Male Pheromone Research Articles

Mating, but Not Male Accessory Gland Products, Changes Female Response to Olfactory Cues in Anastrepha Fruit Flies.

Copulation and/or ejaculate components can alter female physiological state and female post-mating behavior. The objective of the present study was to determine if copulation and male reproductive accessory gland products (MAGs) modify the behavior of female Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart; Diptera: Tephritidae) in response to two stimuli: male-emitted pheromone and oviposition host volatiles. Olfactometry studies revealed that mated females of both A. ludens and A. obliqua have a stronger response for host volatiles compared to unmated females, which have a stronger response for male pheromone. We also examined olfactory responses of females mated to testectomized males who could transfer MAGs but not sperm. In both species, MAGs alone did not cause the change in the olfactory response observed after copulation, unlike what has been found in Ceratitis capitata (Wiedemann). Females mated to testectomized males responded equally to the male sex pheromone or to host volatiles, thus suggesting that the whole ejaculate is needed to elicit the complete behavioral switch in olfactory response. The function of MAGs is still unknown in these two pests of economic importance. The response for host volatiles by mated females has implications for the development of baits and traps that should preferably attract and target this population.

Elevated temperature increases reproductive investment in less preferred mates in the invasive European corn borer moth.

Rapidly changing environments may weaken sexual selection and lead to indiscriminate mating by interfering with the reception of mating signals or by increasing the costs associated with mate choice. If temperature alters sexual selection, it may impact population response and adaptation to climate change. Here, we examine how differences in temperature of the mating environment influence reproductive investment in the European corn borer moth (Ostrinia nubilalis). Mate preference in this species is known to be related to pheromone usage, with assortative mating occurring between genetically distinct E and Z strains that differ in the composition of female and male pheromones. We compared egg production within and between corn borer lines derived from four different populations that vary in pheromone composition and other traits. Pairs of adults were placed in a mating environment that matched the pupal environment (ambient temperature) or at elevated temperature (5°C above the pupal environment). At ambient temperature, we found that within‐line pairs produced eggs sooner and produced more egg clusters than between‐line pairs. However, at elevated temperature, between‐line pairs produced the same number of egg clusters as within‐line pairs. These results suggest that elevated temperature increased investment in matings with typically less preferred, between‐line mates. This increased investment could result in changes in gene flow among corn borer populations in warming environments.

Experimental evidence for female mate choice in a noctuid moth

Sexual signal evolution is shaped by whether only one or both sexes execute mate choice. When mate choice by both sexes is considered, the same signalling modality is generally inferred for males and females. In the noctuid moth Chloridea ( Heliothis ) virescens (Lepidoptera: Noctuidae), both sexes may be signallers and responders, as both emit a sex-specific pheromone. Male mate choice is based on the female sex pheromone, perceived via the antennae, and has been well documented. However, whether females choose partners and whether their choice is based on the male pheromone are unknown. Since female mate choice is expected when males vary in quality, we reared males on two different larval diets that affected their size, which correlated positively with their fitness. When given a choice, more females mated with larger than with smaller males, and these females produced more eggs and larvae. Female choice was not affected by the absolute amount or composition of the male pheromone. Moreover, we found that antennaless females mated as readily as intact females, indicating that antennal sensory input is not required for females to mate. To determine whether females make an active choice, we studied courtship behaviour in detail and observed that females determined the outcome of courtship by moving away from the male (avoidance) or by facilitating copulation with an abdominal bend (acceptance). Additionally, we discovered that tactile sensory stimuli may be involved during courtship. Because tactile interactions may mediate contact-based (chemical) communication, we also investigated putative pheromone components on moth legs, but found no differences between the sexes. Together, our study is the first comprehensive investigation of female mate choice in a heliothine moth. • In the noctuid moth Chloridea virescens , females mated more with larger males. • Larger males were higher quality mating partners than smaller males. • The quality and quantity of male hairpencil pheromone did not explain female choice. • Females showed avoidance and acceptance behaviour, and thus chose partners actively. • Male traits other than the hairpencil pheromone likely affect female choice.

Effects of Age, Phase Variation and Pheromones on Male Sperm Storage in the Desert Locust, Schistocerca gregaria.

