Female-produced Sex Pheromone Components Research Articles

Identification of Two Additional Behaviorally Active Gland Constituents of Female Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae)

The sugarcane borer, Diatraea saccharalis (Fabricius), is the major pest insect attacking sugarcane crops in Brazil. Population control by insecticide treatment is not efficient due to simultaneous presence of all developmental stages of the insect throughout the year, and alternative control methods are needed. Two female-produced sex pheromone components, (Z,E)-hexadeca-9,11-dienal and (Z)- hexadec-11-enal, have previously been reported to elicit antennal activity and behavioral response of males in flight tunnel experiments. However, the attractiveness of these compounds in field tests has been very low. In this study, two additional female-produced compounds in D. saccharalis eliciting consistent antennal response in males were identified as (Z)-hexadec-9-enal and hexadecanal. In flight tunnel assays, the behavioral response to a quaternary blend was significantly higher when compared with the previously identified binary blend. Subtracting (Z)-hexadec-9-enal or hexadecanal from the full blend did not reduce attraction, indicating redundancy in the communication channel. We conclude that additional compounds are part of the sex pheromone of D. saccharalis, which may improve the efficiency of trap lures for monitoring of this pest.

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.

Identification of Sex Pheromone Components of Blueberry Spanworm Itame argillacearia (Lepidoptera: Geometridae)

Blueberry spanworm, Itame argillacearia (Packard), is an important defoliator of lowbush (syn. 'wild') blueberry, Vaccinium angustifolium Aiton, in north-eastern North America. The goal of the present study was to identify the female I. argillacearia sex pheromone, which could be used in traps for monitoring or mass-trapping this pest. Gas chromatography/mass spectrometry (GC/MS) and electroantennogram (EAG) recordings of sex pheromone gland extracts, in combination with chemical synthesis, a Y-tube olfactometer study and field experiments confirmed (2R,3S)-2-ethyl-3-((Z,Z)-tridecadi-2,5-enyl) oxirane (hereafter (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene) and (Z,Z,Z)-3,6,9-heptadecatriene as female-produced sex pheromone components. (Z,Z)-(3R,4S)-3,4-Epoxy-6,9-heptadecadiene elicited a response from male I. argillacearia antennae during EAG recording, and in the Y-tube olfactometer tests males did not discriminate between a live female and (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene. Field-trapping experiments showed that a blend of (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene and (Z,Z,Z)-3,6,9-heptadecatriene was more attractive to male moths than (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene alone.

Synthesis of All the Stereoisomers of 6-Methyl-2-octadecanone, 14-Methyl-2-octadecanone, and 6,14-Dimethyl-2-octadecanone, Sex Pheromone Components of theLyclene dharma dharmaMoth, from the Enantiomers of Citronellal

The enantiomers of citronellal were converted to all the stereoisomers of 6-methyl-2-octadecanone, 14-methyl-2-octadecanone, and 6,14-dimethyl-2-octadecanone, the female-produced sex pheromone components of the Lyclene dharma dharma moth. Three well-established procedures, the Wittig reaction, alkylation of alkynes, and acetoacetic ester synthesis, were employed for the carbon-carbon bond formation to connect the building blocks.

Spatial Organization of Antennal Olfactory Sensory Neurons in the Female Spodoptera littoralis Moth: Differences in Sensitivity and Temporal Characteristics

Single-cell recordings from olfactory sensory neurons (OSNs), housed in sensilla located at the base and at the tip of the antenna, showed selective responses to plant odors and female sex pheromone in this polyphagous moth. A spatial variation existed in sensitivity: OSNs present on the more proximal segment (P) were more sensitive than those on the more distal segment (D). OSNs of the 2 locations also differed in temporal characteristics: OSNs on P had shorter latency and displayed more phasic responses, whereas those on D had more tonic responses, especially at low stimulus concentrations. The 196 OSNs responding to our 35 monomolecular stimuli in the screening were housed in 32 functional sensillum types: 27 in basiconic, 3 in long-trichoid, 2 in coeloconic, and 3 in auricillic sensilla. The OSNs in basiconic, coeloconic, and auricillic sensilla responded to plant-associated odorants, whereas OSNs in long-trichoid sensilla responded to female-produced sex pheromone components. Short-trichoid sensilla showed spontaneous activity, but no responses to any odorant tested. OSN specificity to plant stimuli ranged from highly specific to broadly tuned, but it did not differ clearly from females in more specialized moths. OSN response diversity is discussed in terms of olfactory coding, behavior, and ecological specialization.

