Contact Sex Pheromone Research Articles

ChemInform Abstract: Pheromone Synthesis. Part 194. Synthesis of the Enantiomers of (Z)‐21‐Methyl‐8‐pentatriacontene, the Major Component of the Female‐Produced Contact Sex Pheromone of the Yellow‐Spotted Longicorn Beetle, Psacothea hilaris.

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Insect pheromones—an overview of biosynthesis and endocrine regulation

This overview describes, compares, and attempts to unify major themes related to the biosynthetic pathways and endocrine regulation of insect pheromone production. Rather than developing and dedicating an entirely unique set of enzymes for pheromone biosynthesis, insects appear to have evolved to add one or a few tissue-specific auxiliary or modified enzymes that transform the products of “normal” metabolism to pheromone compounds of high stereochemical and quantitative specificity. This general understanding is derived from research on model species from one exopterygote insect order (Blattodea) and three endopterygote insect orders (Coleoptera, Diptera, and Lepidoptera). For instance, the ketone hydrocarbon contact sex pheromone of the female German cockroach, Blattella germanica, derives its origins from fatty acid biosynthesis, arising from elongation of a methyl-branched fatty acyl–CoA moiety followed by decarboxylation, hydroxylation, and oxidation. Coleopteran sex and aggregation pheromones also arise from modifications of fatty acid biosynthesis or other biosynthetic pathways, such as the isoprenoid pathway (e.g. Cucujidae, Curculionidae, and Scolytidae), or from simple transformations of amino acids or other highly elaborated host precursors (e.g. Scarabaeidae and Scolytidae). Like the sex pheromone of B. germanica, female-produced dipteran (e.g. Drosophilidae and Muscidae) sex pheromone components originate from elongation of fatty acyl–CoA moieties followed by loss of the carbonyl carbon and the formation of the corresponding hydrocarbon. Female-produced lepidopteran sex pheromones are also derived from fatty acids, but many moths utilize a species-specific combination of desaturation and chain-shortening reactions followed by reductive modification of the carbonyl carbon. Carbon skeletons derived from amino acids can also be used as chain initiating units and elongated to lepidopteran pheromones by this pathway (e.g. Arctiidae and Noctuidae). Insects utilize at least three hormonal messengers to regulate pheromone biosynthesis. Blattodean and coleopteran pheromone production is induced by juvenile hormone III (JH III). In the female common house fly, Musca domestica, and possibly other species of Diptera, it appears that during hydrocarbon sex pheromone biosynthesis, ovarian-produced ecdysteroids regulate synthesis by affecting the activities of one or more fatty acyl–CoA elongation enzyme(s) (elongases). Lepidopteran sex pheromone biosynthesis is often mediated by a 33 or 34 amino acid pheromone biosynthesis activating neuropeptide (PBAN) through alteration of enzyme activities at one or more steps prior to or during fatty acid synthesis or during modification of the carbonyl group. Although a molecular level understanding of the regulation of insect pheromone biosynthesis is in its infancy, in the male California fivespined ips, Ips paraconfusus (Coleoptera: Scolytidae), JH III acts at the transcriptional level by increasing the abundance of mRNA for 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in de novo isoprenoid aggregation pheromone biosynthesis.

Synthesis of the Enantiomers of (Z)-21-Methyl-8-pentatriacontene, the Major Component of the Female-Produced Contact Sex Pheromone of the Yellow-Spotted Longicorn Beetle,Psacothea hilaris

Both the enantiomers of (Z)-21-methyl-8-pentatriacontene (1), the major component of the female-produced contact sex pheromone of the yellow-spotted longicorn beetle (Psacotheahilaris), were synthesized by starting from the enantiomers of citronellol (2)

Sites of Synthesis and Transport Pathways of Insect Hydrocarbons: Cuticle and Ovary as Target Tissues

