Dimethyl Alkanes Research Articles

Molecular Indicators of Sources and Biodegradation of Organic Matter in Sediments of Fluid Discharge Zones of Lake Baikal

This paper performs a detailed study of a wide set of organic-geochemical proxies in 15 sediment cores collected from the main basins of Lake Baikal (the northern, the central and the southern) where processes of focused fluid discharge were detected. A variety of studied zones includes sites with gas and hydrothermal seepage, mud volcanoes with or without gas-oil fluid discharge, gas hydrates and authigenic carbonates. The composition of the dispersed organic matter and individual hydrocarbon molecular markers (n-alkanes, dimethyl alkanes, isoprenoids, steranes, terpanes and polycyclic aromatic hydrocarbons) testify to the input from predominantly allochthonous terrestrial and autochthonous microbial and algal sources. The studied sources, maturity and biodegradation parameters of organic matter vary significantly for areas with different fluid discharge. The composition of specific biomarkers including isoprenoids and immature hopanoids reflects the lateral and vertical changes of microbial activity in sediments associated with various environmental conditions. The identified types of terpanes distribution (mature, mixed and immature) correlate well with types of fluid discharge and attest to the development of various methanogenic and methanotrophic microbial communities in sediments. Moreover, the revealed specificity of microbial molecular markers distribution allowed us to suggest the fluid discharge processes in zones where they were not previously detected.

How ants acclimate: Impact of climatic conditions on the cuticular hydrocarbon profile

Abstract Organisms from temperate zones are exposed to seasonal changes and must be able to cope with a wide range of climatic conditions. Especially ectotherms, including insects, are at risk to desiccate under dry and warm conditions, the more so given the changing climate. To adjust to current conditions, organisms acclimate through changes in physiology, morphology and/or behaviour. Insects protect themselves against desiccation through a layer of cuticular hydrocarbons (CHC) on their body surface. Hence, acclimation may also affect the CHC profile, changing their waterproofing capacity under different climatic conditions. Here, we investigated the acclimation response of two Temnothorax ant species to different climatic conditions. We analysed CHC profiles of queens, nurses and foragers that were acclimated to different humidity × temperature regimes, and tested the beneficial acclimation hypothesis by measuring survival of workers under desiccation‐heat stress. Both ants possessed a species‐specific CHC profile. Nevertheless, they showed similar acclimation responses concerning changes of certain CHC classes, and finally similar survival rates under desiccation‐heat stress. Warm‐acclimated individuals generally showed longer n‐alkanes, fewer dimethyl alkanes, and more (workers) or less (queens) monomethyl alkanes. In contrast, dry conditions resulted in more n‐alkanes and fewer mono‐ and dimethyl alkanes, but these acclimatory changes were only observed in workers and not in queens. Warm‐ and dry‐acclimated workers survived desiccation‐heat stress better, but we found no species differences. Our results indicate that both ant species can plastically adjust their cuticular hydrocarbon profile, allowing them to acclimate to different climatic conditions. Although their CHC composition differs in a species‐specific manner, they showed similar chemical adjustments and concomitant changes in survival rate. Hence, chemical plasticity may be critical to determine a species’ climatic range and its survival under changing climatic conditions. A plain language summary is available for this article.

What are the Mechanisms Behind a Parasite-Induced Decline in Nestmate Recognition in Ants?

Social insects have developed sophisticated recognition skills to defend their nests against intruders. They do this by aggressively discriminating against non-nestmates with deviant cuticular hydrocarbon (CHC) signatures. Studying nestmate recognition can be challenging as individual insects do not only vary in their discriminatory abilities, but also in their motivation to behave aggressively. To disentangle the influence of signaling and behavioral motivation on nestmate recognition, we investigated the ant Temnothorax nylanderi, where the presence of tapeworm-infected nestmates leads to reduced nestmate recognition among uninfected workers. The parasite-induced decline in nestmate recognition could be caused by higher intra-colonial cue diversity as tapeworm-infected workers are known to exhibit a modified hydrocarbon signature. This in turn may broaden the neuronal template of their nestmates, leading to a higher tolerance towards alien conspecifics. To test this hypothesis, we exchanged infected ants between colonies and analyzed their impact on CHC profiles of uninfected workers. We demonstrate that despite frequent grooming, which should promote the transfer of recognition cues, CHC profiles of uninfected workers neither changed in the presence of tapeworm-infected ants, nor did it increase cue diversity among uninfected nestmates within or between colonies. However, CHC profiles were systematically affected by the removal of nestmates and addition of non-nestmates, independently from the ants' infection status. For example, when non-nestmates were present workers expressed more dimethyl alkanes and higher overall CHC quantities, possibly to achieve a better distinction from non-nestmates. Workers showed clear task-specific profiles with tapeworm-infected workers resembling more closely young nurses than older foragers. Our results show that the parasite-induced decline in nestmate recognition is not due to increased recognition cue diversity or altered CHC profiles of uninfected workers, but behavioral changes might explain tolerance towards intruders.

