Larry L. Jackson

cis-Vaccenyl acetate as an aggregation pheromone inDrosophila melanogaster.

Pentane extracts of matureDrosophila melanogaster males substantially increased the attractiveness of food odors to both males and females in a wind-tunnel olfactometer. Extracts of females caused no such increase. An active component of the extract was isolated and identified as (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), and synthetic cVA was active in bioassay. Hydrolysis of the ester linkage or movement of the double bond to the 9 position destroyed the activity. Mature virgin males released cVA into their feeding vials, and amounts of synthetic CVA equal to that released per male caused significant bioassay responses. Females, which were known to receive cVA from males during copulation, were found to emit relatively large amounts of the ester into their feeding vials within 6 hr after mating. cVA had been demonstrated previously to be a close-range pheromone inD. melanogaster, discouraging males from courting other males or recently mated females; it now appears to have a longer-range function as well.

Cuticular lipids of insects

Cuticular lipids cover nearly all parts of insect and are the chief agent for restricting water loss. The structure of insect epicuticles is reviewed, with emphasis on the role of cuticular lipids and the metabolism of cuticular lipids. The chemical composition of insect cuticular lipids are discussed with particular emphasis on the types in which hydrocarbons, was esters and fatty alcohols predominate. What little evidence is available on the biosynthesis of insect cuticular lipids is discussed.

Lipid sovent systems are not equivalent for analysis of lipid classes in the microeukaryotic green alga, Chlorella

A comparison of three lipid solvent system indicated that they are not equivalent for the analysis of lipid classes in the green alga, Chlorella. Soxhlet extraction (methylene chloride/methanol, 3 h refulx) recovers more neutral lipid than the other methods but is equivalent to the room-temperature Bligh and Dyer (chloroform/methanol/water) extraction modified with phosphate buffer in glycolipid and polar lipid recovery. The Soxhlet method, however, gave a significantly lower recovery of many polyunsaturated fatty acids. The hexane/isopropanol method is selective for algal neutral lipids with poor recovery of membrane lipids (glyco- and polar lipids). Although this selectivity may have some useful applications, for biochemical studies of lipid synthesis in Chlorella, the modified Bligh and Dyer provides the most quantitative and reproducible recovery of all Chlorella lipid classes while minimizing artifacts due to the extraction procedure.

The efficacy of linalool, a major component of freshly-milled Ocimum canum Sims (Lamiaceae), for protection against postharvest damage by certain stored product Coleoptera

Abstract Linalool was present at 8.6 ± 0.9 mg/g in the dried leaves of Ocimum canum Sims, an annual mint used in Rwanda to protect against postharvest insect damage. Direct exposure of adults of Zabrotes subfasciatus (Bohem.) to milled, dried O. canum leaves resulted in 100% mortality of males and 50% mortality of females after 48 hr. Dose-response curves for linalool were completed with adult Z. subfasciatus, Acanthoscelides obtectus (Say), Rhyzopertha dominica (F.), and Sitophilus oryzae (L.) using a filter paper bioassay. The LC 50 values were: 428 μg/cm 2 for Z. subfasciatus ; 405 μg/cm 2 for A. obtectus ; 428 μg/cm 2 for R. dominica ; 427 μg/cm 2 for S. oryzae . Knockdown was occasionally followed by recovery at doses less than the LC 50 for all species. There are significant differences in the LC 50 and LT 50 values for male and female Z. subfasciatus . At the lower dosages hyperactivity rarely preceded moribundity and mortality where these occurred, while at higher dosages hyperactivity occurred soon after initial exposure and preceded imminent death. A concentration increase from 250 to 750 μg/cm 2 , representing a tripling of dosage, spanned th 10–100% response mortality for all species at 24 hr. Air-exposure of linalool-treated papers (500 μg/cm 2 ) for up to 24 hr significantly decreased toxicity to both sexes of Z. subfasciatus . Quantitative analysis showed the only significant decrease in the amount of linalool to occur after 0.25 hr, and this did not fully correlate with the resulting decrease in efficacy against both sexes of Z. subfasciatus . The results are discussed in terms of the efficacy of using O. canum for the protection against loss due to insects in the traditional food storage systems of Rwanda.

