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The CHC profiles of the bug parasite Scolopostethus pacificus and the ant host Liometopum occidentale. A Velvety tree ants and bugs share a similar color palette. Example GC traces for both ants (top) and bugs (bottom) show that there is nearly no overlap in CHC composition. Main CHCs are labeled and a detailed list can be found in Table 1. The amount of CHCs [μg] for both insects (dot plot inserts) were also similar (see results); horizontal bars represent the min, max, and median. Ant and bug images are at the same scale. B Non-linear multidimensional scaling (NMDS; 2D-stress = 0.12) plot of CHC compositional data based on Bray–Curtis similarities. Each data point represents an individual sample, and ordination ellipses represent 95% confidential space around the group’s centroids. CHCs that majorly contributed to data separation are mapped onto the ordination as vectors. Dark-gray dots represent bugs and light-gray squares ants. C Differences between CHC profiles of bugs (top) and ants (bottom); plots show the mean distribution of different substance classes per chain length
Chemical defense function of the bugs’ metathoracic gland. A The gland exudates of Scolopostethus pacificus are a blend of ketones, aldehydes and esters. The matrix plot shows the composition of twenty individuals. The gland compounds in the order of their retention indices are (2E)-hex-2-enal, isoamyl acetate, 3-methyl-but-2-enyl acetate, (E)-4-oxohex-2-enal, and (2E)-hex-2-enyl acetate. The legend indicates the percentage composition for each compound per specimen. B Amount of MTG secretion [μg] of S. pacificus, in armed control bugs (normal bug pictogram), after artificially disarming via squeezing (red cross bug pictogram) and after bugs had been attacked by ants over a course of 24 h (bug and ant pictogram). Horizontal bars represent the min, max, and median; asterisks indicate significant differences (***p < 0.001) of Mann–Whitney U tests. C Survival [%] of armed vs disarmed bugs after a 24 h exposure to Liometopum occidentale ants. Dots depict the mean estimate and error bars are asymmetric standard errors of the GLM model (***p < 0.001 of the GLM)
Molecular gut-content analysis of Scolopostethus pacificus. Standard ITS2 (CAS5ps + CAS28s) and ant-specific Loc1 and Loc2 primers were used for PCR amplification using S. pacificus body-DNA, gut-DNA, and Liometopum occidentale-DNA. While ITS2 amplified in all cases, no ITS2 fragment was amplified with ant-specific ITS (Loc 1/2) was amplified from dissected bugs’ guts
A vast diversity of parasites associate with ants. Living in and around ant nests these organisms must overcome ant colony defenses. As ant defensive behavior is mainly mediated by species-specific cuticular hydrocarbons (CHCs) or alarm pheromones, ant-associated parasites can either crack their hosts chemical communication code by modifying their own CHC-profiles or use pro-active strategies like chemical weaponry for distraction and repellency. While the chemical nature of ant-parasite interactions has been intensively studied for highly host specific parasites, the chemical-deceptive strategies of the rather rare ant-resembling Heteropterans are unknown. To gain insight into this system, I studied the bug Scolopostethus pacificus (Barber 1918) which can be found near the nests of the ecologically dominant and aggressive velvety tree ant (Liometopum occidentale, Emery 1895). Using behavioral, chemical and molecular approaches I disentangled the relationship of S. pasificus and its host ant. Chemical profiling of the bug and the ant revealed that the bug does not make use of CHC insignificance or mimicry, but instead uses a cocktail of volatile compounds released from its metathoracic glands that likely moderates encounters with its aggressive host. Feeding trials with armed and artificially disarmed bugs revealed a defensive function of the gland exudates. Targeted molecular gut barcoding showed that S. pasificus does not feed on L. occidentale. These results suggest that chemical weaponry, rather than a chemical code-cracking CHC matching or chemical insignificance, enables S. pasificus to get along with and live in close proximity to its host ant.
The attraction of C. medinalis male moths to sex pheromones (SP) in combination with the individual (E)-2-Hexenal (a) or Methyl Salicylate (b) in a rice paddy. Synthetic sex pheromone blend combined with (E)-2-Hexenal (a) or Methyl Salicylate (b) at different concentrations (at a ratio of 1:1, 1:10, and 1:100). The mean number of C. medinalis captured in different traps under field conditions. Treatments were replicated six times in trials. We recorded the number of moths captured by each lure every two days. Asterisks indicate statistically significant differences between mixtures and sex pheromones alone (Tukey test; * P < 0.05)
Total number of C. medinalis male moths captured in traps with mixtures of the sex pheromones (SP) in combination with (E)-2-Hexenal (a) or Methyl Salicylate (b) at different concentrations (at a ratio of 1:1, 1:10, and 1:100) in a rice paddy. Significant differences between different treatments were analyzed by one-way ANOVA followed by Tukey tests (P < 0.05). Significant differences are marked with different letters
Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) is a notorious pest of rice, Oryza sativa L. (Poaceae). Sex pheromones and host-plant volatiles can trap C. medinalis separately. To improve the trap efficiency of synthetic sex pheromone blend, we first tested the synergistic effect of 8 host-plant volatiles, including 2-phenylethanol, 1-hexanol, 1-heptanol, (Z)-3-hexenal, (E)-2-hexenal, octanal, valeraldehyde, and methyl salicylate, on the attraction of C. medinalis to the female-produced sex pheromones in electroantennography. The addition of (E)-2-hexenal, methyl salicylate, valeraldehyde, and (Z)-3-hexenal increased electroantennogram response of C. medinalis to sex pheromones. Further behavioral testing in wind tunnel experiments indicated that additive (E)-2-hexenal or methyl salicylate stimulated the landing behaviors of both male and female C. medinalis compared with sex pheromones alone. Field evaluations showed that mixtures of sex pheromones and (E)-2-hexenal /methyl salicylate resulted in significantly higher catches to male moths than sex pheromones alone. Using 1:1 and 1:10 combinations of the sex pheromones and (E)-2-hexenal, the attraction of C. medinalis to mixtures showed a synergistic effect of 95% and 110%, respectively. Furthermore, 1:1 and 1:10 mixtures of the sex pheromones and methyl salicylate exhibited a synergistic effect of 69% and 146%, respectively. These results may provide the basis for developing efficient pest management strategies against C. medinalis using host-plant volatiles and insect sex pheromones.
Cover crops provide many agroecosystem services, including weed suppression, which is partially exerted through release of allelopathic benzoxazinoid (BX) compounds. This research (1) characterizes changes in concentrations of BX compounds in shoots, roots, and soil at three growth stages (GS) of cereal rye (Secale cereale L.), and (2) their degradation in soil over time following termination. Concentrations of shoot dominant BX compounds, DIBOA-glc and DIBOA were lowest at GS 83 (boot). The root dominant BX compound, HMBOA-glc, concentration was least at GS 54 (elongation). Rhizosphere soil BX concentrations were 1000 times smaller than in root tissues. Dominant compounds in soil were HMBOA-glc and HMBOA. Soil BX compound concentrations were similar near root crowns and between-rows. Soil BX concentrations following cereal rye termination declined exponentially over time in three of four treatments: incorporated shoots (S) and roots (R), no-till S + R (cereal rye rolled flat), and no-till R (shoots removed); no-till S had consistently low concentrations. In treatments showing changes, soil concentrations of HMBOA-glc and HMBOA increased above initial concentrations on the day following cereal rye termination. Concentrations of these two compounds decreased more rapidly than the other compounds. Placement of shoots on the surface of an area where cereal rye had not grown (no-till S) did not increase soil concentrations of BX compounds. The short duration and complex dynamics of BX compounds in soil prior to and following termination illustrate the limited window for enhancing weed suppression directly by cereal rye allelochemicals; valuable information for programs breeding for enhanced weed suppression.
Morphological measurements that were made for M. cerberus (a–c) and M. cassununga (d–f) included head width (a and d), measures of ovary development (biggest oocyte and number of visible oocytes (b and e) and size of the Dufour glands (c and f)
Effect of the hormonal treatments on the total number of eggs laid by the a M. cassununga and b M. cerberus foundresses over the full duration of 5 days of our experiment (effect plot for treatment of Poisson GLMM in function of treatment, species and head width and nest coded as a random intercept, means ± 1-tailed 95% confidence intervals, asterisks represent 1-tailed significance levels: p < 0.001***, p < 0.01**, p < 0.05*, detailed results in Table 1)
Effect of body size (head width) on the total number of eggs laid by the a M. cassununga and b M. cerberus foundresses over the full duration of 5 days of our experiment (effect plot for body size of Poisson GLMM in function of treatment, species and head width and nest coded as a random intercept, means ± 1-tailed 95% confidence intervals, z = 1.89, 1-tailed p = 0.03, detailed results in Table 1)
Principal component analysis (PCA) of Aitchison tranformed relative peak areas of compounds present on the surface of the eggs across the three different treatments (precocene, methoprene and solvent acetone control) for both species studied aM. cerberus and bM. cassununga
Analysis of log-transformed relative peak areas of compounds found on the surface of the eggs in function of fertility (number of eggs laid over 5 days) in aM. cerberus and bM. cassununga for four compounds with significant regressions (FDR adjusted p values < 0.05) in M. cerberus. Regressions were not significant for M. cassununga but are shown here for comparison
Juvenile hormone (JH) is a key insect hormone involved in the regulation of physiological, developmental and behavioural processes. In social insects, it has been shown that JH can play a key role in modulating reproductive division of labour, age-related division of labour and chemical signalling, and can display marked changes in function of the degree of sociality. Here, we checked the efects of JH on reproduction in single foundresses of two neotropical primitively eusocial wasp species, Mischocyttarus cerberus and Mischocyttarus cassununga, by examining how treatments with the JH-analogue methoprene and the anti-JH precocene afect egg-laying, ovarian activation and chemical profles. Our hypothesis was that reproduction and the production of particular fertility-linked cuticular hydrocarbon cues might be under shared JH control already in primitively eusocial wasp species, and this could have been a key enabler to allow such cues to later evolve into full-fedged queen pheromone signals in advanced eusocial species. In line with this hypothesis, we show that our hormone treatments signifcantly afected both egg laying and the production of particular hydrocarbons present on the egg surface. We discuss the relevance of these findings in the context of the evolution of social insect queen pheromones in advanced eusocial species with a morphologically diferentiated queen–worker caste.