Simple SummaryWe investigated male sperm storage in the desert locust Schistocerca gregaria. Phase (solitary or gregarious) did not affect sperm distribution in the vas deferens and seminal vesicle, whereas sperm accumulation of the seminal vesicle in gregarious locusts was promoted more than in solitary ones. Pheromones received from neither mature adults nor nymphs affected sperm distribution in the vas deferens and seminal vesicle. However, sperm accumulation in the seminal vesicle was more promoted in the gregarious locusts which received pheromones from mature adults than those obtained from nymphs at early adult stage, especially seven days after adult emergence.In general, sperm produced in the testis are moved into the seminal vesicle via the vas deferens in insects, where they are stored. How this sperm movement is controlled is less well understood in locusts or grasshoppers. In this study, the effects of age, phase variation and pheromones on male sperm storage were investigated in the desert locust, Schistocerca gregaria (Forskål). In this locust, a pair of ducts, the vasa deferentia, connect the testes to a pair of the long, slender seminal vesicles that are folded approximately thirty times, and where the sperm are stored. We found that phase variation affected the level of sperm storage in the seminal vesicle. Moreover, adult males that detected pheromones emitted by mature adult males showed enhanced sperm storage compared with males that received the pheromones emitted from nymphs: The former, adult male pheromones are known to promote sexual maturation of immature adults of both sexes, whereas the latter, nymphal pheromones delay sexual maturation. Most mature adult males had much sperm in the vasa deferentia at all times examined, suggesting daily sperm movement from the testes to the seminal vesicles via the vasa deferentia. As adult males aged, sperm were accumulated from the proximal part to the distal end of the seminal vesicle. Many sperm remained in the seminal vesicle after mating. These results suggest that young or new sperm located near the proximal part of the seminal vesicle could be used for mating, whereas old sperm not used for mating are stored in the distal part of the seminal vesicle.

Males of a Neotropical spider adjust prey‐gift construction but not mate search in response to sperm competition

AbstractIn scramble competition mating systems, males do not guard females and females usually mate polyandrously, leading to high levels of sperm competition. Mathematical models predict that males facing sperm competition can either decrease or increase their reproductive effort. To test how male reproductive responses vary according to sperm competition risk, we ran two experiments using the polyandrous gift‐giving spiderParatrechalea ornata. First, we tested whether males prefer substrates containing silk of unmated females than substrates containing silk of once‐mated females, competitor males or without silk. Males spent more time on substrates containing silk of females but showed no preference for unmated females, which indicates that males may optimize mate search by prioritizing substrates containing cues of potential mating partners. The lack of preference for unmated females suggests that males cannot detect female mating status from silk or that the costs of searching preferentially for unmated females are high in the field. Second, we tested whether males adjust prey‐gift construction when facing sperm competition risk. Experimental groups (substrate containing silk of an unmated female and silk of another malevs. substrate containing only silk of an unmated female) did not differ in the frequency of gift construction, latency to gift construction and number of flies added to the gift. However, males facing sperm competition risk constructed gifts with less silk, suggesting the occurrence of a less evident form of male mate choice based on differential allocation of resources to prey‐gift. Additionally, given the trade‐off between investing in prey‐gifts quantity or quality, a lower silk investment should enable males to increase the number of gifts constructed and the number of courted females. Taken together, our results indicate that males detect female and male pheromones on substrate and adjust the construction of prey‐gifts in response to apparent sperm competition risk.

Mating increases Drosophila melanogaster females' choosiness by reducing olfactory sensitivity to a male pheromone.

Females that are highly selective when choosing a mate run the risk of remaining unmated or delaying commencing reproduction. Therefore, low female choosiness would be beneficial when males are rare but it would be maladaptive if males become more frequent. How can females resolve this issue? Polyandry would allow mating-status-dependent choosiness, with virgin females selecting their first mate with little selectivity and becoming choosier thereafter. This plasticity in choosiness would ensure timely acquisition of sperm and enable females to increase offspring quality during later mating. Here, we show that Drosophila melanogaster females display such mating-status-dependent choosiness by becoming more selective once mated and identify the underlying neurohormonal mechanism. Mating releases juvenile hormone, which desensitizes Or47b olfactory neurons to a pheromone produced by males, resulting in increased preference for pheromone-rich males. Besides providing a mechanism to a long-standing evolutionary prediction, these data suggest that intersexual selection in D. melanogaster, and possibly in all polyandrous, sperm-storing species, is mainly the domain of mated females since virgin females are less selective. Juvenile hormone influences behaviour by changing cue responsiveness across insects; the neurohormonal modulation of olfactory neurons uncovered in D. melanogaster provides an explicit mechanism for how this hormone modulates behavioural plasticity.