Sex Pheromones ofStenotus rubrovittatusandTrigonotylus caelestialium, Two Mirid Bugs Causing Pecky Rice, and Their Application to Insect Monitoring in Japan

Two mirid bugs,Stenotus rubrovittatusandTrigonotylus caelestialium(Heteroptera: Miridae), are important pests that infest rice crops in many regions of Japan. Males of each species were attracted to traps baited with conspecific, unmated females. Hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal were identified as possible female-produced sex pheromone components forS. rubrovittatus, whereas hexyl hexanoate, (E)-2-hexenyl hexanoate, and octyl butyrate were found to be sex pheromone components forT. caelestialium. Pheromone doses and ratios were optimized for attraction of males of each species. Sticky traps set up close to or below the top of the plant canopy were optimal for monitoring these species, and trap catches were almost constant when traps were placed 7 or more meters in from the edge of a paddy field. Mixed lures, in which the six compounds from both species were loaded onto a single septum, or separate lures for each species, deployed in a single trap, were equally effective for monitoring both species simultaneously.

Glomerular representation of plant volatiles and sex pheromone components in the antennal lobe of the female Spodoptera littoralis.

We studied the projection patterns of antennal lobe (AL) interneurones sensitive to plant volatiles and female-produced sex pheromone components in the female moth, Spodoptera littoralis. Ten compounds (eight plant-derived compounds and two sex pheromone components) were singly applied to the antenna and, using intracellular recording and staining techniques, the physiological and morphological characteristics of responding neurones were investigated. In addition, ALs stained with a synapsin antibody were optically sectioned using confocal microscopy, and a three-dimensional map of glomeruli in the anterior aspect of the AL was reconstructed. We used the map as a reference for identification of glomeruli innervated by projection neurones (PNs) that respond to plant volatiles and/or pheromone components. Nineteen PNs, responding to one to seven compounds of the ten tested stimuli, were stained with neurobiotin. These neurones each arborised in a single glomerulus in the frontal side of the AL. PNs responding to the same compound arborised in different glomeruli and PNs arborising in the same glomerulus responded to different compounds. Accordingly, glomeruli harbouring the dendritic arborisations of PNs responding to each of the tested compounds constituted a unique array of glomeruli that were not necessarily adjacent. It was thus clear that, at the output level, a single plant volatile or a sex pheromone component was not represented within a single glomerulus in the AL. We expect complex patterns of glomeruli to be involved in the coding of plant-derived compounds, as well as sex pheromone components, in female S. littoralis.

Detection of Sex Pheromone Components in Manduca sexta (L.)

The ability of olfactory receptor neurons to detect female-produced sex pheromone components and a limited sample of potential host plant odours was studied by single-sensillum recordings from olfactory sensilla present on male and female antennae in Manduca sexta. The majority of pheromone-sensitive receptor neurons examined in males was specialized for detection of the two major pheromone components, E10,Z12-hexadecadienal and E10,E12,Z14-hexadecatrienal or E10,E12,E14-hexadecatrienal. New olfactory receptor neurons tuned to the minor components E10,E12-hexadecadienal and Z11-hexadecenal were found. In females, olfactory receptor neurons specific to Z11-hexadecanal were discovered. Pheromone components and host volatiles were detected by separate sets of receptor neurons.

Sex pheromone and plant-associated odour processing in antennal lobe interneurons of male Spodoptera littoralis (Lepidoptera: Noctuidae)