a The snapping shrimp Synalpheus stimpsonii under the calyx of a crinoid host Phanogenia distincta. b The crinoid Phanogenia distincta partially hidden in rock anfractuosity.c The crinoid Comanthus wahlbergii partially hidden in rock anfractuosity. d The crinoids Cenometra bella attached to a whip black coral. The scale bar represents 6 mm in (a); 26 mm in (b); 28 mm in (c) and 53 mm in (d)
Results of the behavioral experiments conducted with a Y-tube olfactometer on the symbiotic shrimp Synalpheus stimpsonii with crinoid conditioned water. The horizontal bar charts represent the percentage of shrimps (value in brackets) that remained stationary in the impaired branch after 10 min (white bars), that orientated adequately towards the aquarium A (black bars), or orientated towards the control aquarium B (striped bars). The P value of the statistic results for motion (Pearson’s chi-squared test with Yates continuity correction, χ² = 0.05, df = 1) and orientation (binomial test, 0.5 proportion) behaviors can be found in the corresponding columns. Significant results are in bold and characterized by asterisks (*for p < 0.05; ** for p < 0.01 or *** for p < 0.001). N = 20 replicates for each test except for test n° 3 that was realized on 25 replicates. “vs” stands for versus
Presumptive molecular structures of the anthraquinones detected in the crinoid Phanogenia distincta. a 1,3,8-Trihydroxy-6-[(1S)-1-hydroxypropyl] anthracene-9,10-dione or rhodoptilometrin and b 4-hydroxy-5,6 dimethoxy-2-methylbenzo[g]chromen-8-one or comantherin. The chemical structure of the new anthraquinone c is not shown as it cannot be confirmed only by mass spectrometry
LC–MS consensus chromatogram of Phanogenia distincta anthraquinone extracts from all individuals. a 1,3,8-Trihydroxy-6-[(1S)-1-hydroxypropyl] anthracene-9,10-dione or rhodoptilometrin; b 4-hydroxy-5,6 dimethoxy-2-methylbenzo[g]chromen-8-one or comantherin; c unknown 1. Corresponding MS results can be seen in Table 2 and corresponding chemical structures for (a) and (b) in Fig. 3
Results of the behavioral experiments conducted with a Y-tube olfactometer on the symbiotic shrimp Synalpheus stimpsonii with water conditioned by anthraquinones extracted from Phanogenia distincta or by commercial anthraquinones. The horizontal bar charts represent the percentage of shrimps (values in brackets) that remained stationary in the impaired branch after 10 min (white bars), orientated adequately towards aquarium A (black bars) or orientated towards the control aquarium B (striped bars). The P value of the statistic results for motion (Pearson’s chi-squared test with Yates continuity correction, χ² = 0.05, df = 1) and orientation (binomial test, 0.5 proportion) behaviors can be found in the corresponding columns. Significant results are in bold and characterized by asterisks (*for p < 0.05; ** for p < 0.01 or *** for p < 0.001). N = 20 replicates for each test. “vs” stands for versus
Quinones are one of the major pigment groups that provide such bright colors to feather stars (Echinodermata, Crinoidea). These secondary metabolites also act as defensive molecules rendering crinoids unpalatable and repellent to other organisms. However, feather stars are usually associated with numerous symbiotic organisms, amongst which the ectocommensal snapping shrimp Synalpheus stimpsonii. We investigated the chemical stimulus allowing host selection in S. stimpsonii through the combination of behavioral tests, chemical extractions, and mass spectrometry analyses. The individuals of S. stimpsonii used in the experiments were sampled around the Great Reef of Toliara (Madagascar) where they are found in association with two crinoid species: Comanthus wahlbergii and Phanogenia distincta. The chemical attractiveness of the two crinoid hosts and a non-host species, Cenometra bella, was tested in an olfactometer. The three crinoids produced attractive kairomones allowing the snapping shrimp to recognize them. Mass spectrometry analyses on purified extracts of P. distincta revealed the presence of three different anthraquinones (rhodoptilometrin, comantherin, and a new crinoid anthraquinone). Compared to the existing literature, this anthraquinonic cocktail is specific to P. distincta. When these extracts were injected in the olfactometer, they triggered similar attracting behavior suggesting that crinoid anthraquinones are kairomones allowing host selection for S. stimpsonii. This hypothesis is also supported by the fact that shrimps were chemically attracted by pure commercial anthraquinones. In addition to their traditional defensive role (allomones), anthraquinones would, therefore, also function as kairomones, maintaining the symbiosis between S. stimpsonii and its crinoid hosts.
The scent gland secretion of an undetermined species of Prionostemma from Costa Rica was analyzed by gas chromatography–mass spectrometry and shown to consist of medium-chain carboxylic acids (mainly octanoic acid) and a ß -hydroxy-carboxylic acid, eventually identified as myrmicacin (= ( R )-3-hydroxydecanoic acid). While scent gland secretions in harvestmen have traditionally been considered to be products of de novo synthesis, we here provide evidence for the unusual case of sequestration-derived scent gland constituents: at least myrmicacin appears to be sequestered from leaf-cutter ants that constitute a part of the prey of the Prionostemma -species herein investigated. This is the first report on the scent gland chemistry of the sclerosomatid subfamily Gagrellinae as well as on a possible sequestration mechanism in harvestmen.
Compounds isolated from Thapsia garganica leaves methanolic extract: Luteolin 7-O-glucoside(1),10β-acetoxy-8α-butyryloxy-11α-hydroxy-2β-((2-methylbutanoyl)oxy)-1βH,6αH,7αH,11βH-guaian-3-en-12,6-olide (2), thapsigargin (3)
IC50 values (µM) for Lolium perenne roots exposed for six days to luteolin7-O-glucoside (1), 10β-acetoxy-8α-butyryloxy-11α-hydroxy-2β((2-methylbutanoyl)oxy)-1βH,6αH,7αH,11βH-guaian-3-en-12,6-olide (2) and thapsigargin (3), in descending order of activity. Values are means ± standard errors (S.E) (n = 3). Means followed by at least one same letter are not significantly different at p < 0.05 (Duncan test)
Results of the bioassay in pot culture of Lolium perenne sprayed by individual compounds isolated from Thapsia garganica leaves methanolic extract, and their binary and tertiary mixtures. Pots sprayed by tap water were the negative controls. Results on shoots length (A), roots length (B), and fresh weight (C).Values are means ± standard errors (S.E) (n = 3). Means with at least one same letter are not significantly different at p < 0.05 (Duncan test)
Results of the bioassay in pot culture of Lolium perenne irrigated by individual compounds isolated from Thapsia garganica leaves methanolic extract, and their binary and tertiary mixtures. Pots irrigated by tap water were the negative controls. Results on shoots length (A), roots length (B), and fresh weight (C).Values are means ± standard errors (S.E) (n = 3). Means with at least one same letter are not significantly different at p < 0.05 (Duncan test)
Luteolin 7-O-glucoside (1), 10β-acetoxy-8α-butyryloxy-11α-hydroxy-2β-((2-methylbutanoyl)oxy)-1βH,6αH,7αH,11βH-guaian-3-en-12,6-olide (2) and thapsigargin (3) herbicidal activities’ were evaluated in comparison with their binary and tertiary mixtures, against Lolium perenne. These allelochemicals were isolated from Thapsia garganica leaves methanolic extract. Experiments were carried out by irrigation and spray in pot trials. Each compound was tested at the concentration that inhibits 50% of L. perenne root growth (IC50). Mixtures were prepared at the total concentration determined to inhibit 50% of weed root growth based upon the IC50 value for each compound (1000 µM, 154 µM and 300 µM for 1, 2 and 3, respectively). The greatest herbicidal effect was observed in tertiary mixtures, followed by binary ones, and single compounds showed the lowest phytotoxicity. Moreover, spray treatment was more effective at inhibiting growth of L. perenne, compared with irrigation. For sprayed binary mixtures, the 2 and 3 mixture showed the best inhibitions in shoot (75.79%) and root (91.02%) growth, and fresh weight (89.28%). These values significantly improved those of the most active single compound, 1 (48.01%, 58.62% and 57.14%, respectively, following spray). On the other hand, compound 3, whose structure is related to guaianolide sesquiterpene lactones, was a common constituent of the most active mixtures, suggesting that it plays a more relevant role in the improvement of the phytotoxicity of mixtures. Results obtained for the spray treatment of the tertiary mixture of 1 (333.33 µM), 2 (51.33 µM) and 3 (100 µM) were even more prominent, since weed growth was completely inhibited. After irrigation with a tertiary mixture, the greatest inhibitions in shoot and root growth and fresh weight did not exceed 88.16%, 94% and 90.47%, respectively. The results reported highlight a synergistic behavior of the test allelochemicals which could be applied in the development of bio-herbicides.
Green leaf volatiles (GLVs) are initially formed in the form of aldehydes, and then converted to alcohol and ester forms by the enzymes from plants. However, it remains unclear whether and how plant microbes work with aldehyde GLVs, especially under stressed conditions. Here, transcriptional response of cold-pretreated Pantoea agglomerans KSC03, an endophyte from Astragalus membranaceus var. mongholicus roots to E-2-hexenal was investigated and verified by real-time PCR and GC–MS after the time length of cold pretreatment was optimized. The results revealed that a 12-h cold stress was the most effective for KSC03 to trigger positive response to E-2-hexenal as far as the cell density was concerned. Transcriptome analysis showed that differentially expressed genes induced by E-2-hexenal were enriched in the following pathways: ABC transporter, phosphotransferase system, nitrotoluene degradation, and metabolisms of hexose and butanoate. Amongst, the upregulated transcription of gene3176 and gene4782 encoding N-ethylmaleimide reductase and diacetyl reductase in E-2-hexenal treatment was confirmed by real-time PCR. So did the enhanced production of 2,3-butanediol triggered by E-2-hexenal. Additionally, the transcription of gene3176 and gene4782 and the production of 2,3-butanediol chronologically reached their peaks in the E-2-hexenal-treated cells at the stationary phase. The results also indicated that exogenous E-2-hexanal passed through the cell membrane at the lag/early logarithmic phase and could not be utilized directly. In summary, E-2-hexenal triggers the positive cell response of cold-pretreated KSC03 at the transcriptional and metabolic levels in a time-length dependent manner.
Biosynthesis routes of major secondary metabolite groups found in flowers. Most of these compounds are synthesized from a few primary metabolites derived from plant respiratory pathways (glycolysis, oxidative pentose phosphate pathway, tricarboxylic acid cycle) represented in the grey-shaded region. Nitrogenous side chains are generally sourced from amino acids, e.g. L-glutamic acid. Secondary metabolites shown in this diagram are representative of the most widespread compound classes. AAT alcohol acetyltransferase, DMAPP dimethylallyl diphosphate, DXP 1-deoxy-D-xylulose-5-phosphate, IPP isopentenyl diphosphate, LOX lipoxygenase MT methyltransferase, MVA mevalonic acid, PAL L-phenylalanine ammonia-lyase, VOC volatile organic compound. Symbols of circles labelled ‘P’ denote phosphate groups
Developmental and external factors known to regulate the production of floral secondary metabolites. Dashed straight arrows denote indirect evidence available
Floral displays constitute signals conveyed to potential pollinators by pigments and fragrance compounds, which are secondary metabolites biosynthesized through a limited number of major metabolic pathways. In recent years, the role of defensive secondary metabolites, targeted to tolerate/resist herbivory, pathogen-borne diseases and other kinds of stress, has become apparent in the context of floral displays. Apart from pigments and volatile compounds, these defensive compounds include alkaloids, specialized molecules such as glucosinolates (in Brassicaceae), and proanthocyanidin phenolics. All these functionally overlapping groups of metabolites vary in floral concentrations under different kinds of environmental conditions as well as due to endogenous regulatory factors, resulting in metabolic and functional synergies or trade-offs according to the physiological status of the flowers. In this review, we discuss such associations among varying secondary metabolites in flowers, and their implications in context of plant stress-response mechanisms.
The extend of biogeochemical cycling of nickel (Ni) by tropical hyperaccumulator plants in their native habitat is largely unknown, although these unusual plants are suspected to play a major role in the recycling of this element in ultramafic ecosystems. In this study, we have assessed the biogeochemical cycling of Ni (and other elements, including mineral nutrients) by a tropical Ni hyperaccumulator plant, i.e., Phyllanthus rufuschaneyi, which is one of the most promising species for tropical Ni agromining. The study site was a young secondary forest in Sabah (Malaysia) where Phyllanthus rufuschaneyi occurs as the dominant species on an ultramafic Cambisol. For 2 years, we monitored a 100-m² plot and collected information on weather, biomass increase, soil fertility, water fluxes to the soil and litter fluxes for a wide range of elements, including Ni. The Ni cycle is mainly driven by internal fluxes, notably the degradation and recycling of Ni-rich litter. Over the period of investigation, the Ni litter flux corresponded to the total Ni stock of the litter (5.2 g m⁻² year⁻¹). The results further show that Ni turnover varies significantly with the accumulation properties of the plant cover. This points to the major influence of Ni hyperaccumulator plants in building up Ni available stocks in the topsoils, as has also been shown in temperate ultramafic systems. Litterfall and throughfall contribute substantially to the cycling of phosphorus, sulphur and potassium in this ecosystem, with throughfall contributing 2-, 220- and 20-fold higher to the respective nutrient fluxes relative to litterfall. The magnesium:calcium ratio far exceeded 1 in the soil, but was < 1 in the leaves of Phyllanthus rufuschaneyi. The insights from this study should be taken into account when designing tropical agromining operations; as Ni stocks could be more labile than initially thought. The removal of Ni- and nutrients-rich biomass will likely affect available Ni (and major nutrients) for the next cropping seasons, and requires sustainable fertilisation, to be utilized to replenish depleted major nutrients. These findings also have major ecological implications.
