The surface wax composition of the exuviae and adults of Aleyrodes singularis

Long-chain aldehydes, alcohols, hydrocarbons and wax esters were major components of the external lipids of adult Aleyrodes singularis. In exuviae, acetate esters replaced the hydrocarbons as a major component. The major long-chain alcohol and aldehyde from adults were C32 and were essentially the exclusive components of the wax particles. The major alcohol from exuviae was C26 and the aldehydes were C26, C28, C30 and C32. The major acetate esters were C28 and C30 in both adults and exuviae. There were wax esters of similar carbon number in adults and exuviae although the exuviae had a greater amount of wax esters with unsaturated fatty acids. The fatty acid and alcohol composition of the wax esters differed markedly between adults and exuviae. Wax esters of adults had similar amounts of C16, C18, C20, C22 and C24 fatty acids while those from exuviae contained largely C16 and C18. The major alcohol in the wax esters of adults was C22 and those of exuviae were C26 and C28. The distribution of fatty acids and alcohols among wax esters of varying chain length also differed between adults and exuviae: in adults C22 was the major fatty acid found in the dominant wax ester, C44 and the C22 alcohol was the major alcohol and found in wax esters C42 and C44. In exuviae C16 and C18 were the major fatty acids found in most wax esters and a C28 alcohol was the major alcohol found in wax esters C44 and C46, the two dominant wax esters in exuviae. It was clear that the difference in chemistry of the wax esters between the adults and exuviae is not evident unless the acid and alcohol moieties are characterized.     

Cuticular hydrocarbons and wax esters of the ectoparasitoid Habrobracon hebetor: Ontogenetic,reproductive, and nutritional effects

Hydrocarbon and wax ester components of cuticular lipids of the braconid parasitoid Habrobracon hebetor Say reared at 25 degrees C on larvae of a pyralid moth have been identified by GC-MS and analyzed with respect to adult age, mating status, and diet. The hydrocarbons range in carbon number from C(21) to C(45) and consist of a homologous series of n-alkanes, 11-, 13-, and 15-methyl alkanes, 13,17-dimethyl alkanes, and Z-5, Z-7, and Z-9-alkenes. The wax esters found in the cuticular lipid fraction are a series of homologous compounds with the acid portion being short chain, unbranched, even carbon number acids from C(8) to C(20) (predominately C(8) to C(16)). The alcohol portions of the esters are secondary alcohols with carbon number from C(22) to C(25) (predominately C(23) and C(25)) with the hydroxyl function located at C(6), C(7), C(8), and C(9). Gender, age, and nutritional states were significant factors for variation in several of the individual esters, but mating status did not affect wax ester composition. Ontogenetic examinations indicated that prepupal, and early pupal cuticular lipids contain only hydrocarbons. Low levels of wax esters are detectable in late stage pupae, and somewhat greater quantities of wax esters are present on newly eclosed adults. When pharate adults emerge from the cocoon, however, their cuticular lipids consist of approximately equal amounts of hydrocarbons and wax esters, and 6d post emergence from the cocoon, wax esters are the predominant lipid component.     

Methyl-branched hydrocarbons, major components of the waxy material coating the embryos of the viviparous cockroach Diploptera punctata