Antennal lobe interneurons of male Spodoptera littoralis (Boisd.) were investigated by using intracellular recording and staining techniques. Physiological and morphological characteristics of local interneurons and projection neurons responding to sex pheromone and plant-associated volatiles are described. The interneurons identified were divided into three groups, depending on their physiological response characteristics. Both types of interneurons, local interneurons and projection neurons, were described in all three groups. 1. Interneurons responding exclusively to sex pheromone stimuli, displayed different degrees of specificity. These neurons responded to either one, two, three or all four of the single sex pheromone or sex pheromone-like compounds tested. Most of these neurons also responded to a mixture of the two pheromone components present in the female S. littoralis blend. Two local interneurons and one projection neuron were identified as blend specialists, not responding to the single female produced sex pheromone components, but only to their mixture. Five pheromone specific projection neurons arborized in one or more subcompartments of the macroglomercular complex (MGC) and some of them had axonal branches in the calyces of the mushroom body and in different parts of the lateral protocerebrum. 2. Interneurons responding only to plant-associated volatiles varied highly in specificity. Neurons responding to only one of the stimuli, neurons responding to a variety of different odours and one neuron responding to all stimuli tested, were found. Three specialized local interneurons had arborizations only in ordinary glomeruli. One specialized and three less specialized local interneurons had arborizations within the MGC and the ordinary glomeruli. The projection neurons responding only to plant-associated volatiles had mostly uni- or multiglomerular arborizations within the ordinary glomeruli. 3. Interneurons responding to both sex pheromones and plant-associated stimuli varied in specificity. Individual interneurons that responded to few plant-associated odours mostly responded to several pheromone stimuli as well. Projection neurons responding to most of the plant-associated volatiles also responded to all pheromone stimuli. Two local interneurons responding to both stimulus groups, arborized within the MGC and the ordinary glomeruli. Projection neurons mostly arborized in only one ordinary glomerulus or in one compartment of the MGC. The variation in specificity and sensitivity of antennal lobe interneurons and structure-function correlations are discussed.

Identification and field testing of female-produced sex pheromone components of the spring cankerworm,Paleacrita vernata Peck (Lepidoptera: Geometridae)

Two sex pheromone components, 3(Z),6(Z),9(Z)-nonadecatriene (3Z,6Z,9Z-19 ∶ H), and 3(Z),6(Z),9(Z)-eicosatriene (3Z,6Z,9Z-20∶ H), have been positively identified, and a third component, 6(Z),9(Z)-nonadecadiene (6(Z),9(Z)-19 ∶ H) has been tentatively identified from abdominal tip extracts of female spring cankerworm moths,Paleacrita vernata Peck (Lepidoptera∶ Geometridae). The pheromone components were identified by a combination of gas chromatography, electroantennography, mass spectrometry, chemical tests, comparison with standards, and field testing. Only 3Z,6Z,9Z-20 ∶ H exhibited significant attractant activity when tested alone, and it was potentiated by the other two components. The attractive blend was an 8∶2∶1 ratio of 3Z,6Z,9Z-20∶H/3Z,6Z,9Z-19∶H/6Z,9Z-19∶H. However, the two-component blend of 3Z,6Z,9Z-20 ∶ H and 6Z,9Z-19 ∶ H (8∶1 ratio) was as attractive as the three-component blend in further field tests. A series of related compounds, the diene monoepoxides available from epoxidation of C19 and C20 3Z,6Z,9Z-trienes, some of which have been found in the pheromone blends of other moth species, were tested as behavioral antagonists. The attraction of male moths to synthetic lures was suppressed by the addition of 6Z,9Z-cis-3,4-epoxy-nonadecadiene to the lures. Additional experiments were performed to determine the effects of lure dosage, trap height, and trap design on the numbers of male moths captured.

Electroantennogram responses of the male moth, Argyrotaenia velutinana to mixtures of sex pheromone components of the female

Electroantennogram (EAG) responses were recorded from male redbanded leafroller moth, Argyrotaenia velutinana, antennae using mixtures of the three female-produced sex pheromone components: cis-11-tetradecenyl acetate, trans-11-tetradecenyl acetate, and dodecyl acetate (12:Ac). Binary mixtures containing 3%, 8%, and 15% trans in cis elicited significantly higher amplitude responses than other isomeric mixtures as well as pure cis and trans alone. The higher responses to such mixtures were less than additive at high dosages and additive at lower dosages. Receptor adaptation studies using the two isomers support a previous single unit study demonstrating the presence of at least two functionally different receptor sites on male A. velutinana antennae; adaptation to an airstream containing one isomer did not eliminate response to the opposite isomer presented concurrently. An airstream containing the third component, 12:Ac, caused a significant slowing of the recovery rate during the entire recovery period of EAG responses to cis but not trans, suggesting that a possible temporal modulation of neuronal response by 12:Ac may be a means of coding for this component by antennal sensory neurons.