SYNOPSIS. The outer surface of insects is covered with a lipid layer that provides water-proofing and protection against environmental stresses. Hydrocarbons (HC) are major constituents of this epicuticular wax and they also serve as semiochemicals. In some insects HC are also exploited as biosynthetic precursors for pheromones. HC are synthesized by oenocyteswhich are situated in the integument or hemocoel. Shuttling of HC to the epicuticie, fat body, and gonads requires transport through an aqueous medium. Insects, unlike vertebrates, use a versatile lipoprotein to effect lipid transport and to selectively deliver lipids to specific tissues. A high-density hemolymph lipoprotein (lipophorin [Lp]) serves this function.In adult females of the German cockroach (Blattella germanica), Lp carries both HC and a contact sex pheromone. Lipophorin is a multi-functional lipid carrier serving also as a juvenile hormone binding protein in many insects. Studies ofthe interactions between Lp and HC are beginning to unravel the routes used in delivering HC to target tissues. We discussthe pathways and dynamics of loading of Lp with HC and HC-derived pheromones, their transport through the hemolymph, and deposition in various tissues, including the epicuticie, ovaries, and pheromone-emitting glands.

Synthesis of the four possible stereoisomers of 21-methyl-8-pentatriacontene, the female contact sex pheromone of the yellow-spotted longicorn beetle, Psacothea hilaris

The synthesis of the four possible stereoisomers of 21-methyl-8-pentatriacontene, the ( R)- and ( S)-enantiomers of both ( Z)- and ( E)-geometrical isomers, was achieved by starting from the enantiomers of 3-hydroxy-2-methylpropionate, 1-nonyne and 1,10-decandiol to evaluate the response of the male yellow-spotted longicorn beetle, Psacothea hilaris.

Lipophorin: A hemolymph juvenile hormone binding protein in the german cockroach, Blattella germanica

We examined the binding of [ 3H](10 R) juvenile hormone (JH) III to lipophorin that was purified from the hemolymph of Blattella germanica. Binding was found to be specific, saturable and with high affinity to JH III. Using Scatchard analysis, the equilibrium dissociation constant (K d) and total binding capacity (B max) were estimated to be 9.75±0.64 nM and 0.241±0.02 nmol/mg protein, respectively. Competitive displacement studies with racemic JH III, JH I, cuticular hydrocarbon, contact sex pheromone, and the JH analogs pyriproxyfen, fenoxycarb, and hydroprene showed that only JH III readily displaced [ 3H](10 R)JH III from the binding site. However, hydroprene competed for the JH III binding site more effectively than the other two JH analogs. Photoaffinity labelling using the JH III analog [ 3H]epoxyfarnesyl diazoacetate demonstrated that the JH binding site was on apolipophorin-I, the large subunit of the lipophorin complex.

Reproductive biology of the yellow-spotted longicorn beetle,Psacothea hilaris (pascoe) (Coleoptera: Cerambycidae). III. Identification of contact sex pheromone on female body surface

A major component of female contact sex pheromone of the yellow-spotted longicorn beetle,Psacothea hilaris (Pascoe), was isolated from the elytra and identified as (Z)-21-methyl-8-pentatriacontene. The synthetic compound released the typical mating behavior including holding, mounting, and abdominal bending in males, although its activity was considerably lower than the extract of female elytra when treated on a gelatin capsule as an artificial female model.

Biosynthesis of hydrocarbons and contact sex pheromone and their transport by lipophorin in females of the German cockroach ( Blattella germanica)