Hormonal Prostaglandin F2α Mediates Behavioral Responsiveness to a Species-Specific Multi-component Male Hormonal Sex Pheromone in a Female Fish.

Although hormonally-derived female sex pheromones have been well described in approximately a dozen species of teleost fish, only a few male sex pheromones have been characterized and the neuroendocrine underpinnings of behavioral responsiveness to them is not understood. Herein, we describe a study that addresses this question using the goldfish, Carassius auratus, an important model species of how hormones drive behavior in egg-laying teleost fishes. Our study had four components. First, we examined behavioral responsiveness of female goldfish and found that when injected with prostaglandin F2α (PGF2α), a treatment that drives female sexual receptivity, and found that they became strongly and uniquely attracted to the odor of conspecific mature males, while non-PGF2α-treated goldfish did not discern males from females. Next, we characterized the complexity and specificity of the male pheromone by examining the responsiveness of PGF2α-treated females to the odor of either mature male conspecifics or male common carp odor, as well as their nonpolar and polar fractions. We found that the odor of male goldfish was more attractive than that of male common carp, and that its activity was attributable to both its nonpolar and polar fractions with the later conveying information on species-identity. Third, we hypothesized that androstenedione (AD), a 19-carbon sex steroid produced by all male fish might be the nonpolar fraction and tested whether PGF2α-treated goldfish were attracted to either AD alone or as part of a mixture in conspecific water. We found that while AD was inactive on its own, it became highly attractive when added to previously unattractive female conspecific water. Lastly, in a test of whether nonhormonal conspecific odor might determine species-specificity, we added AD to water of three species of fish and found that while AD made goldfish water strongly attractive, its effects on other species holding water were small. We conclude that circulating PGF2α produced at the time of ovulation induces behavioral sensitivity to a male sex pheromone in female goldfish and that this male pheromone is comprised of AD and a mixture of body metabolites. Because PGF2α commonly mediates ovulation and female sexual behavior in egg-laying fishes, and AD is universally produced by male fishes as a precursor to testosterone, we suggest that these two hormones may have similar roles mediating male-female behavior and communication in many species of fish.

The Adelphocoris lineolatus OBP4: Support for evolutionary and functional divergence of a mirid pheromone-binding protein from that found in lepidopteran moths.

Pheromone-binding proteins (PBPs) have been extensively investigated in lepidopteran moths, but their evolution and function in hemipteran species remain unclear. Our previous study demonstrated that an odorant-binding protein, OBP4, of the mirid bug Adelphocoris lineolatus functions as a candidate hemipteran PBP but clustered with lepidopteran antennae-binding proteins (ABPs) rather than in the PBP/general odorant-binding protein (GOBP) clade. In this study, we hypothesized that origin and function of PBPs in hemipteran bugs may differ from those of lepidopteran moths. To test this hypothesis, we first constructed a phylogenetic tree using insect OBPs from sister hemipteran and holometabolous lineages, and the results indicated that neither OBP4 nor other types of candidate PBPs of mirid bugs clustered with the lepidopteran PBP/GOBP clade. Then, a fluorescence competitive binding assay was employed to determine binding affinities of recombinant OBP4 protein to host plant volatiles, with functional groups different from A. lineolatus sex pheromone components. The results revealed that OBP4 highly bound the female adult attractant 3-hexanone and 15 other mirid bug biologically active plant volatiles. Finally, we examined cellular expression profiles of OBP4 in putative antennal sensilla that are related to female A. lineolatus host plant location. The fluorescence in situ hybridization and immunocytochemical labeling assay showed that the OBP4 gene was highly expressed in the multiporous olfactory sensilla medium-long sensilla basiconica rather than in the short sensilla basiconica or uniporous sensilla chaetica. These results, together with those of our previous studies, indicate that OBP4 not only functions in recognition of bug-produced sex pheromones in males, but is probably involved in detection of host plant volatiles in both A. lineolatus sexes. Our findings support the hypothesis that the origin and function of PBPs in hemipteran bugs differ from those of well-known PBPs in lepidopteran moths, which provides a novel perspective on evolutionary mechanisms of sex pheromone communication across insect orders.

Male pheromones modulate synaptic transmission at the C. elegans neuromuscular junction in a sexually dimorphic manner.

