Temporal pattern of sex pheromone release by female Trichoplusia ni

The release rate of the pheromone component Z-7-dodecenyl acetate was determined for individual female Trichoplusia ni by using small glass tubes filled with Porapak Q to extract pheromone from air in the immediate vicinity of the everted gland. The change in release rate as a function of time was determined by taking sequential 5 min. samples from individual 4-day-old females through each pheromone release period over an entire night. The release rate was found to decline exponentially from a mean of 22 ng per min. initially to 12 ng per min. at the end of 20 min., the average length of a pheromone release period. Pheromone collections were also made from females of different ages, using a single tube of Porapak per female to collect pheromone for an entire night. The nightly mean release rate increased significantly with age, although the time spent releasing pheromone per night decreased significantly with age (to 6 days old).     

Identification by GC-EAD of the two-component trail-following pheromone of Prorhinotermes simplex (Isoptera, Rhinotermitidae, Prorhinotermitinae)

GC/MS analysis confirmed that neocembrene is the major component of the trail pheromone in the three species of the termite genus Prorhinotermes (P. simplex, P. canalifrons, P. inopinatus). In addition, EAG and GC-EAD experiments with P. simplex strongly suggest that dodecatrienol is a quantitatively minor component but a qualitatively important component of this trail pheromone. Trail-following bioassays confirmed the two-component nature of the trail pheromone. This is the first report of the use of the GC-EAD for the identification of trail pheromone in termites. These original results underline once again the special phylogenetic status of the Prorhinotermitinae among Rhinotermitidae.     

A receptor and binding protein interplay in the detection of a distinct pheromone component in the silkmoth Antheraea polyphemus

Male moths respond to conspecific female-released pheromones with remarkable sensitivity and specificity, due to highly specialized chemosensory neurons in their antennae. In Antheraea silkmoths, three types of sensory neurons have been described, each responsive to one of three pheromone components. Since also three different pheromone binding proteins (PBPs) have been identified, the antenna of Antheraea seems to provide a unique model system for detailed analyzes of the interplay between the various elements underlying pheromone reception. Efforts to identify pheromone receptors of Antheraea polyphemus have led to the identification of a candidate pheromone receptor (ApolOR1). This receptor was found predominantly expressed in male antennae, specifically in neurons located beneath pheromone-sensitive sensilla trichodea. The ApolOR1-expressing cells were found to be surrounded by supporting cells co-expressing all three ApolPBPs. The response spectrum of ApolOR1 was assessed by means of calcium imaging using HEK293-cells stably expressing the receptor. It was found that at nanomolar concentrations ApolOR1-cells responded to all three pheromones when the compounds were solubilized by DMSO and also when DMSO was substituted by one of the three PBPs. However, at picomolar concentrations, cells responded only in the presence of the subtype ApolPBP2 and the pheromone (E,Z)-6,11-hexadecadienal. These results are indicative of a specific interplay of a distinct pheromone component with an appropriate binding protein and its related receptor subtype, which may be considered as basis for the remarkable sensitivity and specificity of the pheromone detection system.     

Influence of sex,maturity and host substances on pheromones in the guts of the bark beetles, Ips paraconfusus and Dendroctonus brevicomis

Pheromones and metabolites of host (ponderosa pine) compounds were found in association with the hindgut of both naturally fed and of non-fed, host vapour-exposed bark beetles, Ips paraconfusus and Dendroctonus brevicomis. Much smaller amounts were found in the corresponding heads and mid guts. Sex-specific differences in content of pheromones were observed as in earlier studies. Exposure of I. paraconfusus to vapours of a pheromone component, ipsenol and other monoterpene alcohols resulted in their accumulation in the hindgut but relatively very low amounts in the head. The possible sites of pheromone biosynthesis are discussed. Exposure of male I. paraconfusus to vapours of host compounds, myrcene and α-pinene, revealed that immature adults do not produce the pheromone components, ipsenol and ipsdienol, as mature adults do while both immature and mature sexes produced another pheromone component, cis-verbenol, as well as trans-verbenol and myrtenol. Immature D. brevicomis adults did not contain pheromones until their exposure to vapours of (?)-α-pinene which caused production of trans-verbenol but only about 10% that of mature adults treated similarly. Verbenone, a male-produced inhibitory pheromone of D. brevicomis, apparently was not synthesized from (?)-α-pinene in females nor was its synthesis in males enhanced by exposure to this host compound.     