The sites of synthesis, and transport of hydrocarbons and methyl ketone contact sex pheromone, were examined in the German cockroach. The abdominal integument of 7-day old Blattella germanica females showed linear incorporation of [1- 14C]propionate into hydrocarbon and pheromone for at least 4 h in vitro, whereas other body parts including the head, wings, legs, thorax, fat body, digestive tract, and vitellogenic ovaries produced negligible amounts of hydrocarbon and pheromone. The sternites synthesized significantly more hydrocarbon and methyl ketones than the tergites, and in both, the incorporation of propionate into hydrocarbon correlated well with its incorporation into the methyl ketone pheromone, suggesting that the abdominal oenocytes or epidermal cells synthesize both hydrocarbon and pheromone. The abdomen contained about 55% of the total hydrocarbon and pheromone in the female, and both were located mainly in the ovaries, integumental epidermal cells (including oenocytes), fat body, and hemolymph. Hemolymph contained up to 20% of the internal hydrocarbons and their methyl ketone derivatives, suggesting that hemolymph carries and circulates hydrocarbon and pheromone in the female. A high density lipophorin (1.109 ± 0.002 g/ml) was isolated and purified from hemolymph by KBr gradient ultracentrifugation and was shown to be the only hemolymph protein that carries hydrocarbon and pheromone. This result suggests that lipophorin loads newly synthesized hydrocarbon and pheromone from the abdominal epidermis and transports them to various tissues, including the ovaries, fat body and possibly the epicuticle. After injection of radiolabeled propionate, newly synthesized radiolabeled methyl-branched hydrocarbons appeared first in the epidermal fraction (with oenocytes) and hemolymph, and later on the epicuticle. When veins entering the fore-wings were cut so that hemolymph circulation to the wings was blocked, the amount of newly synthesized hydrocarbon on the wings was significantly lower than on intact fore-wings. Significantly more radiolabeled hydrocarbon which had been topically applied on the sternites was recovered in the hemolymph than on the surface of the wings. These results show that transport of hydrocarbon is mediated by lipophorin, which shuttles newly synthesized hydrocarbon and methyl ketone sex pheromone from the abdominal oenocytes to epicuticular and internal deposition sites, including the ovaries.

Patterns of biosynthesis and accumulation of hydrocarbons and contact sex pheromone in the female German cockroach, Blattella germanica.

De novo synthesis of contact female sex pheromone and hydrocarbons in Blattella germanica was examined using short in vivo incubations. Accumulation of pheromone on the epicuticular surface and the internal pheromone titer were related to age-specific changes in hydrocarbon synthesis and accumulation in normal and allatectomized females. The incorporation of radiolabel from [1-14C]propionate into the cuticular methyl ketone pheromone fraction was positively related to corpora allata activity during two gonotrophic cycles. During peak pheromone production the total internal lipid fraction contained greater titers of pheromone than the cuticular surface, and it too exhibited a cycle internally, preceding the rise in external pheromone. This suggests that synthesis and accumulation of pheromone internally are followed by transport of pheromone to the epicuticular surface where it accumulates. Radiolabel was incorporated efficiently into both cuticular and internal hydrocarbons after the imaginal molt and until the peak of pheromone synthesis, but it declined to lower levels before ovulation and throughout pregnancy. The internal hydrocarbon titer decreased 58% after oviposition, suggesting deposition in the egg case. It remained relatively unchanged during pregnancy and increased again during the second gonotrophic cycle. In allatectomized females, hydrocarbon synthesis was reduced relative to control females until oviposition in the latter. However, subsequent rates of hydrocarbon synthesis in allatectomized females (without oothecae) exceeded the rates in sham-operated females (with oothecae). In the absence of ovarian uptake of hydrocarbons, the internal titer increased without the decline found in control females at oviposition. As internal hydrocarbons increased, so did cuticular hydrocarbons and both internal and cuticular methyl ketone pheromones. These patterns corresponded well with feeding patterns in sham-operated and allatectomized females, suggesting that pheromone production is normally regulated by stage-specific feeding-induced hydrocarbon synthesis (precursor accumulation internally) and juvenile hormone-induced conversion of hydrocarbon to pheromone. They also suggest that both the cuticle and the ovaries might be target sites for hydrocarbon and possibly methyl ketone deposition.

Synthesis of a Stereoisomeric Mixture of 13, 25-, 11, 21- and 11, 23-Dimethylhepta-triacontane, the Contact Sex Pheromone of the Tsetse Fly,Glossina

13, 25- and 11, 23-Dimethylheptatriacontane, the major components of the cuticular hydrocarbons of the tsetse fly, Glossina tachinoides, as well as 11, 21-dimethylheptatriacontane, the minor component, were synthesized as stereoisomeric mixtures by synthetic routes in which the molecular symmetry of the target hydrocarbons was taken advantage of.