How do cuticular hydrocarbons evolve? Physiological constraints and climatic and biotic selection pressures act on a complex functional trait.

Cuticular hydrocarbons (CHCs) cover the cuticles of virtually all insects, serving as a waterproofing agent and as a communication signal. The causes for the high CHC variation between species, and the factors influencing CHC profiles, are scarcely understood. Here, we compare CHC profiles of ant species from seven biogeographic regions, searching for physiological constraints and for climatic and biotic selection pressures. Molecule length constrained CHC composition: long-chain profiles contained fewer linear alkanes, but more hydrocarbons with disruptive features in the molecule. This is probably owing to selection on the physiology to build a semi-fluid cuticular layer, which is necessary for waterproofing and communication. CHC composition also depended on the precipitation in the ants' habitats. Species from wet climates had more alkenes and fewer dimethyl alkanes than those from drier habitats, which can be explained by different waterproofing capacities of these compounds. By contrast, temperature did not affect CHC composition. Mutualistically associated (parabiotic) species possessed profiles highly distinct from non-associated species. Our study is, to our knowledge, the first to show systematic impacts of physiological, climatic and biotic factors on quantitative CHC composition across a global, multi-species dataset. We demonstrate how they jointly shape CHC profiles, and advance our understanding of the evolution of this complex functional trait in insects.

Thermodynamics of liquid–vapor phase equilibrium in dimethyl sulfoxide–alkanol systems in the range of 293.15–323.15 K

Liquid–vapor phase equilibria in dimethyl sulfoxide–alkanol (1-propanol, 1-butanol, and tert-butanol) binary systems are studied using a static method. The total saturated vapor pressure in the temperature range of 293.15–323.15 K is measured. The partial pressures of dimethyl sulfoxide and alkanes have been calculated via integrating the Gibbs–Duhem equation. Excess molar Gibbs energies are described by the Redlich–Kister equation, and the correlation parameters are calculated. The nature of the deviation from the ideal behavior of these solutions is explained by allowing for the presence of competing homo- and heteromolecular interactions and the considerable effect of the length of the alkanols’ hydrocarbon chains has on the values of the thermodynamic parameters.

Comparison of different molecular sieves for the liquid phase separation of linear and branched alkanes

A carbon molecular sieve adsorbent (CMS-IMP12) obtained from the pyrolysis of a poly(vinylidene chloride-co-vinyl chloride) (PVDC-PVC, Saran™) material was tested and compared with other molecular sieve materials for the separation of a multi-component hydrocarbon mixture. Liquid phase experimental adsorption curves at 303K were obtained in a stirred tank using a model mixture composed by n-heptane, 2-methylheptane, 2,5-dimethylhexane and 2,2,4-trimethylpentane, considering the last one as a non-adsorbing solvent. Materials compared against the CMS-IMP12 were zeolites ZSM-5 (Si/Al=15), ZSM-5 (Si/Al=140), ZSM-22, ZSM-23, Silicalite-1 and Silicalite-2. The CMS-IMP12 adsorbed at least three times the amount adsorbed by the other material tested (i.e. 206 versus 79mg/gads for Silicalite-1) mainly because three components of the mixture (linear, methyl and non-geminal dimethyl alkanes) were adsorbed in higher proportions. None of the other tested materials adsorbed non-geminal dimethyl branched compounds. Regarding the kinetics of adsorption as represented by their second order rate constants, all the materials except the CMS-IMP12 adsorbed the methyl alkane molecule at the same rate as the n-alkane. The slower adsorption rate observed for 2-methylheptane as compared to n-heptane in the CMS-IMP12 may be due to the competition for adsorption sites between the two slow diffusing species: 2-methylheptane and 2,5-dimethylhexane.