Chemical and behavioural studies of the trail-following pheromone in the leaf-cutting ant Atta opaciceps,Borgmeier (Hymenoptera: Formicidae)

To understand the significance of the trail pheromone used in chemical communication of the leaf-cutting ants Atta opaciceps we investigated, under laboratory conditions, the trail-following behaviour of different castes. We observed a clear behavioural discrimination of conspecific venom gland extract of foraging ants from those of other species. Additionally, we determined the pheromone composition of A. opaciceps venom gland secretion using a two-dimensional gas chromatography coupled with mass spectrometry. Chemical analyses revealed the presence of three nitrogen-containing compounds, identified as 2,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine and methyl 4-methylpyrrole-2-carboxylate (M4MPC). Four different bioassays performed with workers from different castes of A. opaciceps suggested that the trail pheromone elicits the trail-following behaviour in conspecifics of all castes, but the foragers respond more strongly to their own pheromone than to that of other castes (gardeners, generalists and soldiers). In addition, A. opaciceps foragers follow the trails made with the venom gland extracts of the unrelated Acromyrmex subterraneus subterraneus foragers as well as they follow the trails made with their own venom gland extract. M4MPC was identified to be the most abundant and the most behaviourally active component of the venom gland extract of A. opaciceps foragers.     

Antennal lobe organization and pheromone usage in bombycid moths

We investigated the neuroanatomy of the macroglomerular complex (MGC), which is involved in sex pheromone processing, in five species in the subfamily Bombycinae, including Ernolatia moorei, Trilocha varians, Rondotia menciana, Bombyx mandarina and Bombyx mori. The glomerulus located at the dorsal-most part of the olfactory centre shows the largest volume in moth species examined to date. Such normal glomerular organization has been observed in E. moorei and T. varians, which use a two-component mixture and includes the compound bombykal as a mating signal. By contrast, the other three species, which use another component as a single attractant, exhibited a modified arrangement of the MGC. This correlation between pheromone usage and neural organization may be useful for understanding the process of speciation.     

A male-specific odorant receptor conserved through the evolution of sex pheromones in Ostrinia moth species

In many moths, mate-finding communication is mediated by the female sex pheromones. Since differentiation of sex pheromones is often associated with speciation, it is intriguing to know how the changes in female sex pheromone have been tracked by the pheromone recognition system of the males. A male-specific odorant receptor was found to have been conserved through the evolution of sex pheromone communication systems in the genus Ostrinia (Lepidoptera: Crambidae). In an effort to characterize pheromone receptors of O. scapulalis, which uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone, we cloned a gene (OscaOR1) encoding a male-specific odorant receptor. In addition, we cloned a gene of the Or83b family (OscaOR2). Functional assays using Xenopus oocytes co-expressing OscaOR1 and OscaOR2 have shown that OscaOR1 is, unexpectedly, a receptor of (E)-11-tetradecenol (E11-14:OH), a single pheromone component of a congener O. latipennis. Subsequent studies on O. latipennis showed that this species indeed has a gene orthologous to OscaOR1 (OlatOR1), a functional assay of which confirmed it to be a gene encoding the receptor of E11-14:OH. Furthermore, investigations of six other Ostrinia species have revealed that all of them have a gene orthologous to OscaOR1, although none of these species, except O. ovalipennis, a species most closely related to O. latipennis, uses E11-14:OH as the pheromone component. The present findings suggest that the male-specific receptor of E11-14:OH was acquired before the divergence of the genus Ostrinia, and functionally retained through the evolution of this genus.     