Calling behavior of the female german cockroach,Blattella germanica (Dictyoptera: Blattellidae)

Virgin German cockroach females, Blattella germanica(L.), were observed, for the first time, to exhibit a characteristic calling behavior during which females emit a volatile sex pheromone. Under a photoperiod of 12L∶12D, the percentage of 7-day-old virgin females that exhibited this behavior peaked before the end of the scotophase in a similar pattern to the diel periodicity of mating. A clear relationship was evident between calling and stages of sexual receptivity during successive gonotrophic cycles. Females initiated calling 5–6 days after the imaginal molt, when their basal oocytes were 1.6 mm long. If not mated, females continued to exhibit bouts of calling during the next 3–4 days until 24 h before ovulation. Calling was completely suppressed by mating as well as the presence of an egg case in the genital atrium in both virgin and mated gravid females. We suggest that calling and the emission of a volatile sex pheromone serve to attract males from a distance as well as to potentiate responses to contact sex pheromone in aggregations.

A microsomal fatty acid synthetase from the integument of Blattella germanica synthesizes methyl-branched fatty acids, precursors to hydrocarbon and contact sex pheromone

Methyl-branched fatty acids present in the integument of the German cockroach, Blattella germanica, were identified by gas chromatography-mass spectrometry of their methyl esters and reduction products (alkanes) as n-3-, n-4-, n-5-, n-7-, n-8-, and n-9-monomethyl fatty acids and as n-5,9-, n-3,9-, and n-3,11-dimethyl fatty acids with 16 to 20 total carbons. These fatty acids have the same branching patterns as do the major hydrocarbons of this insect, including 3,11-dimethylnonacosane, the precursor to the major contact sex pheromone, and are presumed to be intermediates in hydrocarbon formation. A novel microsomal fatty acid synthetase (FAS) located in the integument of this insect incorporated [ methyl- 14C]methylmalonyl-CoA into methyl-branched fatty acids as demonstrated by radio-high-performance liquid chromatography. A cytosolic FAS is also present in the integument. Both the microsomal and the soluble FAS incorporated [ methyl- 14C]methylmalonyl-CoA into fatty acids, but only the microsomal FAS was able to efficiently use methylmalonyl-CoA as the sole elongating agent. This is the first report of the characterization of methyl-branched fatty acids from the integument of an insect and of an integumental microsomal FAS that incorporates methylmalonyl-CoA into branched fatty acids.

Evidence of Chemical Signaling in the Sand Scorpion, Paruroctonus mesaensis (Scorpionida: Vaejovida)

AbstractThis study presents evidence of intraspecific chemical communication in scorpions. The subject of our investigation was the nocturnal sand scorpion, Paruroctonus mesaensis. During the mating season, mature males show a sex‐specific wandering behavior ostensibly directed at locating conspecific females that remain in the vicinity of their home burrows. Searching behavior was stimulated in the laboratory by releasing males onto substrates that had previously been occupied by females. Receptive males exhibited changes in locomotory behavior that favored occupation of the female‐exposed area. Males occasionally displayed a precourtship behavior, called juddering, indicating the presence of a pheromone on the substrate. Juddering, and two newly described behavior patterns, tail‐wagging and pedipalp‐reaching, were also induced by solvent extracts of female cuticle. Most behavioral responses began vigorously within the first few s of stimulus contact and gradually adapted within 10 min. The potential importance of specialized sensory appendages, the pectines, for mediating chemosensitivity is discussed. These results are consistent with the hypothesis that mate identification and localization in sand scorpions are mediated in part by a contact sex pheromone.

Reproductive compatibility and mitochondrial DNA restriction site analysis of New World screwworm, Cochliomyia hominivorax, from North Africa and Central America

The reproductive compatibility of New World screwworms, Cochliomyia hominivorax (Coquerel), from North Africa and a strain being mass produced for the Mexican eradication programme was examined to assess the feasibility of using flies from the Mexican screwworm mass production facility for a sterile insect technique eradication programme in North Africa. Males from the production strain mated randomly with females from North Africa and from the production strain when both were present. Neither strain of males discriminated between cuticular extracts of North African and production strain females containing a contact sex pheromone. Interstrain crosses between North African flies and production flies were fertile and produced fertile progeny. Chromosome morphology did not differ significantly between the two strains and homologue pairing was normal in hybrid meiotic and polytene nuclei. Mitochondrial DNA restriction site analyses indicated that the genetic divergence of the North African strain from Mexican and Central American strains was within the range of the diversity observed in Central American, Mexican and Caribbean populations. Test results indicate that New World screwworms from North Africa are reproductively compatible with the strain currently being mass produced in Mexico. Mating barriers should not impede the progress of an eradication programme using the sterile insect technique in North Africa with sterile screwworms from the Mexican mass production facility.