The development of functional synapses in the nervous system is important for animal physiology and behaviors, and its disturbance has been linked with many neurodevelopmental disorders. The synaptic transmission efficacy can be modulated by the environment to accommodate external changes, which is crucial for animal reproduction and survival. However, the underlying plasticity of synaptic transmission remains poorly understood. Here we show that in Caenorhabditis elegans, the male environment increases the hermaphrodite cholinergic transmission at the neuromuscular junction (NMJ), which alters hermaphrodites' locomotion velocity and mating efficiency. We identify that the male-specific pheromones mediate this synaptic transmission modulation effect in a developmental stage-dependent manner. Dissection of the sensory circuits reveals that the AWB chemosensory neurons sense those male pheromones and further transduce the information to NMJ using cGMP signaling. Exposure of hermaphrodites to the male pheromones specifically increases the accumulation of presynaptic CaV2 calcium channels and clustering of postsynaptic acetylcholine receptors at cholinergic synapses of NMJ, which potentiates cholinergic synaptic transmission. Thus, our study demonstrates a circuit mechanism for synaptic modulation and behavioral flexibility by sexual dimorphic pheromones.

Identification and functional characterization of odorant-binding proteins 69a and 76a of Drosophila suzukii

The fruit fly Drosophila suzukii is a fruit crop pest that causes a severe economic threat to soft summer fruit worldwide. The male sex pheromone, cis-vaccenyl acetate (cVA) has multiple functions in intra-species communication in Drosophila melanogaster, which is required in male to suppress male-male courtship. D. suzukii males do not produce cVA; however, the odorant receptor for cVA (Or67d) is still functional. The lack of cVA in D. suzukii casts the question of whether this pheromone might have been replaced by another compound similar to cVA that disrupts mating in D. suzukii. In order to address this question, we cloned two D. suzukii adult antenna-specific odorant-binding proteins (OBPs) DsOBP69a and DsOBP76a and aligned with their D. melanogaster orthologues. Moreover, we examined the binding properties of the newly identified recombinant proteins against 26 potential ligands including cVA, using the fluorescence-based ligand binding assay. The alignment showed that DsOBP69a and DsOBP76a, have six conserved cysteines and belong to the classic OBP family. Furthermore, our results revealed that cVA did not bind to DsOBP69a or DsOBP76a proteins. Interestingly, the floral odorant β-ionone and the bitter substance berberine chloride and coumarin displayed high binding ability. It is also worth noting that DsOBP69a and DsOBP76a have different affinities to (Z)-7-Tricosene that may reflect different functional roles. These findings suggest that DsOBP69a and DsOBP76a are potentially involved in olfaction and gustation of D. suzukii.

Community deployment of a synthetic pheromone of the sand fly Lutzomyia longipalpis co-located with insecticide reduces vector abundance in treated and neighbouring untreated houses: Implications for control of Leishmania infantum.

The rising incidence of visceral leishmaniasis due to Leishmania infantum requires novel methods to control transmission by the sand fly vector. Indoor residual spraying of insecticide (IRS) against these largely exophilic / exophagic vectors may not be the most effective method. A synthetic copy of the male sex-aggregation pheromone of the key vector species Lutzomyia longipalpis in the Americas, was co-located with residual pyrethroid insecticide, and tested for its effects on vector abundance, hence potential transmission, in a Brazilian community study. Houses within eight defined semi-urban blocks in an endemic municipality in Brazil were randomised to synthetic pheromone + insecticide or to placebo treatments. A similar number of houses located >100m from each block were placebo treated and considered as "True Controls" (thus, analysed as three trial arms). Insecticide was sprayed on a 2.6m2 surface area of the property boundary or outbuilding wall, co-located within one metre of 50mg synthetic pheromone in controlled-release dispensers. Vector numbers captured in nearby CDC light traps were recorded at monthly intervals over 3 months post intervention. Recruited sentinel houses under True Control and pheromone + insecticide treatments were similarly monitored at 7-9 day intervals. The intervention effects were estimated by mixed effects negative binomial models compared to the True Control group. Dose-response field assays using 50mg of the synthetic pheromone captured a mean 4.8 (95% C.L.: 3.91, 5.80) to 6.3 (95% C.L.: 3.24, 12.11) times more vectors (female Lu. longipalpis) than using 10mg of synthetic pheromone. The intervention reduced household female vector abundance by 59% (C.L.: 48.7, 66.7%) (IRR = 0.41) estimated by the cross-sectional community study, and by 70% (C.L.: 56.7%, 78.8%) estimated by the longitudinal sentinel study. Similar reductions in male Lu. longipalpis were observed. Beneficial spill-over intervention effects were also observed at nearby untreated households with a mean reduction of 24% (95% C.L.: 0.050%, 39.8%) in female vectors. The spill-over effect in untreated houses was 44% (95% C.L.: 29.7%, 56.1%) as effective as the intervention in pheromone-treated houses. Ownership of chickens increased the intervention effects in both treated and untreated houses, attributed to the suspected synergistic attraction of the synthetic pheromone and chicken kairomones. The variation in IRR between study blocks was not associated with inter-household distances, household densities, or coverage (proportion of total households treated). The study confirms the entomological efficacy of the lure-and-kill method to reduce the abundance of this important sand fly vector in treated and untreated homesteads. The outcomes were achieved by low coverage and using only 1-2% of the quantity of insecticide as normally required for IRS, indicating the potential cost-effectiveness of this method. Implications for programmatic deployment of this vector control method are discussed.

