Volatile organic chemicals of a shore-dwelling cyanobacterial mat community

The main components of a cyanobacterial mat community of a hypersaline lake shore consist of edaphic, mat-forming strains (ecophenes), and littoral strains ofOscillatoria animalis Agardh andO. subbrevis Schmidle, other microorganisms associated with these cyanobacteria, several species ofBembidion (Carabidae: Coleoptera), and two halophytic flowering plants:Puccinellia nuttalliana (salt meadow grass) andSalicornia europaea rubra (samphire). The volatile organic compounds of this community are a blend of those emitted by each of these components such as the C₁₇ alka(e)nes, geosmin, 2-methylisoborneol,-cyclocitral,-ionone, dimethyl sulfide, and dimethyl trisulfide of cyanobacteria and associated microorganisms; alcohols, esters, and aldehydes usually associated with flowering plants; and possibly some insect-derived esters, particularly isopropyl tetradecanoate. The dominant compounds were: C₁₁, C₁₃, C₁₅, and C₁₇ alka(e)nes, methyl esters of C₁₆ and C_18:2 acids, isopropyl tetradecanoate, heptanal, 3-octanone and 2-nonanone, the acyclic terpene linalool, and the alcohols 1-heptanol, 1-hexanol, 1-octanol, 3-hexen-1-ol, and 2-octen-1-ol. It is concluded that this community may be distinguished from related communities by its repertoire of volatile organic compounds.     

Defense-Inducing Volatiles: In Search of the Active Motif

Herbivore-induced volatile organic compounds (VOCs) are widely appreciated as an indirect defense mechanism since carnivorous arthropods use VOCs as cues for host localization and then attack herbivores. Another function of VOCs is plant–plant signaling. That VOCs elicit defensive responses in neighboring plants has been reported from various species, and different compounds have been found to be active. In order to search for a structural motif that characterizes active VOCs, we used lima bean (Phaseolus lunatus), which responds to VOCs released from damaged plants with an increased secretion of extrafloral nectar (EFN). We exposed lima bean to (Z)-3-hexenyl acetate, a substance naturally released from damaged lima bean and known to induce EFN secretion, and to several structurally related compounds. (E)-3-hexenyl acetate, (E)-2-hexenyl acetate, 5-hexenyl acetate, (Z)-3-hexenylisovalerate, and (Z)-3-hexenylbutyrate all elicited significant increases in EFN secretion, demonstrating that neither the (Z)-configuration nor the position of the double-bond nor the size of the acid moiety are critical for the EFN-inducing effect. Our result is not consistent with previous concepts that postulate reactive electrophile species (Michael-acceptor-systems) for defense-induction in Arabidopsis. Instead, we postulate that physicochemical processes, including interactions with odorant binding proteins and resulting in changes in transmembrane potentials, can underlie VOCs-mediated signaling processes.     

Chemical Defense in the Plant Bug Lopidea robiniae (Uhler)

Secretions from the metathoracic glands (MTG) of the black locust bug, Lopidea robiniae (Uhler) (Heteroptera: Miridae) contained six major compounds, including (E)-2-hexenal, (E)-2-hexen-1-ol, (E)-2-octenal, (E)-2-octen-1-ol (E)-2-heptenal, and (Z)-3-octen-1-ol. Males and females did not differ significantly in the relative compositions of identified compounds. In feeding trials, six bird species [robin (Turdus migratorious), blue jay (Cyanocitta cristata), brown thrasher (Toxostoma rufum), killdeer (Charadrius vociferus), starling (Sturnus vulgaris), and house wren (Troglodytes aedon)] demonstrated feeding aversions towards L. robiniae, implying that black locust bugs are chemically defended. Bugs discharged the liquid contents of their MTG when attacked, thereby producing a strong and distinct odor. Some birds immediately ejected bugs out of their mouth after biting them, suggesting that the MTG secretion was a deterrent.     