Biochemistry and regulation of pheromone production in Blattella germanica (L.) (Dictyoptera, Blattellidae)

Females of the German cockroach, Blattella germanica, produce a contact sex pheromone consisting of the methyl ketones 3,11-dimethyl-2-heptacosanone, 3,11-dimethyl-2-nonacosanone, 29-hydroxy- and 29-oxo-3,11-dimethyl-2-nonacosanone. We review evidence in support of the hypothesis that in adult females the hydrocarbon 3,11-dimethylnonacosane is oxidized to the corresponding methyl ketone pheromone. Recent studies on the precursors and directionality of synthesis of the methyl-branched alkane indicate that it is formed by the insertion of methylmalonyl units derived from propionate, isoleucine, valine, methionine and succinate early in chain elongation. The hydrocarbon is then hydroxylated and oxidized at the 2-position to form the methyl ketone pheromone. The in vivo synthesis of pheromone and its accumulation on the cuticle are correlated to the synthesis of juvenile hormone (JH) by the corpora allata (CA) in vitro and to oocyte development, suggesting common regulation by JH of pheromone production as well as other reproductive events. The patterns of pheromone and hydrocarbon production in starved, allatectomized and head-ligated females, as well as in females rescued with hormone-replacement therapy, suggest two mechanisms of regulation of pheromone production: a JH-induced conversion of hydrocarbon to pheromone is related to the CA cycle and to oocyte development, while a JH-independent mechanism, which is probably related to feeding, supplies precursors for hydrocarbon biosynthesis.

A new component of the female sex pheromone ofBlattella germanica (L.) (Dictyoptera: Blattellidae) and interaction with other pheromone components

A fourth component, 3,11-dimethyi-2-heptacosanone, was identified as a cuticular contact sex pheromone of the female German cockroach,Blattella germanica. In behavioral assays, higher dosages of 3,11-dimethyl-2-heptacosanone were needed to elicit similar sexual responses in males to those elicited by the major pheromone component, 3,11-dimethyl-2-nonacosanone. A 15∶85 blend of the C27 and C29 methyl ketone homologs resulted in a dose-response curve intermediate between that of each of the components alone, indicating independence of activity of each component and lack of synergism. Moreover, the activity of 3,11-dimethyl-2-nonacosanone was not enhanced by female cuticular hydrocarbons. The relationship between sexual responses of males to females and to isolated female antennae, and the amount of cuticular pheromone on whole females was investigated. Cuticular sex pheromone found on females increased with the age of the female, as did the male response to whole females. However, a bimodal male response was elicited by isolated female antennae. Differences between behavioral and analytical assays of pheromone are discussed.

Endocrine regulation of female contact sex pheromone production in the German cockroach, Blattella germanica

ABSTRACT The amount of the major component of the cuticular sex pheromone, 3, 11‐dimethyl‐2‐nonacosanone, on individual female German cockroaches, Blattella germanica (L.), as a function of age was determined by gas‐liquid‐chromatographic analysis. Accumulation of phermone increased with age in both virgin and mated females. During the first gono‐trophic cycle, the pheromone accumulated most rapidly when oocyte growth rates were maximal (days 5–10), and least rapidly while the female carried an ootheca (days 11–32). Pheromone accumulation was similar in virgin and mated females when the same physiological stages (determined by oocyte maturation) were considered. Inhibition of Juvenile Hormone release, through allatectomy, chemicals (precocene or fluoromevalonate), or through mechanical egg case implants, suppressed or delayed pheromone production and oocyte growth. The Juvenile Hormone analogue ZR512 induced allatectomized or head‐ligated females and females with chemically or mechanically inhibited corpora allata to produce pheromone and enlarge their basal oocytes. Finally, ZR512 applied to intact females stimulated pheromone production in a dose‐dependent manner.