Mating-induced changes in responses of female Queensland fruit fly to male pheromones and fruit: A mechanism for mating-induced sexual inhibition

In order to reproduce, female tephritid fruit flies need both mates for fertilization and fruit for oviposition. Virgin females are prone to mating and approach males, attracted by their pheromones. Mated females, however, may experience an abrupt reduction of mating propensity and prioritise the search for suitable fruit rather than additional mates. Accordingly, mating in fruit flies may induce a switch in olfactory preferences of females from pheromones to fruit stimuli, and this switch may also be an important mediator of mating-induced sexual inhibition. To test for mating-induced switches in olfactory preference of female Queensland fruit fly, Bactrocera tryoni, we used wind tunnel assays to assess attraction of mated and virgin females to (1) male sex pheromone delivered through a perforated glass sphere or (2) an entire fruit. Electroantennogram (EAG) responses were also used to test for mating-induced changes in olfactory sensitivity to pheromones and fruit odours. Pheromones elicited quicker upwind responses in virgin females than in mated females; during the first six minutes of trials more virgin females than mated females were observed in the upwind end of the wind tunnel where pheromone odours were released. Fruit cues, in contrast, elicited stronger association with the upwind end of the wind tunnel in mated females than in virgin females from the fifth minute onwards. Also, mated females were observed on the fruit for longer periods than virgin females. EAG responses to pheromones and fruit odours were similar in virgin and mated females, indicating that changes in preferences are not a consequence of changes in peripheral sensitivity of antennae to odours but instead appear to be mediated by post-receptor processing. Our results show that mating reduces attraction to male-produced pheromones and increases attraction to fruit stimuli in B. tryoni females. We propose that this behavioural switch from mating stimuli to oviposition stimuli is an important mediator of mating-induced sexual inhibition in this species.

Acetone application for administration of bioactive substances has no negative effects on longevity, fitness, and sexual communication in a parasitic wasp.

Administration of defined amounts of bioactive substances is a perseverative problem in physiological studies on insects. Apart from feeding and injection, topical application of solutions of the chemicals is most commonly used for this purpose. The solvents used should be non-toxic and have least possible effects on the studied parameters. Acetone is widely used for administration of chemical substances to insects, but possible side-effects of acetone application on fitness and behavioral parameters have been rarely investigated. Here we study the effects of acetone application (207 nl) on fitness and sexual communication in the parasitic wasp Nasonia giraulti Darling. Application of acetone had neither negative effects on longevity nor on offspring number and offspring sex ratio of treated wasps. Treatment of females hampered courtship and mating of N. giraulti couples neither directly after application nor one day after. Male sex pheromone titers were not influenced by acetone treatment. Three application examples demonstrate that topical acetone application is capable of bringing active amounts of insect hormones, neuromodulators, and biosynthetic precursors even in tiny insects. We advocate the use of acetone as a convenient, conservative, and broadly applicable vehicle for studying the effects of bioactive substances in insects.