The viviparous cockroach Diploptera punctata carries a wax-coated batch of embryos in a brood sac. When the embryos are expelled into saline, flakes of wax from the surface of the embryos float to the surface. In contrast, embryos of the ovoviviparous species such as Rhyparobia maderae are not nourished by the mother during embryogenesis and do not have a copious waxy coating. As a first step in determining the function of this copious wax layer on the batch of embryos of D. punctata, its composition was compared to that of the waxy material on the outer cuticular surface of the mother (female cuticle) by thin-layer chromatography (TLC) and gas chromatography-mass spectrometry. The major lipid class on the embryos was hydrocarbons with lesser amounts of wax esters and long-chain alcohols. Hydrocarbons from both sources had similar elution times and chemical composition, but were markedly different in the amounts of the major methyl-branched hydrocarbon components. A mixture of 3,X-dimethyl alkanes were 44% of the hydrocarbons on the embryos and were only 29% on the female cuticle. However, trimethylalkanes were only 22% of the hydrocarbons on the embryos and were 34% of the hydrocarbons on the female cuticle. The major hydrocarbons from both sources were mixtures of methyl-branched alkanes with backbones of 33 and 35 carbon atoms. Methyl-branched tritriacontanes were 59% of embryo and 35% of female cuticular hydrocarbons; methyl-branched pentatriacontanes were 19% of embryo and 42% of female hydrocarbons. The difference in proportions of the similar hydrocarbons on the outer cuticular surface of the female and those covering the embryos may suggest that the evolution of copious nutrient secretion for the embryos was accompanied by selection for a mixture of hydrocarbons that prevents water loss by the embryos and protects them against invasion by microorganisms without preventing the movement of nutrient fluid into the embryos.     

Waxes of the social spider Anelosimus eximius (Araneae,Theridiidae): Abundance of novel n-propyl esters of long-chain methyl-branched fatty acids

The pentane extract of the social spider, Anelosimus eximius (Araneae, Theridiidae), contains hydrocarbons, fatty acids and their methyl esters, and a series of novel propyl esters of long-chain methyl-branched fatty acids. The propyl esters comprise almost three-fourths of the extract and consist predominantly of odd-numbered carbon chain components. Mass spectrometric analyses of the propyl esters, their methyl esters and cyanide derivatives showed that mono-, di- and trimethyl branched components with methyl branches on even numbered carbons predominate. The major components are propyl 4,20- and 4,30-dimethylhentriacontanoate and propyl 6,20- and 6,30-trimethylhentriacontanoate. The hydrocarbon fraction consists of n-, monomethyl- and dimethylalkanes, containing a relatively high proportion of even-numbered carbon chain components. The abundance of even-numbered carbon chain length alkanes and odd-numbered carbon chain length fatty acyl groups, along with abundant methyl-branches suggest that the propionyl-CoA and its carboxylated product, methylmalonyl-CoA, play important roles in the biosynthesis of these unique waxes. Arch. Insect Biochem. Physiol. 36:295–314, 1997. © 1997 Wiley-Liss, Inc.     

Cuticular hydrocarbons of the flea beetles,Aphthona lacertosa and Aphthona nigriscutis,biocontrol agents for leafy spurge (Euphorbia esula)

The adult beetles Aphthona lacertosa and Aphthona nigriscutis, used as biocontrol agents for leafy spurge, had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes and alkadienes as determined by gas chromatography-mass spectrometry. A trace amount of wax esters were present. In both species, the hydrocarbons were the major cuticular lipid class and the gas chromatographic profiles of the total hydrocarbons were similar. However, the profiles for the saturated hydrocarbon fraction were distinct for each species. Alkanes (n-alkanes and methyl-branched alkanes), alkenes and alkadienes comprised 26, 44 and 30%, respectively, for A. lacertosa, and 48, 26 and 26%, respectively, for A. nigriscutis, of the total hydrocarbons. The major methyl-branched hydrocarbons were 2-methylalkanes: 2-methyloctacosane and 2-methyltriacontane. The major monoene was hentriacontene and the major diene was tritriacontadiene. The species were unique in that a number of di- and trimethyl-branched alkanes were present in minor quantities in which the first methyl branch was on carbon 2 or 3. Examples of structures were 2,10-, 2,12-, 2,6-, 2,4- and 3,7-dimethylalkanes. 2,10,12-Trimethylalkanes and a 2,10,12,24-tetramethylalkane with one methylene between adjacent methyl branch points also were identified. The adjacent methyl branch points of the 2,4- and 2,10,12- and 2,10,12,24-methyl-branched alkanes appeared to cause additional fragmentations in the mass spectra. Dimethylalkanes with an odd number of carbons in the backbone of the molecule were identified as 2,23-dimethylnonacosane and 2,25-dimethylhentriacontane; their mass spectra also corresponded to mass spectra expected for a 2,6 branching sequence. However, a 2,6 branching sequence is not biosynthetically feasible because such a structure has a straight-chain tail with an odd number of carbon atoms beyond the last methyl branch point. The 2,23 and 2,25 branching sequences could be synthesized starting with a primer derived from the amino acid leucine which would account for both the even number of carbons between the branch points and an even number of carbons beyond the last methyl branch point.     