Essential Compounds in Herbivore-Induced Plant Volatiles that Attract the Predatory Mite <Emphasis Type="Italic">Neoseiulus womersleyi</Emphasis>

Carnivorous arthropods use volatile infochemicals emitted from prey-infested plants in their foraging behavior. Although several volatile components are common among plant species, the compositions differ among prey–plant complexes. Studies showed that the predatory mite Neoseiulus womersleyi is attracted only to previously experienced plant volatiles. In this study, we identified the attractant components in prey-induced plant volatiles of two prey–plant complexes. N. womersleyi reared on Tetranychus kanzawai-infested tea leaves showed significant preference for a mixture of three synthetic compounds [mimics of the T. kanzawai-induced tea leaves volatiles: (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), and (E,E)-α-farnesene] at a level comparable to that for T. kanzawai-induced tea plant volatiles. However, mixtures lacking any of these compounds did not attract the predatory mites. Likewise, N. womersleyi reared on T. urticae-infested kidney bean plants showed a significant preference for a mixture of four synthetic compounds [mimics of the T. urticae-induced kidney bean volatiles: DMNT, methyl salicylate (MeSA), β-caryophyllene, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene] at a level comparable to that for T. urticae-induced kidney bean volatiles. The absence of any of the four compounds resulted in no attraction. These results indicate that N. womersleyi can use at least four volatile components to identify prey-infested plants.     

Assignment of13C nuclear magnetic resonance signals in fatty compounds with allylic hydroxy groups

¹³C Nuclear magnetic resonance (NMR) signals in several fatty compounds with allylic mono- and dihydroxy groups were assigned by comparing compounds with and without other functional groups (allylic hydroxy, carboxylic acid, respectively, methyl ester at C₁). The simple¹³C NMR spectra of hydroxylated compounds derived from symmetrical alkenes are particularly useful in making assignments. The compounds whose signals were partially assigned are 8-hydroxy-9(E)-octadecenoic acid, 11-hydroxy-9(E)-octadecenoic acid, 8, 11-dihydroxy-9(E)-octadecenoic acid, 9(E)-octadecen-8-ol, and 9(E)-octadecene-8, 11-diol. The present evaluation can be used for assigning signals in other fatty compounds.     

Syntheses of pure (9Z, 11Z), (9E, 11E), (9E, 11Z), and (9Z,11E)-9,11-hexadecadienals-possible candidate pheromones

The title compounds were prepared by six different routes, and recommendations are given for the more convenient procedures in laboratory-scale syntheses. Modifications in the literature preparations of the 9E,11E and 9E,11Z isomers are described. Baseline separation of a prepared mixture of all four isomers of the (9Z, 11Z), (9E, 11E), (9E, 11Z), and (9Z, 11E)-9,11-hexadecadienals was achieved using GC methods with standard capillary columns. [¹³C]NMR spectroscopy of the alkene carbon atoms clearly differentiates between theZ,Z, E,E and eitherE,Z orZ,E isomers of the precursor dienols and thus of the dienals.     

Cuticular hydrocarbons ofReticulitermes virginicus (Banks) and their role as potential species- and caste-recognition cues

The cuticular hydrocarbon components of four castes ofReticulitermes virginicus (Banks) have been identified and quantitated. Components identified includen-alkanes; 2-, 3-, 11-, 13-, and 15-methyl-alkanes; 11,15-dimethylalkanes, (Z)-9-alkenes; (Z,Z)-7,9-dienes; and (E/Z)-6,9-dienes ranging in carbon number from C₂₁ to C₄₀. All caste forms ofR.virginicus contained the same components, but showed caste-specific proportions. Comparison of these hydrocarbons with those of the sympatric termiteR. flavipes (Kollar) suggest that cuticular hydrocarbons might serve as species- and caste-recognition cues. A bioassay was developed to test this species-recognition hypothesis, with the experimental results supporting the hypothesis.Isoptera: Rhinotermitidae.     

