A GABA Receptor Modulator and Semiochemical Compounds Evidenced Using Volatolomics as Candidate Markers of Chronic Exposure to Fipronil in Apis mellifera

Among the various "omics" approaches that can be used in toxicology, volatolomics is in full development. A volatolomic study was carried out on soil bacteria to validate the proof of concept, and this approach was implemented in a new model organism: the honeybee Apis mellifera. Emerging bees raised in the laboratory in pain-type cages were used. Volatolomics analysis was performed on cuticles, fat bodies, and adhering tissues (abdomens without the digestive tract), after 14 and 21 days of chronic exposure to 0.5 and 1 µg/L of fipronil, corresponding to sublethal doses. The VOCs analysis was processed using an HS-SPME/GC-MS method. A total of 281 features were extracted and tentatively identified. No significant effect of fipronil on the volatolome could be observed after 14 days of chronic exposure. Mainly after 21 days of exposure, a volatolome deviation appeared. The study of this deviation highlighted 11 VOCs whose signal abundances evolved during the experiment. Interestingly, the volatolomics approach revealed a VOC (2,6-dimethylcyclohexanol) that could act on GABA receptor activity (the fipronil target) and VOCs associated with semiochemical activities (pheromones, repellent agents, and compounds related to the Nasonov gland) leading to a potential impact on bee behavior.

Mandibular gland secretions of two parasitoid wasps (Hymenoptera: Ichneumonidae)

Males ofRhyssa persuasoria andMegarhyssa nortoni nortoni exhibit marked aggregation behavior prior to and during the emergence of females from host trees, and this has been linked with the secretion of an odorous liquid from the mandibular glands. The volatile components of these secretions were examined by combined gas chromatography-mass spectrometry. While both species contained 6-methylhept-5-en-2-one,M. nortoni nortoni was characterized by a series of alkyl spiroacetals andR. persuasoria contained 3-hydroxy-3-methylbutan-2-one. The same spiroacetals have previously been isolated from the mandibular glands of other Hymenoptera and have been directly associated with aggregation behavior in some species. The chemical and behavioral aspects of the two species are discussed.

Asymmetric synthesis of naturally occurring spiroketals

Spiroketals are widely found as substructures of many naturally occurring compounds from diverse sources including plants, animals as well as microbes. Naturally occurring spiroketals are biologically active and most of them are chiral molecules. This article aims at reviewing the asymmetric synthesis of biologically active spiroketals for last 10 years (1998-2007).

Chemical communication by behaviour-guiding olfactory signals

Chemical Ecology is a new interdisciplinary research area with close collaborations between chemists and biologists of different descriptions. It has developed during the last 40 years because of an interest in the structure, function and evolution of chemical signalling among organisms and also because of the hope to be able to use the ubiquitous phenomenon to control organisms, like pest insects. This feature article highlights the growth of the discipline and the progress made, through examples from the author's own work on chemical communication in insects and flowering plants. The research deals with olfactory signals, i.e. volatile chemical compounds perceived by the sense of smell. Analytical techniques and methods are an important part of the work.

Volatile emission by contest losers revealed by real-time chemical analysis

Animal interactions often involve chemical exchange but simultaneous evaluation of chemistry and behaviour has been problematical. Here we report findings from a novel method, atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) coupled with manipulation of molecular-mass achieved by rearing organisms on deuterium-enhanced nutrients. This allows real-time monitoring of the occurrence and quantity of volatile chemicals released by each of two interacting individuals, in tandem with behavioural observations. We apply these methods to female-female contests in the parasitoid wasp Goniozus legneri. We show that this species emits the spiroacetal 2-methyl-1,7-dioxaspiro[5.5]undecane. Chemical release is most common in more behaviourally aggressive contests, which occur when prior resource owners successfully resist take-over by similar-sized intruder females. Volatiles released during contests are always emitted by the loser. Aggression in contests is reduced after spiroacetal release. We suggest that the spiroacetal functions as a weapon of rearguard action. We anticipate that APCI-MS, which is rapid, non-intrusive and relatively inexpensive to operate, will be widely applied in studies linking chemistry and behaviour.

Chemical ecology = chemistry + ecology!

Chemical ecology (CE) is an active, interdisciplinary field between chemistry and biology, which, stimulated by natural curiosity and possible applied aspects, has grown to its present position during the last 40-odd years. This area has now achieved a degree of maturity with its own journals, its own international society with annual meetings, and many enthusiastic scientists in laboratories around the world. The focus is on chemical communication and other chemical interactions between organisms, including volatile chemical signals, which guide behaviors linked to various vital needs. It reflects both biodiversity and chemodiversity. All living organisms have these important signal systems, which go back to the origins of life. Successful work in this area has called for close collaboration between chemists and biologists of different descriptions. It is thus a good example of chemistry for biology. The aim of the article is to give a short introduction to the field, with an emphasis on the role of chemistry in a biological context by: giving an overview of the development of the area; showing some examples of studies of chemical communication in insects and plants, basically from our own work; and describing some current trends and tendencies and possible future developments.

The Chafer Pheromone Buibuilactone and Ant Pyrazines are also Produced by Marine Bacteria

Headspace extracts obtained from agar plate cultures of two marine bacteria from the North Sea (Germany), Loktanella strain BIO-204 and Dinoroseobacter shibae strain DFL-27, were analyzed by GC-MS. Several gamma-lactones and one delta-lactone were identified, besides pyrazines and some sulfur compounds. The absolute configuration of the major lactone (R,Z)-dodec-5-en-4-olide, known as buibuilactone, a pheromone of several scarab beetles, was determined by a new catalytic enantioselective synthesis and GC on a chiral stationary phase. Unsaturated lactones in the extracts included (E)-dodec-5-en-4-olide and the regioisomer (Z)-dodec-6-en-4-olide, previously identified as a component of black-tailed deer urine. The pyrazines 2-butyl-3,6-dimethylpyrazine and 2-isopentyl-3,6-dimethylpyrazine were identified by comparison with synthesized material. The latter compound is a known ant pheromone, as is another identified pyrazine, 2-ethyl-3,6-dimethylpyrazine. The striking similarity between insect pheromones and these bacterial volatiles is discussed, suggesting the possibility of more widespread occurrence of symbiosis between microorganisms and insects than previously thought.

Carbon hydroxylation of alkyltetrahydropyranols: a paradigm for spiroacetal biosynthesis in Bactrocera sp

[figure: see text] In a number of Bactrocera species the penultimate step in the biosynthesis of spiroacetals is shown to be the hydroxylation of an alkyltetrahydropyranol followed by cyclization. The monooxygenases that catalyze this side chain hydroxylation show a strong preference for oxidation four carbons from the hemiketal center, to produce the spiroacetal. The hydroxy spiroacetals observed in Bactrocera appear to derive from direct oxidation of the parent spiroacetals and not from alternate precursors.