Novel diterpenoids and hydrocarbons in the Dufour gland of the ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae)

Chemical constituents contained in the Dufour gland of the ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) were characterized. Three terpenes, beta-springene, a homo-beta-springene, and a homo-geranyllinalool constitute approximately 37% of the gland components, with the remaining 63% all being hydrocarbons. The hydrocarbons consist of a homologous series of n-alkanes (n-C21 to n-C31), a trace amount of 3-methyl C23, a homologous series of internally methyl-branched alkanes (11-methyl C23 to 13-methyl C35), one dimethylalkane (13,17-dimethyl C33), a homologous series of monoenes (C(25:1) to C(37:1)) with the double bonds located at Delta9, Delta13 and Delta15 for alkenes of carbon number 25 to 31 and at Delta13 and Delta15 for carbon numbers 33 to 37 and three homologous dienes in very low amounts with carbon numbers of 31, 32, and 33. The terpenoid and hydrocarbon composition of the Dufour gland was similar in virgin and mated females. However, in contrast to the hydrocarbons, the amount of beta-springene and homo-geranyllinalool increased significantly with time after adult emergence from the cocoon. Although many hydrocarbons in the Dufour gland are the same as those on the cuticle of this species [Howard and Baker, Arch. Insect Biochem. Physiol. 53:1-18 (2003)], substantial differences also occur. Of particular note is the chain length of alkenes and location of the double bonds: cuticular alkenes have a chain length of C23 to C29 and double bond locations at Delta5, Delta7, and Delta9, whereas the Dufour gland alkenes contains a greater range of carbon numbers and have no Delta5 or Delta7 alkenes. The Dufour gland contains only one of the long-chain dimethylalkanes found on the cuticle. Also, no terpenoids are found on the cuticle, and the Dufour gland contains none of the secondary wax esters that are major components on the cuticle. GC-MS analysis of lipids carried in the hemolymph of H. hebetor indicated that all hydrocarbons found on both the cuticle and in the Dufour gland are present, as are some of the wax esters. However, none of the terpenoids were detected in the hemolymph. This suggests that the hydrocarbons are synthesized in other tissues or cells, probably by oenocytes, and differentially partitioned between the cuticle and the Dufour gland. The terpenoids are most likely synthesized within the Dufour gland. Analysis of surface lipids from eggs laid within 18 h indicated that no diterpenoids were present. Rather, the lipids present on the eggs were n-alkanes, monomethylalkanes, alkenes, and secondary alcohol wax esters. This composition did not reflect that of the Dufour gland, hence eggs are not being coated with Dufour gland components during oviposition.     

