean Fruit Flies from Traps Baited with Males

Field tests in Homestead, Fla., during spring and summer, 1972, demonstrated that virgin male Caribbean fruit flies, Anastrepha suspensa (Loew), caged in sticky board traps attracted virgin females. Apparently much of the attraction was related to release of a volatile sex attractant. More females were trapped in the late afternoon than during other parts of the day. Traps baited with 10 live males were as effective as the McPhail traps currently used and were substantially more effective when baited with 20 or 40 males. The pure pheromone, when available, may be easy to use in traps and may be a more sensitive survey tool than those presently available.

Preliminary biological studies on the pheromone produced by male Acanthoscelides obtectus (Say) (Coleoptera, Bruchidae)

Virgin female Acanthoscelides obtectus (Say) placed in a closed 12·5 cm Petri dish were attracted to a caged male by a pheromone which could be extracted with hexane and was extremely stable in solution. Surfaces which had been exposed to males attracted virgin females. The male did not respond to a caged female although on coming into contact with a free female he usually pursued her and attempted to mate. Mating lasted about 10 min after which females usually resisted any further attempts made by males during the 8 hr period of observation. After mating or removal of antennae females were not attracted by caged males and remained unresponsive for the rest of their lives. Virgin females given the choice between male pheromone and the smell of beans chose the former. Male extract presented on a variety of substrates usually attracted virgin females but a few failures occurred. When extract was run on a thin layer chromatogram and presented to virgin females they were only attracted to the region carrying the allenic ester (−)-methyl n-tetradeca-trans-2,4,5-trienoate, and extract without it (removed using chromatographic techniques) proved inactive. The allenic ester therefore appears to be at least closely related to the pheromone.