Effective trap density for mass trapping of fruit flies, Bactrocera dorsalis (Hendel) and Bactrocera zonata (Saunders) in mango

Fruit flies are among the major pests of fleshy fruits which affect production throughout the world and represent the most economically important group of polyphagous Diptera. Use of male pheromone traps is a widely followed approach to manage fruit flies, Bactrocera dorsalis (Hendel) and Bactrocera zonata (Saunders) (Tephritidae: Diptera) in mango. Using effective trap density is critical for achieving adequate control of fruit flies. In this regard, an investigation was conducted to evaluate the trap densities for mass trapping of the mango fruit fly. Results revealed that the highest numbers (2710.33 fruit flies/trap/month) of fruit flies were trapped with density of 25 traps/ha, followed by 20 traps/ha (2247.90). While, the lowest numbers (885.89 fruit flies/trap/month) of fruit flies were trapped in 5 traps/ha. Based on the findings, use of 25 methyl eugenol traps per hectare is considered optimum to reduce fruit fly population in mango.

Biology of a putative male aggregation-sex pheromone in Sirex noctilio (Hymenoptera: Siricidae).

A putative male-produced pheromone has recently been described for the global pest of pines, Sirex noctilio, but field-activity has not been demonstrated. This study aimed to investigate the pheromone biology of S. noctilio in more detail. Specifically, we i) analysed effluvia and extracts for additional compounds by gas chromatography coupled with electro-antennographic detection (GC-EAD), mass spectrometry (GC-MS) and two dimensional time of flight mass spectrometry (GC X GC TOF MS), ii) conducted dose-response experiments for putative pheromone components, iii) determined the site of synthesis/ storage of the putative pheromone and iv) determined the release rate of the putative pheromone from males and three types of lures. A blend of four compounds was identified, including the previously described (Z)-3-decenol and (Z)-4-decenol, and two new compounds (Z)-3-octenol and (Z)-3-dodecenol. All compounds elicited a response from both male and female antennae, but the strength of the response varied according to sex, compound and dose tested. (Z)-3-Decenol and (Z)-3-octenol at lower and higher doses, respectively, elicited larger responses in males and females than the other two compounds. (Z)-3-Octenol and (Z)-4-decenol generally elicited larger female than male antennal responses. The site of synthesis and/or storage in males was determined to be the hind legs, likely in the leg-tendon gland. The relative release rate of the major compound by male wasps was shown to be 90 ± 12.4 ng/min, which is between 4 and 15 times greater than that observed from typical lures used previously. These observations are consistent with the hypothesis that these compounds may mediate lek formation in S. noctilio males and lek location in females.

Clustering of loci controlling species differences in male chemical bouquets of sympatric Heliconius butterflies.

The degree to which loci promoting reproductive isolation cluster in the genome—that is, the genetic architecture of reproductive isolation—can influence the tempo and mode of speciation. Tight linkage between these loci can facilitate speciation in the face of gene flow. Pheromones play a role in reproductive isolation in many Lepidoptera species, and the role of endogenously produced compounds as secondary metabolites decreases the likelihood of pleiotropy associated with many barrier loci. Heliconius butterflies use male sex pheromones to both court females (aphrodisiac wing pheromones) and ward off male courtship (male‐transferred antiaphrodisiac genital pheromones), and it is likely that these compounds play a role in reproductive isolation between Heliconius species. Using a set of backcross hybrids between H. melpomene and H. cydno, we investigated the genetic architecture of putative male pheromone compound production. We found a set of 40 significant quantitative trait loci (QTL) representing 33 potential pheromone compounds. QTL clustered significantly on two chromosomes, chromosome 8 for genital compounds and chromosome 20 for wing compounds, and chromosome 20 was enriched for potential pheromone biosynthesis genes. There was minimal overlap between pheromone QTL and known QTL for mate choice and color pattern. Nonetheless, we did detect linkage between a QTL for wing androconial area and optix, a color pattern locus known to play a role in reproductive isolation in these species. This tight clustering of putative pheromone loci might contribute to coincident reproductive isolating barriers, facilitating speciation despite ongoing gene flow.