Cuticular hydrocarbons of triatomines

Triatomine insects (Hemiptera) are the vectors of Chagas disease. Their cuticular surface is covered by a thin layer of lipids, mainly hydrocarbons, wax esters, fatty alcohols, and free or esterified fatty acids. These lipids play a major role in preventing a lethal desiccation, altering the absorption of chemicals and microorganism penetration, they also participate in chemical communication events. Lipid components are biosynthetically related, the synthesis of long chain and very long chain fatty acids was first shown in the integument of Triatoma infestans through the concerted action of fatty acid synthases (FAS's) and fatty acyl-CoA elongases. A final decarboxylation step produces the corresponding hydrocarbon. Capillary gas chromatography coupled to mass spectrometry analyses showed that cuticular hydrocarbons of Triatominae comprise saturated straight and methyl-branched chains, from 18 to more than 43 carbon atoms. Odd-chain hydrocarbons, mostly from 27 to 33 carbons, are the major straight chains. Different isomers of mono, di, tri, and tetramethylcomponents, mostly from 29 to 39 atoms in the carbon skeleton, account for the major methyl-branched hydrocarbons. The presence, absence, and relative quantities of these hydrocarbons represent characters for their chemical phenotype, and are useful for differentiating genera, species and populations. In this review, we will discuss the metabolic pathways involved in hydrocarbon formation, and their structure, together with their role in insect survival. We will also review the utility of cuticular hydrocarbon fingerprints in chemotaxonomy.     

Composition of sugarcane waxes in rum factory wastes

Wastes produced during fermentation and distillation of crude sugarcane juice in rum factories were evaluated as a new source of waxes. The chemical composition of the crude wax extracted from adsorbat of the wastes on fuller's earth was studied by GC-mass spectrometry. Series of linear alkanes (C19-C33), and wax esters constitute the main components. In addition, phytosterols, triterpene methyl ethers, ethyl and methyl esters of fatty acids, and free fatty acids were found as minor components. Acid (predominance of C16 and C18) and alcohol portions (C26-C32) of the wax esters were analysed after saponification.     

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.     

Discovery of novel trimethylalkanes in the internal hydrocarbons of developing pupae of Heliothis virescens and Helicoverpa zea

Novel trimethyl-branched alkanes which eluted with the monomethylalkanes were identified in the internal lipids of Helicoverpa zea but were not present in Heliothis virescens. Their structures were unique in that the first methyl branch occurred on carbon 2 and the 2nd and 3rd methyl branch points were separated by a single methylene. Novel trimethylalkanes identified from their chemical ionization and electron impact mass spectra were 2,18,20-trimethyltetratriacontane, 2,18,20-trimethylhexatriacontane, and 2,24,26-trimethyldotetracontane. Previous reports did not find these trimethylalkanes in the cuticular surface lipids of larvae, pupae or adults of either species. The internal pupal hydrocarbons of H. virescens and H. zea amounted to 123 μg and 304 μg per pupa, respectively. They consisted of n-alkanes (8 and 4%, respectively) and methyl-branched alkanes (88 and 94%, respectively). The n-alkanes ranged in chain length from approximately 21 to 35 carbons and the methyl-branched alkanes from approximately 26 to 55 carbons vs. methyl-branched alkanes from 28 to 37 carbons previously reported for hydrocarbons from the pupal cuticular surface. The major n-alkane was heptacosane (3.3 and 1.2%, respectively, in H. virescens and H. zea). The major methyl-branched alkanes in H. virescens were methylhentriacontane (15%), methyltritriacontane (12%) and dimethyltritriacontane (10%), and in H. zea were methylnonacosane (17%), dimethylnonacosane (9%) and methylhentriacontane (20%). Except for the novel trimethylalkanes, the methylalkane branch points were predominantly on odd-numbered carbons as has been reported for these and other species.     

Composition of suberin-associated waxes from the subterranean storage organs of seven plants

The waxes associated with the suberin in the periderm of the underground storage organs of parsnip (Pastinaca sativa L.), carrot (Daucus carota L.), rutabaga (Brassica napobrassica Mill.), turnip (Brassica rapa L.), red beet (Beta vulgaris L.), sweet potato (Ipomoea batatas L.) and potato (Solanum tuberosum L.) were isolated, fractionated into hydrocarbon, wax ester, free fatty alcohol and free fatty acid fractions, and analyzed by combined gas chromatography and mass spectrometry. The amount of wax extracted from the periderm of the storage organs ranged from 2 to 32 μg/cm². The hydrocarbons from the suberin layer have a broader chain-length distribution, a predominance of shorter carbon chains, and a higher proportion of even-numbered carbon chains than the leaf alkanes from the same plants. The major components of the free and esterified fatty alcohols and fatty acids have an even number of carbon atoms, and are similar in chain-length distribution to their counterparts found covalently attached to the suberin polymers; however, these suberin components are shorter in chain length than their cuticular analogues from the leaves. Also extracted from the storage organs were polar components which included fatty alcohols and fatty acids in a conjugated form, and ω-hydroxy acids and dicarboxylic acids. Evidence is presented that removal of the wax from the periderm of whole storage organs results in a decrease in diffusion resistance to moisture. Scientific Paper No. 5516, Project 2001, College of Agriculture Research Center, Washington State University, Pullman, WA 99164, USA     

