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  1. Wee SL, Tan KH, Nishida R
    J. Chem. Ecol., 2007 Jun;33(6):1272-82.
    PMID: 17443401 DOI: 10.1007/s10886-007-9295-0
    After pharmacophagy of methyl eugenol (ME), males of Bactrocera carambolae (Diptera: Tephritidae) produced (E)-coniferyl alcohol (CF) along with its endogenously synthesized pheromonal compounds. CF was shown to be released into the air by the ME-fed males only during the courtship period at dusk and attracted significantly more males and females than the ME-deprived males in wind tunnel assays. However, earlier onset of sexual attraction and a higher mating success were observed only in the wind tunnel and field cage assays on the third day posttreatment of ME. Field cage observations on the male-to-male interaction indicated that the ME-deprived males did not exhibit aggregation behavior, but that ME feeding promoted aggregation behavior in B. carambolae. Field cage observations revealed that the ME-deprived males were not only attracted to the ME-fed males, but also appeared to feed on their anal secretions. The secretions were subsequently confirmed to contain CF along with endogenously produced pheromonal compounds. Results obtained for B. carambolae were compared to those previously obtained from its sibling species, Bactrocera dorsalis, and are discussed in light of species advancement in fruit fly-plant relationships.
  2. Tan KH, Tan LT, Nishida R
    J. Chem. Ecol., 2006 Nov;32(11):2429-41.
    PMID: 17082990 DOI: 10.1007/s10886-006-9154-4
    It is widely believed that most orchid flowers attract insects by using deception or chemical rewards in the form of nectar. Flowers of Bulbophyllum vinaceum produce a large array of phenylpropanoids that lure tephritid fruit fly males and also act as floral reward, which the flies subsequently convert to pheromone components. The major floral volatile components identified are methyl eugenol (ME), trans-coniferyl alcohol (CF), 2-allyl-4,5-dimethoxphenol (DMP), and trans-3,4-dimethoxycinnamyl acetate, whereas the minor components are eugenol, euasarone, trans-3,4-dimethoxy cinnamyl alcohol, and cis-coniferyl alcohol. Among the various floral parts, the lip (which is held in a closed position up against the sexual organs) has the highest concentration of the major compounds. An attracted male fly normally lands on one of the petals before climbing up onto and forcing the "spring loaded" floral lip into the open position, hence exposing the floral sexual organs. The architecture and location of chemical attractants of the lip compel the fly to align itself along the lip's longitudinal axis in a precise manner. As the fly laps up the compounds and moves towards the base of the lip, it passes the point of imbalance causing the lip to spring back to its normal closed position. The fly is catapulted headfirst into the column cavity, and its dorsum strikes the protruding sticky base of the hamulus and adheres to it. The momentum of the fly and the structural morphology of the long stiff hamulus act to pry out the pollinia from its anther cover. Hence, the pollinarium (pollinia + hamulus) is detached from the flower and adhered to the fly's dorsum. In this unique mutualistic association, both species receive direct reproductive benefits--the flower's pollinarium is transported for cross pollination, and the fly is offered a bouquet of phenylpropanoids (synomone) that it consumes, converts, and/or sequesters as sex pheromonal components, thus enhancing sexual attraction and mating success.
  3. Hee AK, Tan KH
    J. Chem. Ecol., 2004 Nov;30(11):2127-38.
    PMID: 15672660 DOI: 10.1023/B:JOEC.0000048778.02561.70
    Pharmacophagy of methyl eugenol (ME)--a highly potent male attractant, by Bactrocera papayae results in the hydroxylation of ME to sex pheromonal components, 2-ally-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (CF). These compounds, which are also male attractants, are then sequestered and stored in the rectal gland prior to their release during courtship at dusk. Chemical analyses of the digestive tract (excluding the crop and rectal gland) showed the absence of the sex pheromonal components and their precursor, ME. However, B. papayae males were attracted to and fed on the ME-fed male hemolymph extracts but not on hemolymph extracts of ME-deprived males. After thin layer chromatography in a hexane:ethyl acetate solvent system, flies were attracted to and fed on the original point on the TLC plate where the hemolymph extract had been spotted, suggesting that the pheromone components were bound in polar complexes. Chemical analyses of the ME-fed male hemolymph and crop extracts revealed the presence of the sex pheromonal components. The presence of the ME-derived pheromonal components and the absence of ME in the hemolymph suggest that the hemolymph is involved in the transportation of sex pheromonal components from the crop to the rectal gland.
