Frontalin: a chemical message of musth in Asian elephants (Elephas maximus)

Musth is an important male phenomenon affecting many aspects of elephant society including reproduction. During musth, the temporal gland secretions (as well as the urine and breath) of adult male Asian elephants (Elephas maximus) discharge a variety of malodorous compounds together with the bicyclic ketal, frontalin. In contrast, teenage male elephants in musth release a sweet-smelling exudate from their facial temporal gland. We recently demonstrated that the concentration of frontalin becomes increasingly evident as male elephants mature. In the present study, we demonstrate that behaviors exhibited towards frontalin are consistent and dependent on the sex, developmental stage and physiological status of the responding conspecific individual. To examine whether frontalin functions as a chemical signal, perhaps even a pheromone, we bioassayed older and younger adult males, and luteal- and follicular-phase and pregnant females for their chemosensory and behavioral responses to frontalin. Adult males were mostly indifferent to frontalin, whereas subadult males were highly reactive, often exhibiting repulsion or avoidance. Female chemosensory responses to frontalin varied with hormonal state. Females in the luteal phase demonstrated low frequencies of responses, whereas pregnant females responded significantly more frequently, with varied types of responses including those to the palatal pits. Females in the follicular phase were the most responsive and often demonstrated mating-related behaviors subsequent to high chemosensory responses to frontalin. Our evidence strongly suggests that frontalin, a well-studied pheromone in insects, also functions as a pheromone in the Asian elephant: it exhibits all of the determinants that define a pheromone and evidently conveys some of the messages underlying the phenomenon of musth.     

Purification, Identification, Concentration and Bioactivity of (Z)-7-Dodecen-1-yl Acetate: Sex Pheromone of the Female Asian Elephant, Elephas maximus

In their natural ecosystems, adult male and female Asian elephants,Elephas maximus, live separately. For several weeks prior toovulation, female elephants release a substance in their urinewhich elicits a high frequency of non-habituating chemosensoryresponses, especially flehmen responses, from male elephants.These responses occur prior to, and are an integral part of,mating. Using bioassay-guided fractionation, quantitativelydependent on these chemosensory responses, a specific sex pheromonewas isolated and purified by an alternating series of organicand/or aqueous extractions, column chromatography, gas chromatographyand high-performance liquid chromatography. Using primarily¹H-proton nuclear magnetic resonance (NMR) spectrometry andgas chromatography-mass spectrometry (GC-MS) of the urine-derivedpheromone and its dimethyl disulfide derivative, we determinedthe structure of the active compound to be (Z)-7-dodecen-1-ylacetate (Z7-12:Ac). Concentrations of Z7-12:Ac in the femaleurine increased from non-detectable during the luteal phaseto 0.48µg/ml (0.002 mM) early in the follicular phaseand to 33.0µg/ml (0.146 mM) just prior to ovulation. Bioassayswith commercially available authentic synthetic Z7-12:Ac, using10 Asian male elephants at several locations in the US, demonstratedquantitatively elevated chemosensory responses that were robustduring successive tests, and several mating-associated behaviors.Bioassays with Z7-12:Ac with adult male elephants dwelling inmore natural social situations in forest camps in Myanmar revealedsome differing contextual pre-mating behavioral components.The remarkable convergent evolution of this compound suggeststhat compounds identified in mammalian exudates that are alsopresent in pheromone blends of insects should be re-evaluatedas potential mammalian chemosignals. Chem. Senses 22: 417–437,1997.     

