Odor correspondence betweenMelitta females and males of their nest parasiteNomada flavopicta K. (Hymenoptera: Apoidea)

Analyses have been performed with the help of combined capillary gas chromatography and mass spectrometry on volatile secretions emanating from the Dufour glands of femaleMelitta haemorrhoidalis andM. leporina and heads of maleNomada flavopicta, a nest parasite of theMelitta species. It was found that the cephalic secretions ofN. flavopicta males have definite similarities with the Dufour gland secretions of the two species ofMelitta. They all contain octadecyl butyrate as a major component. Monounsaturated alcohols of different chain lengths are also present in the secretions. Beside these compounds,Melitta has some other esters, notably C₁₂-, C₁₄-, C₁₆-, and C₂₀-butyrates as well as C₁₂- and C₁₆-acetates.     

Chemistry of metapleural gland secretions of three attine ants,Atta sexdens rubropilosa,Atta cephalotes,andAcromyrmex octospinosus (Hymenoptera: Formicidae)

The chemical composition of the secretions of the metapleural glands of workers and soldiers of twoAtta species,Atta sexdens rubropilosa andA. cephalotes, and workers ofAcromyrmex octospinosus, has been studied. As indicated by infrared spectrometry and confirmed by the ninhydrin test, the secretions contain chiefly proteins. Of the volatile acidic portion, which is present as ionized salts, phenylacetic acid is the major component in workers and soldiers ofA. s. rubropilosa andA. cephalotes. BothAtta species also contain 3-hydroxydecanoic acid and its homolog as minor components together with indoleacetic acid. While there are qualitative similarities in the acidic composition in the secretions ofA. s. rubropilosa andA. cephalotes, they differ quantitatively. The secretion ofAcromyrmex octospinosus contains 3-hydroxydecanoic and indoleacetic acids, but lacks phenylacetic acid. The bactericidal and fungicidal actions of the three major substances have been confirmed.     

Responses by canids to scent gland secretions of the western diamondback rattlesnake (Crotalus atrox)

Many snakes discharge malodorous fluids from paired scent glands in the base of the tail when they are disturbed. A number of authors suggest that these secretions repel predators. Scent gland secretions of the western diamondback rattlesnake (Crotalus atrox), or dichloromethane extracts of them, were presented to coyotes (Canis latrans) in three field tests, and to domestic dogs (Canis familiaris) in two kennel tests, to determine whether responses of possible benefit to snakes are elicited. Free-ranging coyotes visited and rubbed and rolled at stations containing scent gland secretions in perforated plastic capsules more frequently than at those containing untreated or dichloromethane-treated capsules. Responses to dichloromethane extracts of scent gland secretions subjected to rotary evaporation were not significantly different from those to dichloromethane. Pure and mixed breeds of dogs presented with filter papers treated with dichloromethane or a dichloromethane extract of scent gland secretions mouthed (licked, bit, or ate) secretion-treated papers more frequently. Staffordshire terriers presented with filter papers treated with dichloromethane or dichloromethane extracts of snake scent gland and alligator (Alligator mississippiensis) paracloacal gland secretions exhibited urination postures to snake secretion-treated papers more frequently than to dichloromethane-treated papers, but responses to snake- and alligator-treated papers did not differ significantly. There was no indication that canids are repelled by scent gland secretions.     

Responses by domestic cats (Felis catus) to snake scent gland secretions

The scent gland secretions of snakes are thought to repel predators, but few predator species have been tested for responses to these exudates. Domestic cats (Felis catus) were tested for responses to scent gland secretions of the gray rat snake (Elaphe obsoleta), or to choloroform extracts of them, applied to filter paper or food. More cats salivated or rubbed on filter papers treated with scent gland secretions than on control papers. Scent gland exudates elicited rubbing and pawing in cats more frequently than did chemicals from a shed snake skin. Cats offered food pieces treated either with water or with scent gland secretions ate fewer of the latter; this result is consistent with the hypothesis that scent gland secretions deter feeding.     