Specificity of Systemically Released Cotton Volatiles as Attractants for Specialist and Generalist Parasitic Wasps

Cotton plants under herbivore attack release volatile semiochemicals that attract natural enemies of the herbivores to the damaged plant. The volatiles released in response to herbivory are not only released from the damaged leaves but from the entire cotton plant. We found that cotton plants that released myrcene, (Z)-3-hexenyl acetate, (E)--ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)--farnesene, and (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene systemically from undamaged leaves of caterpillar damaged plants were attractive to the generalist parasitoid Cotesia marginiventris and the specialist parasitoid Microplitis croceipes. Plants from which the caterpillar damaged leaves were removed and that released those compounds systemically were significantly preferred over undamaged control plants in two-choice experiments in a flight tunnel. Artificially damaged cotton plants that released green leafy volatiles and constitutive terpenoids were less attractive for M. croceipes and C. marginiventris. Only C. marginiventris preferred artificially damaged plants over undamaged control plants, whereas M. croceipes showed no preference. The apparent lack of specificity of systemically released compounds in response to different herbivores feeding on the lower leaves is discussed.     

Preparation and properties of new lactose-based surfactants

A new group of nonionic saccharide-based surfactants, N-alkanoyl-N-methyllactitolamines (alkanoyl: decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl), were synthesized and characterized. Surface properties such as critical micelle concentration, standard free energy of adsorption, standard free energy of micellization, surface tension reduction efficiency, effectiveness of surface tension reduction, surface excess concentration, and surface area demand per molecule as well as foaming properties (i.e., foam volume and foam stability), contact angle, antiraicrobial activity, and biodegradability were determined. The selected performance properties were evaluated in relation to commercially available alkyl polyglucosides (Glukopon 600 EC(HH)-a Henkel product), and oligooxyethylenated decyl (C₁₀E₄) and dodecyl (E₁₂E₅) alcohols. The foaming-stabilizing effect and contact angle suggest that the lactose-derived surfactants that were studied share some common properties with alkyl polyglucosides that are different from those with an oligooxyethylene grouping. All tested N-alkanoyl-N-methyllactitolamines were practically nontoxic to bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle test inoculated with activated sludge. N-Alkanoyl-N-methyllactitolamines with lower chain lengths (C₁₀–C₁₄) biodegraded at a slightly faster rate. Biological properties showed that this class of compounds fulfills all requirements needed for environmental acceptance.     

Nature and role of sexual pheromones emitted by males ofAcrolepiopsis assectella (LEP.)

Seven compounds that do not exist in the extracts from legs of males have been isolated in the hair-pencil extracts of maleAcrolepiopsis assectella. By combining techniques of GC-MS and GC-FT-IR, six of these compounds have been identified. They are sixn-alkanes: hexadecane (C₁₆), heptadecane (C₁₇), octadecane (C₁₈), nonadecane (C₁₉), eicosane (C₂₀), and heneicosane (C₂₁). Twelven-alkanes of the homologous series, from the C₁₄–C₂₅ compounds were presented to virgin females, mated females, and males. At the end of the scotophase, four of then-alkanes (C₁₆, C₁₇, C₁₉, C₂₁) present in the hair-pencil extract induced the virgin females to adopt the acceptance posture after having induced the virgin females to remain stationary. The two othern-alkanes (C₁₈ and C₂₀) present in the extract have less effect on the females similar to then-alkanes not present in the males. The blends tested do not seem to indicate any synergy between the most active compounds. The threen-alkanes with an odd number of carbons and the C₁₆ compound would thus be the principle components of the male pheromone ofA. assectella. As well as their role of female aphrodisiac, they tend to make males and fertilized females flee.     

New components in defensive secretion of the striped skunk,Mephitis mephitis

GC-MS analysis of the anal sac secretion of the striped skunk (Mephitis mephitis), shows seven major components: (E)-2-butene-1-thiol, 3-methyl-1-butanethiol, S-(E)-2-butenyl thioacetate,S-3-methylbutanyl thioacetate, 2-methylquinoline, 2-quinolinemethanethiol, andS-2-quinolinemethyl thioacetate. The following compounds previously reported from this secretion could not be confirmed: bis(2-butenyl) sulfide, (E)-2-Butenyl methyl disuffide, (E)-2-butenyl propyl sulfide, butyl 3-methylbutyl disulfide, and 2-butenyl butyl disulfide.     

