Journal of Chemical Ecology

Ballhorn, Daniel

doi: 10.1007/s10886-010-9905-0pmid: 21221741

The existence of tradeoffs among plant defenses is commonly accepted, however, actual evidence for these tradeoffs is scarce. In this study, I analyzed effects of different direct defenses of wild lima bean plants (Phaseolus lunatus) that were simultaneously exposed to a fungal pathogen (Colletotrichum lindemuthianum) and an insect herbivore, the Mexican bean beetle (Epilachna varivestis). Although plants were derived from spatially widely separated populations, I observed a common tradeoff between resistance to pathogens and herbivores. Plants with high levels of anti-herbivore defense (cyanogenesis) showed low levels of resistance to pathogens (polyphenol oxidase activity and phenolic compounds), and vice versa. Competition for resources generally is considered to be the basis for tradeoffs. However, I report direct inhibition of polyphenol oxidase by cyanide, making simultaneous expression of both defenses at high levels impossible. I argue that populations composed of individuals investing in one type of defense have an advantage in environments that periodically favor either pathogen or herbivore plant antagonists.

Hilário, Renato; Ferrari, Stephen

doi: 10.1007/s10886-011-9911-xpmid: 21271277

The typical diet of Callithrix marmosets is based on gums, although fungi are the dietary staple of a single group of Callithrix flaviceps studied in the Augusto Ruschi Biological Reserve, in southeastern Brazil. Here, we present the nutritional composition of two species of Mycocitrus fungi consumed by C. flaviceps, and discuss possible determinants of the preference of the marmosets for fungi over gums. The fungi were high in sugar/fiber and poor in proteins, and were similar in composition to the gums exploited by other marmosets and to the fungi consumed by Callimico goeldii. The reduced protein content of the fungi may be offset by the arthropod component of the diet of the Callithrix flaviceps study group. The low relative metabolic rate and enlarged cecum of Callithrix enable these marmosets to exploit foods with a high fiber content. In addition, the greater digestibility of chitin in comparison with plant fiber may make fungi a nutritionally more valuable resource to marmosets than gums. Marmosets, thus, may prefer to feed on fungi when an adequate supply of this resource is available in the environment.

Kappers, Iris; Hoogerbrugge, Hans; Bouwmeester, Harro; Dicke, Marcel

doi: 10.1007/s10886-011-9906-7pmid: 21249432

In response to herbivory by arthropods, plants emit herbivory-induced volatiles that attract carnivorous enemies of the inducing herbivores. Here, we compared the attractiveness of eight cucumber varieties (Cucumis sativus L.) to Phytoseiulus persimilis predatory mites after infestation of the plants with herbivorous spider mites (Tetranychus urticae) under greenhouse conditions. Attractiveness differed considerably, with the most attractive variety attracting twice as many predators as the least attractive variety. Chemical analysis of the volatiles released by the infested plants revealed significant differences among varieties, both in quantity and quality of the emitted blends. Comparison of the attractiveness of the varieties with the amounts of volatiles emitted indicated that the quality (composition) of the blend is more important for attraction than the amount of volatiles emitted. The amount of (E)-β-ocimene, (E,E)-TMTT, and two other, yet unidentified compounds correlated positively with the attraction of predatory mites. Quantities of four compounds negatively correlated with carnivore attraction, among them methyl salicylate, which is known to attract the predatory mite P. persimilis. The emission of methyl salicylate correlated with an unknown compound that had a negative correlation with carnivore attraction and hence could be masking the attractiveness of methyl salicylate. The results imply that the foraging success of natural enemies of pests can be enhanced by breeding for crop varieties that release specific volatiles.