Rectal gland exudates and emissions of Bactrocera bryoniae: chemical identification, electrophysiological and pheromonal functions

Bactrocera bryoniae is a polyphagous and economically significant fruit fly found in Indonesia, Papua New Guinea and Australia. To understand chemical-mediated sexual communication, and the potential for novel pheromone-based attractants for monitoring and mass-trapping of B. bryoniae, rectal gland exudates and emissions from sexually mature males and females were investigated. Gas chromatography–mass spectrometry showed that male rectal glands contained six compounds, of which 1,7-dioxaspiro[5,5]undecane elicited electroantennographic (EAD) and electropalpographic (EPD) responses in both sexes, ethyl 3-acetoxybutanoate elicited EPD responses in both sexes, N-(3-methylbutyl)acetamide elicited EAD response from males and 4-hydroxy-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and females and EPD responses in females. Female rectal glands contained 23 compounds with the esters ethyl laurate and ethyl myristate as major components. Amongst the female rectal gland constituents, ethyl laurate, ethyl myristate and ethyl palmitate elicited EAD responses in males and females, N-(3-methylbutyl)acetamide elicited EAD responses in males only, (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and EPD responses in females, and 2,7-dimethyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane, (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, (E,E)-2-propyl-8-methyl-1,7-dioxaspiro[5.5]undecane and ethyl caprate elicited EPD responses in females only. Y-tube bioassays indicated that male rectal gland extracts and headspace volatiles attracted females and males, while female rectal gland extracts and headspace volatiles only attracted males. The results suggest that ethyl 3-acetoxybutanoate, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male-produced sex pheromone in B. bryoniae while (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, N-(3-methylbutyl)acetamide, ethyl laurate, ethyl myristate and ethyl palmitate may be components of female-produced sex pheromone. Ethyl 3-acetoxybutanoate, N-(3-methylbutyl) acetamide, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male aggregation pheromone. These findings contribute to the understanding of pheromone communication in B. bryoniae and provide a foundation for developing pheromone-based monitoring and control methods.

Analysis of Chemosensory Genes in Full and Hungry Adults of Arma chinensis (Pentatomidae) Through Antennal Transcriptome.

The predatory insect Arma chinensis (Hemiptera: Pentatomidae) is widely distributed in China, where it is also used to control many agricultural and forest pests. The chemosensory genes expressed in its antennae play crucial roles in food-seeking and mating behaviors. To better understand the olfaction of A. chinensis antennae, we identified the genes related to food-seeking and mating. Sequencing of the antennal transcriptomes of full and hungry male and female A. chinensis revealed 38 odorant-binding proteins (OBPs), 1 chemosensory protein (CSP), 1 Niemann–Pick C2 protein (NPC2), 3 odorant receptors (ORs), 12 ionotropic receptors (IRs), 2 gustatory receptors (GRs), and 3 sensory neuron membrane proteins (SNMPs). These results were used to construct phylogenetic trees. A quantitative real-time PCR (qRT-PCR) analysis showed that the relative transcript levels of AchiGR1, AchiGR2, and AchiOBP28 were higher in female than in male antennae in both full and hungry insects, but that the expression of AchiOBP13 and AchiOBP16 was higher only in full A. chinensis females. Thus, the latter genes may encode proteins involved in oviposition selection behavior. AchiGRs (1 and 2), AchiIR6, and AchiOBPs (6–8, 12, 20–22, 28, and 34) were highly expressed only in the antennae of full males, indicating the participation of these genes in mate-searching or male pheromone recognition. The expression of AchiOBP31 in the antennae of starved males, AchiOBPs (15, 18, and 29) in the antennae of starved females, and AchiOBPs (3, 4, and 24) in the antennae of starved males and females suggested that these genes encode food-seeking functions. Our identification of chemosensory genes in A. chinensis antennae and their differential expression in full and hungry insects provides the basis for further functional studies on the chemoreception system of A. chinensis and the sex hormones of predatory insects.

Interactions between oxidative stress and attractiveness to mates and individual mate choice in the beetle Tenebrio molitor

AbstractMale mating signals are sexual traits that may provide females with information about the physiological quality of the individual. Males of the yellow mealworm beetle, Tenebrio molitor, use pheromones to attract mating partners. The level of pheromone production in males has been identified as a signal of the male condition. We tested whether male sex pheromones also signal the oxidative stress status of their bearers. We used the herbicide paraquat to manipulate the oxidative stress status of individual beetles. We found that healthy males and females preferred healthy mates to those experiencing oxidative stress. If the individual choosing mates was experiencing oxidative stress, females but not males maintained their preference for healthy mating partners. Our study demonstrates a chemical signal indicating the oxidative stress status of a potential partner and reveals that the decisions based on this signal depend upon the condition and gender of the individual making a choice.

Pheromones: Stink Fights in Lemurs

Some primates, in particular lemurs, have long been known to communicate by smell. However, no bona fide primate pheromones have been identified. A recent study of ring-tailed lemurs offers some- disputed- candidate molecules for a male pheromone.