Sex pheromone components of the carpenterworm moth,Holcocerus vicarius

Extracts of the female sex pheromone gland of the carpenterworm moth, Holcocerus vicarius (Walker) (Lepidoptera: Cossidae), a pest of Ulmus pumila L. (Ulmaceae), were found to contain Z7‐tetradecenyl acetate (Z7‐14Ac), E3‐tetradecenyl acetate (E3‐14Ac), (Z3,E5)‐tetradecenyl acetate (Z3,E5‐14Ac), and Z7‐tetradecenyl alcohol (Z7‐14OH) by coupled gas chromatographic‐electroantennographic detection (GC‐EAD) and coupled gas chromatography‐mass spectrometry (GC‐MS). Field trapping studies with impregnated rubber septa indicated that Z7‐14Ac was essential for attraction of males of H. vicarius. However, the most attractive blend contained Z7‐14Ac, E3‐14Ac, Z3,E5‐14Ac, and Z7‐14OH in a 50:22:17:10 ratio. Our results demonstrated that a blend of Z7‐14Ac, E3‐14Ac, Z3,E5‐14Ac, and Z7‐14OH represented the sex pheromone of H. vicarius. The optimized four‐component lure blend may be useful for monitoring H. vicarius infestations and mating disruption.     

Independence of Sexual and Anti-Predator Perceptual Functions in an Acoustic Moth: Implications for the Receiver Bias Mechanism in Signal Evolution

The receiver bias model for the evolution of mating signals proposes that selection favors male displays that happen to stimulate a general, ancestral perception in females such that receptivity and successful courtship increase. If these male signals do arise, however, the female perception will operate in two contexts, the original, typically non‐sexual, one and courtship. We may then ask whether these two functions represent the same or distinct traits, which may be under separate neural and genetic control. We studied this question in Achroia grisella, a pyralid moth species in which males attract females, with an ultrasonic mating song. Hearing in pyralid moths is widespread and originated in an anti‐predator context – the perception and avoidance of echolocating bats – and it is inferred that the male song found in A. grisella, and in several other pyralid species, arose subsequently via a receiver bias mechanism: Females perceiving male‐produced ultrasound and responding with anti‐predator behavior normally exhibited in the presence of bat echolocations may have inadvertently increased the likelihood of successful courtship. We measured hearing responses in both sexual and anti‐predator contexts in inbred lines developed from an A. grisella population. Significant inter‐line variance was observed for sensitivity thresholds for female response to male song and for both female and male responses to synthetic bat echolocation signals. Female responses to male song and to synthetic echolocations differed markedly in sensitivity, and the median sexual and anti‐predator responses in the various lines were not correlated. However, a higher level of similarity occurs between the female and male anti‐predator responses. Thus, genetic variance for sexual and anti‐predator responses appears to exist, and the two responses may represent independent traits. These results imply that when male signals originate via a receiver bias mechanism, female perception does not necessarily remain fixed in its ancestral state but has the potential for continued modification.     

Sex pheromone of a North American population of the spotted tentiform leafminer, Phyllonorycter blancardella

The major sex pheromone compound of the spotted tentiform leafminer, Phyllonorycter blancardella (F.) (Lepidoptera: Gracillariidae), from Ontario, Canada, was identified as (10E)‐dodecen‐1‐yl acetate (E10‐12:Ac) using chemical analysis and field trapping experiments. The minor compounds (10E)‐dodecen‐1‐ol (E10‐12:OH) (4.6%), dodecan‐1‐ol (12:OH) (2.3%), and (10Z)‐dodecen‐1‐yl acetate (Z10‐12:Ac) 1.6% were also identified. The dienic acetate (4E,10E)‐dodecadien‐1‐yl acetate (E4,E10‐12:Ac), a compound reported to be attractive to P. blancardella, was not found in the glands of this population. A two‐component blend of the major and one of each the three minor compounds, in ratios similar to those found in the sex pheromone gland, did not increase the attractiveness of traps baited with synthetic pheromone. The minor compounds E10‐12:OH and 12:OH were not attractive to P. blancardella when tested individually. Z10‐12:Ac was attractive to P. blancardella, although traps baited with this compound captured only 2% of the moths that were captured in traps baited with the main compound. A four‐component blend of the major and each of the three minor compounds (100 : 1 : 1 : 1) was not more attractive than the major compound alone. The related species Phyllonorycter mespilella was captured in traps baited with E10‐12:Ac.     