Sex pheromone biosynthesis,storage and release in a female moth: making a little go a long way

Moth pheromone research has pioneered much of our understanding of long-distance chemical communication. Two important characteristics of this communication have, however, remained largely unaddressed: the release of small quantities of pheromone by most moth species, despite potential advantages of releasing greater amounts, and the intermittency of release in some species, limiting the time of mate attraction. We addressed the proximate mechanisms underlying these characteristics by manipulating biosynthesis, storage and release of pheromone in females of the noctuid moth Chloridea virescens. We found that (i) mass release is determined by pheromone mass on the gland surface; (ii) amounts synthesized are limited by pheromone biosynthesis activating neuropeptide concentration, not precursor availability; (iii) some gland structural feature limits mass release rate; (iv) intermittent calling enables release at a mass rate greater than biosynthetic rate; and (v) at typical mass release rates, the periodicity of pheromone availability on the gland surface roughly matches the periodicity (intermittency) of calling. We conclude that mass release in C. virescens and possibly many other species is low because of constraints on biosynthesis, storage and gland structure. Further, it appears the behaviour of intermittent calling in C. virescens may have evolved as a co-adaptation with pheromone availability, allowing females to release pheromone intermittently at higher mass rates than the biosynthesis rate.     

Sex pheromone analysis and effective attraction of males of the cabbage webworm,Hellula undalis,inhabiting the Mekong Delta of Vietnam

Hellula undalis is a harmful insect pest of green mustard in the Mekong Delta of Vietnam. In order to establish a tool for a sustainable pest control program, the sex pheromone of H. undalis inhabiting the Mekong Delta was examined. GC-EAD and GC–MS analyses of pheromone gland extracts from the virgin females elucidated three new components, (Z)-11-tetradecenyl acetate (Z11-14:OAc), (Z)-11-hexadecenal (Z11-16:Ald), and (11E,13E)-11,13-hexadecadien-1-ol, in addition to the known pheromone component (11E,13E)-11,13-hexadecadienal (E11,E13-16:Ald). Double bond positions of the two monoenyl components were determined by GC–MS analysis of the pheromone extract treated with dimethyl disulfide. On the other hand, GC–MS analysis of the female body extract detected the unsaturated hydrocarbon (3Z,6Z,9Z)-3,6,9-tricosatriene (Z3,Z6,Z9-23:H). Field examinations of their synthetic compounds indicated the significant role of E11,E13-16:Ald as a major component and a clear synergistic effect of the two monoenyl compounds as a minor component. Although the 3:3:7 mixture of Z11-14:OAc, E11-16:Ald, and E11,E13-16:Ald captured the largest number of males among the tested mixtures, the activity was still quite a bit lower than that of virgin females. However, the 3:3:7:1 mixture, which was prepared by adding a small amount of Z3,Z6,Z9-23:H to the 3:3:7 ternary lure, succeeded in attracting males more powerfully than the females did. This strong synergistic effect was not observed when the triene was added to unmixed E11,E13-16:Ald, indicating important roles of not only the triene but also the two monoenyl compounds as natural pheromone components.     

Investigation of a sex pheromone for the oriental cockroach,Blatta orientalis

A sex pheromone for adult male oriental cockroaches Blatta orientalis was isolated from the faeces of adult virgin female oriental cockroaches. It elicited a sexual response at 10 pg and 1 ng with B. orientalis and Periplaneta americana adult males, respectively. The site of production appers to be the crop, oesophagus, and proventriculus. Electroantennogram responses of male antennae toward the isolated pheromone were greater than those of the female antennae. The adult male oriental cockroach also responded to the American cockroach sex pheromone. The isolated pheromone with a mol. wt of 232 may be similar to one of the components of the American cockroach sex pheromone.     

