Tappey H. Jones

Disulfooxy fatty acids from the American bird grasshopper Schistocerca americana, elicitors of plant volatiles

A previously unidentified class of compounds has been isolated from the regurgitant of the grasshopper species Schistocerca americana. These compounds (named here “caeliferins”) are composed of saturated and monounsaturated sulfated α-hydroxy fatty acids in which the ω-carbon is functionalized with either a sulfated hydroxyl or a carboxyl conjugated to glycine via an amide bond. The regurgitant contains a series of these compounds with fatty acid chains of 15–20 carbons and in varying proportions. Of these, the 16-carbon analogs are predominant and are also most active in inducing release of volatile organic compounds when applied to damaged leaves of corn seedlings. Caeliferins are nonlepidopteran elicitors identified in insect herbivores. This adds a category of insect herbivore-produced elicitors of plant responses, providing further evidence of the ability of plants to detect and respond to a broad range of insect herbivore-produced compounds.

IDENTIFICATION AND SYNTHESIS OF VOLICITIN AND RELATED COMPONENTS FROM BEET ARMYWORM ORAL SECRETIONS

Oral secretion of beet armyworm caterpillars (BAW), when applied to damaged tissues of corn seedlings, induces the seedlings to emit volatile compounds that attract the natural enemies of the caterpillars. The key elicitor present in BAW oral secretions is N-[17-hydroxylinolenoyl]-L-glutamine (volicitin). Analysis of the oral secretion showed that it also contained N-[17-hydroxyolinoleoyl]-L-glutamine, free 17-hydroxylinolenic, and 17-hydroxylinoleic acid, the glutamine conjugates of linolenic and linoleic acid as well as free linolenic and linoleic acid. Here we present the identification and synthesis of the hydroxy acids and of glutamine conjugates.

Further Alkaloids Common to Ants and Frogs: Decahydroquinolines and a Quinolizidine

Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.

Characterization, synthesis, and behavioral responses to sex attractiveness pheromones of red-sided garter snakes (Thamnophis sirtalis parietalis).

The sex attractiveness pheromone of the red-sided garter snake,Thamnophis sirtalis parietalis, has been characterized as a mixture of 13 long-chain (C29-C37) saturated and monounsaturated methyl ketones. Samples of the major unsaturated ketones in the mixture, (Z)-24-tritriaconten-2-one (7) and (Z)-26-pentatriaconten-2-one (10), and their saturated analogs, 2-tritriacontanone (8) and 2-pentatriacontanone (11) were prepared by unambiguous synthesis. In field bioassay tests, male garter snakes were presented with natural and synthetic pheromone components both individually and as a mixture. Males exhibited courtship behavior to the synthetic compounds approximating the natural blend.

Venom alkaloids in Monomorium rothsteini Forel repel other ants : is this the secret to success by Monomorium in Australian ant communities?

SummarySpecies of the cosmopolitan ant genus Monomorium are small, slow-moving and non-aggressive ants that are extremely successful members of diverse Australian ant communities. Unlike other abundant taxa, they have no obvious specializations enabling them to co-exist with the highly aggressive species of Iridomyrmex that dominate these communities. Here we report results which suggest that Monomorium species owe their success to the topical application of venom alkaloids which repel other ants. The venom alkaloids (trans-2-ethyl-5-undecylpyrrolidine and trans-2-ethyl-5-tridecylpyrrolidine) of Monomorium “rothsteini” were identified and synthesized, and the repellency to other ants of the synthetic alkaloids were tested using bioassays involving the attraction to honey baits of three native species of Iridomyrmex, three tropical “tramp” species, and M. “rothsteini” itself. Repellency to all other ant species was total or nearly so, but only partial to M. “rothsteini”. Defensive alkaloids produced from a variety of glands are found in other ant genera, and may be a potent yet poorly appreciated force in interference competition between ant species and thereby the structure of ant communities.

Heteropteran chemical repellents identified in the citrus odor of a seabird (crested auklet: Aethia cristatella): evolutionary convergence in chemical ecology.

Abstract. The exogenous application of chemical repellents is widespread in birds, but endogenous production is exceedingly rare. We herein report a new class of avian defensive compounds isolated from the feathers and volatile odor of the crested auklet (Aethia cristatella). Mass spectra indicate that n-hexanal, n-octanal, n-decanal, Z-4-decenal and a 12-carbon unsaturated aldehyde comprise the auklet odorant. Octanal and hexanal are also secreted in the repugnant metasternal gland emissions of heteropteran insects and are known to be potent invertebrate repellents. We suggest that the auklet odorant functions as an ectoparasite repellent and a signal of mate quality. This would represent a rare and direct link between vigor, quality and parasite resistance, one of several putative bases for mate selection. This is the first report of defensive compounds produced by a seabird or colonial bird and one of the few examples of chemical defense in a polar or subpolar marine vertebrate.