Density, Viscosity, Speed of Sound, and Bulk Modulus of Methyl Alkanes, Dimethyl Alkanes, and Hydrotreated Renewable Fuels

The density, viscosity, and speed of sound were measured in this work for pure component branched alkanes (2-methyloctane, 4-methyloctane, 2-methylnonane, 2-methyldecane, 3-methylundecane, 2-methylpentadecane, 7-methylhexadecane, 3,6-dimethyloctane, and 3,5-dimethylheptane) commonly found in hydrotreated renewable fuels (HRFs) and for HRFs from tallow, camelina oil, and algae and waste cooking oil blended 50/50 with petroleum diesel. The density and viscosity were measured at temperatures from (283.15 to 373.15) K and ranged from (661 to 788) kg·m–3 for density and (0.261 to 5.36) mPa·s for viscosity. Speed of sound data were measured at temperatures from (283.15 to 323.15) K and spanned from (1081 to 1393) m·s–1. The bulk modulus was calculated from the density and speed of sound data, and its values varied from (809 to 1527) MPa. All values increased as the carbon chain length on the alkane increased. All physical property values for the HRFs fell between those measured for individual pure component bra...

Changes in cuticular hydrocarbons in different developmental stages of the bean bug, Riptortus pedestris (Hemiptera: Alydidae)

The function of “cuticular hydrocarbons” (CHCs) in insects is to protect the body as well as chemical communication and recognition between species. Gas chromatography and mass spectrometry were used to compare the composition of CHCs in eggs, all nymph instars, and male and female adults of the bean bug, Riptortus pedestris (Hemiptera: Alydidae). CHC carbon chain numbers of each developmental stage ranged from 14 to 19 in eggs to the fourth nymph and were 24 in the last nymph. CHCs' carbon chain numbers in male and female adults increased from 16 to 23 and 16 to 27 until 6days of age, respectively. Major components consisted of n-nonacosane in the larval stages, which changed to n-hentriacontane, n-heptacosane and 13,17-;15,19-demethyltritriacontane in adults. The major component from eggs was not identified. The major component from newly emerged adults was n-heptacosane. CHCs in different developmental stages of the bean bug consisted of n-alkanes with saturated hydrocarbons (27–63%), followed by mono or di-methyl alkanes. However, the CHCs of newly emerged female and male adults consisted mostly of methyl-alkanes. The major constituents of CHCs in the developmental stages of R. pedestris were proportionally different but showed only slight differences in composition.

Identification and composition of cuticular hydrocarbons of the major Afrotropical malaria vector Anopheles gambiae s.s. (Diptera: Culicidae): analysis of sexual dimorphism and age‐related changes

Forty-eight cuticular hydrocarbons (CHCs) were characterized by gas chromatography-mass spectrometry from the epicuticular surface of the major Afrotropical malaria vector Anopheles gambiae. The hydrocarbons identified were 14 n-alkanes, 16 monomethyl alkanes, 13 dimethyl alkanes, 5 alkenes, with main-chain lengths ranging from C(17) to C(47), and the results are consistent with those from other Culicidae species. Qualitative differences were not observed between laboratory pools of three females and males, between different age-groups (0-16 days) and between single field specimens, whereas quantitative differences in CHC profiles were observed. Differences between sexes were more marked in individuals aged 0-2 days than in older ones. Both sexes undergo strong CHC profile changes with age, and individuals aged 0-2 days differ remarkably from the older ones. The possibility of exploiting these changes for estimating the age of mosquito was explored through multivariate analyses of the relative abundance of the compounds, using either the whole CHC profile or a subset of CHCs. Such a method allows us to assign more than 85% of females and 75% of males to the correct age-group. Although preliminary, these results show that the method is promising, as it has already been shown in Aedes aegypti and An. stephensi. The correct determination of the vector age (particularly in the case of the An. gambiae complex of sibling species) provides valuable information in malaria epidemiology and in evaluation of the effectiveness of vector control strategies. Further efforts will be made to validate this method on single specimens reared in seminatural conditions before being proposed to medical entomologists working in the Afrotropical region.