Pharmacophagy of Methyl Eugenol by Males Enhances Sexual Selection of <Emphasis Type="Italic">Bactrocera carambolae</Emphasis>

After pharmacophagy of methyl eugenol (ME), males of Bactrocera carambolae (Diptera: Tephritidae) produced (E)-coniferyl alcohol (CF) along with its endogenously synthesized pheromonal compounds. CF was shown to be released into the air by the ME-fed males only during the courtship period at dusk and attracted significantly more males and females than the ME-deprived males in wind tunnel assays. However, earlier onset of sexual attraction and a higher mating success were observed only in the wind tunnel and field cage assays on the third day posttreatment of ME. Field cage observations on the male-to-male interaction indicated that the ME-deprived males did not exhibit aggregation behavior, but that ME feeding promoted aggregation behavior in B. carambolae. Field cage observations revealed that the ME-deprived males were not only attracted to the ME-fed males, but also appeared to feed on their anal secretions. The secretions were subsequently confirmed to contain CF along with endogenously produced pheromonal compounds. Results obtained for B. carambolae were compared to those previously obtained from its sibling species, Bactrocera dorsalis, and are discussed in light of species advancement in fruit fly–plant relationships.     

Behavioral correlates for minor volatile compounds from stink bugs (Heteroptera: Pentatomidae)

Many terrestrial Heteroptera have small, but functional, dorsal abdominal glands as adults. The chemistry, and associated intra- and inter-specific behavior, for dorsal abdominal gland secretions from 10 species representing four genera of Pentatomidae was investigated. Eighteen volatile compounds were identified in species-specific blends from the dorsal abdominal gland secretions ofEuschistus, Acrosternum, andEurydema adults, including aliphatic, aromatic, and terpenoid constituents. Evidence from bioassays is presented that parasitic Tachinidae (Diptera) and Scelionidae (Hymenoptera) use these secretions as kairomones. A field experiment was performed to test the hypothesis that minor volatiles increase the specificity of the main pheromone component from NearcticEuschistus species, methyl (2E,4Z)-decadienoate. However, significantly fewer individuals ofE. tristigmus were captured in traps baited with the complete blend for this species than in traps baited with methyl (2E,4Z)-decadienoate alone. Thus, at the concentrations tested, these kinds of dorsal abdominal gland secretions may be epideictic, promoting spacing in the natural habitat.     

Do Caterpillars Secrete “Oral Secretions”?

The oral secretions or regurgitant of caterpillars contain potent elicitors of plant induced responses. These elicitors are recognized by host plants to differentiate between simple mechanical injury and the presence of herbivores. In some cases, this level of recognition is highly specific. Despite the in-depth chemical characterization of these elicitors, little is known about the amounts delivered in regurgitant during feeding. In this study, we use a fluorescent dye to label regurgitant in order to visualize caterpillar regurgitation during feeding. The procedure is highly sensitive and allows us to visualize nanoliter amounts of regurgitant. We examined the propensity of larval Helicoverpa zea, Heliothis virescens, Spodoptera exigua, Spodoptera frugiperda, and Manduca sexta to regurgitate on various host plants. These species were selected because they have been among the most intensely studied in terms of elicitors. Our results indicate that most larvae did not regurgitate following a brief feeding bout (∼10 min) during which they ate ca. 0.40 cm² of leaf. When larvae did regurgitate, it was typically less than 10 nl. This is several orders of magnitude less than is typically used in most studies on oral secretions. The frequency of regurgitation appears to vary depending upon the host plant. Larval H. zea are less likely to regurgitate when feeding on tomato leaves compared to corn mid-whorl tissue. Our results have importance in understanding the role of oral secretions in plant recognition of herbivory. Because caterpillars did not routinely regurgitate during feeding, it is likely that they avoid the elicitation of some plant defensive responses during most feeding bouts.     

