Identification of new homoterpene esters from Dufour's gland of the ponerine ant Gnamptogenys striatula

Extracts of Dufour's gland of the ponerine ant, Gnamptogenys striatula, were analyzed by using the combination of gas chromatography and mass spectrometry. Series of esters of the new homoterpenoids (2E,6)-3,4,7-trimethyl-2,6-octadiene-1-ol (4-methylgeraniol) and (2E,6)-3,4,7-trimethyl-2,6-nonadiene-1-ol (bishomogeraniol) with unbranched medium-chain fatty acids were identified. Transformation of the chiral natural products into 1,4-di (trifluoroacetoxy)-3-methylpentane and comparison of its gas chromatographic retention time on a modified cyclodextrin phase with that of synthetic optically active reference samples proved the stereogenic center to keep (S)-configuration. (2E,4S,6)-3,4,7-Trimethyl-2,6-octadien-1-yl decanoate and the corresponding dodecanoate are the main volatiles in the extracts.

Trail pheromone of ponerine ant Gnamptogenys striatula: 4-methylgeranyl esters from Dufour's gland

Dufour's gland is the origin of the trail pheromone of Gnamptogenys striatula. Chemical analysis of the glandular extracts revealed a series of new natural products, especially esters of (2E)-3,4,7-trimethyl-2,6-octadien-1-ol (4-methylgeraniol), and (2E)-3,4,7-trimethyl-2,6-nonadien-1-ol (a bishomogeraniol isomer) with medium-chain fatty acids. Bioassays with synthetic racemates of the esters revealed that the 4-methylgeranyl esters are highly active as trail pheromones, while the bishomogeranyl esters are either marginally active or not active at all. Assays with the individual 4-methylgeranyl esters showed each of them to be inferior to the glandular secretion in eliciting trail following. However, the mixture of racemic 4-methylgeranyl octanoate and the corresponding decanoate and dodecanoate, the main Dufour's volatile constituents, is as active as the natural secretion at similar concentration. We conclude that the trail pheromone constitutes a mixture of at least the 4-methylgeranyl esters identified in the gland. Since G. striatula generally preys on small arthropods rather than monopolizing large resources, we assume that trails are rarely used during foraging, but more often during nest migration. Production of new societies in this species is generally performed by budding, a period of considerable predation risk. Utilizing trails for efficient displacement in this context is, therefore, highly adaptive. This behavioral repertoire may also provide the ants with additional means of food resource exploitation.

Female sex pheromone of Cameraria ohridella Desch. and Dim. (Lepidoptera: Gracillariidae): structure confirmation, synthesis and biological activity of (8E,10Z)-8,10-tetradecadienal and some analogues

Mass spectrometric investigations confirmed the structure of the female produced sex pheromone of the horse-chestnut leafminer Cameraria ohridella Desch. and Dim. to be (8E,IOZ)-8,10-tetradecadienal. Pure samples, prepared in a straightforward synthesis, were highly attractive in field tests and proved to be suitable for monitoring of flight activities and population dynamics. In mixtures with the synthetic pheromone, analogues like 9-tridecynal and 7-dodecynyl formate were shown to reduce trap catches. In electroantennographic experiments, pheromone analogues were less active than the pheromone. 9-Tridecynal was the most EAG active analogue tested, followed by 7-dodecyn-1-yl formate and 7-undecyn-1-yl formate.

Enantiospecific antennal response of bark beetles to spiroacetal (E)-conophthorin

Optically pure synthetic enantiomers of (E)-conophthorin [(E)-7-methyl-1,6-dioxaspiro[4.5]decane], one of the volatiles affecting coniferophagous bark beetles, were tested on antennae of Ips typographus, I. duplicatus, I. subelongatus, Dendroctonus micans, and five Scolytus spp. by using combined gas chromatography-electroantennographic detection (GC-EAD). EAD dose-responses indicated that all three Ips species perceived only the naturally occurring and quantitatively dominant (5S,7S)-enantiomer, while its antipode, (5R,7R)-(E)-conophthorin was antennally inactive. Response thresholds for the Ips species were estimated as between 0.1 ng and 1 ng, or lower. The antennal responses of the Ips species caused by 100 ng of the (5R,7R)-enantiomer might be due to 1% impurity-(the active (5S,7S)-enantiomer) in the (5R,7R)-sample. At the 50-ng level, D. micans and five angiosperm Scolytus species (S. intracatus, S. mali, S. ratzeburgi, S. rugulosus, and S. scolytus) responded strongly to the (5S,7S)-enantiomer, while the (5R,7R)-enantiomer was antennally inactive. Currently updated knowledge on the natural occurrence, and electrophysiological and behavioral activity of (E)-conophthorin is summarized.