Carotenoids play multiple roles in insects, including coloration and protection. Most insects can obtain carotenoids only from their diet. Therefore, carotenoids are proposed to reflect trophic chains and lifestyles of insects. We investigated the mini-ecosystem of a gall on a hawkweed Hieracium × robustum induced by the gall wasp Aulacidea hieracii (Hymenoptera: Cynipidae) that is attacked by parasitoid wasp Eurytoma cynipsea (Hymenoptera: Eurytomidae). The parasitoid larvae consume the gall wasp larvae that consume the gall tissues. We employed resonance Raman spectroscopy to trace the fate of carotenoids in living larvae and pupae of these insects. We showed that carotenoid composition in the parasitoid closely corresponds to that of its diet—the gall wasp. On the contrary, carotenoid composition in the gall wasp was independent of that in the gall tissues, and the carotenoid concentration increases as non-feeding larvae mature. Thus, A. hieracii is suggested as a candidate among insects to have the ability to synthesize and modify carotenoids. Our findings give rise to the question of the relevance of using carotenoids as markers of trophic flow in the gall community.
Species-specific pheromone communication in moths is often achieved by the precise control of the production of a multi-component sex pheromone blend in females and selective perception of pheromone compounds in males. Reproductive isolation mediated by sex pheromone can be enhanced by the sensitive detection of structurally related non-pheromone components that are not used as pheromone in the same species but used as pheromone components in similar species. Here, we identified several unsaturated aliphatic acetates inhibiting the attraction of male moths to conspecific female sex pheromone in the lightbrown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), through electroantennogram (EAG) and field trapping studies. In EAG screening with 46 pheromone and structurally related compounds, eleven compounds exhibited significant male-specific EAG responses at 1 µg dose. The EAG-active compounds were mainly mono- or di-unsaturated 14-carbon acetates. In subsequent field trapping tests to evaluate the behavioral activities of the EAG-active compounds on male attraction to the binary blend (E11-14:Ac + E9E11-14:Ac) of female sex pheromone of E. postvittana, each of nine compounds (E9-12:Ac, Z9-12:Ac, E9-14:Ac, Z9-14:Ac, Z10-14:Ac, Z11-14:Ac, Z12-14:Ac, Z9E11-14:Ac and Z9E12-14:Ac) displayed clear inhibition of male moths to the sex pheromone blend in a dose-dependent manner. Our findings provide useful information in understanding the pheromone communication system of E. postvittana and related species.
Non-hierarchical cluster analysis by Ward’s method based on evaluated biological parameters of A. gemmatalis and S. frugiperda fed younger and older leaves of vegetative- and reproductive-stage plants of resistant and susceptible soybean genotypes and their corresponding concentrations of nutrients and flavonoids. RR reproductive-stage resistant genotype, RV vegetative-stage resistant genotype, RO older-leaf resistant genotype, SR reproductive-stage susceptible genotype, SV vegetative-stage susceptible genotype, SO older-leaf susceptible genotype, SY younger-leaf susceptible genotype, RY younger-leaf resistant genotype
Numerous species of herbivorous insects are associated with soybeans, including the specialist velvetbean caterpillar (VBC), Anticarsia gemmatalis, and the generalist fall armyworm (FAW), Spodoptera frugiperda. Expression of plant resistance is influenced by factors intrinsic to host plants, such as leaf age and plant stage, which can differentially affect specialist and generalist insects due to varying levels of plant defense and corresponding insect adaptation. In this study, four experiments were carried out to test the hypotheses that levels of antibiosis-resistance to VBC and FAW in the resistant genotype PI 227,687 and susceptible genotype IGRA RA 626 RR are related to leaf age and plant stage of soybean. Furthermore, the concentrations of nutrients and selected flavonoids were quantified to give insights into possible chemical mechanisms underlying the resistance. As results, development of VBC and FAW were negatively affected when larvae fed leaves of the resistant genotype, older leaves from the lower part of plants, or leaves from reproductive-stage soybeans. The effects were partly different for each insect species, and the generalist FAW was more affected by higher resistance levels in the older leaves of soybean than the specialist VBC. Distribution and concentrations of nutrients and flavonoids in soybean in function of leaf age and plant stage may explain the varying levels of antibiosis-resistance to VBC and FAW. These results can benefit developments of specific protocols for screening resistant soybean genotypes and pest management strategies focused in plant parts and growth stages that insect-resistance levels are lowest.
MS-spectra showing (a) the major male specific compound F, (b) (Z)-DMCHE and (c) (E)-DMCHE
Example of EAG responses of P. subopacus antennae. a n-Hexane (0), (b) (Z)-DMCHE (XX) and (c) (E)-DMCHA (X). XX = strong, X = weak and 0 = none (≤ n-hexane)
Chromatograms showing male-specific peaks from SPME–GC–MS analyses of a representative P. subopacus male and female. The insects were sampled 7 days after they started boring into the bark. A HP5-ms column was used for the analyses with a temperature program that started at 50 °C for 2 min and then the temperature was increased by 10 °C per minute up to 230 °C where it was held for 5 min
GC-chromatograms from SPME–GC–MS analysis of (a) P. subopacus male, and synthetic references of (b) (Z)-DMCHE and (c) (E)-DMCHE. A VF23-ms column was used for the analyses with a temperature program that started at 50 °C for 2 min and then the temperature was increased by 10 °C per minute up to 230 °C where it was held for 5 min
Structures of male specific compounds found when sampling with SPME when Polygraphus subopacus were boring into spruce logs
Bark beetles of the genus Polygraphus have recently been involved in large bark beetle outbreaks in central Sweden, together with the European spruce bark beetle Ips typographus . Three species of Polygraphus can be found in this region; Polygraphus poligraphus , Polygraphus punctifrons and Polygraphus subopacus . Efficient pheromone traps would facilitate further investigations of these species and their role in bark beetle outbreaks. Pheromone compounds have previously been identified in P. poligraphus and P. punctifrons , but not in P. subopacus . Thus, we allowed males and females of P. subopacus to bore in the bark of stem sections of Norway spruce ( Picea abies ) in the laboratory. Volatile organic compounds from boring insects were sampled with SPME and analysed with GC–MS and several male-specific compounds were observed. The male specific compounds were 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, 3-methyl-2-butenal, grandisol, fragranol, ( Z )-2-(3,3-dimethylcyclohexylidene)-ethanol, ( E )-2-(3,3-dimethylcyclohexylidene)-ethanol, ( Z )-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, ( E )-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, geranial and γ-isogeraniol. ( Z )-2-(3,3-dimethylcyclohexylidene)-ethanol, [( Z )-DMCHE], was identified from GC–MS analysis to be the major male-specific compound while the ( E )-isomer, [( E )-DMCHE], was found as a minor compound. These two compounds gave positive responses in EAG analyses with antennae from males and females of P. subopacus . Thus, ( Z )- and ( E )-DMCHE were used in a field experiment in central Sweden but only ( Z )-DMCHE was found to be attractive to males and females of P. subopacus . Consequently, ( Z )-DMCHE was established to be a component of P. subopacus aggregation pheromone.
Effects of different chemicals on soluble protein (A), MDA content (B), SOD activity (C), chlorophyll a (D), chlorophyll b (E) and carotene (F) of Bidens pilosa seedlings. Data are means ± standard errors. Different lowercase letters indicate significant differences between the different concentrations of the same allelochemicals at the 0.05 level. Numbers in abscissa indicate different tested chemicals: 1.α-Terpineol, 2. Caryophyllene, 3. β-Myrcene, 4.β- Ocimene, 5.α-Pinene
Volatilization, one of the most important mechanisms of the allelopathic effects of an exotic noxious weed Mikania micrantha, has not been adequately investigated to date. In this study, laboratory bioassays showed that the effects of volatiles from the leaves and flowers of M. micrantha on seed germination and seedling growth were negative for all four tested plants (Lactuca sativa, Chrysanthemum coronarium, Bidens pilosa, Abutilon theophrasti). Moreover, the inhibitory effect of the leaf volatiles was generally greater than that of the flower volatiles. To assess the reason for the above differences and further explore which compounds played the most crucial roles, the volatiles from the two tissues were absorbed by solid phase microextraction (SPME) and identified by gas chromatography and mass spectrometry (GC–MS). Then, 19 and 10 terpenes were determined respectively. α-Terpineol, β-ocimene, β-myrcene, α-pinene and caryophyllene had the maximum differences in content and concentration, which were selected for further bioassays with B. pilosa. The results indicated that morphological indices and SOD activity decreased with increasing concentrations of chemicals, whereas the contents of chlorophyll, soluble protein and MDA represented adverse changes. In addition, significant responses were observed in the treatments with α-terpineol at 1.0 μL·L−1 and lower concentrations, while similar trends were observed in the treatments with β-ocimene, β-myrcene, α-pinene and caryophyllene at 10 μL·L−1 and higher concentrations. It was concluded that terpenoids released through volatilization have an important role in the allelopathic effect of M. micrantha, and the oxygenated monoterpene α-terpineol played a crucial role in these effects.
Chemical communication is fundamental to maintain cohesion in social insect colonies, and in this communication process, cuticular hydrocarbons act as cues exchanged during interactions between nestmates. However, few studies have investigated intraspecific variation of these compounds in Neotropical swarm-founding wasps. We undertook the present investigation by performing two assessments. First, we assessed whether the cuticular chemical composition of females in Polybia sericea varies according to the degree ovarian development, relative age and different body parts. Second, we assessed whether the cuticular chemical profile of colony members and compounds found in nest materials could be used as complementary tools to assess population differences. To make these determinations, samples were collected from three different populations, and the compounds were analyzed by gas chromatography coupled with mass spectrometry. Linear alkanes were found to be the most abundant compounds in the cuticle of females and nest material. Considering the cuticular composition, it was possible to distinguish the females according to degree of ovarian development, relative age and different body parts. In addition, cuticular compounds and nest material were different in the three analyzed populations; therefore, both the cuticular chemical profile of colony members and the chemical profile of nest material can be used as complementary tools to assess population differences.
The predator-predator naïveté hypothesis suggests that non-native predators benefit from being unknown to native predators, resulting in reduced intraguild interference with native predators. This novelty advantage should depend on the ability of native predators to recognize cues of non-native predators. Here, we compared ant aggression and lady beetle reaction in four native and the invasive lady beetle species Harmonia axyridis . In addition, we tested whether lady beetle cuticular hydrocarbons (CHCs) are involved in species recognition, which might explain naïveté if the invasive species has a specific CHC profile. To this end, we conducted behavioral assays confronting two native ant species with both living lady beetles and lady beetle elytra bearing or lacking CHCs of different lady beetle species. Finally, we characterized CHC profiles of the lady beetles using GC–MS. In general, the aggression of Lasius niger was more frequent than that of Myrmica rubra and L. niger aggression was more frequent towards most native lady beetle species compared to H. axyridis . The removal of CHCs from lady beetle elytra reduced aggression of both ant species. If CHCs of respective lady beetle species were added on cue-free elytra, natural strength of L. niger aggression could be restored. CHC analyses revealed a distinct cue composition for each lady beetle species. Our experiments demonstrate that the presence of chemical cues on the surface of lady beetles contribute to the strength of ant aggression against lady beetles. Reduced aggression of L. niger towards H. axyridis and reduced avoidance behavior in H. axyridis compared to the equally voracious C. septempunctata might improve the invasive lady beetle’s access to ant-tended aphids.
Chromatograms of frozen sampled CHC extracts of Odynerus spinipes females stored at − 20 °C. The retention time differ slightly between alkenes of females displaying chemotype 1 (top), which have the double bond at an uneven position, compared to alkenes of females displaying chemotype 2 (bottom), which have the double bond at an even position
Number of all studied female samples for which the year of collection was known to us (N = 910; the year of collection was unknown for 99 female museum samples), identified (left y axis) as chemotype 1 (c1 in orange), chemotype 2 (c2 in purple), and as deviant (deviant c2 in light purple) in different time periods (in years). Unidentified samples are represented in grey (NA). Dry-mounted samples had been collected between 1826 and 2017; freshly collected samples had been collected between 2014 and 2019. The dark blue line shows the percentage (right y axis) of successfully identified chemotypes in a given time period
Geographical differences in the frequency at which Odynerus spinipes females display chemotype 1 (orange) and chemotype 2 (purple). The diameter of the pie charts is proportional to the number of females analyzed from a given location. Note that the pie charts on the two maps have different scales. The approximate distribution of the species is indicated by the continuous black line
The mason wasp Odynerus spinipes shows an exceptional case of intrasexual cuticular hydrocarbon (CHC) profile dimorphism. Females of this species display one of two CHC profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC–MS the CHC profile of 1042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC profile dimorphism that O. spinipes females exhibit.