  4. Keng-Hong T, Nishida R
    J. Chem. Ecol., 2005 Mar;31(3):497-507.
    PMID: 15898497
    Bulbophyllum apertum flower (Orchidaceae) releases raspberry ketone (RK) in its fragrance, which attracts males of several fruit fly species belonging to the genus Bactrocera. Besides RK as a major component, the flower contains smaller amounts of 4-(4-hydroxylphenyl)-2-butanol, plus two minor volatile components, veratryl alcohol and vanillyl alcohol. Within the flower, the lip (labellum) had the highest concentration of RK with much smaller quantities present in petals; other flower parts had no detectable RK. Male fruit flies attracted to the flower belong to RK-sensitive species--such as Bactrocera albistragata, B. caudatus, B. cucurbitae (melon fly), and B. tau. Removal and attachment of the pollinarium to a fly's thoracic dorsum occurred when a male of B. albistragata was toppled into the floral column cavity, due to an imbalance caused by it shifting its body weight while feeding on the see-saw lip, and then freeing itself after being momentarily trapped between the lip and column. During this process, the stiff hamulus (the pollinia stalk protruding prominently towards the lip) acted as a crowbar when it was brushed downwards by the toppled fly and lifted the pollinia out of the anther. If the fly was big or long for the small triangular lip, it would not be toppled into the column cavity and would just walk across the column, during which time the pollinarium could be accidentally removed by the fly's leg, resulting in a failed transport of the pollinarium. This suggests an unstable situation, where the orchid relies only on a particular pollinator species in the complex ecosystem where many RK-sensitive species inhabit. Wild males of B. caudatus (most common visitors) captured on Bulbophyllum apertum flowers were found to sequester RK in their bodies as a potential pheromonal and allomonal ingredient. Thus, RK can act either as a floral synomone (pollinarium transported) or kairomone (accidental removal of pollinarium leading to total pollen wastage), depending on the body size of the male fruit flies visiting the flowers.
  5. Wee SL, Tan KH
    J. Chem. Ecol., 2005 Apr;31(4):845-58.
    PMID: 16124255 DOI: 10.1007/s10886-005-3548-6
    Bactrocera carambolae and B. papayae are major fruit fly pests and sympatric sibling species of the B. dorsalis complex. They possess distinct differences in male pheromonal components. In the 1990's, wild Bactrocera fruit flies with morphological traits intermediate between those of B. carambolae and B. papayae were often captured in traps baited with methyl eugenol (ME). Chemical analyses of rectal glands of ME-fed males revealed that the laboratory Fl, F2, and backcross hybrids possessed ME-derived sex pheromonal components ranging from that typical of B. papayae to that of B. carambolae without any specific trend, which included a combination of pheromonal components from both parental species within an individual hybrid. ME-fed hybrids without any ME-derived pheromonal components were also detected. Further chemical analysis of rectal glands from wild Bactrocera males, after ME feeding in the laboratory, showed a combination of pheromonal components similar to that found in the ME-fed, laboratory-bred hybrids. These findings present circumstantial evidence for the occurrence of a natural hybrid of the two Bactrocera species.
  6. Chuah CH
    J. Chem. Ecol., 2005 Apr;31(4):819-27.
    PMID: 16124253
    The chemicals of the defense secretions of Malaysian Bulbitermes, B. singaporensis, B. germanus, B. sarawakensis, and Bulbitermes sp. B, show that B. singaporensis is distinct from the other species, which are themselves closely related; the genetic distance between B. singaporensis and B. germanus is 0.71. B. singaporensis contains tetracyclic kempane, and B. germanus and B. sarawakensis contain tricyclic trinervitene; Bulbitermes sp. B contains a mixture of kempane and trinervitene. The mono- and diterpenoid compositions are species-specific.
  7. van der Ent A, Mulligan D
    J. Chem. Ecol., 2015 Apr;41(4):396-408.
    PMID: 25921447 DOI: 10.1007/s10886-015-0573-y
    Information about multi-elemental concentrations in different plant parts of tropical Ni hyperaccumulator species has the potential to provide insight into their unusual metabolism relative to a range of essential and non-essential elements, but this information is scant in the literature. As Ni hyperaccumulation, and possibly co-accumulation of other toxic elements, has been hypothesized to provide herbivore (insect) protection, there is a need to quantify a range of these elements in plant tissues and transport fluids to at least verify the possibility of this explanation. In this study, multiple elements were analyzed in a range of different plant parts and transport fluids from Ni hyperaccumulator species collected from Sabah (Malaysia). The results show preferential accumulation of Ni in leaves over woody parts, but the highest concentrations were found in the phloem tissue (up to 7.9 % in Rinorea bengalensis) and phloem sap (up to 16.9 % in Phyllanthus balgooyi), visible by a bright green coloration in the field fresh material. The amount of Ni contained in one mature R. bengalensis tree was calculated at 4.77 kg. The high Ni concentration in the flowers of Phyllanthus securinegoides could affect insect floral visitors and pollination. High concentrations of Ni in the seeds of this species also could supply the seedling with Ni and aid in herbivory protection during the first stages of development. Foliar Ca and Ni in P. cf. securinegoides and R. bengalensis are positively correlated. Low accumulation of Ca is desirable for phytomining but concentrations of Ca are high in most Ni hyperaccumulators examined, and this could have consequences for the economic viability of Ni extraction from bio ore if these species were to be used as 'metal crops'.