Two terpenoids activates close mating behavior and enhances trap efficiency of sex pheromone of Grapholita molesta

Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a notorious pest of many Rosaceae crops worldwide. Enhancement of trap efficiency of its sex pheromone was devised by addition of E-β-ocimene and E-β-farnesene. The addition of E-β-ocimene or E-β-farnesene to sex pheromone increased electroantennogram response of male G. molesta compared to sex pheromone alone. Blend of pheromone and E-β-ocimene or E-β-farnesene in 1:0.1 increased the upwind flight and landing behaviors. Furthermore, field experiments showed that sex lures with E-β-ocimene, or /and E-β-farnesene, enhanced trapping efficiency compared to sex pheromone alone. These results may provide the basis for the development of efficient pest management systems against G. molesta using plant volatiles and insect sex pheromones.     

Site of pheromone biosynthesis and isolation of HMG-CoA reductase cDNA in the cotton boll weevil, Anthonomus grandis

Isolated gut tissue from male cotton boll weevil, Anthonomus grandis (Coleoptera: Curculionidae), incorporated radiolabeled acetate into components that co-eluted with monoterpenoid pheromone components on HPLC. This demonstrates that pheromone components of male A. grandis are produced de novo and strongly suggests that pheromone biosynthesis occurs in gut tissue. A central enzyme in isoprenoid biosynthesis is 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-R), and a full-length HMG-R cDNA was isolated from A. grandis. The predicted translation product was 54 and 45% identical to HMG-R from Ips paraconfusus and Drosophila melanogaster, respectively. HMG-R gene expression gradually increased with age in male A. grandis, which correlates with pheromone production. However, topical application of JH III did not significantly increase HMG-R mRNA levels.     

Location,morphology and histology of sex pheromone glands of the female gypsy moth, Lymantria dispar (L.)

Scanning electron microscopy, histology and a male wing fanning bioassay were used in this study to locate the sex pheromone-producing glands of the female gypsy moth, Lymantria dispar. When exposed to female sex pheromone, adult males exhibit a strong wing fanning behaviour prior to take off. We found that adult males showed positive response to calling females and to tissue extract from both dorsal and ventral portions of the intersegmental membrane between 8th and 9th-abdominal segments. A typical male response usually starts with elevation of antennae, movement of head in different directions, walking, wing fanning and onset of search flight. Histological and scanning electron microscopic studies suggested that the sex pheromone glands are located on the dorsal and ventral aspects of the intersegmental membrane. The glands appear as two highly convoluted integumentary areas with hypertrophied glandular epidermal cells.     

An aphid circadian rhythm: Factors affecting the release of sex pheromone by oviparae of the greenbug, Schizaphis graminum

Adult oviparae of Schizaphis graminum emit a sex pheromone from scent plaques on the metathoracic tibiae, as do oviparae of other aphid species. By allowing males to walk along a wire walkway, a turning response and an increased rate of antennation were observed when the aphids were within 1–2 cm of a pheromone source. Adult males responded but 4th instar larval males did not.The onset of the release of the pheromone by the oviparae is triggered by the initiation of the light phase in a LD-cycle, and is governed by a circadian rhythm with a free-running period of 25.6 hr under continuous illumination of 15 lx. Daily pheromone release peaks 4–7 hr after lights-on and reaches a maximum on days 6–8 of adulthood.     

Determination of the site of pheromone emission in the virgin females Culicoides nubeculosus Meigen (Diptera: Ceratopogonidae)

The zone of emission of the sex pheromone from the body of Culicoides nubeculosus was investigated. The amount of pheromone emitted was evaluated by counting the number of matings between males and females exposed to a flow of air coming from a chamber containing virgin females. The number of matings is higher than that recorded when the air flow comes from an empty chamber (control). Three parts of the body were examined: head, thorax and abdomen. Each part was studied by neutralizing the effect of the others. The head was neutralized by decapitation and the females continued to emit pheromone. The head is, therefore, not indispensible for pheromone emission. The roles of the thorax and abdomen were studied by coating these with paraffin wax. When the thorax is coated, pheromone emission continues, but when the abdomen is coated, it stops. It appears that the abdomen alone is responsible for emission of the sex pheromone.     