Stage-specific surface chemicals of Plodia interpunctella: 2-acyl-1,3-cyclohexanediones from larval mandibular glands serve as cuticular lipids

Cuticular lipid compositions of all life stages of the stored product moth Plodia interpunctella have been determined. Eggs and adults of P. interpunctella have cuticular lipids consisting solely of hydrocarbons. The composition of eggs and adult females is qualitatively nearly identical with ca. 86 hydrocarbons (11 n-alkanes, 39 monomethyl alkanes, 19 dimethyl alkanes, 11 trimethyl alkanes and 6 monoenes) except females lack the 2-methyl alkanes found in eggs. Adult males have a hydrocarbon composition qualitatively nearly identical to females with the exception that they lack the monoenes. Larval and pupal cuticular lipids are dominated by a mixture of ca. 20 previously described 2-acyl-1,3-cyclohexanediones, with only minute amounts of n-alkanes on the larvae and pupae. The 2-acyl-1,3-cyclohexanediones are continuously secreted onto their silk webbing and food particles by the paired mandibular glands found in all larvae. Extracts from dissected mandibular glands have a qualitatively identical composition to larval cuticular extracts. The pupal stage (which does not have mandibular glands) is enclosed in a silk cocoon also coated with 2-acyl-1,3-cyclohexanediones laid down while the wandering stage larvae spin the cocoon. The 2-acyl-1,3-cyclohexanediones have physical properties which closely mimic those of cuticular hydrocarbons, including melting point and boiling point range and hydrophobicity. This is the first report of an insect with a life stage that does not use conventional cuticular lipids for conservation of water.

Cuticular lipids of the booklouse, Liposcelis bostrychophila: hydrocarbons, aldehydes, fatty acids, and fatty acid amides.

The booklouse, Liposcelis bostrychophila, is an increasingly common pest of stored food products worldwide. We report here the cuticular lipid composition of this pest (the first report of the hydrocarbons of any member of the Order Psocoptera and the first report of fatty acid amides as cuticular components for any insect). No unsaturated hydrocarbons were present. A homologous series of n-alkanes (C21-C34), monomethyl alkanes (3-, 4-, 5-, 7-, 9-, 11-, 12-, 13- and 15-methyl-) with a carbon chain range of C28-C42, and dimethyl alkanes (3, 7-; 9, 13-; 11, 15-; 13, 17-; 9, 21-; 11, 19-; and 13, 21-) with a carbon number range of C31-C41 were identified. The relative abundances of these hydrocarbons were low, comprising approximately 0.0125% of total biomass. The amides were a homologous series (C16-C22 in chain length), with the major amide being stearoyl amide. In addition to the amides, free fatty acids (C16:1, C16:0, C18:2, C18:1, and C18:0 in chain length) and three straight chain aldehydes (C15, C16, and C17:1 in chain length) also occurred as cuticular components. These findings are discussed in terms of the chemical and physiological ecology of this species.

Cuticular hydrocarbons of the ectoparasitic wasp Cephalonomia hyalinipennis (Hymenoptera: Bethylidae) and its alternative host, the stored product pest Caulophilus oryzae (Coleoptera: Curculionidae).

Cuticular hydrocarbons of an ectoparasitic wasp attacking two beetle hosts have been identified and examined for the influence of age, gender, mating status, and host on hydrocarbon composition. The 37 wasp hydrocarbons identified consisted of a series of n-alkanes (C16 to C33), 3-, 5-, 9-, 10-, 11-, and 12-methyl alkanes and a series of Z-7 and Z-9 monoenes (C23:1 to C27:1). One C25:2 diene was found. No effects of hydrocarbon composition as a function of age, gender, or mating status were found for the wasps. Wasps reared on Hypothenemus hampei, however, had 12/37 significant abundance differences to those reared on Caulophilus oryzae, although all but one of these differences were for components in less than 2% relative abundance. The C25:2 diene from wasps reared on H. hampei was present in about 10% whereas from wasps reared on C. oryzae it was present in about 2%. The hydrocarbons of one host for this wasp, the coffee berry borer (Coleoptera: Scolytidae), have been previously reported [Howard and Infante, Ann. Entomol. Soc. Am. 89:700-709 (1996)]. The hydrocarbons of the alternative host, C. oryzae (Coleoptera: Curculionidae) consists of n-alkanes (C17 to C31), 3-, 4-, 5-, 7-, 9-, 11-, 12-, 13-, 14-, and 15-methyl alkanes, and a series of dimethyl alkanes of the series 3, 17-; 5, 11-; 5, 17-; 7, 11-; 7, 13-; 13, 17-; and 15, 19-. No unsaturated hydrocarbons were found. No significant differences in hydrocarbon composition were found between male and female C. oryzae. Hydrocarbon patterns of four species of Cephalonomia are compared and shown to be species-specific. The data are discussed in terms of ecological and physiological parameters.