Concentration of air-borne pheromone required for long-lasting peripheral adaptation in the obliquebanded leafroller, Choristoneura rosaceana

Abstract. Electroantennogram (EAG) responses of male obliquebanded leafrollers, Choristoneura rosaceana (Harris), to the main component of its pheromone blend and traces of geometric isomer ((Z)11‐14:Ac and (E)11‐14:Ac, respectively) were recorded before and after 1 h of continuous exposure to pheromone in laboratory experiments, and 24 h of exposure under field conditions. Concentrations of pheromone ranging from 56 to below 1 ng mL^?1 air in Teflon chambers with regulated air exchange reduced peripheral sensory responses by 40–60% as measured by amplitudes of the EAG. Adaptation did not increase in a dosage‐dependent fashion over most of this range; an identical reduction of responsiveness was observed at each exposure to an effective concentration. Exposure of C. rosaceana at a loading dosage of 1 ng of pheromone in 100 µL of mineral oil (air concentration below the GLC detection limit) did not induce measurable adaptation. Caging C. rosaceana in apple trees adjacent to one, two or four Isomate OBLR/PLR Plus polyethylene pheromone dispensers for 24 h resulted in long‐lasting adaptation similar to that seen in laboratory experiments. Adaptation was not observed for C. rosaceana caged at a distance of 2 m from Isomate dispensers in 1‐ha plots treated with 500 dispensers per ha. Whenever observed, this type of adaptation was expressed for more than 5 min after exposure to pheromone ceased. Collectively, this adaptation phenomenon in C. rosaceana is consistent with the third of Zufall & Leinders‐Zufall's types of olfactory adaptation that is ‘long‐lasting’. Although the dosage of pheromone required to induce long‐lasting adaptation in this moth is judged high relative to that for normal sexual communication, we suggest this type of adaptation may come into play for some but not all moths under pest‐control regimes using the tactic of pheromone‐disruption, particularly those using high‐dosage release technologies like pheromone rope dispensers or Microsprayers.     

Variation of acceptance thresholds in the blowfly by increasing sugar concentrations in the food

Summary Aduld blowflies,Phormia regina M., were raised on different concentrations of sucrose. The thresholds of the behavioral responses to tarsal stimulation were elevated in blowflies raised on high concentrations of sucrose. The relationship between the median acceptance thresholds and the raising concentration of sucrose was logarithmically linear. Two groups of experimental flies were prepared: (1) coated flies, in which only D-type chemosensory hairs could respond physiologically, and (2) treated flies, in which all chemosensory hairs except D-type hairs functioned physiologically. Proboscis extension responses were ascertained in both groups. Median acceptance thresholds for the coated and treated flies, respectively, were presumed to be logarithmically linear in relation to the raising concentration of sucrose. It was supposed that D-type sugar receptor impulses initiate mainly the proboscis extension responses under the 0.01 M sucrose threshold and that B-type sugar receptor impulses initiate the responses above the 0.01 M sucrose threshold. Median acceptance thresholds for whole labellar stimulation were elevated to 0.026 M sucrose in blowflies raised on 1.0 M sucrose. Median acceptance thresholds were again lowered in blowflies raised on sucrose of more than 1.0 M.This research was supported in part by ITO foundation and Scientific Research Fund from the Ministry of Education of Japan.     

SEX CHROMOSOME LINKED GENETIC VARIANCE AND THE EVOLUTION OF SEXUAL DIMORPHISM OF QUANTITATIVE TRAITS

Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here, we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex‐linked genetic variance (h²_z). Of 17 traits examined, eight showed a nonzero h²_Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak color in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex‐linked genetic variance. Sexually selected traits did not show higher h²_Z than morphological traits and there was only a weak positive relationship between h²_Z and sexual dimorphism. However, given the relative scarcity of empirical studies, it is premature to make conclusions about the role of sex chromosome linkage in the evolution of sexual dimorphism.     