Cuticular lipids of insects. VI. Cuticular lipids of the grasshoppers Melanoplus sanguinipes and Melanoplus packardii

The cuticular lipids of the grasshoppers Melanoplus sanguinipes and Melanoplus packardii contain 60 and 68% alkanes and 28 and 18% secondary alcohol wax esters, respectively, with lesser amounts of normal and sterol wax esters, triglycerides, alcohols, sterols, and free fatty acids. All the hydrocarbons are saturated, and four types of alkanes are present: n-alkanes, 3-methylalkanes, internally branched monomethylalkanes, and internally branched dimethylalkanes. The principal n-alkanes in both insects are C(29) and C(27), with a range from C(21) to C(33). Trace amounts of 3-methylalkanes of 28, 30, and 32 total carbons are present. The principal internally branched monomethylalkanes are C(32) and C(34), whereas the main dimethylalkane contains 35 carbons. The n-alkanes do not correspond in chain length to the secondary alcohols. The primary alcohols range from C(22) to C(32) in both insects, with C(24) and C(26) predominating. The fatty acids in the triglyceride and free fatty acid fractions range from C(12) to C(24) in M. sanguinipes and from C(12) to C(18) in M. packardii.     

In vitro studies of the metabolism of [14C]- n-alkanes using ruminal fluid of sheep as substrate

Whether the rumen microbes are able to synthesize and/or degrade long-chain alkanes in anaerobic conditions remains a question to be answered before these hydrocarbons can be confidently used as duodenal flow or rumen transit markers. In this context, an experiment in vitro was carried out to establish whether within a rumen liquor fermentation system, n-alkanes can be derived from de-waxed structures of the plant or from non-alkane wax components (long-chain fatty alcohols, long-chain fatty acids and esters), or may be metabolized by bacteria to other components or to shorter-chain hydrocarbons. Ryegrass was labelled with 14C in growth chambers under controlled conditions in order to use it as a substrate. The labelled material obtained was separated in three fractions: labelled alkanes, labelled de-waxed plant and labelled wax components without the alkanes. These fractions were used for three different incubations in vitro, which objectives were as follows: 1. To check whether rumen bacteria can synthesize alkanes from carbon structures other than waxes (e.g. sugars). 2. To verify whether rumen bacteria can metabolize the n-alkanes to other compounds. 3. To check whether rumen bacteria can synthesize n-alkanes from other carbon compounds from waxes. The results showed that there was neither bacterial synthesis nor metabolism of the n-alkanes in in vitro conditions.     

Biosynthesis of triacylglycerols in the intestines of rainbow trout (Salmo gairdnerii) fed marine zooplankton rich in wax esters

Intestinal preparations from rainbow trout fed a diet rich in wax esters incorporated [1(-14)C]hexadecanoic acid and [1(-14)C]hexadecanol into triacylglycerols at the same rate. The ratio of the number of H atoms from C1 of hexadecanol to the number of molecules of hexadecanol incorporated into triacylglycerols was 1.6 : 3.0. [U-14C]Glucose was incorporated much faster into the glycerol moiety of triacylglycerols than was [U-14C]aspartic acid. We conclude that the oxidation of absorbed fatty alcohol to fatty acid and its subsequent incorporation into triacylglycerols is closely linked with the reductive formation of triacylglycerol-glycerol from glucose. The ability of trout intestines to metabolise fatty alcohol to triacylglycerols was the same in fish fed wax esters as in those fed triacylglycerols.     