Investigation of entropy effects during sorption of mixtures of alkanes in MFI zeolite

We have carried out a comprehensive study of sorption of mixtures of alkanes, in the 1–7 C atom range, in MFI zeolite using configurational-bias Monte Carlo (CBMC) simulations. The isotherm characteristics of various binary, ternary and quaternary mixtures have been investigated. Our studies show that two types of entropy effects have a significant influence on mixture sorption: 1. Size entropy effects arise due to differences in the saturation loading of the pure components. Size entropy effects favour the component with the smaller number of C atoms because the smaller molecule finds it easier to fill in the “gaps” within the zeolite matrix at high molecular loadings. 2. Configurational entropy effects come into play for mixtures of alkanes that differ in the degree of branching. For a mixture of linear and mono-methyl alkanes with the same number of C atoms, configurational entropy effects favour the linear isomer because such molecules “pack” more efficiently within the MFI matrix. For a mixture of mono-methyl and di-methyl alkanes with the same number of C atoms, configurational entropy effects favour the single branched isomer. Configurational entropy effect comes into play when the loading exceeds four molecules per unit cell, when all the intersection sites are occupied, and results in the following hierarchy of sorption strengths: linear alkanes ⪢ mono- methyl alkanes ⪢ di- methyl alkanes . In all cases, the mixture isotherms can be predicted with good accuracy using the ideal adsorbed solution theory (IAST). CBMC simulations of sorption of an 8-component mixture containing n-pentane ( n-C 5), 2-methylbutane (2MB), n-hexane ( n-C 6), 2-methylpentane (2MP), 2,2-dimethylbutane (22DMB), n-heptane ( n-C 7), 2-methylhexane (2MH) and 2,2-dimethylpentane (22DMP) show that both size and configurational entropy effects contribute, leading to a sorption hierarchy depending on the degree of branching, linear alkanes ⪢ mono- methyl alkanes ⪢ di- methyl alkanes . This result has considerable potential for commercial application in the petroleum industry in catalytic isomerization process where it is necessary to isolate the di-branched alkanes which are preferred ingredients in gasoline.

Cuticular Hydrocarbons of <I>Kapala sulcifacies</I> (Hymenoptera: Eucharitidae) and Its Host, the Ponerine Ant <I>Ectatomma ruidum</I> (Hymenoptera: Formicidae)

Cuticular hydrocarbons from the ponerine ant Ectatomma ruidum Roger and a highly integrated eucharitid myrmecophile, Kapala sulcifacies (Cameron), associated with it, have been characterized. Ninety hydrocarbons were identified from the ant, 55 hydrocarbons from the female wasp and 54 hydrocarbons from the male wasp. The wasps and ants share 40 hydrocarbons. These shared 40 hydrocarbons represent 92.6% of their hydrocarbon composition for female Kapala, 84.3% for male Kapala and 67.7% for the ants. The wasps have a carbon number range of C27 to C35; the ants have a range of C23 to C35. Both species possess n-alkanes, C27 to C33 for the wasps, C23 to C34 for the ants. Both species also possess major quantities of Z-7- and Z-9 alkenes: C29 to C33 for the wasps; C23 to C35 for the ants. The female wasps possess a low amount of a conjugated C31 diene (neither the ants nor the male wasps possess this hydrocarbon), and the ants, but not the wasps, contain low quantities of nonconjugated dienes (carbon numbers of C23 to C29) with double bonds at Δ9, and Δ14. Both wasps and ants share homologous series of 3-, 5-, 10-, 11-, 12-, 13-, 15- and 17-methyl branched alkanes. Ants and wasps also share a homologous series of 3,7-dimethyl alkanes. Other internally branched dimethyl alkanes are found in both ants and wasps, but only 11, 15-DiMeC29 is shared. Wasps have 7, 15- and 10, 14-dimethyl alkanes while the ants have 15,19-dimethyl alkanes. Kapala sulcifacies and E. ruidum both possess hydrocarbons of the 5, X-, 11, X-, 12, X- and 13, X-DiMe series, but the compounds involved are not shared because they represent different compounds. Behavioral observations indicate that the ants accept the newly emerged adult parasitoids with no evidence of agonistic behavior for a period of time after adult eclosion. Nevertheless, the chemical deception is not completely efficient because young adult Kapala are soon ejected from the nest by transportation by their host. These transportations frequently occur after seizure at the base of the wasps’ characteristic scutellar spines, such structures allowing for easy transportation without injury for the parasite. Moreover, if no method of escaping the colony is provided, the ants ultimately attack the parasitoids. The substantial chemical overlap of the cuticular hydrocarbon profiles of the ants and wasps are discussed in the context of the social life of the colony.