Unelius, C.; El-Sayed, Ashraf; Twidle, Andrew; Bunn, Barry; Zaviezo, Tania; Flores, M.; Bell, Vaughn; Bergmann, Jan

doi: 10.1007/s10886-010-9904-1pmid: 21243408

The absolute configuration of the sex pheromone of the citrophilous mealybug, Pseudococcus calceolariae, was determined to be (1R,3R)-[2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropyl]methyl (R)-2-acetoxy-3-methylbutanoate. NMR, derivatization reactions, chiral gas chromatography-mass spectrometry, and comparison with synthetic chiral reference compounds, were used to determine the absolute configuration of this compound. This activity of this compound was further confirmed by testing synthetic stereoisomers of the compound as lures in traps for adult male mealybugs. Traps baited with 1,000 μg of the pheromone compound caught 36 times more males than traps baited with virgin females. A mixture of stereoisomers of the pheromone compound can be used for field trapping without adverse effects on trap catch. A comparison with the structures of other sex pheromones of mealybugs is presented.

Ray, Ann; Žunič, Alenka; Alten, Ronald; McElfresh, J.; Hanks, Lawrence; Millar, Jocelyn

doi: 10.1007/s10886-011-9908-5pmid: 21274597

We report the identification, synthesis, and field bioassays of a female-produced sex attractant pheromone component of the cerambycid beetle Ortholeptura valida (LeConte). Headspace volatiles from females contained a female-specific compound, (Z)-11-octadecen-1-yl acetate, which elicited a strong response from antennae of adult males in coupled gas chromatography-electroantennogram analyses. In field bioassays, significant numbers of males were collected by traps baited with this compound. The pheromone represents a new structural class of cerambycid pheromones, and is the first pheromone identified for a cerambycid species in the subfamily Lepturinae.

Sillam-Dussès, David; Hanus, Robert; Abd El-Latif, Ashraf; Jiroš, Pavel; Krasulová, Jana; Kalinová, Blanka; Valterová, Irena; Šobotník, Jan

doi: 10.1007/s10886-011-9910-ypmid: 21318399

Within the complex network of chemical signals used by termites, trail pheromones and sex pheromones are among the best known. Numerous recent papers map the chemical identity and glandular origin of these pheromones in nearly all major isopteran taxa. In this study, we aimed to describe the sex pheromone and the trail pheromone of a poorly known sand termite, Psammotermes hybostoma. We identified (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol (dodecatrienol) as the sex pheromone released by tergal and sternal glands of female imagos and, at the same time, as the trail pheromone secreted from the sternal gland of workers. We conclude that chemical communication in Psammotermes does not differ from that of most other Rhinotermitidae, such as Reticulitermes, despite the presence of a diterpene as a major component of the trail pheromone of Prorhinotermes to which Psammotermes is presumed to be phylogenetically close. Our findings underline once again the conservative nature of chemical communication in termites, with dodecatrienol being a frequent component of pheromonal signals in trail following and sex attraction and, at the same time, a tight evolutionary relationship between the trail following of working castes and the sex attraction of imagos.

Tolzin-Banasch, Karla; Dagvadorj, Enkhmaa; Sammer, Ulrike; Kunert, Maritta; Kirsch, Roy; Ploss, Kerstin; Pasteels, Jacques; Boland, Wilhelm

doi: 10.1007/s10886-011-9913-8pmid: 21301937

Larvae of Chrysomela lapponica (Coleoptera: Chrysomelidae) sequester characteristic O-glucosides from the leaves of their food plants, namely Betula and/or Salix The present study focuses on birch-feeding larvae of C. lapponica from the Altai region in East Kazakhstan. As in other sequestering leaf beetle larvae, the compounds are transported intact via different membrane barriers into the defensive system, followed by glucoside cleavage and subsequent transformations of the plant-derived aglycones. Unlike previous studies with model compounds, we studied the sequestration of phytogenic precursors by analyzing the complex pattern of glucosides present in food plant Betula rotundifolia (39 compounds) and compared this composition with the aglycones present as butyrate esters in the defensive secretion. In addition to the analytic approach, the insect’s ability, to transport individual glucosides was tested by using hydrolysis-resistant thioglucoside analogs, applied onto the leaf surface. The test compounds reach the defensive system intact and without intermediate transformation. No significant difference of the transport capacity and selectivity was observed between larvae of birch-feeding population from Kazakhstan, and previous results for larvae of birch-feeding population from the Czech Republic or willow-feeding populations. Overall, the transport of the phytogenic glucosides is highly selective and highly efficient, since only minor compounds of the spectrum of phytogenic glucoside precursors contribute to the limited number of aglycones utilized in the defensive secretion. Interestingly, salicortin 44 and tremulacin 60 were found in the leaves, but no aldehyde or esters of salicylalcohol. Surprisingly, we observed large amounts of free glucose, together with small amounts of 6-O-butyrate esters of glucose (27a/b and 28a/b).