  8. Wee SL, Tan KH
    J. Chem. Ecol., 2001 May;27(5):953-64.
    PMID: 11471947 DOI: 10.1023/A:1010387020135
    Methyl eugenol (ME), is converted into two major phenylpropanoids, 2-allyl-4,5-dimethoxyphenol and trans-coniferyl alcohol, following consumption by the male fruit fly Bactrocera papayae. Chemical analysis of wild male B. papayae rectal glands, where the compounds are sequestered, revealed the presence of ME metabolites in varying quantities. These phenylpropanoids are shown to be involved in the fruit fly defense both in no-choice and choice feeding tests against the Malayan spiny gecko, Gekko monarchus. After being acclimatized to feeding on fruit flies, geckos consumed significantly fewer ME-fed male flies than controls that consumed all the ME-deprived male flies offered throughout a two-week period. Diagnosis of dissected livers from geckos that consumed ME-fed male flies revealed various abnormalities. These included discoloration and hardening of liver tissue, whitening of the gallbladder, or presence of tumor-like growths in all geckos that consumed ME-fed male flies. Control geckos fed on ME-deprived male flies had healthy livers. When given an alternative prey, geckos preferred to eat untreated house flies, Musca domestica to avoid preying on ME-fed fruit flies.
  9. Tan KH, Nishida R, Toong YC
    J. Chem. Ecol., 2002 Jun;28(6):1161-72.
    PMID: 12184394 DOI: 10.1023/A:1016277500007
    The major fruit fly attractant component in the floral fragrance of Bulbophyllum cheiri (fruit fly orchid) is methyl eugenol (ME). In the lowland rain forest of Malaysia, the solitary and nonresupinate flowers of the fruit fly orchid attract only males of the ME-sensitive fruit fly species (Bactrocera carambolae, B. papayae. and B. umbrosa. During the morning, the fruit fly orchid flower is visited by many fruit flies, which can sometimes cover the whole flower. The number of visitors dwindles in the afternoon. Headspace analysis of the flower shows a high ME peak in the morning, a small one between 12:00 and 14:00 hr, and no detectable ME peak after 14:00 hr. The process of pollination in the wild is initiated by attraction of fruit flies to floral ME. The flower, with the aid of its specialized hinged see-saw lip (labellum), temporarily traps (< 1 min) a fruit fly pollinator between its lip and column. Just prior to this, the fly is rewarded by the opportunity to feed on the floral attractant found on surfaces of petals, sepals, and lip. The pollinaria borne by two wild B. papayae males (caught on and near the fruit fly orchid flower) are identical in morphology and structure with those obtained from the flower. Many of the B. papayae males (17 of 22 analyzed) attracted to the fruit fly orchid already possessed both ME metabolites, trans-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, in their rectal glands. indicating that they had previously consumed ME. In this orchid-fruit fly association, both organisms gain direct reproductive benefits: the orchid flower gets pollinated without having to offer nectar, while the fruit fly boosts its pheromone and defense system, as well as its sexual competitiveness by feeding on the ME produced by the flower.
  10. Chuah CH, Goh SH, Tho YP
    J. Chem. Ecol., 1990 Mar;16(3):685-92.
    PMID: 24263584 DOI: 10.1007/BF01016479
    The defense secretions of the soldiers of the Malaysian rhinotermitid,Parrhinotermes aequalis (Havilandi) andP. pygmaeus (John),Termitogeton planus (Havilandi) andSchedorhinotermes malaccensis (Holmgren) consist mainly of vinyl ketones, whereas that ofProrhinotermes flavus (Bugnion & Popoff) gives (E)-1-nitropentadecene. The chemistry of the defense secretions ofParrhinotermes andTermitogeton is documented and based on their chemical relationships;Termitogeton shows a closer affinity to the Rhinotermitinae than Heterotermitinae.
  11. Goh SH, Chuah CH, Vadiveloo J, Tho YP
    J. Chem. Ecol., 1990 Feb;16(2):619-30.
    PMID: 24263517 DOI: 10.1007/BF01021792
    Soldiers of free-ranging termites of the genusLacessititermes (Isoptera, Nasutitermitinae) secrete from their frontal glands a mixture of monoterpenes, sesquiterpenes, and diterpenes.Lacessititermes ransoneti, L. laborator, andL. species A produce species-specific secretions, the composition being most complex forL. laborator. Apart from known mono- and dihydroxytrinervitadienes, the following new diterpenes were isolated and tentatively assigned as trinervita-1(15),8(19)-dien-2β,3α,9α,14α-tetraol 2,3,14-O-triacetate, trinervita-1(15),8(19)-dien-2β,3α,9β,14α-tetraol 2,3,14-O-triacetate, 2β,3α,9α, 14α-tetraacetoxy-1 (15), 8(19)-trinervitadiene, and 2β,3α,11α,13α-tetraacetoxy-1(15),8(19)-trinervitadiene. Data on intragenus chemical variations were subjected to canonical discriminant analysis and genetic distances among the species were calculated to depict intragenus identities and affinities.