Evolution of sexually dimorphic pheromone profiles coincides with increased number of male‐specific chemosensory organs in Drosophila prolongata

Binary communication systems that involve sex‐specific signaling and sex‐specific signal perception play a key role in sexual selection and in the evolution of sexually dimorphic traits. The driving forces and genetic changes underlying such traits can be investigated in systems where sex‐specific signaling and perception have emerged recently and show evidence of potential coevolution. A promising model is found in Drosophila prolongata, which exhibits a species‐specific increase in the number of male chemosensory bristles. We show that this transition coincides with recent evolutionary changes in cuticular hydrocarbon (CHC) profiles. Long‐chain CHCs that are sexually monomorphic in the closest relatives of D. prolongata (D. rhopaloa, D. carrolli, D. kurseongensis, and D. fuyamai) are strongly male‐biased in this species. We also identify an intraspecific female‐limited polymorphism, where some females have male‐like CHC profiles. Both the origin of sexually dimorphic CHC profiles and the female‐limited polymorphism in D. prolongata involve changes in the relative amounts of three mono‐alkene homologs, 9‐tricosene, 9‐pentacosene, and 9‐heptacosene, all of which share a common biosynthetic origin and point to a potentially simple genetic change underlying these traits. Our results suggest that pheromone synthesis may have coevolved with chemosensory perception and open the way for reconstructing the origin of sexual dimorphism in this communication system.     

Identification and field and laboratory tests of the sex pheromone of Cerconota anonella Sepp. (Lepidoptera: Oecophoridae)

The Annona fruit borer, Cerconota anonella Sepp., is a serious agricultural pest in many tropical areas of the world. The identification of an attractant for male C. anonella could offer new methods for pest detection and control. A mixture of compounds extracted from female C. anonella elicited antennal depolarization in the male borer. These compounds were identified as octadecanal, 1‐octadecanol, octadecyl acetate, (Z)‐octadec‐9‐enal (Z9‐18:Ald), (Z)‐octadec‐9‐en‐1‐ol (Z9‐18:OH) and [(Z)‐octadec‐9‐enyl] acetate (Z9‐18:Ac) by one‐ and two‐dimensional gas chromatography–mass spectrometry. In laboratory bioassays, synthetic individual compounds as well as synthetic mixtures were found to be attractive to males. In addition, field tests using Delta traps with 1 mg of the ternary mixture composed of Z9‐18:Ac, Z9‐18:Ald and Z9‐18:OH in the ratio of 1 : 3 : 5 caught as many males as traps containing virgin females. The ternary mixture of Z9‐18:Ac, Z9‐18:Ald and Z9‐18:OH was identified as attractant to C. anonella males and can be used to detect and control populations of this insect in Annonaceae plantations.     

The conformational properties of dehydrobutyrine and dehydrovaline: theoretical and solid‐state conformational studies

Dehydrobutyrine is the most naturally occurring dehydroamino acid. It is also the simplest dehydroamino acid having the geometrical isomers E/Z. To investigate its conformational properties, a theoretical analysis was performed on N‐acetyl‐α,β‐dehydrobutyrine N′‐methylamides, Ac‐(E)‐ΔAbu‐NHMe and Ac‐(Z)‐ΔAbu‐NHMe, as well as the dehydrovaline derivative Ac‐ΔVal‐NHMe. The ?, ψ potential energy surfaces and the localised conformers were calculated at the B3LYP/6‐311 + + G(d,p) level of theory both in vacuo and with inclusion of the solvent (chloroform, water) effect (SCRF method). The X‐ray crystal structures of Ac‐(Z)‐ΔAbu‐NHMe and Ac‐ΔVal‐NHMe were determined at 85 and 100 K, respectively. The solid‐state conformational preferences for the studied residues have been analysed and compared with the other related structures. Despite the limitations imposed by the C^α = C^β double bond on the topography of the side chains, the main chains of the studied dehydroamino acids are more flexible than in standard alanine. The studied dehydroamino acids differ in their conformational preferences, which depend on the polarity of the environment. This might be a reason why the nature quite precisely differentiates between ΔVal and each of the ΔAbu isomers, and why, particularly so with the latter, they are used as a conformational tool to influence the biological action of usually small, cyclic dehydropeptides. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Optimization of pheromone lure and trap design for monitoring the fir coneworm, Dioryctria abietivorella