Biosynthesis of methyl branched hydrocarbons of the German cockroach Blattella germanica (L.) (orthoptera, blattellidae)

The precursors and directionality of synthesis of the methyl branched cuticular hydrocarbons and the female contact sex pheromone, 3,11-dimethyl-2-nonacosanone, of the German cockroach, Blattella germanica, were investigated by radiotracer and carbon-13 NMR techniques. The amino acids [G- 3H]valine, [4,5- 3H]isoleucine and [3,4- 14C 2]methionine labeled the hydrocarbon fraction in a manner indicating that the carbon skeletons of all three amino acids serve as the methyl branch group donor. The incorporation of [1,4- 14C 2]- and [2,3- 14C 2]succinates into the hydrocarbon and acylglycerol/polar lipid fractions indicated that succinate also served as a precursor to methylmalonyl-CoA. Carbon-13 NMR analyses showed that [1- 13C]propionate labeled the carbon adjacent to the tertiary carbon, and, for the 3, x-dimethylalkanes, that carbon-4 and not carbon-2 was enriched. [1- 13C]Acetate labeled carbon-2 of these hydrocarbons. This indicates that the methyl branching groups of the 3, x-dimethylalkanes were inserted early in the chain elongation process. [3,4,5- 13C 3]Valine labeled the methyl, tertiary and carbon adjacent to the tertiary carbon of the methyl branched alkanes. Thus, the methyl branched hydrocarbon was formed by the insertion of methylmalonyl units derived from propionate, isoleucine, valine, methionine and succinate early in chain elongation.

Structural correlation between cuticular hydrocarbons and female contact sex pheromone of German cockroachBlattella germanica (L.)

The structural relationships between the cuticular hydrocarbons and the contact sex pheromone of the female German cockroach,Blattella germanica, were investigated. Cuticular hexane extracts were separated into hydrocarbon and ketone fractions by TLC or silicic acid column chromatography. The ketone fraction (which contains the major contact sex pheromone component) was analyzed by GC-MS before and after reduction to ydrocarbon. In addition to 3,11-dimethyl-2-nonacosanone, 3,11-dimethyl-2-heptacosanone was also identified. Females have the 3,11- and 3,9-dimethyl C27 and C29 alkanes, but only the 3,11- isomer of the dimethylketones. Inddition to the hydrocarbon components previously reported, a number of new components were characterized. Although the ratios of cuticular hydrocarbons differ among nymphs, adult males, and adult females, they have qualitatively identical hydrocarbon profiles, suggesting that the production of the contact sex pheromone results from the sex-specific oxidation of 3,11-imethylalkanes to pheromone components by the female.

Evidence for occurrence of mounting sex pheromone on body surface of femaleDermacentor variabilis (Say) AndDermacentor andersoni (Stiles) (Acari: Ixodidae)

MaleDermacentor variabilis andD. andersoni respond to an unknown chemical or chemicals present on the body surfaces of partially engorged conspecific female ticks. Following contact, the males mount the females and apply their mouthparts and legs against the female dorsal body surface. Then, the males turn with these appendages still in close contact and crawl to the female's venter, whereupon they locate the gonopore, probe the vulva, and copulate. Similar responses are elicited by heterospecific as well as conspecific females. However, the response is lost when the female cuticle is cleaned (delipidized) with organic solvents. It can be restored by applying hexane extracts prepared from female cuticle to the previously cleaned females. Males do not use surface texture as the primary stimulus for mate recognition. Male ticks also respond to hexane extracts applied to spherical inanimate objects, ("dummy" female), suggesting that a chemical or chemicals soluble in organic solvents has been transferred to these objects. These findings suggest the existence of a previously undescribed pheromone, the mounting sex pheromone (MSP). This contact sex pheromone enables males excited and attracted by 2,6-dichlorophenol to identify the female as a potential mating partner. The MSP is the second in the series of three sex pheromones guiding the hierarchy of behavioral responses which constitute tick courtship behavior.