Kather, Ricarda; Drijfhout, Falko; Martin, Stephen

doi: 10.1007/s10886-011-9909-4pmid: 21271278

Social insects are defined by their ability to divide labor among their numerous nestmates. This is achieved via a complex system of chemical communication that allows colonies to organize task activity so as to maximize the productivity of the colony. However, the mechanism by which social insects distinguish task groups among morphologically identical individuals remains unknown. Using the honey bee, Apis mellifera, as our model species, we investigated the presence of task-specific patterns in the cuticular lipids (n-alkanes, fatty acids, and alkenes) of bees. Cuticular lipids are known to play an essential role in the recognition processes of insects. We found task-specific features in the n-alkane and alkene profiles of bees, but no task-specific patterns in the fatty acid profile. Foragers, in particular, had elevated levels of n-alkanes relative to nurse and newly emerged bees, suggesting increased waterproofing. Newly emerged bees had low levels of cuticular lipids, supporting the Blank Slate theory and potentially explaining their acceptance into foreign colonies.

Saporito, Ralph; Norton, Roy; Andriamaharavo, Nirina; Garraffo, Hugo; Spande, Thomas

doi: 10.1007/s10886-011-9914-7pmid: 21318398

Poison frogs are chemically defended from predators by diverse alkaloids, almost all of which are sequestered unchanged from alkaloid-containing arthropods in the frog diet. Oribatid mites recently have been proposed as a major dietary source of poison frog alkaloids. Here, we report on alkaloids common to an oribatid mite and poison frogs. Gas chromatographic-mass spectrometric analysis of methanol extracts of adult Scheloribates laevigatus (Oribatida: Scheloribatidae) revealed nine alkaloids. Five of these have been detected previously in the skin glands of poison frogs: two isomers of the pumiliotoxin 291G, two isomers of the 5,6,8-trisubstituted indolizidine 209C, and the 5,6,8-trisubstituted indolizidine 195G. The other four alkaloids, a pumiliotoxin, a tricyclic (coccinelline-like), and two isomers of an izidine, were not previously known, but are similar in structure to alkaloids found in poison frogs. Alkaloids were not detected in immature S. laevigatus, suggesting that they are adult-specific and possibly the result of mite biosynthesis. Although most of the alkaloids detected in S. laevigatus are common to poison frogs, the geographic distributions of these organisms are not sympatric. The findings of this study indicate that oribatid mites, and in particular, members of the genus Scheloribates, represent a relatively unexplored arthropod repository for alkaloids and a significant dietary source of alkaloids in poison frogs.

Levesque, Haude; Scaffidi, Donelle; Polkinghorne, Christine; Sorensen, Peter

doi: 10.1007/s10886-011-9907-6pmid: 21274598

Although it has been established that sexually-immature goldfish and their relatives recognize members of their own species by using chemicals that they release, the identity of this cue(s) and whether it might be produced and used by other life stages is not yet known. To address this question, this study tested the behavioral responses of sexually immature and mature goldfish to each other’s body washings, their sensitivity to this cue, the role of the olfactory sense in detecting it, and whether it is comprised of either polar and/or non-polar compounds. Tests that used two-choice mazes discovered that juvenile, immature, mature male, and mature female goldfish all release and respond to a common chemical cue(s). Dilution studies next demonstrated that this cue is active when diluted over 10 times and thus capable of functioning as a short range attractant/identifier. Olfactory occlusion demonstrated that it is detected by the olfactory sense. Finally, chemical fractionation demonstrated that it is comprised of both polar and non-polar components but likely does not include bile acids. Together, these results suggest that all life stages of goldfish use a complex multicomponent pheromonal odor to discern species identity, and that this odor has the potential to function with hormonal metabolites to identify sexual condition in behaviorally active fish of many species.