Volatile compounds released by disturbed and calm adults of the tarnished plant bug,Lygus lineolaris

Volatile compounds released by disturbed and calm female and male Lygus lineolaris were collected and analyzed. Six major compounds were present in samples from disturbed bugs and from calm females: (E)-2-hexenal, 1-hexanol, (E)-2-hexenol, hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-2,4-oxohexenal. (E)-2-hexenal was lacking in volatiles collected from calm males. Hexyl butyrate accounted for approximately 68% and 66% of volatiles released by agitated and calm females, and 87% and 88% of volatiles released by agitated and calm males, respectively. Blends released by disturbed insects differed quantitatively from blends released by calm insects, with amounts of compounds increasing 75–350 times in samples from disturbed insects. In static air bioassays, both females and males were repelled by natural volatiles collected from females and by five-component [(E)-2,4-oxohexenal excluded] and six-component synthetic blends at doses of 1 and 10 bug-hours, indicating that these volatiles may serve an alarm or epideictic function, as well as a possible role as defensive allomones. Adults also avoided hexyl butyrate, (E)-2-hexenyl butyrate, (E)-2-hexenol, and (E)-2,4-oxohexenal, but not 1-hexanol and (E)-2-hexenal when compounds were assayed individually in static air bioassays at doses equal to 1 bug-hour. When tested over 1 day in two-choice cage trials, adults did not prefer untreated bean plants over bean plants surrounded by vials releasing up to 8.1 mg/hr (=234 bug-hours) of the five-component synthetic blend. Therefore, the volatiles produced by disturbed adults would not be useful as a repellent for L. lineolaris.     

Female sex pheromone of the melonworm,Diaphania hyalinata (Lepidoptera: Pyralidae), and analysis of male responses to pheromone in a flight tunnel

Ten C₁₆ chain-length compounds were identified from heptane extracts of ovipositors of female melonworm,Diaphania hyalinata (L.). The major constituents of the extracts were (E)-11-hexadecenal and (E,E)-10,12-hexadecadienal [(E,E)-10,12–16:Ald] and the alcohols and acetates of these olefins were found in trace amounts (<2%). Extracts also contained traces of (E,Z)- and (Z,Z)-10,12-16:Ald, hexadecanal, and 1-hexadecanol. Analysis of the behavioral responses of males to synthetic mixtures of these compounds and responses to ovipositor extracts in a flight tunnel showed that a synthetic mixture of the 10 compounds elicited a behavioral repertoire from males that was indistinguishable from that elicited by ovipositor extract. Flight tunnel studies also indicated that six of the 10 compounds probably represent the essential components of the female's sex pheromone.Supported in part by USDA Cooperative Agreement No. 58-32U4-1-299. Scientific Article No. A-4073, Contribution No. 7058 of the Maryland Agricultural Experiment Station. Mention of a commercial product in this paper does not constitute a recommendation by the U.S. Department of Agriculture.     

Volatile compounds in anal gland of Siberian weasels (Mustela sibirica) and steppe polecats (M. eversmanni)

The volatile constituents in anal gland secretions of two sympatric Mustela species, the Siberian weasel (M. sibirica) and steppe polecat (M. eversmanni), were studied by the headspace technique, followed by gas chromatography–mass spectrometry (GC-MS) analysis. Nine sulfur-containing compounds were identified. They were 2,2-dimethylthietane, (Z)- or (E)-2,4-dimethylthietane, (E)-2,3-dimethylthietane, 2-ethylthietane, (E)-2-ethyl-3-methylthietane, (Z)-2-ethyl-3-methylthietane, 2-propylthietane, 3,3-dimethyl-1,2-dithiacyclopentane, and (Z)-3,4-dimethyl-2,2-dithiacyclopentane. Among them, (E)-2-ethyl-3- methylthietanes, (Z)-2-ethyl-3-methylthietanes, and (Z)-3,4-dimethyl-1,2-dithiacyclopentane were present in the polecat but not in the weasel. The predominant compound was 2,2-dimethylthietane in the weasel and (E)- or (Z)-2,4-dimethylthietane in the polecat. These differences were consistent between the two species, regardless of sex and age and, therefore, could possibly be used for species recognition. In the weasel, 2-ethylthietane was found only in the female, and the relative abundance of several compounds was significantly different between males and females. In the polecat, although no sex-specific volatile compounds were found, males and females differed in the relative abundance of several of the compounds. In both species, the relative abundance of some compounds varied with age. We conclude that these volatile compounds can be used to communicate information about species, sex, and age.     