The major components of the sex pheromone of Dioryctria abietivorella (Groté) (Lepidoptera: Pyralidae) were recently identified as (9Z,11E)‐tetradecadien‐1‐yl acetate (9Z,11E‐14:Ac) and a polyunsaturated, long‐chain hydrocarbon (3Z,6Z,9Z,12Z,15Z)‐pentacosapentaene (C25 pentaene). The optimal ratio of these components and the role of potential minor components were not fully determined in the initial short report on the pheromone's identification. We tested different ratios of the two major components loaded into grey halobutyl rubber septum dispensers, placed in sticky traps deployed in conifer breeding arboreta. The optimal ratio of the two components was 200 µg 9Z,11E‐14:Ac to 2000 µg C25 pentaene. (Z)‐9‐Tetradecen‐1‐yl acetate, which had been identified previously in female pheromone gland extracts, and five other potential minor pheromone components, were tested individually as additions to the optimized two‐component lure blend. None of the ternary blends were more attractive than the optimized two‐component blend, at the ratios tested. Two lure adjuvants, a UV stabilizer (Sumisorb 300) and the antioxidant butylated hydroxytoluene, added individually or together, did not affect the attractiveness of the optimized lure blend. The Pherotech diamond sticky trap baited with the optimized lure blend was the most effective trap design among eight types of sticky trap and a bucket style trap that were tested. Traps baited with synthetic lures were as attractive as traps baited with virgin female moths. The optimized two‐component lure blend in the Pherotech diamond trap is recommended for monitoring fir coneworm infestations. The availability of an effective synthetic pheromone opens the possibility for control tactics using mating disruption or attract‐and‐kill techniques.     

Sex pheromone composition of the variegated cutworm,Peridroma saucia (Lepidoptera: Noctuidae), in Korea

This study was conducted to investigate the sex pheromone composition of the variegated cutworm (Peridroma saucia Hübner) in Korea. The sex pheromone components of P. saucia were identified as (Z)-9-tetradecenyl acetate (Z9-14:Ac) and (Z)-11-hexadecenyl acetate (Z11-16:Ac) through GC-EAD and GC–MS analysis. EAG tests of the male antennae revealed that the Z9-14:AC exerted significantly larger responses than other compounds. The female moths primarily called and copulated between 6 h and 7 h after the lights off, and the ratio of two pheromone components, Z9-14:Ac and Z11-16:Ac, in the sex pheromone gland during this period was 1:2.1 to 1:2.4. In the field trapping studies, a large number of male moths were caught in the traps baited with the mixtures of Z9-14:Ac and Z11-16:Ac at the ratios ranging from 2.3:1 to 1:4, with the highest trap catches at 1:1 to 1:2.3 ratios of the two components. The seasonal flight activities of P. saucia monitored by using pheromone lures revealed complicated patterns in Korea. Specifically, the first flight period was spread over a long period and irregular, while the second flight period differed among the localities examined.     

Fine‐scale group structure and demography of African savanna elephants recolonizing lands outside protected areas

Aim Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human‐dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships. Location Rift Valley province of Kenya. Methods We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure. Results We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (R = 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher‐order genetic relationships among female groups. Males detected together were unrelated (R = 0.003 ± 0.030). Main conclusions Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non‐invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.     

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

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

Population structure and behaviour of crop-raiding elephants in Kibale National Park, Uganda

We examined patterns of crop raiding by elephants across gender and age classes in relation to elephant life history and sociobiology and estimated the quantitative contribution of crops to elephant diet in Kibale National Park (KNP). Elephant dung‐boli sizes were used to estimate age and sex, while the presence of crop remains in the dung of crop‐raiding elephants was used as evidence of repeated raiding. To estimate the expected proportion of elephants raiding per age class, the age distribution of raiders was compared with the age distribution of all KNP elephants. Elephants raiding crops were predominantly males. They began raiding in expected proportions at 10–14 years while a higher than expected proportion raided crops at 20–24 years. These results suggest that crop raiding is initiated at an age when male elephants leave their families and a large proportion of elephants raid when they are approaching reproductive competition. Evidence from dung of crop raiders, suggests that repeated raiding increases with age. Crop raiders derived 38% of their daily forage from the short time spent raiding, consistent with expectations of foraging theory. Males may be more likely to learn crop raiding because they are socially more independent and experience intense mating competition than females.     