Wind tunnel model. a A fan; b Two filters; c The insect flight arena; d Adult C. sinensis; e A litchi mimic model; f Wind speed 30 cm/s; g The upwind tunnel; h The downwind tunnel
Electroantennogram (EAG) responses of C. sinensis females and males to single volatile components. 1. β-caryophyllene; 2. β-elemene: 3. ( +)-aromadendrene; 4. α-humulene (isocaryophyllene); 5. β-guaiene; 6. β-farnesene; 7. 1-β-bisabolene; 8. α-pinene. The concentration of each volatile component was 0.01 μg/μL. Each component was evaluated using ten (each) C. sinensis females and males, with three technical replicates. The means ± SE of EAG responses in female and male C. sinensis individuals are shown. Different lowercase (uppercase) letters above the bars indicate significant differences between treatments with different individual components in female (male) C. sinensis (p < 0.05)
Electroantennogram (EAG) responses of C. sinensis females to mixed volatile components. 1. β-caryophyllene; 2. β-elemene: 3. ( +)-aromadendrene; 4. α-humulene (isocaryophyllene); 5. β-guaiene; 6. β-farnesene; 7. 1-β-bisabolene; 8. α-pinene. Each mixture contained equal proportions of components and the concentration of each component in a mixture was the same as that in its single form (0.01 μg/μL). The × in the columns indicates which components were present in each volatile component mixture. Each compound mixture was evaluated using ten female C. sinensis individuals, with three technical replicates. The means ± SE of the EAG responses of female C. sinensis individuals are shown. The different small letters above the bars indicate significant differences in the EAGs of C. sinensis females to each volatile component mixture (p < 0.05)
Behavioral responses of adult C. sinensis females to single and mixed volatile components. Components: 1. β-caryophyllene; 2. β-elemene: 3. (+)-aromadendrene; 4. α-humulene (isocaryophyllene); 5. β-guaiene; 6. β-farnesene; 7. 1-β-bisabolene; 8. α-pinene. Blank control: no treatment. Negative control: treatment with paraffin oil. Different colors indicate different behavioral responses of C. sinensis females and these reactions were continuous from FW to SD. FW flap wings, TF taking flight, UF oriented upwind flight, CUF continued upwind flight, AA arriving at the attractant, SD staying at and detecting the attractant. Each attractant was evaluated using 20 C. sinensis females. The means of the behavioral responses from C. sinensis females are shown. *Indicates a significant difference at the 0.05 level
Expression of olfactory genes in the antenna of C. sinensis females after treatment with the mixed attractant (α-pinene + β-farnesene). OBP odorant-binding protein, GOBP general odorant-binding protein, CSP chemosensory protein, IR ionotropic receptor, OR odorant receptor, SNMP sensory neuron membrane protein, CXE carboxyl esterase
Insect olfactory systems can efficiently distinguish important host signals in a complex background of odor. Notably, Conopomorpha sinensis Bradley (Lepidoptera: Gracillariidae), a host-specific pest of Litchi chinensis and Euphoria longan, causes periodic outbreaks in southern China. However, little is known about the functions of host volatiles and olfactory mechanisms through which C. sinensis senses host taxa. Consequently, the present study analyzed the Electroantennogram (EAG) responses of C. sinensis antennae to host volatile compounds and their mixtures. The results showed that volatile components were more stimulatory to female than to male C. sinensis antennae. In addition, the highest EAG responses were observed following the stimulation of female antennae by the individual volatile component β-guaiene, followed by β-caryophyllene and β-elemene. However, odorant mixtures containing β-farnesene and α-pinene significantly altered EAG responses in female antennae. This was further confirmed by behavioral responses to host volatile compounds based on the flight orientation of females and males in a wind tunnel. These findings demonstrated that the behavior of C. sinensis can be affected by single compounds or a mixture of compounds. Moreover, real-time fluorescence quantitative PCR suggested that a combination of α-pinene with β-farnesene could alter the expression of olfactory genes. Therefore, screening for odors that can effectively alter the behavior of insects provides a theoretical basis for exploring host recognition and utilizing the olfactory networks of C. sinensis for biocontrol, at the molecular level.
Two components of the Synanthedonbicingulata sex pheromone, (E,Z)-3,13-octadecadienyl acetate (E3,Z13-18:OAc) and (Z,Z)-3,13-octadecadienyl acetate (Z3,Z13-18:OAc), were synthesized to investigate the effect of pheromone blends, trap type and trap color on the capture of S.bicingulata males. The optimal sex pheromone ratio for E3,Z13-18:OAc and Z3,Z13-18:OAc was approximately 4.3:5.7 based on the purity of the two pheromone components in all test areas. A significant difference was observed in the number of S.bicingulata adult males caught in bucket and delta traps. The mean numbers of males caught in bucket and delta traps were 13.2 ± 2.2 and 7.6 ± 2.0, respectively. Trap color affected the number of adult males caught in bucket traps. More adult males were attracted to a yellow bucket trap than to green, white, blue, black and red traps. An analysis of the relationship between trap capture and trap surface-color values (L*a*b*) revealed a positive relationship between trap capture and b* value.
Preliminary screening for fungi and their taxonomic identification. a Rice seedlings were treated with two living fungi (SG-17 and QY-1) and their fermentation broth after ultra-sonication (SG-17U and QY-1U). All seedlings were fully flooded for 4 days and then allowed to resume normal growth for another 4 days. b–d The SG-17’s colony, micromorphology, and phylogenetic tree based on the ITS sequence and applying the neighbor-joining (NJ) method. Numbers above the branches are the bootstrap values. e–g Taxonomic identification of QY-1
Active compounds in SG-17 and QY-1. a Beneficial effects of different substances and concentrations on the flooding tolerance in rice. Each pot of seedlings was sprayed with 1 mL of solution 4 h before complete immersion, unit: mg/mL, bar = 1 cm. b, c Structure of NFA in the endophyte SG-17 and its HPLC analysis. d, e Structure of CheA in the endophyte QY-1 and its HPLC analysis
Antioxidant capacity of NFA and CheA. a Total antioxidant analysis. b DPPH free radical scavenging rate. The positive control is 1 µg/mL vitamin. Data are expressed as the means ± standard deviation, and n = 3. The * indicates a significant difference at p < 0.05, and likewise *** at p < 0.001 when compared with the control group
Physiological responses of flooded rice seedlings to NFA and CheA. a–d corresponds to the content or activity of MDA, SOD, ADH, and NADPH oxidase. Data are expressed as the means ± SD, and n = 20. The *, ** and ***, respectively, represent significant differences at p < 0.05, < 0.01, and < 0.001 when compared with the non-flooded control group. The # and ## indicate a significant difference at p < 0.05 and < 0.01, respectively, when compared with the flooded control group
Effects of the two endophyte-derived antioxidants on the expression levels of OsRboh genes and H2O2 content in rice plants under flooding stress. a Semi-quantitative RT-PCR analysis of the OsRboh family responding to flooding in the absence of the antioxidants. b The relative contents of OsRbohA and OsRbohB with the prolongation of 0.1 mg/mL of NFA or CheA treatment under normal growth. c The relative contents of OsRbohB in the presence of antioxidants, before or after imposed flooding of rice for 4 days. Data are expressed as the means ± SD, and n = 3. The * and # denote, respectively, comparisons with the before flooding group and the after flooding group. d H2O2 content under the treatment of antioxidants, before or after imposed flooding of rice
Endophytic fungi have the potential to enhance plant resistance to various stresses and promote the ecological adaptation of the hosts. To evaluate the effects of the riparian endophytes on rice seedlings to flooding tolerance, here we screened out two fungi from the plant Myricaria laxiflora growing in the Yangtze River zone. Through morphological characteristics and rDNA ITS (internal transcriber region) sequence, the two strains were, respectively, identified as Aspergillus fumigatus and Chaetomium globosum. Metabolites derived from both fungi were capable of increasing tolerance of rice to flooding. Systematic separation and purification coupled to bioassays revealed that two natural antioxidants, Z-N-4-hydroxystyryl formamide (NFA) and chaetoglobosin A (CheA), were effective for alleviating flooding stress. Both NFA and CheA can reverse the decline trend of oxidative parameters caused by long-term flooding, such as malondialdehyde, superoxide dismutase, ethanol dehydrogenase, and NADPH oxidase. Gene expression analyses of NADPH oxidase families indicated that OsRbohB could be involved in conferring flooding tolerance mediated by the two natural antioxidants. These findings contribute to understanding the role of the natural antioxidants in riparian endophytic fungi and providing a basis for improvement of flooding tolerance of rice and other crop plants.
Spiroacetals such as E-7-methyl-1,6-dioxaspiro[4,5]decane (trans-conophthorin; tC) and acetamides [predominantly N-(3-methylbutyl)acetamide; N3MBA], are two major groups of volatiles discovered in venoms of many Vespidae. In the course of testing the attractiveness of tC and N3MBA to Vespidae using Rescue® Wasp TrapStiks, a significant number of female milichiids, Desmometopa nearctica Sabrosky and D. sordida (Fallén) (Diptera: Milichiidae) were trapped as well. However, the attraction of vespid wasps was not significant at the dosages tested. We found a significant synergistic effect of tC and N3MBA in attracting Desmometopa flies. Both D. nearctica and D. sordida are kleptoparasitic species; and we conclude that females of these two milichiid flies use tC and N3MBA (and likely other volatiles) released from venom glands of the social vespids (yellowjackets, paper wasps and hornets) as kairomones to locate disturbed, injured, or freshly killed insects (vespids and/or their prey) as a protein-rich food source for egg development and production.
Social wasps build their nests using plant material and can thereby occupy different types of habitats. The organization of their colonies is generally based on complex communication systems that include chemical compounds of the cuticle that are shared with the material of their nests thus contributing to the specific chemical signature of their colony. These compounds can vary by environmental factors, in this case the nesting substrate may interfere with this composition. However, no study to date has investigated whether there is any relationship between the chemical signature of the colony and the nesting substrate of their nests. Therefore, in this study we investigated the relationship between the colonial chemical signature and the plant in which the colonies were nesting. Colonies of three species of social wasps and samples of plants where they nested were collected, then extractions of the chemical composition of adult wasps, nest material and plants were performed. The results show that the colonies of social wasps investigated here share their chemical composition with the plants where their nests were built. Our results suggest that the plant can provide the colony with more than just a place with ideal physical conditions and safety, but also compounds that compose the colonial chemical signature.