Historical Perspective and the Interpretation of Ecological Patterns: Defensive Compounds of Tiger Beetles (Coleoptera: Cicindelidae)

The defensive compounds produced by pygidial glands of adult tiger beetles were analyzed for 83 species from North America, India, and Peru. Benzal-dehyde, the most common defensive compound detected, was found in 39 species. The presence of this compound, which has evolved independently in only a few other arthropod groups, indicates a cyanogenic precursor. Each of these 83 tiger beetle species occurred primarily in one of seven distinct habitats, such as forest floor, sand dune, water edge, and saline flat. All 83 species were also grouped according to genitalic similarities into distinct systematic taxa that represent closely related species. We predicted two alternative patterns of benzaldehyde presence among these tiger beetle species. (1) Through historical influences of systematic relatedness, benzaldehyde should be either present or absent nonrandomly among closely related species regardless of habitat and associated ecological similarities and differences. (2) Through convergence of defense against similar predators within each habitat type, benzaldehyde should be present nonrandomly among species in some habitats and absent nonrandomly in others, regardless of geographical location and systematic relationship. Our results show that in systematic groups with four or more species analyzed, 34 of 39 pooled species were consistent within a group for the presence or absence of benzaldehyde, regardless of habitat type (P < 0.001). However, for only one of the seven habitats (sandy water edge) was benzaldehyde present nonrandomly regardless of geographical location and systematic relationship. We conclude that historical (phylogenetic) factors are likely to be generally important in interpreting ecological data, as either alternative or interactive processes.

Behavioral Evidence for a Contact Sex Pheromone Component of the Emerald Ash Borer, Agrilus Planipennis Fairmaire

The cuticular hydrocarbon profiles of emerald ash borers, Agrilus planipennis, were examined to determine if there are differences in these compounds between the sexes. We also assessed feral male EAB in the field for behavioral changes based on the application of a female-specific compound to dead, solvent-washed beetles. Males in the field spent significantly more time attempting copulation with dead, pinned female beetles coated with a three-beetle-equivalent dose of 3-methyltricosane than with solvent-washed beetles or those coated in 3-methyltricosane at lower concentrations. Males in the field spent the most time investigating pinned dead, unwashed female beetles. In the laboratory, sexually mature males were presented with one of several mixtures applied in hexane to filter paper disks or to the elytra of dead female beetles first washed in solvent. Male EAB also spent more time investigating dead beetles treated with solution applications that contained 3-methyltricosane than dead beetles and filter paper disks treated with male body wash or a straight-chain hydrocarbon not found on the cuticle of EAB.

Chemical Odorant of Colonial Seabird Repels Mosquitoes

Abstract The crested auklet, Aethia cristatella, emits a class of aldehydes shown to be potent invertebrate repellents when used by heteropterans against their predators. Our aim was to determine the efficacy of these aldehydes against mosquitoes in the laboratory. Synthetic analogues of the auklet odorant were strongly repellent to mosquitoes in controlled laboratory trials. Furthermore, the efficacy was similar to previous reports for commercial mosquito repellents. These results, in combination with a previously published study, show that constituents of the aldehyde odorant are broad spectrum in efficacy against ectoparasitic arthropods of birds. Our report is the first empirical evidence for an endogenous mosquito repellent in birds.

Interspecific Differences in Aethia Spp. Auklet Odorants and Evidence for Chemical Defense Against Ectoparasites

The true auklets (Genus Aethia) are small planktivorous seabirds of the Bering Sea and North Pacific. Two species, the crested and whiskered auklets produce volatile citrus-like odorants. We here show that the whiskered auklet odorant is composed predominantly of two odd-numbered aldehydes (heptanal and nonanal) with no detectable unsaturated aldehydes. By comparison the crested auklet odorant is dominated by even-numbered aldehydes, both saturated and monounsaturated, ranging in size from 6 to 12 carbons. This is evidence of species-specific acquisition or biosynthetic pathways. We clarify the chemistry of the crested auklet odorant. We cite evidence that the C-12:1 aldehyde in crested auklets is actually two isomers, (Z)-4-dodecenal and (Z)-6-dodecenal. We also report on experimental evidence that aldehyde constituents kill and repel ectoparasites. Efficacy of the aldehydes may increase when they are combined in a mixture. The repellency of the mixture increases with chemical concentration. This suggests that individuals with higher chemical production are likely to repel ectoparasites more effectively.