Separation of linear, mono-methyl and di-methyl alkanes in the 5–7 carbon atom range by exploiting configurational entropy effects during sorption on silicalite-1

We have developed a novel concept for separating alkane mixtures, in the 5–7 carbon atom range, into three separate fractions consisting of linear, mono-methyl and di-methyl alkanes by adsorption on silicalite. We make use of the fact that with increased degree of branching, the “ packing efficiency” within the silicalite matrix is significantly lower. This configurational entropy effect comes into play when the loading exceeds 4 molecules per unit cell, when all the intersection sites are occupied, and results in the following hierarchy of sorption strengths: linear alkanesmono-methyl alkanesdi-methyl alkanes. To demonstrate the feasibility of the entropy-based separation concept we carried out configurational-bias monte carlo simulations for a variety of binary, ternary and quaternary mixtures of alkanes, n-pentane (n-C5), 2-methylbutane (2MB), n-hexane (n-C6), 2-methylpentane (2MP), 3-methylpentane (3MP), 2,2-dimethylbutane (22DMB), n-heptane (n-C7), 2-methylhexane (2MH), 2,2-dimethylpentane (22DMP). The entropy-driven separation concept has been verified, in part, by comparison with the experimental sorption data of Santilli (J. Catal., 1986, 99, 335) for the mixture n-C6–3MP–22DMB.

Reconnaissance sedimentology and hydrocarbon biomarkers of Ediacarian microbial mats and acritarchs, lower Ungoolya Group, Officer Basin

Reconnaissance sedimentology and hydrocarbon biomarkers of Ediacarian microbial mats and acritarchs, lower Ungoolya Group, Officer Basin

Evidence for cyanobacterial inputs and heterotrophic alteration of lipids in sinking particles in the Alboran Sea (SW Mediterranean)

Abstract The different sources of lipid compounds present in sinking particles collected in a sediment trap mooring deployed in the Alboran Sea (SW Mediterranean) were elucidated using the molecular marker concept. A significant contribution of cyanobacterial lipids was identified based on the occurrence of a series of 3- and 5-methylalkanes and dimethylalkanes. Further evidence of cyanobacterial inputs was obtained by principal component analysis of all data showing diploptene and n -alkanes in the range C 14 –C 22 clustered together with those branched alkanes. The use of methyl and dimethyl alkanes to trace cyanobacterial sources in the water column is proposed with advantage to sterols which are usually masked by phytoplanktonic sterols. The sterol distribution indicates phytoplankton as a major source with a contribution from heterotrophic zooplanktonic. Both fossil and biogenic sources can be contributors to the large unresolved complex mixture (UCM) found in these samples.

Hydrocarbon profiles of diapausing and reproductive adult face flies (Musca autumnalis)