Identification of sex pheromone composition of click beetle Agriotes brevis candeze

Geranyl butyrate (GB) and (E, E)-farnesyl butyrate (FB) were identified in the pheromone gland extract of females of the click beetle, Agriotes brevis (Candeze) (Coleoptera: Elateridae) as the major sex pheromone components. Polyethylene vial dispensers containing 20-200 mg of a 1:1 mixture caught high numbers of beetles. Captures did not decrease even after 73 days of field exposure of dispensers. At sites where both Agriotes sputator L. and A. brevis were present, the above baits were selectively catching only A. brevis, despite the fact that GB is also the main pheromone component of A. sputator, suggesting that FB has a role in reproductive isolation. In the early part of the season, traps into which the insects could both crawl and fly captured more A. brevis than designs where the insects could only fly in. Trap design was not important later in the season. This indicates the need for future development of a trap suitable for use throughout the whole season.

Structural characterisation of humic acid-bound PAH residues in soil by 13C-CPMAS-NMR-spectroscopy: evidence of covalent bonds

The fate of 13C-labelled phenanthrene and fluoranthene in different soil systems during biodegradation was studied. The soil humic acid fraction was isolated followed by structural characterisation using 13C-cross polarisation magic angle spinning nuclear magnetic resonance spectroscopy (13C-CPMAS-NMR). It could be demonstrated that especially the ratio between the concentrations of polycyclic aromatic hydrocarbons (PAHs) and soil humus matrix limits the usefulness of this analytical tool. Based on these results a ratio of 13C-activity(PAH)/13C-activity(soil) approximately 1.5/1.0 in the test material was suggested. The chemical transformation of a PAH and its bound residue formation in a soil system detected by changes of chemical shifts in the 13C-NMR spectrum was proven for the first time. Structural information obtained by NMR spectra were verified by alkaline hydrolysis of PAH/humus-associations and following identification of cleavage products. Ester-bound phenanthrene metabolites such as 1-hydroxy-2-naphthoic acid, ortho-phthalic acid and 3,4-dihydroxybenzoic acid were detected. Additional structural assignments indicated the presence of ether-bound phenanthrene derivatives as well. Using isotopic labelling techniques a quantitative evaluation of bound residue distribution was undertaken. Fifty to seventy percent of phenanthrene metabolites which could be related to the added 13C(1)-phenanthrene were ester bound via their carboxyl groups.

Alcoholism in cockchafers: orientation of male Melolontha melolontha towards green leaf alcohols

Chemical orientation of the European cockchafer, Melolontha melolontha L., a serious pest in agriculture and horticulture, was investigated by field tests and electrophysiological experiments using plant volatiles. In total, 16 typical plant volatiles were shown to elicit electrophysiological responses in male cockchafers. Funnel trap field bioassays revealed that green leaf alcohols (i.e. (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol and 1-hexanol) attracted males, whereas the corresponding aldehydes and acetates were behaviourally inactive. Furthermore, male cockchafers were attracted by volatiles from mechanically damaged leaves of Fagus sylvatica L., Quercus robur L. and Carpinus betulus L. However, volatiles emitted by damaged leaves of F. sylvatica attracted significantly more males than those from the other host plants. Odour from intact F. sylvatica leaves was not attractive to M. melolontha males. Females were not attracted by any of the tested volatile sources. The results suggest that plant volatiles play a similar role as a sexual kairomone in mate finding of M. melolontha, as has been shown for the forest cockchafer, Melolontha hippocastani F. Nevertheless, both species show remarkable differences in their reaction to green leaf alcohols.

Specialized olfactory receptor neurons mediating intra- and interspecific chemical communication in leafminer moths Eriocrania spp.(Lepidoptera: Eriocraniidae)

We performed a physiological and morphological characterization of sensilla auricillica in male Eriocrania semipurpurella moths. Each auricillic sensillum contained three olfactory receptor neurons. Responding neurons (87 of 139) could be grouped into five physiological types. Type 1 responded to(R,Z)-6-nonen-2-ol and type 2 to its enantiomer(S,Z)-6-nonen-2-ol, both of which are pheromone components of E. semipurpurella. Type 3 responded to both (R)-heptan-2-ol and(R,Z)-4-hepten-2-ol, which are pheromone components of the sympatric species E. cicatricella. Types 4 and 5 responded to the ketones(Z)-6-nonen-2-one and/or nonan-2-one, which are found in the pheromone glands of female E. semipurpurella.

