Male-Produced Aggregation Pheromone of the Sloe Bug, Dolycoris baccarum L. (Hemiptera: Heteroptera: Pentatomidae)

Bergamotenes: A comprehensive compile of their natural occurrence, biosynthesis, toxicity, therapeutic merits and agricultural applications

Sesquiterpenoids constitute the largest subgroup of terpenoids that have numerous applications in pharmaceutical, flavor, and fragrance industries as well as biofuels. Bergamotenes, a type of bicyclic sesquiterpenes, are found in plants, insects, and fungi with α-trans-bergamotene as the most abundant compound. Bergamotenes and their related structures (Bergamotane sesquiterpenoids) have been shown to possess diverse biological activities such as antioxidant, anti-inflammatory, immunosuppressive, cytotoxic, antimicrobial, antidiabetic, and insecticidal effects. However, studies on their biotechnological potential are still limited. This review compiles the characteristics of bergamotenes and their related structures in terms of occurrence, biosynthesis pathways, and biological activities. It further discusses their functionalities and potential applications in pharmaceutical, nutraceuticals, cosmeceuticals, and pest management sectors. This review also opens novel perspectives in identifying and harnessing bergamotenes for pharmaceutical and agricultural purposes.

Ontogenetic change in effectiveness of chemical defence against different predators in Oxycarenus true bugs

Many prey species change their antipredator defence during ontogeny, which may be connected to different potential predators over the life cycle of the prey. To test this hypothesis, we compared reactions of two predator taxa - spiders and birds - to larvae and adults of two invasive true bug species, Oxycarenus hyalinipennis and Oxycarenus lavaterae (Heteroptera: Oxycarenidae) with life-stage-specific chemical defence mechanisms. The reactions to larvae and adults of both true bug species strikingly differed between the two predator taxa. The spiders were deterred by the defences of adult bugs, but the larval defences were ineffective against them. By contrast, birds attacked the larvae considerably less often than the adult bugs. The results indicate a predator-specific ontogenetic change in defence effectiveness of both Oxycarenus species. The change in defence is likely linked to the life-stage-specific composition of secretions in both species: whereas secretions of larvae are dominated by unsaturated aldehydes, secretions of adults are rich in terpenoids, which probably serve dual function of defensive chemicals and pheromones. Our results highlight the variation in defence between different life stages and the importance of testing responses of different types of predators.

Evolution of stridulatory mechanisms: vibroacoustic communication may be common in leaf-footed bugs and allies (Heteroptera: Coreoidea)

Intra- and interspecific communication is crucial to fitness via its role in facilitating mating, territoriality and defence. Yet, the evolution of animal communication systems is puzzling-how do they originate and change over time? Studying stridulatory morphology provides a tractable opportunity to deduce the origin and diversification of a communication mechanism. Stridulation occurs when two sclerotized structures rub together to produce vibratory and acoustic (vibroacoustic) signals, such as a cricket 'chirp'. We investigated the evolution of stridulatory mechanisms in the superfamily Coreoidea (Hemiptera: Heteroptera), a group of insects known for elaborate male fighting behaviours and enlarged hindlegs. We surveyed a large sampling of taxa and used a phylogenomic dataset to investigate the evolution of stridulatory mechanisms. We identified four mechanisms, with at least five evolutionary gains. One mechanism, occurring only in male Harmostini (Rhopalidae), is described for the first time. Some stridulatory mechanisms appear to be non-homoplastic apomorphies within Rhopalidae, while others are homoplastic or potentially homoplastic within Coreidae and Alydidae, respectively. We detected no losses of these mechanisms once evolved, suggesting they are adaptive. Our work sets the stage for further behavioural, evolutionary and ecological studies to better understand the context in which these traits evolve and change.

Stink Bug Communication and Signal Detection in a Plant Environment

Plants influenced the evolution of plant-dwelling stink bugs' systems underlying communication with chemical and substrate-borne vibratory signals. Plant volatiles provides cues that increase attractiveness or interfere with the probability of finding a mate in the field. Mechanical properties of herbaceous hosts and associated plants alter the frequency, amplitude, and temporal characteristics of stink bug species and sex-specific vibratory signals. The specificity of pheromone odor tuning has evolved through highly specific odorant receptors located within the receptor membrane. The narrow-band low-frequency characteristics of the signals produced by abdomen vibration and the frequency tuning of the highly sensitive subgenual organ vibration receptors match with filtering properties of the plants enabling optimized communication. A range of less sensitive mechanoreceptors, tuned to lower vibration frequencies, detect signals produced by other mechanisms used at less species-specific levels of communication in a plant environment. Whereas the encoding of frequency-intensity and temporal parameters of stink bug vibratory signals is relatively well investigated at low levels of processing in the ventral nerve cord, processing of this information and its integration with other modalities at higher neuronal levels still needs research attention.

Identification of Zingiberenol and Murgantiol as Components of the Aggregation-Sex Pheromone of the Rice Stink Bug, Mormidea v-luteum (Heteroptera: Pentatomidae)

Mormidea v-luteum (Lichtenstein, 1796) feeds on commercial crops, such as rice and ryegrass, causing damage that slows growth and reduces productivity. With the aim of developing an eco-friendly control technique, we investigated the compounds involved in chemical communication in this species. The volatiles produced by a group of seven males or females allocated to different aerated glass chambers were collected for 24 h and analyzed by gas chromatograph/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy. The analyses showed six male-specific compounds, identified as two isomers of zingiberenol (compounds 1 and 2), three isomers of murgantiol (3, 5 and 6) and sesquipiperitol (4). Compounds 1 and 5 were the major components and were produced in a ratio of 6:4. The absolute stereochemistry of the two isomers of zingiberenol was established as (1S,4R,1'S)-1 and (1R,4R,1'S)-2 by chiral gas chromatography. Stereochemistry was not determined for all the other molecules. To confirm the attractiveness of these chemicals, bioassays were performed in a Y-tube olfactometer, first using crude extracts and, subsequently, synthetic compounds. Male volatiles were attractive to both sexes, demonstrating an aggregation pheromone. In bioassays with synthetic compounds, (1'S)-zingiberenol was highly attractive to both males and females. However, when (1'S)-murgantiol was tested, only females were attracted. Interestingly, when a mixture of zingiberenol and murgantiol isomers was tested, it was attractive to both sexes, with females more attracted to the mixture than to zingiberenol alone; males did not distinguish between treatments. Thus, the bioassay data suggest that the molecules have different functions in chemical communication of this species: zingiberenol acts primarily as an aggregation pheromone, while murgantiol plays a role as a sex pheromone.