Hydrocarbons present on the cuticle surface of adult face flies, Musca autumnalis, were identified by GC-MS and quantified by GC. Hydrocarbons consisted of n-, monomethyl, and dimethyl alkanes ranging in chain length from 23–29 carbons. Also present were monounsaturated alkenes with chain lengths of 23, 25, 27, and 29 carbons. Wild-caught flies were extracted and hydrocarbon profiles determined for both diapausing and reproductive adult males and females. Few qualitative differences were found between males and females in the hydrocarbon profile. Differences in percent composition were found between diapausing and reproductive flies in monounsaturated alkenes, 4 and 45%, n-alkanes, 24 and 37%, monomethylalkanes, 57 and 15%, and dimethylalkanes, 15 and 2%, respectively, for females. A small difference was found in the total amount of hydrocarbon present, 7.3 ± 0.6 and 9.7 ± 1.1 μg/fly, between diapausing and reproductive female flies, respectively. Adult males also exhibited a similar change in hydrocarbon profile and amount between diapausing and reproductive flies. A laboratory strain of face flies originating in Minnesota was also analyzed, and again similar differences were observed in both male and female flies that were kept under a reproductive or diapause condition. Arch. Insect Biochem. Physiol. 37:206–214, 1998. © 1998 Wiley-Liss, Inc.

Cuticular Hydrocarbons of the Host-Specific Ectoparasitoid Cephalonomia stephanoderis (Hymenoptera: Bethylidae) and Its Host the Coffee Berry Borer (Coleoptera: Scolytidae)

Cuticular hydrocarbons have been identified from larvae and adults of the bethylid wasp Cephalonomia stephanoderis Betrem and larval, prepupal, pupal, and adult stages of its host, the scolytid beetle Hypothenemus hampei (Ferrari). Larval, male and female wasps have the same cuticular hydrocarbons, but in different relative abundances. The major components of adults are n-alkanes (C21−C33), monomethyl alkanes (3-, 5-, 7-, 9-, 10-, 11-, 12-, 13-, 14-, 15-, 16-, and 17-methyl), and Z-(10)-monomethyl alkenes (with the methyl branch at C14−C19). Minor components include a series of 3,X-; 4,X-; 5,X-; 6,X-; 7,X-, and 8,X- dimethyl alkanes (with X at C14−C19) and a series of 3,9,13- and 3,11,15-trimethyl alkanes. Male C. stephanoderis are characterized by high proportions of n-alkanes and lower proportions of the monomethyl alkanes and methylbranched alkenes. Female wasps are characterized by lower proportions of n-alkanes and higher proportions of the monomethyl alkanes and methylbranched alkenes. Larval C. stephanoderis are characterized by high proportions of the methylbranched components and lower proportions of the n-alkanes and the n- and methylbranched alkenes. Host scolytid beetle cuticular hydrocarbons are totally saturated. Major components of all stages and sexes include n-alkanes (C22 − C31), monomethyl alkanes (3-, 4-, 5-, 13-, 14-, 15-, 16- and 17-methyl), a series of dimethyl alkanes (3,7-; 3,9-; 3,15-; 3,17-; and 3,19-), and a series of trimethyl alkanes (3,7,13-; 3,9,13-; and 3,11,15-). Minor components are a series of 4,14- and 4,16-dimethyl alkanes and 5,17- and 5,19-dimethyl alkanes. All immature beetle stages had similar hydrocarbon compositions, which differed moderately from those of the adults. As with the adult wasps, relative compositions of male and female beetles differed. Males were characterized by a greater proportion of n-alkanes and lesser proportions of monomethyl alkanes and trimethyl alkanes. Females had lesser proportions of n-alkanes and greater proportions of monomethyl alkanes and trimethyl alkanes. The cuticular profiles of the parasitoid and host are compared and discussed in terms of both intraspecific and interspecific semiochemical interactions.

Structural and chemical ontogeny of the postpharyngeal gland in the desert ant Cataglyphis niger

Abstract. The postpharyngeal gland of Cataglyphis niger (André, 1881) workers is characterized, at the ultrastructural level, by a well‐developed smooth endoplasmic reticulum, Golgi apparatus, and numerous mitochondria and lamellar inclusions suggesting an involvement in lipid metabolism. In addition, the microvillar differentiation of the apical membrane and basal invaginations of the cell imply a transportation process.The gland shows a clear structural as well as chemical age‐dependent development. Epithelial thickness increases with age, reaching its maximum within the first week after emergence. Concurrently there is a progressive development of microvilli and appearance of the lamellar inclusions. The gland's secretion consists mainly of hydrocarbons, with a predominance of monomethyl and dimethyl alkanes. Congruency was found between the hydrocarbon composition of glandular exudates and those of the epicuticular washes. An age‐dependent increase in the total amount of hydrocarbons was found to correlate with the ultrastructural development and gross morphology (thickness of epicuticular lining) of the gland.