Field-trapping showed that type 3 receptor neurons mediate strongly antagonistic effects of (R)-heptan-2-ol and(R,Z)-4-hepten-2-ol on E. semipurpurella, while nonan-2-one should possibly be included as a synergist in the sex pheromone blend of this species. The attraction of E. cicatricella and E. sparrmannella to compounds mixed with the pheromone blend of E. semipurpurella shows that the pheromone components of E. semipurpurella have little or no antagonistic effects on these species.

The morphology and physiology of eriocraniid pheromone sensilla are very similar to those found in the order Trichoptera (caddisflies), suggesting a homology between pheromone detection systems in the two sister orders Lepidoptera and Trichoptera.

1,4-benzoquinone attracts males of Rhizotrogus vernus Germ

Two candidate attractants, phenol and 1,4-benzoquinone, a synthetic mixture of typical compounds from green-leaf odours [(Z)-3-hexenyl acetate: (Z)-3-hexen-1-ol: benzaldehyde: (E)-2-hexen-1-ol: 1-hexanol; 100:20:10:1:1] and freshly damaged oak leaves were screened for field attractancy in funnel traps in Hungary. Males of two Rhizotrogus spp. (Coleoptera, Scarabaeidae, Melolonthinae), R. aestivus 01. and R. vernus Germ. were caught in larger numbers. While R. aestivus catches were probably chance captures, male R. vernus was significantly attracted to the baits containing 1,4-benzoquinone. This compound represents a promising basis for the development of a monitoring trap for R. vernus.

Halogenated organic contaminants in sediments of the Havel and Spree rivers (Germany). Part 5 of organic compounds as contaminants of the Elbe river and its tributaries

To give a detailed and comprehensive view on the state of pollution of the Havel and Spree rivers nontarget screening as well as quantitative (target) analyses were applied to anoxic sedimentsamples. Based on nontarget GC/MS analysis a significant contribution to the anthropogenic contamination could be attributed to halogenated compounds. Three groups of contaminants corresponding either to diffuse or local contamination could be distinguished. Several commonly observable compounds including pentachloroanisol, polychlorinated biphenyles, 2,4-dichlorobenzoic acid, and chlorinated benzenes were detected with a distribution reflecting the contribution of nonpoint source emissions. A second group of chlorinated as well as brominated compounds was attributed to a strong point source emission at the Teltow Canal. At the sampling locations influenced by this point source the amount of mono- and dibrominated naphthalenes, chlorinated naphthalenes, and hexachlorocyclohexanes as well as DDT- and methoxychlor-related compounds increased significantly as compared to the background concentrations. A third group of halogen compounds emitted at this site consisted of the pesticides bromopropylate, methoxychlor, and chlorfensone as well as specific brominated aromatics including 2,4,6-tribromoaniline, 4,4'-dibromobenzophenone, and brominated benzenes. In addition, tetrabromochlorotoluenes, tribromodichlorotoluenes, dibromotrichlorotoluenes, and 2,2-bis(4-bromophenyl)acetic acid isopropyl ester were identified and are reported for the first time as environmental contaminants. The amounts of brominated compounds detected in Teltow Canal sediments occurred at a similar concentration level as their chlorinated analogues. Therefore, investigations on the occurrence of such a broad spectrum of brominated compounds as established in this work are presumably required more frequently to assess the environmental impact of this type of emissions.

Identification of a four-component sex pheromone blend in Bonagota cranaodes (Lepidoptera: Tortricidae)

Analysis of sex pheromone glands of the apple leafroller Bonagota cranaodes Meyrick by gas chromatography coupled with mass spectrometry or electroantennographic detection showed the presence of 14 structurally related acetates and alcohols of the chain length 10-18, including the main pheromone component (E,Z)-3,5-dodecadienyl acetate (E3,Z5-12Ac). Male antennae responded to the main compound, its Z,Z isomer, (E,Z) -3,5-tetradecadienyl acetate (E3,Z5-14Ac), and the monoenes (Z)-5-dodecenyl acetate (Z5-12Ac) and (Z)-9-hexadecenyl acetate (Z9-16Ac). Traps baited with a four-component blend of E3,Z5-12Ac, Z5-12Ac, E3,Z5-14Ac, and Z9-16Ac in a 100:5:5:100 ratio were significantly more attractive than the main compound alone. This improved trap lure is more suitable for monitoring population densities of B. cranaodes, and for detection of the onset of the seasonal flight period. A more complete pheromone blend is of importance also with respect to current attempts to develop mating disruption for control of this major pest of apple in Brazil.