Factors affecting the reproductive biology of Melittobia digitata and failure to meet the sex ratio predictions of Hamilton's local mate competition theory

Melittobia digitata Dahms (Eulophidae, Tetrastichini), a species of parasitic wasp satisfying all of Hamilton's local mate competition requisites, does not exhibit the predicted change in sex ratio with increased foundress number. A multifactorial design was used to test how age, oviposition experience, feeding experience, mating, and foundress number affect host‐acceptance, number of offspring, and sex ratio of this species developing on honey bee pupae, Apis mellifera (L.) (Apidae, Apini). All factors significantly affected the time it took for oviposition to commence. Females oviposited soonest when they were 2 days old, mated, had previous feeding and oviposition experience, and were placed on hosts with multiple foundresses. Although the age difference between 2‐ and 5‐day‐old females is small, it significantly affected reproductive behavior. Age, mating, and foundress number were found to have an effect on sex ratio, however, the foundress effect was found to be a mathematical artifact of the limited host size. After correcting for this variable, females were found to have a constant sex ratio of approximately 0.05. Several 2‐way interactions between factors were revealed: age and experience, age and foundress number, age and mating, foundress number and experience, and foundress number and mating. One 3‐way interaction was found between age, mating, and foundress number. This study demonstrates that the sex ratio of M. digitata is not altered with increased foundresses, as predicted by Hamilton , and that slight changes in preconditioning may modify reproductive behavior.     

β-turn tendency in N-methylated peptides with dehydrophenylalanine residue: DFT study

The tendency to adopt β‐turn conformation by model dipeptides with α,β‐dehydrophenylalanine (ΔPhe) residue in the gas phase and in solution is investigated by theoretical methods. We pay special attention to a dependence of conformational properties on the side‐chain configuration of dehydro residue and the influence of N‐methylation on β‐turn stability. An extensive computational study of the conformational preferences of Z and E isomers of dipeptides Ac‐Gly‐(E/Z)‐ΔPhe‐NHMe ( 1a / 1b ) and Ac‐Gly‐(E/Z)‐ΔPhe‐NMe₂ ( 2a / 2b ) by B3LYP/6‐311++G(d,p) and MP2/6‐311++G(d,p) methods is reported. It is shown that, in agreement with experimental data, Ac‐Gly‐(Z)‐ΔPhe‐NHMe has a great tendency to adopt β‐turn conformation. In the gas phase the type II β‐turn is preferred, whereas in the polar environment, the type I. On the other hand, dehydro residue in Ac‐Gly‐(E)‐ΔPhe‐NHMe has a preference to adopt extended conformations in all environments. N‐methylation of C‐terminal amide group, which prevents the formation of 1←4 intramolecular hydrogen bond, change dramatically the conformational properties of studied dehydropeptides. Especially, the tendency to adopt β‐turn conformations is much weaker for the N‐methylated Z isomer (Ac‐Gly‐(Z)‐ΔPhe‐NMe₂), both in vacuo and in the polar environment. On the contrary, N‐methylated E isomer (Ac‐Gly‐(E)‐ΔPhe‐NMe₂) can easier adopt β‐turn conformation, but the backbone torsion angles (?₁, ψ₁, ?₂, ψ₂) are off the limits for common β‐turn types. © 2012 Wiley Periodicals, Inc. Biopolymers 97:518–528, 2012.     