Comparison of the content of the three terpene subgroups (MT monoterpene, ST sesquiterpene, DT diterpene) and of the total content (means ± SD) among species. Means were calculated from the total terpene content of each individual. For each terpene subgroup, different letters indicate significant differences between species (p < 0.05). Lowercase letters indicate significant differences between species for each terpene subgroup
Flammability variables (mean and standard deviation, n = 30) recorded on the four species studied: a ignition temperature (tTTI) and maximum temperature (Tmax), b flaming duration (FD) and time-to-ignition (TTI)
Best correlations obtained between terpene content (subgroup or compound) or fuel moisture content (FMC) and flammability variables (TTI: time-to-ignition; FD: flaming duration; Tmax: maximum temperature) for the four species studied (simple regression analyses, F fisher test, p probability, R correlation coefficient, R² coefficient of determination; MT monoterpnes, ST sesquiterpenes, DT diterpenes)
Scaled and centered regression coefficients of the significant parameters (when |value| > 0.2) among terpene subgroups (DT diterpene, ST sesquiterpene, MT monoterpene) and fuel moisture content (FMC) highlighting the drivers of each flammability variable (FD: flaming duration; TTI: time-to-ignition; Tmax: maximum temperature; tTTI: ignition temperature). Partial least squares regression analyses were performed on the studied species’ datasets excluding (a) or not (b) FMC as an independent variable along with terpenes in the models. Results were not significant for Hesperocyparis arizonica
Scaled and centered regression coefficients of the significant parameters (|value| > 0.2) among terpene compounds (DT diterpene, ST sesquiterpene, MT monoterpene) and fuel moisture content (FMC) highlighting the drivers of each flammability variable (FD: flaming duration; TTI: time-to-ignition; Tmax: maximum temperature; tTTI: ignition temperature). Partial least squares regression analyses were performed on the studied species’ datasets (aCupressocyparis leylandii, bCupressus sempervirens, cHesperocyparis arizonica, dPinus halepensis) including or not FMC as an independent variable along with terpenes in the models (only the significant results are shown)
In flammability assessment, the terpene effect is usually studied using their total or subgroup content, missing, therefore, the information that could be provided by the molecules themselves. In this study, the specific role of terpenes on leaf flammability was sought comparing different levels of terpene identification—total, subgroup (i.e. mono-, sesqui-, and diterpene), and single compound—as well as their interactions with fuel moisture content (FMC) in four species common in Mediterranean Wildland–Urban Interfaces (Pinus halepensis, Cupressocyparis leylandii, Hesperocyparis arizonica, Cupressus sempervirens). Pinus halepensis was the most flammable species (low FMC and higher sesquiterpene content but low terpene diversity) while Cupressocyparis leylandii presented the highest terpene diversity and total terpene content (higher mono- and diterpene content). Flammability was differently affected according to the terpene identification level used in the models. The effects ranged from non-significant for most species studied, using subgroup or total terpene content, to mostly significant, using single compound content. Regarding the former, the lack of significant results could be due to opposite effects of different single compounds within a terpene subgroup. For the latter, terpene molecules driving flammability and their effects (positive or negative) differed among species. A cumulative effect with FMC was also highlighted in some cases but terpenes mostly remained the main flammability drivers regardless of the species. Using the refined terpene level in modelling allowed a better understanding of the compounds’ role on flammability, which is useful in the identification of plant traits linked to flammability.
a Oviposition plugs laid by female pepper weevil near the calyx of a jalapeno pepper b Teflon tape oviposition sachets and c volatile collection on Tenax filters from oviposition plugs deposited on Teflon tape
GC–MS chromatographic analysis of TMS/diazomethane methylated female pepper weevil oviposition plug extracts. a Electron impact (EI) ionization trace of derivatized oviposition plug extract, b A close up of the C18 fatty acid area of the chromatogram, c Isobutane chemical ionization GC/MS analysis of the same methylated extract showing composite chromatogram of extracted M + 1⁺ ions 293, 295 and 297 (for linolenic, linoleic and oleic acid, respectively). d The same type pf composite ion chromatogram for a derivatized seed extract and e for a derivatized pepper flesh extract. To show the dietary available lipid bound fatty acids, the two tissue extracts were subject to methanolysis
GC–MS chromatogram of oviposition plug volatiles collected on Tenax from Teflon sachets and analyzed by thermal desorption GC/MS showing dominating acetophenone and benzoic acid peaks. Background volatiles were subtracted
Insects in several orders deposit marking pheromones following oviposition. In addition to preventing the female from visiting the same site again, the pheromone also signals the presence of eggs to conspecific females. This form of chemical marking is particularly prevalent in species which oviposit on discrete hosts with limited resources available for developing larvae. The pepper weevil is a major pest of cultivated pepper throughout the southern United States, Mexico and the Caribbean. The weevil deposits eggs singly in a cavity chewed in flower buds and small fruits and caps these cavities with a plug derived from an anal secretion. The deterrent was found to be located in this oviposition plug and comprised of volatile and contact-acting components. Plug volatiles were collected by inducing oviposition into Teflon tape sachets containing pepper leaves and collecting volatiles from plugs laid on the tape surface. Of the two major components observed by GC/MS analyses, only acetophenone elicited a behavioral response by the female weevil in small arena and wind tunnel assays. Investigations of the oviposition plug matrix identified several free unsaturated and saturated fatty acids as major constituents of the plug which was in stark contrast to pepper tissue and seeds that contained only trace levels of free fatty acids and a distinctly different total fatty acid composition. The combined free fatty acids as well as acetophenone tested singly gave no significant reduction in oviposition while a plug-mimicking blend of unsaturated fatty acids tested in combination with acetophenone as artificial ‘plug spots,’ decreased oviposition on treated peppers by up to 75%. We propose that the combination of volatile and contact acting marking components improves oviposition site selection efficiency by pepper weevils on discrete hosts.
Reconstructed 3D-printed model and printed samples of A. fragariae, and glass bead used in the present study. a Reconstructed 3D model; b black 3D-printed model; c white 3D-printed model; d black glass bead. For the 3D models, the columns from left to right are the dorsal view, lateral view, and 45° view
Representative gas chromatogram profiles of cuticular hydrocarbons of Altica fragariae, hexane control, glass bead, and 3D-printed beetles. a Male A. fragariae; b female A. fragariae; c hexane control; d black glass bead; e black 3D-printed model; f white 3D-printed model
Mating preference of male Altica fragariae comparing black 3D-printed beetles coated with female CHCs (right hand column) to alternative models (left hand column). a Black 3D-printed beetle coated with male CHCs versus black 3D-printed beetle coated with female CHCs; b black glass bead coated with female CHCs versus black 3D-printed beetle coated with female CHCs; c white 3D-printed beetle coated with female CHCs versus black 3D-printed beetle coated with female CHCs; d dead female with CHCs removed and reapplied versus black 3D-printed beetle coated with female CHCs; e dead female with antennae and legs removed and CHCs removed and reapplied versus black 3D-printed beetle coated with female CHCs. Asterisks indicate significant differences in mating preference (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001). “Mated” refers to the number of males that mounted the mate, waved his antennae quickly and exhibited aedeagus-protruding behavior for longer than 10 s
A variety of models have been used in mating bioassays of insects to assess the contribution of chemical and visual signals to mate location and mate selection. Although the use of such ‘dummies’ has had varying degrees of success, some insect species refuse to accept simplistic models. In the present study, we developed a 3D-printed model to explore whether more realistic models will be more successful than simplistic models in mating assays of difficult to manipulate species such as the flea beetle Altica fragariae. We ran five experiments to test (1) whether males could discriminate between males and females solely based on differences in cuticular hydrocarbons (CHCs), (2) whether males use shape or (3) color to choose mates, and (4) whether males can discriminate between 3D-printed models and freshly killed beetles either with or (5) without legs and antennae. The results of these experiments confirmed that male A. fragariae preferred models coated with CHCs of females over that of male CHCs, providing strong support for the role of CHCs in mate choice in Altica. We also showed that males use both shape and color in mate selection, and that males are capable of discriminating between the models and real beetle specimens. Together, the results indicate that 3D-printed models can provide a feasible and cost-effective method for mating studies of insects.
In insects, chemical communication is the most common form of communication, and cuticular hydrocarbons (CHCs) are employed in recognition processes. In social insects, CHCs also help define colony identity and thus contribute to social cohesion among nestmates. Individuals can deposit their chemical signatures on nest surfaces. This information serves as a reference for newly emerged individuals and allows them to obtain the odor specific to their colony. This study examined nest chemical profiles in an inbred invasive species: the yellow-legged hornet, Vespa velutina nigrithorax. We demonstrated that nest structures (i.e., envelopes, combs, and pillars) had specific hydrocarbon profiles, which were colony specific. There were similarities between the chemical profiles of the nests and the CHC signatures of hornets. The loss of genetic diversity previously documented in the yellow-legged hornet population in France does not appear to have constrained nest chemical diversity.
Behavioral responses of adult Cimex lectularius and Cimex hemipterus to conspecific aldehyde sources (exuviae or synthetic blend) in olfactometers. Numbers in bars indicate the percent of bed bugs responding to the volatile cue and sample size
The behavioral responses of two bed bug species, Cimex lectularius L. and C. hemipterus (F.), to conspecific or heterospecific nymphal aldehyde blends were examined using a two-choice olfactometer. Volatile cues from exuviae or a synthetic blend containing (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal, and 4-oxo-(E)-2-octenal were tested. In both species, the adults settled preferentially on the olfactometer treatment side when conspecific volatile aldehyde cues were provided. When tested with heterospecific volatile aldehyde cues, only adult C. lectularius preferentially responded to C. hemipterus volatile cues. Adult C. hemipterus was indifferent to the aldehyde blend of C. lectularius. Potential implications of the finding on bed bug biology and practical pest management are discussed.
Neotropical poison frogs possess alkaloid-based antipredator defenses which they sequester from a diet of arthropods such as oribatid mites and myrmicine ants. Alkaloid sequestration is still poorly understood and although several studies have examined its uptake, most experiments directly feed alkaloids to the frogs. Here, we examined the alkaloid uptake system in the poison frog species Dendrobates auratus by feeding it an alkaloid-containing prey item, the red imported fire ant Solenopsis invicta (Formicidae, Myrmicinae). Captive bred frogs were either fed live ants or fruit flies dusted with powdered ants for 4 months. Using GC–MS, we confirm that S. invicta contain previously described piperidine alkaloids known as solenopsins; however, none of these piperidine alkaloids was detected in the skin of D. auratus, suggesting the frogs are incapable of sequestering solenopsins from S. invicta. It is possible that D. auratus are unable to sequester fire ant piperidines due to their long hydrocarbon side chains, a feature that makes them structurally different than most known alkaloids in poison frogs.
The real-time odor environment (ROE) and odor detection of an herbivorous insect under certain conditions and optimal plume-tracking routes for the insect. a There are five odors: O1 (host), O2 (non-host), O3 (non-host), O4 (non-host) and O5 (non-host) in the ROE the host-finding insect is passing through. All the odors except O5 are attractive relative to air. O1 occupies the highest rank, O2 occupies the second rank, O3 and O4 occupy the third rank, O5 occupies the lowest rank in their attractiveness. The olfactory receptors in odorant receptor neurons enclosed inside the sensilla on the antennae can be stimulated by the odorants and produce neural signals, these signals are subsequently processed at various levels in the central nervous system and ultimately decoded into the “final perceptive signals” which “tell” the host-finding insect what kinds of odor it is encountering. Then specific behavioral responses are decided according to the odors’ ranks. If the composition/chemical structure of the main components in O3 is same/similar to O4 or the insect lacks chemoreceptors sensitive to certain odorant components that are different between O3 and O4, O3 and O4 might be recognized as the same odor. b Facing the intertwined odor plume strands in the ROE, the host-finding insect is prone to switch to the higher rank odor plumes and there are 4 optimal plume-tracking routes for it
Simplified diagram about the influence of odor mixing degree and real-time odor environment (ROE) on host finding of a specific insect. Odor plumes are visualized by different colors and their ranks are labeled as 1, 2, 3 and 4 from high to low. a When the mixing degree of different odor plumes is low, the insect can easily discriminate and track the host odor strands to locate its host. Under this situation, non-host odors can be attractive to the insect in the long-distance ROE (L-ROE; an example is marked in the figure), although the concentrations and ranks of different odors may change. The higher the non-host odors’ ranks are, the more pests might be attracted to the vicinity of the host plant, increasing the chance that the insect encounters host plant odor strands. When the insect comes into the short-distance ROE (S-ROE; an example is marked in the figure), the non-host plant odors become “repellent” relative to host plant odor (highest rank), which can even facilitate the insect moving towards and loading on the host plant. The non-host plant odors either have no effects or produce the opposite (enhancing) effects. b The non-host odor cannot affect the insect ability to locate the host plant until the mixing degree of the given host and non-host volatiles reaches a certain level (threshold value). Under this situation, the host-finding insect may spend much more time to discriminate and track the host odor strands and probably cannot find the host plant, give up or turn to other directions. Except the extreme case that host and non-host plant volatiles have very different compositions, masking effects might be observed
Olfaction plays a major role in the host-finding behaviors of insects. However, the irregularity of insect responses to odor interactions has hindered our efforts to draw broad conclusions about how a host-finding insect uses the complex mixture of various odor plumes in natural environments. Particularly, it is still unclear so far why the use of non-host odors to control insect pests in practices have met with mixed results. To further understand the host-finding of a specific insect, we highlight the role of the real-time odor environment (ROE) that the host-finding insect is passing through. The ROE may contain various odors with different ranks and changes during the insect’s host finding. A host-finding insect may always prone to switch to the higher rank odor plumes in each ROE regardless of the distance is “short” or “long” from the odor source. For a specific herbivorous insect, only mixing degree of the given host and non-host plant odors reaches some certain level (threshold value), can the non-host odors significantly affect its ability to locate host plants. When the odor mixing degree is low, masking effects may not occur or the non-host plant odors’ “attractive” effects at long distances and “repellent” effects at short distances can even increase the pest loads. In forests, the mixing degree of different plant odors is determined by turbulence intensity which is mainly affected by plant structures. These may further advance our understanding of herbivorous insects’ host finding and have important implications for the development of pest management strategies.