Effect of whitefly parasitoids on the cuticular lipid composition of Bemisia argentifolii (Homoptera: aleyrodidae) nymphs

Experiments were conducted to determine the effects of whitefly parasitoids on the cuticular lipid composition of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring [=sweetpotato whitefly, Bemisia tabaci (Gennadius), Biotype B] nymphs. The cuticular lipids of B. argentifolii nymphs that had been attacked by parasitic wasps, either Eretmocerus mundus Mercet or Encarsia pergandiella Howard, were characterized by capillary gas chromatography and CGC-mass spectrometry and the results compared with the cuticular lipids of unparasitized nymphs. Previous studies with B. argentifolii nymphs had shown that wax esters were the major components of the cuticular lipids with lesser amounts of hydrocarbons, long-chain aldehydes, and long-chain alcohols. No appreciable changes in lipid composition were observed for the cuticular lipids of E. pergandiella-parasitized nymphs as compared to unparasitized controls. However, the cuticular lipids from nymphs parasitized by E. mundus contained measurable quantities of two additional components in their hydrocarbon fraction. Analyses and comparisons with an authentic standard indicated that the two hydrocarbons were the even-numbered chain length methyl-branched alkanes, 2-methyltriacontane and 2-methyldotriacontane. The occurrences and possible functions of 2-methylalkanes as cuticular lipid components of insects are discussed and specifically, in regard to host recognition, acceptance, and discrimination by parasitoids. Published 2000 Wiley-Liss, Inc.     

Intraspecific Variation in the Epicuticular Wax Composition of Four Species of Chionochloa

Intraspecific variation in four New Zealand species of Chionochloa, C. flavescens, C. pallens, C. rigida; and C. rubra, was investigated by examining the major carbon chain lengths of fatty acids, alcohols, aldehydes, wax esters and alkanes of the epicuticular waxes. The major even-carbon chain lengths ranged generally from C₂₄ to C₃₂ in the acids, alcohols and aldehydes; C₂₉ to C₃₃ in the alkanes; and even-carbon chains between C₃₆ and C₅₂ in the wax esters. A computer program was used to calculate the degree of similarity between samples in terms of chain length distribution. In C. rigida eastern and western South Island localities were identified; in C. flavescens Canterbury and Nelson, western South Island and southern North Island regions were recognized; and C. pallens and C. rubra were divisible into four regions; Canterbury, Nelson, western South Island and southern North Island. The possible elongation-decarboxylation pathways and the specificity of the enzymes in the biosynthetic pathways of epicuticular wax synthesis suggest the possibility that the northwest Nelson region could be a biogenetic centre from which wax synthesis has diversified along three routes, one to the western South Island, another to eastern South Island and the third to southern North Island. Identification of each of the four species based on the distribution of the carbon chain lengths in the individual lipid fractions is impossible unless the locality of collection is known. Intraspecific variation in lipid composition is not coincident with patterns of variation already reported.     

Neutral lipids of leaves and stems of Trifolium repens

The neutral lipids of white clover leaves and stems have been separated into wax esters, free fatty acids, free fatty alcohols, free sterols, triglycerides and hydrocarbons. The wax esters were mainly of C₁₈ di- and tri-unsaturated fatty acids and C₃₀ fatty alcohol. Linolenic acid was the predominant free fatty acid and triacontanol was the principal free fatty alcohol. Of the hydrocarbons, C₂₉ and C₃₁ were present in the largest amounts.     