Odour quality discrimination for behavioural antagonist compounds in three tortricid species

The antennal and behavioural response of three tortricid species (Lepidoptera: Tortricidae) to their corresponding sex pheromones and known or putative behavioural antagonists was tested by electroantennography and in field trials. The species and their pheromones and known or proposed behavioural antagonist were lightbrown apple moth, Epiphyas postvittana (Walker) [pheromone: 95% (E)‐11‐tetradecenyl acetate (E11‐14Ac) and 5% (E,E)‐9,11‐tetradecadienyl acetate (E9E11‐14Ac); antagonist: (Z)‐11‐tetradecenyl acetate (Z11‐14Ac)], codling moth, Cydia pomonella (L.) [pheromone: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone); antagonist: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate)], and gorse pod moth, Cydia ulicetana (Haworth) [pheromone: (E,E)‐8,10‐dodecadienyl acetate (codlemone acetate); putative antagonist: (E,E)‐8,10‐dodecadien‐1‐ol (codlemone)]. In all three species, the antennal response to the antagonists was not significantly different from the antennal response to con‐specific sex pheromone compounds. In the field trapping experiments, significantly fewer males of all three species were attracted to the respective pheromone when blended with the behavioural antagonist compound. However, this response varied between the species, with lightbrown apple moth and codling moth showing stronger responses to the antagonist compounds than gorse pod moth. Both lightbrown apple moth and codling moth males were able to discriminate between pure pheromone and pheromone blended with the antagonist when placed in traps side‐by‐side separated by ca. 10 cm. The presence of the behavioural antagonist not only affected the catch of males of both species within their own traps but also affected the catch in the neighbouring trap that contained con‐specific sex pheromone; the catch of gorse pod moth was not reduced by the presence of codlemone in the neighbouring trap. These results suggest that strong behavioural antagonists such as codlemone acetate for codling moth and Z11‐14Ac for lightbrown apple moth induce their inhibition effect at a substantial distance downwind from the odour source; however, most of those males that were able to overcome this inhibition effect at the early stage of orientation to odour source, were able to discriminate between the pheromone source and the pheromone source admixed with behavioural antagonist. Moderate behavioural antagonists such as codlemone for gorse pod moth did not elicit a discrimination effect.     

Plant volatiles in the sexual communication of Melolontha hippocastani: response towards time-dependent bouquets and novel function of (Z)-3-hexen-1-ol as a sexual kairomone

1. Swarming males of Melolontha hippocastani are known to locate females that stay feeding within the host trees by orienting towards damage‐induced plant volatiles (green leaf volatiles) and a sex pheromone. Thus, volatiles emitted by freshly damaged leaves might indicate to a male the presence of currently feeding females. 2. The hypothesis was studied that volatiles from freshly damaged leaves are more attractive to males than volatiles from old damaged leaves. The odour bouquets of damaged leaves from three plant species that have been shown to attract male M. hippocastani in the field were analysed 10 min (fresh damage) and 1.5 h (old damage) after damaging, using coupled gas chromatography–mass spectrometry. The results showed clear differences between the bouquets: the bouquet of freshly damaged leaves of all species consisted of typical leaf aldehydes, i.e. hexanal, (Z)‐3‐hexenal, (Z)‐2‐hexenal, (E)‐2‐hexenal, the leaf alcohol (Z)‐3‐hexen‐1‐ol, and the corresponding acetate. One and a half hours after damage, aldehydes had almost vanished and (Z)‐3‐hexen‐1‐ol and (Z)‐3‐hexenyl acetate predominated; however males of M. hippocastani were equally attracted to traps baited with volatiles from old and freshly damaged leaves in field experiments. When traps were baited with synthetic volatile mixtures mimicking the bouquets of old and freshly damaged leaves, M. hippocastani males even preferred the old damage mixture. 3. Experiments addressing the role of individual green leaf volatiles revealed that only (Z)‐3‐hexen‐1‐ol was highly attractive while the other compounds tested individually were behaviourally inactive, however all tested compounds elicited comparable electrophysiological responses on male M. hippocastani antennae. 4. In analogy to the term aggregation kairomone used for feeding‐induced plant volatiles that attract both sexes of an insect, the term sexual kairomone is suggested to describe the novel function of (Z)‐3‐hexen‐1‐ol in the sexual communication of M. hippocastani.