Stink bugs (Pentatomidae) produce volatile chemical substances in the scent glands, with unpleasant odors that function as alarm and defense signals against natural enemies. The contents of the scent glands of the predatory Podisus nigrispinus and its prey, the phytophagous Euschistus heros were used to evaluate the behavioral interactions between these two insects. Quantitative and qualitative analyses of odor components were performed by gas chromatography (GC/FID and GC/MS) and behavioral response evaluated by video-tracking system. The chemical composition of the odor produced by P. nigrispinus and E. heros contains aldehydes and hydrocarbons. The chemical mixture has quantitative and qualitative component differences between species and sexes, with 20 compounds identified for P. nigrispinus and 17 compounds for E. heros. The compounds (E)-2-hexenal, hexenoic acid, (E)-2-decenal, tridecane, tetradecane, and pentadecane occur in both species, but with different amounts between males and females. The secretion of the scent gland of P. nigrispinus and E. heros produces repellent and irritant effects between species and between sexes of the same species, supporting the defensive function of these compounds. Chemical identification of the Pentatomidae scent gland compounds may influence in insect behavior cause side effects in other insects. Overall, these compounds can be a sustainable and novel source of insecticides with potential to agricultural pest control.
Photograph of a 3-chamber Pyrex glass olfactometer (with lids removed from each chamber) depicting the central chamber (3.5 × 10 cm ID) interconnected by glass tubes (each 2.5 × 1 cm ID) to two lateral chambers. For each replicate, a single spider was introduced into the central chamber, and 18–21 h later its position in the Treatment (T) or the Control (C) chamber was recorded. A spider found in the central chamber or the interconnecting glass tubes (an area delineated by the two black lines) was deemed a ‘non-responder’ (NR) and was excluded from statistical analyses
Responses of Steatoda grossa in experiments 1–11 (n = 30 each) in 3-chamber olfactometers (Fig. 1) to treatment stimuli consisting of seven herbivore-induced plant volatiles (HIPVs) and an HIPV-elicitor [(±)-jasmonic acid] tested singly (10 µg/10 µL) or as an ‘8-component blend’ [ocimene, (−)-linalool, (E)-β-caryophyllene, (E)-4,8-dimethyl-1,3,7-nonatriene (= DMNT), (E)-β-farnesene, (E/Z)-nerolidol, ( ±)-jasmonic acid, methyl salicylate] (10 µg/10 µL), with all components at equal proportion. Control stimuli consisted of the corresponding volume and type of solvent, or no solvent (Exp. 11) (see Table 1 for details). Numbers in bars indicate the number of spiders responding to treatment or control stimuli, whereas numbers in square inserts denote the number of non-responding spiders. For each of experiments 9 and 10, the asterisk (*) denotes a statistically significant treatment effect [(p < 0.05; one-tailed binominal tests with Benjamini–Hochberg adjustment for each test group (Exps. 1–8, 9–10, and 11, respectively)]
Responses of Steatoda grossa, Pholcus phalangioides, Eratigena agrestis, and Latrodectus hesperus in experiments 12–19 (n = 28 each) in 3-chamber olfactometers (Fig. 1) to treatment stimuli consisting of herbivore-induced plant volatiles (HIPVs) and an HIPV-elicitor [( ±)-jasmonic acid], tested as a ‘3-component blend’ (10 µg/10 µL) [(−)-linalool, (E/Z)-nerolidol, ( ±)-jasmonic acid at equal proportions], or as an ‘8-component blend’ (10 µg/10 µL) [ocimene, (−)-linalool, (E)-β-caryophyllene, (E)-4,8-dimethyl-1,3,7-nonatriene (= DMNT), (E)-β-farnesene, (E/Z)-nerolidol, ( ±)-jasmonic acid, methyl salicylate at equal proportions]. Control stimuli consisted of the corresponding volume and type of solvent(s) (see Table 1 for details). Numbers in bars indicate the number of spiders responding to treatment or control stimuli, whereas numbers in square inserts denote the number of non-responding spiders. There was no statistically significant deterrent effect caused by any test stimulus
An underlying assumption of optimal foraging models is that animals are behaviorally, morphologically, and physiologically adapted to maximize their net energy intake. Here we explored whether this concept applies to web-building spiders in a multi-trophic context. If a spider were to build her web next to herbivore-fed-on plants that signal the herbivores' enemies for help by emitting herbivore-induced plant volatiles (HIPVs), that spider may maximize web captures in the short term. However, she would also risk predation by generalist predators that "listen" to signaling plants to find both herbivore and spider prey, likely resulting in lower overall reproductive fitness for the spider. We tested the hypothesis that HIPVs trigger avoidance responses by web-building spiders. We selected seven common HIPVs and one HIPV elicitor, and in two-choice olfactometer bioassays tested their effect on four synanthropic spider species (false black widow, Steatoda grossa; common cellar spider, Pholcus phalangioides; hobo spider, Eratigena agrestis; western black widow, Latrodectus hesperus). The 8-component HIPV/HIPV elicitor blend had a weak deterrent effect on S. grossa, but the effect did not extend to P. phalan-gioides, E. agrestis, and L. hesperus. Our findings imply that there was insufficient selection pressure for these spiders to recognize HIPVs in a multi-trophic context, where spiders themselves could become prey if generalist predators or spider-hunting parasitoid wasps were to respond to signaling plants.
Larval colour change during manifestation of the typical symptoms of EFB disease, from pearly white, yellow, brown to greyish black. Age (days post-grafting) of the larvae at each sampling point are marked with arrows. Three individuals of the same colour, according to this colour scheme, and same age were used for one GC–MS sample
Representative cuticular hydrocarbon profiles of 8-day-old infected (upper panel) and non-infected (lower panel) honey bee larvae analysed by GC–MS. PCA-relevant peaks are labelled according to Table 1. Peaks with raw ion counts < 300,000 are zoomed and shown separately
Discriminant analysis of honey bee larvae cuticular hydrocarbon profiles separated by age (5 vs. ≥ 8 days post-grafting) and treatment (infected vs. control), by the two first dimensions (49.9% of the total variance). Sample labels contain larval age (day post-grafting), treatment (infected—triangles, control—circles) and colour (w white, y yellow, y/br yellow/brown, br brown, bl black) according to Table 1 and Fig. 1. Ellipses highlight distinct sample groups
Discriminant analysis of honey bee larvae brood pheromone profiles with a clear cluster (encircled) for older infected larvae, surrounded by older healthy and young (day 5) healthy and infected larvae. Sample labels contain larval age (day post-grafting), treatment (infected—triangels, control—circles) and colour (w white, y yellow, y/br yellow/brown, br brown, bl black) according to Fig. 1
European foulbrood (EFB), caused by Melissococcus plutonius, is a globally distributed bacterial brood disease affecting Apis mellifera larvae. There is some evidence, even if under debate, that spreading of the disease within the colony is prevented by worker bees performing hygienic behaviour, including detection and removal of infected larvae. Olfactory cues (brood pheromones, signature mixtures, diagnostic substances) emitted by infected individuals may play a central role for hygienic bees to initiate the disease-specific behaviour. However, the mechanisms of cue detection and brood removal, causing hygienic behaviour in EFB affected colonies, are poorly understood. Here, coupled gas chromatography-mass spectrometry (GC–MS) was used to detect disease-specific substances, changes in cuticular hydrocarbon (CHC) profiles, and brood ester pheromones (BEPs) of honey bee larvae artificially infected with M. plutonius. Although no diagnostic substances were found in significant quantities, discriminant analysis revealed specific differences in CHC and BEP profiles of infected and healthy larvae. β-Ocimene, a volatile brood pheromone related to starvation and hygienic behaviour, was present in all larvae with highest quantities in healthy young larvae; whereas oleic acid, a non-volatile necromone, was present only in old infected larvae. Furthermore, γ-octalactone (newly discovered in A. mellifera in this study) was detectable in trace amounts only in infected larvae. We propose that the deviation from the olfactory profile of healthy brood is supposed to trigger hygienic behaviour in worker bees. To confirm the relevance of change in the chemical bouquet (CHCs, BEPs, γ-octalactone, etc.), a field colony bioassay is needed, using healthy brood and hygienic bees to determine if bouquet changes elicit hygienic behaviour.
Stackplot of total ion chromatograms showing cuticular hydrocarbon profiles of representative Gonipterus and Oxyops weevils
Non-metric multidimensional scaling (nMDS) ordination based on Bray–Curtis clustering of fourth root transformed data according to genus (left) and species (right)
Gonipterus weevils have been a taxonomic challenge for many years, with implications on our understanding of invasive species, host plant relationships and natural enemies. We assessed cuticular hydrocarbon (CHC) analysis as a tool for discrimination of some of the many species of Gonipterus occurring in Australia. Weevils were collected across several localities and kept under identical conditions prior to a whole-body wash for extraction of CHCs in hexane. Weevil identifications were confirmed using morphology and molecular tools. CHC extracts were analyzed by gas chromatography–mass spectrometry (GC–MS) and the relative peak areas in profiles were compared; compounds were identified according to MS fragmentation and retention indices. CHC profiles of the seven species of Gonipterus analyzed differed from each other, and from another weevil genus (Oxyops), used as an outgroup. The compounds that contributed most to species differences were alkanes, alkenes and methyl branched alkanes. Within some species, locality of collection affected CHC profiles. Our study presents CHC analysis as a promising tool for distinction of Gonipterus species.
Nickel hyperaccumulation in Blepharidium guatemalense Standl. (Rubiaceae) was found in the tropical forests of south-eastern Mexico. This study aimed to document the geographic extent of nickel hyperaccumulation in this species, to understand its process of hyperaccumulation and to explore nickel distribution within the tissues of this plant. Rhizosphere soils and plant tissues were collected in Mexico and analyzed for physical-chemical parameters. Non-destructive elemental screening of herbarium specimens was performed with a hand-held X-ray fluorescence spectrometer. Elemental distribution maps of nickel and other elements in plant tissues were obtained by X-ray fluorescence spectroscopy and microscopy. Blepharidium guatemalense is distributed throughout Chiapas, Tabasco and Campeche, reaching the maximum nickel concentration in leaves (4.3 wt%) followed by roots and seeds (2.0 wt%) and bark (1.8 wt%). Simultaneous hyperaccumulation of cobalt and nickel was found in 15% of the herbarium specimens. Phloem has the highest nickel-enriched tissue from all parts of the plant (from roots to leaves). A high total nickel (mean of 610 µg g-1) was found in rhizosphere soils even though no evidence of ophiolite emplacement in that area has been reported. Blepharidium guatemalense has uncommon re-distribution mechanisms via phloem. It represents the first hypernickelophore (>1 wt% Ni) to be reported as growing in soils that are neither ultramafic nor enriched by anthropogenic pollutants. Keywords: hypernickelophore; XRF scanning; Rubiaceae; biogeochemistry; ionomics; agromining.