A chiral sex pheromone system in the pea midge, Contarinia pisi

The sex pheromone of the pea midge consists of 2-acetoxytridecane, (2S,11S)-diacetoxytridecane and (2S,12S)-diacetoxytridecane. The responses of male pea midges to the corresponding stereoisomers of (2S,11S)-diacetoxytridecane and (2S,12S)-diacetoxytridecane were tested in field trapping experiments and by electroantennographic recordings. When added at 20% of the pheromone component to the sex pheromone blend, the (2S,11R)- and (2R,11S)-stereoisomers of (2S,11S)-diacetoxytridecane, were shown to have a strong inhibitory effect on male attraction in the field. At the same dose, (2R,11R)-diacetoxytridecane, (2R,12R)-diacetoxytridecane, and meso-2,12-diacetoxytridecane, did not have a significant effect on male behavior. It was also shown that substitution of either (2S,11S)-diacetoxytridecane or (2S,12S)-diacetoxytridecane with the related stereoisomers reduced trap catches to the level of blank traps. The electroantennographic recordings showed similar dose-response curves for the pheromone components and the stereoisomers shown to have an inhibitory effect. It seems likely that male antennae have receptors for bothpheromone components and for inhibitory stereoisomers. Scanning electron microscopy and transmission electron microscopy of the antennae revealed three types of sensilla involved in chemoreception: sensilla circumfila, sensilla trichodea, and sensilla coeloconica. The sensilla circumfila and trichodea are both innervated by two sensory cells, whereas the sensilla coeloconica are innervated by four to five cells.

Biotransformation of biphenyl by Paecilomyces lilacinus and characterization of ring cleavage products

We examined the pathway by which the fungicide biphenyl is metabolized in the imperfect fungus Paecilomyces lilacinus. The initial oxidation yielded the three monohydroxylated biphenyls. Further hydroxylation occurred on the first and the second aromatic ring systems, resulting in the formation of five di- and trihydroxylated metabolites. The fungus could cleave the aromatic structures, resulting in the transformation of biphenyl via ortho-substituted dihydroxybiphenyl to six-ring fission products. All compounds were characterized by gas chromatography-mass spectroscopy and proton nuclear magnetic resonance spectroscopy. These compounds include 2-hydroxy-4-phenylmuconic acid and 2-hydroxy-4-(4'-hydroxyphenyl)-muconic acid, which were produced from 3,4-dihydroxybiphenyl and further transformed to the corresponding lactones 4-phenyl-2-pyrone-6-carboxylic acid and 4-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid, which accumulated in large amounts. Two additional ring cleavage products were identified as (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)-acetic acid and [5-oxo-3-(4'-hydroxyphenyl)-2,5-dihydrofuran-2-yl]-acetic acid. We found that P. lilacinus has a high transformation capacity for biphenyl, which could explain this organism's tolerance to this fungicide.

Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes: how does flower-specific variation of odor signals influence reproductive success?

The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.

The secretion of the ventral glands in Cladius, Priophorus and Trichiocampus sawfly larvae

The volatile secretion from ventral glands of the larvae of Cladius pectinicornis, Priophorus morio, P. pallipes and Trichiocampus grandis was found to be principally composed of long-chain acetogenins, in majority of the esters and hydrocarbons, with more than 15 carbon atoms. The scarcity of more volatile compounds may be considered as plesiomorphic for the tribe Cladiini to which the four species belong. Further chemotaxonomic significance and chemical ecological implications of the glandular secretions are discussed. Moreover, the function of the well-developed pubescence covering the body of Cladiini larvae is discussed as a part of their defensive mechanism.

Task-related variation of postpharyngeal and cuticular hydrocarbon compositions in the ant Myrmicaria eumenoides

In the ant Myrmicaria eumenoides we investigated postpharyngeal and cuticular hydrocarbons. At eclosion the glands contained almost no hydrocarbons and there were no lipid inclusions in the glandular epithelium. During the first 3 weeks of adult life the amount of hydrocarbons in the gland increased until day 5, and then remained constant while the lipid content in the epithelium increased steadily. Intracolonial hydrocarbon compositions were not uniform. Compositions of post-pharyngeal and cuticular hydrocarbons in individual ants varied simultaneously, but in different manner depending on the tasks of the ant (brood-tenders, foragers, scouts). Variations on the cuticle were greater than in the gland, but they were strongly correlated. Independent of ants' age and task, cuticular hydrocarbon compositions were dominated by alkenes and alkadienes. Task-specific differences in cuticular compositions were mainly in the amount of alkenes (high in foragers) and alkadienes (high in brood-tenders). Variation of hydrocarbons was low in ants up to 10 weeks old. Thereafter, ants fell into two groups: (1) ants that did not change their hydrocarbons and remained in the nest, and (2) ants that changed their hydrocarbon compositions and became foragers. These results contribute to an ongoing discussion of the dynamic relationship between post-pharyngeal and cuticular hydrocarbons.