Role of cuticular hydrocarbons of aphid parasitoids in their relationship to aphid-attending ants

Lysiphlebus cardui, the dominant aphidiid parasitoid of the black bean aphid,Aphis fabae cirsiiacanthoidis (Afc), on creeping thistle, is able to forage in ant-attended aphid colonies without being attacked by ants. Several behavioral observations and experimental studies led to the hypothesis thatL. cardui mimics the cuticular hydrocarbon profile of its host aphid. Chemical analysis of the cuticular extracts revealed that bothL. cardui and Afc exclusively possess saturated hydrocarbons:n-alkanes, monomethyl (MMA), dimethyl (DMA), and trimethyl alkanes (TMA). Comparison of the hydrocarbon profiles of parasitoid and aphid showed great qualitative resemblance between parasitoid and host:L. cardui possesses almost all host-specific compounds in addition to species-specific hydrocarbons of mainly higher molecular weight (>C₃₀). However, there is a lesser quantitative correspondence between parasitoid and host aphid. Furthermore, we analyzed the cuticular hydrocarbon profile of another parasitoid of Afc,Trioxys angelicae. This aphidiid species is vigorously attacked and finally killed by honeydewcollecting ants when encountered in aphid colonies. Its cuticular hydrocarbon profile is characterized by the presence of large amounts of (Z)-11-alkenes of chain lenghts C₂₇, C₂₉, C₃₁, and C₃₃, in addition to alkanes and presumably trienes. The role of the unsaturated hydrocarbons onT. angelicae as recognition cues for aphid-attending ants is discussed.     

Vicia faba–Lygus rugulipennis Interactions: Induced Plant Volatiles and Sex Pheromone Enhancement

The profiles of volatile chemicals emitted by Vicia faba plants damaged by Lygus rugulipennis feeding, and by feeding plus oviposition, were shown to be quantitatively different from those released by undamaged plants. Samples of volatile chemicals collected from healthy plants, plants damaged by males as a consequence of feeding, plants damaged by females as a consequence of feeding and oviposition, plants damaged by feeding with mated males still present, and plants damaged by feeding and oviposition with gravid females still present, showed significant differences in the emission of hexyl acetate, (Z)-β-ocimene, (E)-β-ocimene, (E)-β-caryophyllene, and methyl salicylate. In particular, treatments with mated females present on plants had a significant increase in emission levels of the above compounds, possibly due to eggs laid within plant tissues or active feeding, compared with undamaged plants and plants damaged by males feeding, with or without insects still present. Furthermore, the pheromonal blend released by mated L. rugulipennis females, mainly comprising hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal, was enhanced when females were active on broad bean plants, whereas such an increase was not observed in males. Both sexes gave electroantennogram responses to green leaf volatiles from undamaged plants and to methyl salicylate and (E)-β-caryophyllene emitted by Lygus-damaged plants, suggesting that these compounds may be involved in colonization of host plants by L. rugulipennis. In addition, mated males and females were responsive to hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal released by mated females on V. faba, indicating that these substances could have a dual function as a possible aggregation pheromone in female–female communication, and as a sex pheromone in female–male communication. An erratum to this article can be found at     

Surface Properties and Biological Activity of Select Cationic Surfactants

A series of cationic surfactants, N-(decyl N-tri-ethanol ammonium Bromide) (C₁₀), N-(dodecyl N-triethanol ammonium Bromide) (C₁₂), N-(hexadecyl N-triethanol ammonium Bromide) (C₁₆) were synthesized. These compounds have been evaluated by studying their surface properties, surface parameters, biodegradability and antimicrobial and antifungal activities.