Plants that naturally accumulate aluminium (Al) may also inadvertently accumulate rare earth elements (REEs) due to the similar chemical properties of Al and REE trivalent ions, and vice versa. In this study, an Al hyperaccumulator plant species, Melastoma malabathricum, and a species known to have a propensity to hyperaccumulate REEs (in addition to Al), Dicranopteris linearis, were evaluated for potential REEs accumulation in a one-year pot dosing trial in Sabah, Malaysia. To test whether the Malaysian accessions of D. linearis and M. malabathricum hyperaccumulate REEs (and Al), both species were grown in pots containing soil treated with yttrium (Y), lanthanum (La), neodymium (Nd), and a mixture of these three REEs. The results showed that both M. malabathricum and D. linearis accumulated > 1000 µg g−1 Al in their leaves as expected. The shoots of M. malabathricum contained lower REEs than the roots (50 µg g−1 compared to 905 µg g−1). In D. linearis, the mean foliar REE concentrations ranged from 145 to 315 µg g−1, which is below the hyperaccumulation threshold set for REEs (> 1000 µg g−1 REEs). This study revealed that the Malaysian accessions of both M. malabathricum and D. linearis are Al hyperaccumulators, but their REE hyperaccumulation status requires further testing.
Free-ranging giant pandas (Ailuropoda melanoleuca) in China recently were reported to rub and roll in horse manure, a behavior that was observed frequently at low ambient temperatures. Two sesquiterpenes, β-caryophyllene (BCP) and caryophyllene oxide (BCPO), that are abundant in fresh horse manure elicited rolling in captive giant pandas. Mice and rats treated with BCP/BCPO exhibited enhanced cold tolerance in behavioral assays, and BCP/BCPO inhibited cold-activated ion channels of mammals expressed in human kidney cells; these laboratory results were cited in support of the contention that giant pandas tolerate low ambient temperatures by applying horse manure to their integument. The demonstrated biocidal activities of BCP and BCPO against insects and ticks, and the reported elicitation of anointing in giant pandas with materials other than horse manure, including substances or constituents thereof known to act as arthropod biocides, are consistent with an anti-consumer function of anointing by giant pandas. Anointing with the scents of heterospecifics as a defense against nuisance arthropods constitutes a viable hypothesis for the rubbing and rolling behaviors of giant pandas and other ursids.
Bactrocera bryoniae is a polyphagous and economically significant fruit fly found in Indonesia, Papua New Guinea and Australia. To understand chemical-mediated sexual communication, and the potential for novel pheromone-based attractants for monitoring and mass-trapping of B. bryoniae, rectal gland exudates and emissions from sexually mature males and females were investigated. Gas chromatography–mass spectrometry showed that male rectal glands contained six compounds, of which 1,7-dioxaspiro[5,5]undecane elicited electroantennographic (EAD) and electropalpographic (EPD) responses in both sexes, ethyl 3-acetoxybutanoate elicited EPD responses in both sexes, N-(3-methylbutyl)acetamide elicited EAD response from males and 4-hydroxy-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and females and EPD responses in females. Female rectal glands contained 23 compounds with the esters ethyl laurate and ethyl myristate as major components. Amongst the female rectal gland constituents, ethyl laurate, ethyl myristate and ethyl palmitate elicited EAD responses in males and females, N-(3-methylbutyl)acetamide elicited EAD responses in males only, (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and EPD responses in females, and 2,7-dimethyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane, (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, (E,E)-2-propyl-8-methyl-1,7-dioxaspiro[5.5]undecane and ethyl caprate elicited EPD responses in females only. Y-tube bioassays indicated that male rectal gland extracts and headspace volatiles attracted females and males, while female rectal gland extracts and headspace volatiles only attracted males. The results suggest that ethyl 3-acetoxybutanoate, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male-produced sex pheromone in B. bryoniae while (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, N-(3-methylbutyl)acetamide, ethyl laurate, ethyl myristate and ethyl palmitate may be components of female-produced sex pheromone. Ethyl 3-acetoxybutanoate, N-(3-methylbutyl) acetamide, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male aggregation pheromone. These findings contribute to the understanding of pheromone communication in B. bryoniae and provide a foundation for developing pheromone-based monitoring and control methods.
Attraction of Anastrepha obliqua females and males to two ripen guava cultivars in field-cage tests. One trap was baited with one Creole guava fruit, while another was baited with Thai guava fruit. Bars with the same letter are not significantly different according to Tukey test at P > 0.05
Attraction of Anastrepha obliqua females and males to three ripeness stages of Creole guava in field-cage tests. One trap was baited with one ripe fruit, another was baited with half-ripe fruit, and the other was baited with unripe fruit. Bars with the same letter are not significantly different according to Tukey test at P > 0.05
Simultaneous responses of flame ionization detector (FID) and electroantennographic detection (EAD) using the antennae of mated Anastrepha obliqua females to headspace collected from a Creole and b Thai guava fruit on a nonpolar column. Numbered peaks indicate EAD-active compounds (see also Table 1)
Attraction of Anastrepha obliqua females and males to synthetic compounds of three Creole guava ripening stages in field-cage tests. One trap was baited with a rubber septum loaded with 100 µl of a six-component mixture (ripe), another was baited with a septum loaded with 100 µl of a four-component mixture (half-ripe), and the other was baited with a septum loaded with 20 µl of cis-3-hexenyl acetate (unripe). Bars with the same letter are not significantly different according to Tukey test at P > 0.05
The West Indian fruit fly, Anastrepha obliqua (Macquart), infests a wide diversity of tropical fruit. Previous studies suggest that A. obliqua adults are attracted to volatile compounds common in different hosts. However, to date, most studies have used ripe fruit for the identification of attractive compounds. In this study, we investigated the attraction of sexually mature A. obliqua females and males to two cultivars and three ripening stages of guava. We also identified the attractive compounds to A. obliqua by combined gas chromatography-electroantennographic detector (GC-EAD) and gas chromatography-mass spectrometry (GC–MS) and evaluated the biological activity of the identified compounds in field-cage tests. We found that individuals of both sexes of A. obliqua showed no preference to the volatiles of either of the two cultivars of guava evaluated. In contrast, flies were more attracted to ripe and half-ripe fruit than to unripe ones. GC-EAD analyses of extracts of ripe “Creole” or “Thai” cultivars identified six compounds that elicited antennal responses by A. obliqua females and males. The compounds were identified by GC–MS as ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, cis-3-hexenyl acetate, ethyl benzoate, and ethyl octanoate. Half-ripe guava emit ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, and cis-3-hexenyl acetate, while only traces of cis-3-hexenyl-acetate were found in unripe guava. Field-cage tests with synthetic standards confirmed that the compounds identified are responsible for the attraction of A. obliqua flies to ripe guava.
A major hypothesis for the evolution of chemical signals is that pheromones arise from non-communicative precursor compounds. However, data supporting this hypothesis are rare, primarily because the original functions of the antecedent compounds often have been lost. A notable exception, however, is the parasitoid wasp species Leptopilina heterotoma, whose compound (−)-iridomyrmecin is used as a defensive secretion, a cue for females to avoid competition with con-and hetero-specific females, and as the primary component of the females' sex pheromone. To better understand the evolution of sex pheromones from defensive compounds, we examined the chemical ecology of L. pacifica, the sister species of L. heterotoma. Here, we show that L. pacifica also produces a defensive secretion containing a species-specific mixture of mostly iridoid compounds. However, the composition of the secretion is more complex than in L. heterotoma, and iridomyrmecin is only a minor component. Moreover, in contrast to L. heterotoma, conspecific female competitors were not avoided by female subjects, and a role of the iridoids in the female sex pheromone of L. pacifica can be excluded, as only the females' cuticular hydrocarbons (CHCs) resulted in the elicitation of courtship by males. Although closely related, the two sister species show substantial differences in the use of the defensive secretion for communicative purposes. Variation in pheromone usage in this genus still presents a conundrum, highlighting the need for additional studies to understand the selective forces shaping the evolution of pheromone composition.
Map showing the examined populations of the E. ruidum species complex
Two-dimensional Nonmetric Multidimensional Scaling ordination of the chemical profiles of E. ruidum sp. 3–4
Mean proportions of a cuticular hydrocarbons and b odd-chain hydrocarbons of ants E. ruidum sp. 3–4 by class
The PCA’s plot of the nine traits describing the cuticular hydrocarbon profiles of ants of E. ruidum sp. 3–4
Two-dimensional nonmetric multidimensional scaling ordination of the chemical profiles of the E. ruidum species complex
In social insects, chemical communication is the main communication mode among colony members, which use the blends of cuticular hydrocarbons as recognition cues to discriminate between nestmates and non-nestmates and to prevent the exploitation of their nest resources by aliens. The aim of this study was to assess the variation of nestmate recognition cues in the ant Ectatomma ruidum, a species complex with a considerably conserved morphology and one of the few ant species where intraspecific thievery, a form of cleptoparasitism, has been reported. We analyzed the cuticular hydrocarbon profiles of ants collected from a number of geographically separated populations and examined DNA sequence data to assess their species identity. We focused on one species of the complex, E. ruidum sp. 3–4, whose species delineation remains controversial. We documented that several quantitative and qualitative traits of the cuticular hydrocarbon profiles varied significantly between populations, indicating that this species harbors more cuticular chemical phenotypic diversity than expected within a single species. In particular, there was a striking divergence among populations in the proportion of methylalkanes, alkenes, alkadienes and odd-chain components, which likely play a major role in nestmate/non-nestmate discrimination, a process which might have been crucial in these cleptobiotic ants. Further investigations are needed to test the hypothesis that biotic pressures, such as the need to discriminate conspecific intruders and limit thievery, could have played an important role in promoting the evolutionary divergence between populations in this ant species complex.
Schematic representation of a chemically-supplemented minimal carrion trap, showing the location of a microcentrifuge tube containing a chemical supplement near the top of the funnel. The trap was buried such that the top was level with the ground
Number of beetles per trap-night attracted to four treatments: control (mouse only), mouse + MeSAc, mouse + DMTS and mouse + MeSAc + DMTS. Shown are medians (horizontal lines), the middle quartiles (boxes), and outliers (markers) for adults of all species and larvae of Necrophila americana. The upper stem and cap bars represent the upper quartile + 1.5*interquartile distance (SAS Institute Inc 2007). Different letters above the bars indicate significant differences (P < 0.05, Wilcoxon’s Matched Pairs Signed Ranks test)
Volatile organic compounds derived from microbes recruit insects to carrion, shaping community assembly and ecological succession. The importance of individual volatiles and interactions between volatiles are difficult to assess in the field because of (1) the myriad compounds from decomposing animals and (2) the likelihood that complex volatile blends are important for the final approach to carrion. On the assumption that searching carrion-frequenting beetles may use simpler cues to orient at a distance, we employed a chemically-supplemented minimal trap that uses test chemicals associated with active decay to attract from a distance and a minimal carrion bait (a small fresh mouse carcass) to induce trap entry. Traps supplemented with both methyl thiolacetate (MeSAc) and dimethyl trisulfide (DMTS) attracted greater numbers of beetles including adult silphids (Necrophila americana and Oiceoptoma noveboracense) and the histerid Euspilotus assimilis than the combined totals of DMTS-only and MeSAc-only traps, demonstrating a synergism. The attraction of larval Necrophila americana to traps left in the field for less than 24 h suggests that larvae move between carrion sources. The use of such species for forensic applications requires caution.