Cuticular Hydrocarbons of Drosophila birchii and D. serrata: Identification and Role in Mate Choice in D. serrata

The cuticular hydrocarbon compositions of two sympatric species of Australian Drosophila in the montium subgroup of the melanogaster group that use cuticular hydrocarbons in mate recognition have been characterized. Drosophila birchii has 34 components in greater than trace amounts, with a carbon number range of C20 to C33. Drosophila serrata has 21 components above trace level and a carbon number range of C24 to C31. These two species share eight hydrocarbon components, with all but two of them being monoenes. For both species, the (Z)-9-monoenes are the predominant positional isomer. The hydrocarbons of D. birchii are n-alkanes, n-alkenes (Z)-5-, (Z)-7-, (Z)-9-, and (Z)-11-), low to trace levels of homologous (Z,Z)-7,11- and (Z,Z)-9,13-dienes; and trace amounts of (Z,Z)-5,9-C25:2, a major component of D. serrata. Only one methyl branched hydrocarbon was detected (2-methyl C28), and it occurred at very low levels. The hydrocarbons of D. serrata are dominated by a homologous series of (Z,Z)-5,9-dienes, and notably, are characterized by the apparent absence of n-alkanes. Homologous series of (Z)-5-, (Z)-7-, and (Z)-9-alkenes are also present in D. serrata as well as 2-methyl alkanes. Drosophila serrata females display strong directional mate choice based on male cuticular hydrocarbons and prefer D. serrata males with higher relative abundances of the 2-methyl alkanes, but lower relative abundances of (Z,Z)-5,9-C24:2 and (Z)-9-C25:1.

Comparative analysis of cuticular hydrocarbons in the Drosophila virilis species group

Abstract 1. 1. Chemical structures were determined for the cuticular alkanes, alkenes, and certain of the alkadienes for 11 D. virilis group species. 2. 2. Male-specific hydrocarbons occurred in five species: these were 9-heneicosene in D. americana and D. novamexicana , 10-heneicosene in D. virilis , 5,13- and 5,15-pentacosadienes in D. kanekoi , and 9-pentacosene in one strain of D. lummei . 3. 3. Hydrocarbon profiles of newly emerged flies always differed from mature files. 4. 4. Relationships among the species, with respect to hydrocarbon profiles, were investigated by cluster analysis.

Incorporation of labelled dietary n-alkanes into cuticular lipids of the grasshopper Melanoplus sanguinipes

Abstract Dietary hydrocarbons are incorporated into cuticular lipids of the grasshopper Melanoplus sanguinipes . Dietary secondary alcohols and ketones, however, are not incorporated into the cuticular lipids. In typical experiments from 8 to 28 per cent of the fed labeled n-alkanes are recovered in the cuticular lipids. Most of the radioactivity recovered from feeding the C 23 n-alkane and a significant amount from the C 25 was found as a secondary alcohol in the form of a wax ester. The C 29 and C 31 n-alkanes were recovered primarily unchanged as the n-alkane. Eighty-five per cent of injected acetate incorporated into the hydrocarbon fraction is in the branched hydrocarbons. These results show that the insect synthesizes its branched hydrocarbons, whereas a large part of the normal hydrocarbons can be dietary.

Cuticular lipids of adult fleshflies, Sarcophaga bullata

Abstract A major component of the adult fleshfly, Sarcophaga bullata , cuticular lipid is hydrocarbon. There are on average about 100 μg. of hydrocarbon per fly; however, only about one-third of the hydrocarbon is extractable by hexane washing the flies just after the pupal-adult ecdysis. Seven days after adult emergence the cuticular hydrocarbons are nearly all extracted by hexane washing. Some high molecular weight hydrocarbons are absent in newly emerged adults but are clearly present in low, but measurable, amounts in older adults. The major hydrocarbons are n -alkanes and monomethylalkanes with minor amounts of other branched alkanes, monoenes, and alkadienes. Every possible odd-numbered monomethylalkane was identified through the use of mass fragmentation chromatography. Even-numbered monomethylalkanes are strikingly absent.

Cuticular lipids of insects—III. The surface lipids of the aquatic and terrestrial life forms of the big stonefly, Pteronarcys californica newport

Abstract 1. 1. Surface lipid composition of the adult and naiad big stonefly differ in that a larger percentage of hydrocarbons, wax esters, free fatty acids and sterols are found on the adult, while the naiad surface lipid has more triglyceride. 2. 2. Major qualitative differences between adult and naiad surface lipids exist in the hydrocarbon fraction. Significant quantitative differences were found in all fractions except the sterol fractions. 3. 3. Results of this investigation show that the aquatic naiad form and the terrestrial adult form of the big stonefly have different surface lipid compositions. It appears that this insects surface lipid composition varies with life stage depending upon the needed water conservation mechanism.

Cuticular lipids of insects: II. Hydrocarbons of the cockroachesPeriplaneta australasiae, Periplaneta brunnea andPeriplaneta fuliginosa

The major cuticular hydrocarbons of the cockroachesPeriplaneta australasiae, Periplaneta brunnea andPeriplaneta fuliginosa aren-tricosane,cis-9-tricosene, 3-methyltricosane, 11-methyltricosane and 13-methylpentacosane. There are as yet unexplained quantitative differences between the hydrocarbon compositions of males and females ofP. australasiae andP. fuliginosa, cis-9-tricosene being a major hydrocarbon of the males only. A series of mono-methyl internally branched hydrocarbons ranging in chain length from 23 to 26 carbons with the methyl branch on the 13th carbon from one end was observed. Minor quantities of other hydrocarbons have been identified.