  12. Chuah CH, Goh SH, Tho YP
    J. Chem. Ecol., 1986 Mar;12(3):701-12.
    PMID: 24306909 DOI: 10.1007/BF01012103
    Soldier defense secretions of the genus Hospitalitermes (Isoptera, Termitidae, Nasutitermitinae) were chemically analyzed by GC-MS and were found to contain volatile monoterpenes and polyoxygenated diterpenes. Interspecific and intraspecific chemical variations for H. umbrinus, H. hospitalis, H. flaviventris, and H. bicolor are described. Interspecific variations in monoterpene and diterpene structures and compositions were evident. A remarkable example of large intraspecific variation from a single species was observed inH. umbrinus, indicating that colonies of this species can be separable into two chemically distinct groups. The diterpenes found in one of these groups have unusually high molecular weights.
  13. Beevor PS, Cork A, Hall DR, Nesbitt BF, Day RK, Mumford JD
    J. Chem. Ecol., 1986 Jan;12(1):1-23.
    PMID: 24306393 DOI: 10.1007/BF01045587
    The cocoa pod borer,Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae), is the most serious pest of cocoa in Southeast Asia. Analyses of ovipositor washings and entrained volatiles from virgin female moths by gas chromatography (GC) linked to electroantennography (EAG), and comparison of EAG responses from the male moth to synthetic compounds indicated the presence of theE,Z,Z andE,E,Z isomers of 4,6,10-hexadecatrienyl acetate and the corresponding alcohols, and of hexadecyl alcohol. Amounts of pheromone produced were less than 0.1 ng/female, and no peaks for the unsaturated components were observed on GC analysis. Extensive field testing of synthetic mixtures in Sabah, East Malaysia, showed that traps baited with a polyethylene vial impregnated with 1.2 mg of a mixture of the above five components in 40∶60∶4∶6∶10 ratio caught more maleC. cramerella moths than traps baited with a virgin female moth.
  14. Chuah CH, Goh SH, Prestwich GD, Tho YP
    J. Chem. Ecol., 1983 Mar;9(3):347-56.
    PMID: 24407404 DOI: 10.1007/BF00988454
    Trinervita-1(15),8(19)-dien-2β,3α-diol and the new trinervita-1(15),8(19)-dien-2β, 3α-diol 2-O-acetate constitute the major diterpene constituents of the soldier defense secretions of the NasutitermiteHospitalitermes umbrinus of Malaysian region. Studies on the intraspecific variations on sympatric and allopatric populations indicate two distinct patterns of chemical composition.
  15. Chuah CH, Goh SH, Tho YP
    J. Chem. Ecol., 1989 Feb;15(2):549-63.
    PMID: 24271798 DOI: 10.1007/BF01014700
    The defense secretions of five species of MalaysianNasutitermes,N. longinasus, N. matangensis, N, havilandi, N. johoricus, andNasutitermes species 01, are compared.N. longinasus andN. species 01 provide trinervitene alcohols,N. havilandi mainly tricyclic trinervitene and tetracyclic kempane alcohols and acetates, whereasN. matangensis furnish acetyl/propionyl derivatives of trinervita-11(12),15(17)-dien-3α,9β,13α-triol (XXI and XXII). A new diterpene, assigned as trinervita-11(12),15(17)-dien-3α,13α-diol-3,13-O-diacetate (XVII), is isolated fromN. havilandi. The mono- and diterpenoid compositions, being species-specific, are useful for chemotaxonomic and phylogenetic studies.
  16. Goh SH, Chuah CH, Tho YP, Prestwich GD
    J. Chem. Ecol., 1984 Jun;10(6):929-44.
    PMID: 24318785 DOI: 10.1007/BF00987974
    The chemical defense secretions of major and minor soldiers of over 18 colonies of the primitive glue-squirting nasute termiteLongipeditermes longipes (Isoptera, Termitidae, Nasutitermitinae) were analyzed chormatographically. The colonies, collected from four rainforest sites in peninsular Malaysia, showed monoterpene patterns rich in pinenes and limonene but with few quantitative differences between colonies. In marked contrast, the diterpene chemistry is high variable, and includes tricyclic (trinervitane), tetracyclic (rippertane), bicyclic (secotrinervitane), and a new spirotetracyclic (longipane) skeleton. Three new natural products are included in this remarkable and unprecedented example of structural diversity among different colonies of a single species.
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