Chromatogram showing six compounds detected in the rectal gland of Bactrocera tryoni male; top and bottom for control and RK-fed, respectively. N-(2-methylbutyl)acetamide, (c1), N-(3-methylbutyl)acetamide,(c2), N-(2-methylbutyl)propanamide, (c3), N-(3-methylbutyl)propanamide, (c4), N-(2-methylbutyl)-2-methylpropanamide (c5), and N-(3-methylbutyl)-2-methylpropanamide (c6), raspberry ketone, 4-(4-hydroxyphenyl)-2-butanone, (RK), and hexadecane (Internal standard)
Total amount of endogenously produced volatile compounds in rectal gland of RK-fed and control (RK-unfed) Bactrocera tryoni male. Vertical bars represent standard error
The amount of compounds, c1–c6 and RK in volatiles of rectal gland of RK-fed and control (RK-unfed) Bactrocera tryoni male fed on S diet. Vertical bars represent standard error
The amount of compounds, c1–c6 and RK in volatiles of rectal gland of RK-fed and control (RK-unfed) Bactrocera tryoni males fed on yeast hydrolysate + sugar (YH + S) diet. Vertical bars represent standard error
Raspberry ketone (RK) supplements provided together with sugar and yeast hydrolysate accelerate sexual maturation and increase mating success of Queensland fruit fly ('Qfly') males. However, the mechanisms underlying this enhanced mating ability are currently unknown. Volatiles are an important element of Qfly sexual calling and courtship and so changes in volatiles quantity or quality may be involved, and the present study investigated this possibility. Flies were fed a diet of sugar only (S) or yeast hydrolysate mixed with sugar (YH + S) (1:3) that contained 0% RK (control) and 5% RK (treated) for 2 days after emergence. Volatile compounds were extracted from rectal glands when flies were 6, 8, 10, 20, and 30 days old. Males fed on RK exhibited a significant increase in total volatile production in rectal glands compared to RK-unfed males (control). Males fed on RK with YH + S produced significantly higher amount of volatiles than males fed on RK with sugar only. Males fed on YH + S diet produced more volatiles in the presence of RK compared to males fed on YH + S diet only. Two compounds, N-(3-methylbutyl)acetamide and N-(3-methylbutyl)propanamide were dominant in endogenously produced rectal gland volatiles comprising ca. more than 90% of the total amount in both RK-fed and control males. Considering exogenous and endogenous compounds together, unaltered RK was dominant along with these two endogenous compounds in RK-fed males in rectal gland until 30 days of age in both diet groups.
In this work, we discussed and counter-commented Paul J. Weldon's comments on our recent paper (Zhou et al. Proc Natl Acad Sci USA 117:32493, 2020a), where we reported that BCP/BCPO (beta-caryophyllene/caryophyllene oxide) in fresh horse manure is sufficient to drive manure rolling behavior (HMR) in giant panda and attenuate the cold sensitivity of mice by directly targeting and inhibiting transient receptor potential melastatin 8 (TRPM8), an archetypical cold-activated ion channel of mammals. The main question we arise in this response is: “which is the reasonable target of BCP/BCPO? Parasites or TRPM8?” Based on the knowledge of TRPM8-mediated cooling sensation, interaction between BCP/BCPO and TRPM8, BCP/BCPO concentration in horse manure samples, correlation between HMR frequency and habitat temperature, insecticidal activity of BCP/BCPO and thermal ecology of parasites, we prefer a simple idea that BCP/BCPO-induced TRPM8 antagonism bestows the wild giant pandas with cold tolerance at low-ambient temperatures. Compared with the speculation of insecticidal activity induced by HMR behavior, our study provided a comprehensive mechanism to confirm a physiological target of BCP/BCPO during the highly cold-correlated behavior.
Two pseudergates and one soldier of Serritermes serrifer (the size of the soldier is about 3 mm long)
Contour plot of the two-dimensional GC–MS analysis of an extract of 100 sternal gland equivalents of Serritermes serrifer pseudergates. The elongated spot corresponding to (10Z,13Z)-nonadeca-10,13-dien-2-one is marked with arrow and the chemical structure is provided
Identification by two-dimensional GC–MS of (10Z,13Z)-nonadeca-10,13-dien-2-one in Serritermes serrifer pseudergates. a Deconvoluted spectrum, b NIST spectrum with the specific masses highlighted, c extracted ion chromatogram, showing the specific masses of the target compound in the sub-figure b
The Neotropical family Serritermitidae is a monophyletic group of termites including two genera, Serritermes and Glossotermes, with different way-of-life, the former being the sole obligatory inquiline among “lower” termites, while the latter is a single-site nester feeding on dry rotten red wood. Like the most advanced termite’s family, the Termitidae, the Serritermitidae is an inner group of the paraphyletic family “Rhinotermitidae”, but unlike the Termitidae, it has been poorly studied so far. In this study, we bring new insights into the chemical ecology of this key taxon. We studied the trail-following pheromone of Serritermes serrifer and we identified (10Z,13Z)-nonadeca-10,13-dien-2-one as the only component of the trail-following pheromone of this termite species, as it is the case in Glossotermes, the other genus belonging to Serritermitidae. This result makes the family Serritermitidae clearly distinct from other Rhinotermitidae, such as the termites Psammotermes and Prorhinotermes, that use (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol and/or neocembrene as trail-following pheromones.
Behavioral response of greenhouse whiteflies to vegetative and flowering basil; and vegetative and flowering Mexican marigold vs clean air (a) and tomato (b) in a Y-tube olfactometer test. n number of responding insects, total number of insects tested per pairing was 60. Asterisks represent the significance level of x² tests at *P < 0.05, (Chi-square with Bonferonni correction)
Behavioral response of greenhouse whiteflies to five major Mexican marigold volatiles tested individually and as a blend mixed at the ratio of 27:26:20:11:16 vs. clean air or tomato tested at 0.01% (a), 0.1% (b), and 1% (c) concentration in a Y-tube olfactometer test. n number of responding insects, total number of insects tested per pairing was 60. Asterisks represent the significance level of x² tests at *P < 0.05, (Chi-square with Bonferonni correction)
Behavioral response of greenhouse whiteflies to four major basil volatiles, i.e. linalool, 1,8-cineole, eugenol and β-elemene tested individually and as a lend mixed at the ratio of 34:29:27:10 vs. clean air or tomato tested at 0.01% (a), 0.1% (b), and 1% (c) concentration in a Y-tube olfactometer test. n number of responding insects, total number of insects tested per pairing was 60. Asterisks represent the significance level of x² tests at *P < 0.05, (Chi-square with Bonferonni correction)
The use of chemical pesticides as a main pest control strategy has been highly criticised due to environmental pollution and negative effects on natural enemies of pests. In modern farming, it is essential to implement integrated pest management approaches that seek to control insect pests without causing environmental damage, e.g. the use of companion plants. Basil and Mexican marigold are often used as companion plants to attract greenhouse whiteflies, hence reducing damage to solanaceous crops, but the mechanism and role of volatile cues in crop protection strategies are unknown. This study found that both flowering basil and marigold were preferred to tomato by the greenhouse whitefly (Trialeurodes vaporariorum) in Y-tube olfactometer bioassays. PCA revealed that some volatiles were more correlated to one stage than to another. The dominant volatile constituents of Mexican marigold are limonene, dihydrotagetone, (Z)-β-ocimene, α-pinene, (Z)-3-hexenyl acetate, and those from basil are linalool, 1,8-cineole, eugenol and β-elemene. Among these dominant compounds, 1,8-cineole and (Z)-3-hexenyl acetate elicited strong attraction in greenhouse whitefly at 0.01%, whereas (Z)-β-ocimene and linalool elicited strong repellence at 0.1% and 1% dosages. This suggested that the basil flowering stage attraction is due to 1,8-cineole. These volatiles demonstrated potential as lures or bio-repellents and could be used in a “push–pull” semiochemical approach for greenhouse whitefly management.
Olfactory responses of the predatory earwig Doru luteipes to volatiles emitted by undamaged (UD) and herbivore-damaged (HD) perennial teosinte (Zea diploperennis), annual teosinte (Z. mays L. ssp. mexicana) and modern maize (Z. mays L. spp. mays). Herbivore-damaged plants were infested by a single third-instar larva of Spodoptera frugiperda for 24 h. Pie charts represent proportions of non-responsive (light grey) and responsive insects (dark grey). Asterisks indicate significant difference between treatments according to a chi-square test (*P < 0.05, **P < 0.01, ***P < 0.001). n.s not significant
Schematic drawing of the results. Plants, from left to right, represent annual teosinte, perennial teosinte and maize. Caterpillars feeding on the plant are Spodoptera frugiperda larvae, and the earwig in front of the plants represents Doru luteipes, a night-active predator of fall armyworm larvae. Red crosses on fall armyworm larvae indicate that feeding on the plant negatively affected the herbivore. Pupae in the soil near the plant basis indicate that the fall armyworms reached the pupal stage after feeding on the plant. Arrows near the predatory earwig Doru luteipes indicate its olfactory preference for herbivore-induced plant volatiles. Compositions of the blends emitted by herbivore-damaged plants are indicated by the size of molecules and colour intensity. Size of C6-molecules and green intensity of circles surrounding the plant represent relative total amounts of green leaf volatiles emitted by fall armyworm-damaged plants. Sizes of terpene molecules represent relative amounts of total terpenes emitted by fall armyworm-damaged plants
Principal component analysis (PCA) of the composition of volatiles emitted by herbivore-damaged perennial teosinte (Zea diploperennis) (HD perennial), herbivore-damaged annual teosinte (Z. mays ssp. mexicana) (HD annual), herbivore-damaged maize (Z. mays ssp. mays) (HD maize), undamaged perennial teosinte (UD perennial), undamaged annual teosinte (UD annual) and undamaged maize (UD maize). Vectors represent volatile compounds: 1: (Z)-3-hexenal; 2: (E)-2-hexenal; 3: (Z)-3-hexen-1-ol; 4: β-myrcene; 5: (Z)-3-hexenyl acetate; 6: linalool; 7: phenylmethyl acetate; 8: decanal; 9: indole; 10: geranyl acetate; 11: (E)-β-caryophyllene; 12: (E)-α-bergamotene; 13: (E)-β-farnesene; and 14: β-sesquiphellandrene
The transition from a perennial to an annual life cycle, as well as domestication, are expected to increase plant growth and reproduction at the same time that anti-herbivore defences are reduced. Here, we investigated the effects of the life-history transition (the perennial teosinte Zea diploperennis to the annual teosinte Z. mays ssp. mexicana) and domestication of Zea (annual teosinte to the modern maize Z. mays ssp. mays) on direct and indirect defences against the fall armyworm Spodop-tera frugiperda. The direct defence of Zea was assessed by larval survival and nutritional indices based on food intake and utilisation. Indirect defence was measured in terms of the olfactory preference of the night-active predatory earwig Doru luteipes for nocturnal herbivore-induced plant volatiles (HIPVs) from the teosintes and maize. Larval growth and survival were reduced on teosintes relative to maize. Whilst larvae fed on perennial teosinte had lower food intake indices, those on annual teosinte showed lower food utilisation indices relative to maize. The earwig preferred HIPVs emitted by teosintes over those by maize, but it did not discriminate between odours of herbivore-damaged annual and perennial teosinte. The nocturnal HIPV blend from maize contained the lowest total amount of fatty acid derivatives, while it had higher total amounts of terpenes compared to teosintes. Our study shows that the teosintes are better defended than maize in terms of direct and indirect defences; however, the perennial teosinte have stronger direct defences against the fall armyworm than the annual teosinte.
Apple proliferation disease is caused by the phloem-dwelling bacterium ‘Candidatus Phytoplasma mali’, inducing morphological changes in its host plant apple, such as witches’ broom formation. Furthermore, it triggers physiological alterations like emission of volatile organic compounds or phytohormone levels in the plant. In our study, we assessed phytoplasma-induced changes in the phloem by sampling phloem sap from infected and non-infected apple plants. In infected plants, the soluble sugar content increased and the composition of phloem metabolites differed significantly between non-infected and infected plants. Sugar and sugar alcohol levels increased in diseased plants, while organic and amino acid content remained constant. As ‘Ca. P. mali’ is vectored by the phloem-feeding insect Cacopsylla picta (Foerster, 1848), we assessed whether the insect–plant interaction was affected by ‘Ca. P. mali’ infection of the common host plant Malus domestica Borkh. Binary-choice oviposition bioassays between infected and non-infected apple leaves revealed C. picta’s preference for non-infected leaves. It is assumed and discussed that the changes in vector behavior are attributable to plant-mediated effects of the phytoplasma infection.
Top-cited authors
Michael A Wall
  • San Diego Natural History Museum
Kevin Balkwill
  • University of the Witwatersrand
Robert Boyd
  • Auburn University
Heiko G. Rödel
  • Université Sorbonne Paris Nord
Emilie M. Deletre
  • Cirad - La recherche agronomique pour le développement