Neutral Lipids and Phospholipids of Free-Living and Bacteroid Forms of Two Strains of Rhizobium Infective on Lotus pedunculatus

The neutral lipids and phospholipids of two strains of rhizobia in their free-living state and in symbiosis with a host plant are described. The principal lipid classes found were the polymer poly-beta-hydroxybutyrate, phospholipids, free fatty acids, glycerides, methyl esters, aliphatic alcohols, and hydrocarbons. The lipids include unusual unsaturated methyl-branched and saturated methoxy-branched fatty acids. Most components were found to be common to both forms of both strains, although the proportions varied. A number of strain differences could be discerned.     

柑橘真棉蚧蜡泌物的超微形态、红外光谱与化学成分特征

采用扫描电镜、红外光谱、气相色谱/质谱联用技术研究了柑橘真棉蚧Eupulvinariacitricola(Kuwana)(半翅目:蚧科)蜡泌物的超微形态、红外光谱和卵囊蜡质的化学成分特征。结果发现:该蚧雌虫背面腺体分泌湿蜡,在体表面形成薄的半透明蜡壳,背面蜡壳分为6个小区,表面由湿蜡凝结成片状和蜡块状构造。雌成虫产卵期由腹面多格腺分泌丝状蜡结成卵囊。雄若虫也分泌湿蜡,雄蛹的蜡茧薄,表面有浅的凹凸花纹。用雌成虫卵囊、背面蜡壳和雄茧的蜡质作红外光谱分析,它们的谱图具有共同的基本特征,吸收峰群分为5个区域:2900cm-1附近的3个强吸收峰组成的峰群是>CH2和—CH3的特征吸收峰;1800cm-1~1500cm-1之间的吸收峰群是羰基(>C=O)和C=C键的伸缩振动;1500cm-1~1400cm-1区域是>CH2和—CH3基团的吸收峰;1400cm-1~1000cm-1之间为饱和碳链—C—C—C—骨架振动。730cm-1附近为环状化合物的基团吸收峰群。由此确定它们的组成都是长碳链结构的脂肪酸、脂肪醇、烃类、酯类或带有环状结构的化合物。其主要区别在第2、3、4区吸收峰的形式、强度和数量,反映出基团的种类和数量不同。雌成虫卵囊蜡质甲酯化后GC/MS检测出7个组分(表1),全部为长链脂肪酸。未经甲酯化的蜡质检测出4类16个组分(表2),可分为长链烃、酸、醇、酯。第一类为饱和长链烃,5个组分,占总组分的38.38%;第二类是长链脂肪酸,包括直链饱和酸和不饱和酸共6个组分,占31.59%;第三类是直链饱和醇,占2.87%;第四类是酯类化合物,4个组分,占总组分的27.16%。     

The cuticular hydrocarbons of the Triatoma sordida species subcomplex (Hemiptera: Reduviidae)

The cuticular hydrocarbons of the Triatoma sordida subcomplex (Hemiptera: Reduviidae: Triatominae) were ana-lysed by gas chromatography and their structures identified by mass spectrometry. They comprised mostly n-alkanes and methyl-branched alkanes with one-four methyl substitutions. n-alkanes consisted of a homologous series from C21-C33 and represented 33-45% of the hydrocarbon fraction; n-C29 was the major component. Methyl-branched alkanes showed alkyl chains from C24-C43. High molecular weight dimethyl and trimethylalkanes (from C35-C39) represented most of the methyl-branched fraction. A few tetramethylalkanes were also detected, comprising mostly even-numbered chains. Several components such as odd-numbered 3-methylalkanes, dimethylalkanes and trimethylalkanes of C37 and C39 showed patterns of variation that allowed the differentiation of the species and populations studied. Triatoma guasayana and Triatoma patagonica showed the most distinct hydrocarbon patterns within the subcomplex. The T. sordida populations from Brazil and Argentina showed significantly different hydrocarbon profiles that posed concerns regarding the homogeneity of the species. Triatoma garciabesi had a more complex hydrocarbon pattern, but it shared some similarity with T. sordida. The quantitative and qualitative variations in the cuticular hydrocarbons may help to elucidate the relationships between species and populations of this insect group.