The aggregation-attachment pheromone of the tropical bont tick Amblyomma variegatum Fabricius (Acari,Ixodidae): Isolation,identification and action of its components

Combining a new in vitro bioassay with the analytical method capillary gas chromatography-mass spectrometry, the aggregation-attachment pheromone produced by fed males of the tropical bont tick Amblyomma variegatum was shown to consist of o-nitrophenol, methyl salicylate and pelargonic acid in the approximate amounts of 2/1/8 × 10^?6 g/tick. A synthetic pheromone blend composed of those three volatile compounds evoked an aggregation response in unfed males and females in a bioassay comparable to the response to a natural pheromone source. Of the individual components. only o-nitrophenol induced a significant, although not complete aggregation response. Methyl salicylate and pelargonic acid contribute to complete pheromone activity, but induce no aggregation response at all, when offered separately.     

Moth sex pheromones affect interspecific competition among sympatric species and possibly population distribution by modulating pre-mating behavior

Premating behaviors mediated by pheromones play pivotal roles in animal mating choices. In natural populations of the striped stem borer Chilo suppressalis and the rice leaf roller Cnaphalocrocis medinalis in the rice field habitat, we discovered that Z11-16:Ald, a major component of the C. suppressalis pheromone, modulated the premating behavior of C. medinalis. Z11-16:Ald evoked a strong olfactory response in male antennae and strongly inhibited the sex pheromone trapping of male C. medinalis in the field. The functions of three C. medinalis sex pheromone receptor genes (CmedPR1–3) were verified through heterologous expression in Xenopus oocytes. CmedPR1 responded to Z11-18:OH and Z11-18:Ald, as well as the interspecific pheromone compound Z11-16:Ac of sympatric species; CmedPR2 responded to Z13-18:OH and Z13-18:Ald, as well as the sex pheromone compounds Z11-16:Ald and Z9-16:Ald of sympatric species; and CmedPR3 responded to Z11-18:OH and Z13-18:OH, as well as the interspecific pheromones Z11-16:OH, Z9-16:Ald, Z11-16:Ac, and Z11-16:Ald of sympatric species. Thus, CmedPR2 and CmedPR3 share the ligand Z11-16:Ald, which is not a component of the C. medinalis sex pheromone. Therefore, the sex pheromones of interspecific species affected the input of neural signals by stimulating the sex pheromone receptors on the antennae of male C. medinalis moths, thereby inhibiting the olfactory responses of the male moths to the sex pheromones. Our results demonstrate chemical communication among sympatric species in the rice field habitat, the recognition of intra- and interspecific sex pheromones by olfactory receptors, and how insect premating behaviors are modulated to possibly affect resource partitioning.     

Discovery and Functional Study of a Novel Genomic Locus Homologous to Bα-Mating-Type Sublocus of Lentinula edodes

The interaction of mating pheromone and pheromone receptor from the B mating-type locus is the first step in the activation of the mushroom mating signal transduction pathway. The B mating-type locus of Lentinula edodes is composed of Bα and Bβ subloci, each of which contains genes for mating pheromone and pheromone receptor. Allelic variations in both subloci generate multiple B mating-types through which L. edodes maintains genetic diversity. In addition to the B mating-type locus, our genomic sequence analysis revealed the presence of a novel chromosomal locus 43.3 kb away from the B mating-type locus, containing genes for a pair of mating pheromones (PHBN1 and PHBN2) and a pheromone receptor (RCBN). The new locus (Bα-N) was homologous to the Bα sublocus, but unlike the multiallelic Bα sublocus, it was highly conserved across the wild and cultivated strains. The interactions of RcbN with various mating pheromones from the B and Bα-N mating-type loci were investigated using yeast model that replaced endogenous yeast mating pheromone receptor STE2 with RCBN. The yeast mating signal transduction pathway was only activated in the presence of PHBN1 or PHBN2 in the RcbN producing yeast, indicating that RcbN interacts with self-pheromones (PHBN1 and PHBN2), not with pheromones from the B mating-type locus. The biological function of the Bα-N locus was suggested to control the expression of A mating-type genes, as evidenced by the increased expression of two A-genes HD1 and HD2 upon the treatment of synthetic PHBN1 and PHBN2 peptides to the monokaryotic strain of L. edodes.