The Involvement of Volatile Infochemicals from Spider Mites and from Food-Plants in Prey Location of the Generalist Predatory Mite <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>

We investigated volatile infochemicals possibly involved in location of the generalist predatory mite Neoseiulus californicus to plants infested with spider mites in a Y-tube olfactometer. The predators significantly preferred volatiles from lima bean leaves infested with Tetranychus urticae to uninfested lima bean leaves. Likewise, they were attracted to volatiles from artificially damaged lima bean leaves and those from T. urticae plus their visible products. Significantly more predators chose infested lima bean leaves from which T. urticae plus their visible products had been removed than artificially damaged leaves, T. urticae, and their visible products. These results suggest that N. californicus is capable of exploiting a variety of volatile infochemicals originating from their prey, from the prey-foodplants themselves, and from the complex of the prey and the host plants (e.g., herbivore-induced volatiles). We also investigated predator response to some of the synthetic samples identified as volatile components emitted from T. urticae-infested lima bean leaves and/or artificially damaged lima bean leaves. The predators were attracted to each of the five synthetic volatile components: linalool, methyl salicylate, (Z)-3-hexen-1-ol, (E)-2-hexenal, and (Z)-3-hexenyl acetate. The role of each volatile compound in prey-searching behavior is discussed.     

Female Sex Pheromone of a Carpenter Moth, Cossus insularis (Lepidoptera: Cossidae)

This study describes the identification of a sex pheromone component of a cossid moth, Cossus insularis. Coupled gas chromatographic–electroantennographic detection (GC–EAD) analysis of solid-phase microextraction (SPME) collections of volatiles released by live female moths showed that two compounds elicited EAG responses from the antennae of male moths. These compounds were identified as (E)-3-tetradecenyl acetate (E3-14:Ac) and (Z)-3-tetradecenyl acetate (Z3-14:Ac) by mass spectral analysis and retention index comparisons with synthetic standards. The ratio of E3-14:Ac and Z3-14:Ac was 95:5 in the effluvia of a female. In field bioassays, sticky traps baited with blends of E3-14:Ac and Z3-14:Ac showed that E3-14:Ac is an essential component of the pheromone. However, the role of Z3-14:Ac is unclear, because E3-14:Ac as a single component was as attractive to male moths as blends of E3-14:Ac and Z3-14:Ac, including the 95:5 blend released by live female moths.     

Volatile Emissions from an Odorous Plant in Response to Herbivory and Methyl Jasmonate Exposure

Induced volatile terpenes have been commonly reported among diverse agricultural plant species, but less commonly investigated in odorous plant species. Odorous plants synthesize and constitutively store relatively large amounts of volatiles, and these may play a role in defense against herbivores. We examined the effect of herbivory and methyl jasmonate (MeJA) exposure on the release of volatile organic compounds (VOCs) in the marsh elder, Iva frutescens, which contains numerous constitutive VOCs, mainly mono- and sesquiterpenes. Our specific goal was to test for the presence of inducible VOCs in a naturally occurring plant already armed with VOCs. The abundant, native specialist leaf beetle Paria aterrima was used in herbivore induction trials. VOCs were sampled from herbivore wounded and unwounded, and from MeJA treated and untreated I. frutescens. Total VOC emissions were significantly greater in response to herbivory and MeJA treatment compared to unwounded controls. Herbivore wounding caused a substantial shift in the emission profile (42 VOCs from wounded, compared to 8 VOCs from unwounded I. frutescens), and MeJA had a similar yet less substantial influence on the emission pattern (28 VOCs from MeJA treated compared to 8 VOCs from untreated I. frutescens). Constitutive VOC emissions predominated, but some VOCs were detected only in response to herbivory and MeJA treatment, suggesting de novo synthesis. Several VOCs exhibited a delayed emission profile in contrast to the rapid release of constitutive VOCs, and principal components analysis revealed they were not associated with constitutive emissions. While I. frutescens contains many constitutive VOCs that are released immediately in response to herbivory, it also produces novel VOCs in response to feeding by the specialist P. aterrima and MeJA treatment.