The Mandibular Gland Secretions of the Leaf-Cutting Ants Atta sexdens sexdens and Atta opaciceps Exhibit Intercaste and Intercolony Variations

The mandibular gland secretions of worker castes from wild colonies of the leaf-cutting ants Atta sexdens sexdens and Atta opaciceps were analyzed quantitatively by gas chromatography–mass spectrometry. The secretions comprised a complex mixture of volatile, mainly oxygenated compounds, and their profiles exhibited considerable qualitative and quantitative variations among species and castes. The known alarm pheromone 4-methyl-3-heptanone was common to both species. The elevated relative proportions of this ketone found in the secretions of gardeners and generalists suggest that such castes are primarily responsible for the production and release of the alarm pheromone. Quantitative variations (but no qualitative differences) in the profiles of secretions of soldiers from different colonies of A. sexdens sexdens were detected, supporting the view that intraspecific colony recognition is mediated through mandibular gland secretions. Subsequent laboratory assays showed that, among the compounds identified by GC–MS, 4-methyl-3-heptanone elicited a strong alarm response in workers of A. sexdens sexdens and A. opaciceps.     

Chemical composition of precloacal secretions of two Liolaemus fabiani populations: are they different?

The chemical composition of secretions of precloacal pores from two populations of the lizard Liolaemus fabiani (Puilar and Punta-Brava) were compared. This is an endemic species from the Atacama Salt Flat (26^°46'S 68^°14'W; 2400 m) in northern Chile, restricted to the internal lakes of the salt flat. Interpopulational differences in the chemical composition of the secretions were expected considering that populations have genetic differences and are subject to different thermal conditions. By using GC-MS, a total of 44 compounds were found belonging to three categories: n-alkanes, long-chain carboxylic acids, and steroids. Six compounds were found in all the individuals studied: tetradecanoic, pentadecanoic, hexadecanoic, hexadecenoic, octadecanoic, and octadecenoic acids. The secretions of both populations had similar types and proportions of the different compounds, except for cholesterol and hexanoic acid, which were more abundant in the Puilar population. These differences can be ascribed to the different environmental conditions to which populations are subjected. The adaptive meaning of these differences is discussed.     

Chemical defense secretions of some species of Malaysian rhinotermitidae (Isoptera,Rhinotermitidae)

The defense secretions of the soldiers of the Malaysian rhinotermitid,Parrhinotermes aequalis (Havilandi) andP. pygmaeus (John),Termitogeton planus (Havilandi) andSchedorhinotermes malaccensis (Holmgren) consist mainly of vinyl ketones, whereas that ofProrhinotermes flavus (Bugnion & Popoff) gives (E)-1-nitropentadecene. The chemistry of the defense secretions ofParrhinotermes andTermitogeton is documented and based on their chemical relationships;Termitogeton shows a closer affinity to the Rhinotermitinae than Heterotermitinae.     

Antimicrobial Activity of Exocrine Glandular Secretion of Chrysomela Larvae

The exocrine glandular secretions of leaf beetle larvae of the taxon Chrysomela are well-known defensive devices used against some generalist predators. Salicylaldehyde is the major repellent component of secretions emitted by larvae of Chrysomela vigintipunctata and C. lapponica, which feed on salicin-rich Salicaceae. In this study, we examined whether salicylaldehyde is also active against the entomopathogenic fungus Metarhizium anisopliae. The germination and growth of this fungus was strongly inhibited when salicylaldehyde was applied directly onto the blastospores. The salicylaldehyde concentration of the larval secretions of the tested willow feeding Chrysomela larvae was much higher than the one necessary to display this antifungal activity. Additionally, salicylaldehyde was shown to reduce germination and growth of M. anisopliae via the gas phase over a distance of 45 mm. Further studies on the antimicrobial activity of the salicylaldehyde-containing secretions of Chrysomela larvae revealed that they act nonspecifically against prokaryotic (Escherichia coli) and eukaryotic cells (Saccharomyces cerevisiae and Trichoplusia ni). All antimicrobial and cytotoxic effects detected proved to be due to salicylaldehyde. The larval secretions of the birch-feeding allospecies of C. lapponica, that do not contain salicylaldehyde, but mainly carboxylic acids and their esters, showed no detectable effects on bacteria or fungi and no cytotoxic effects against insect cells. The results are discussed with respect to their ecological relevance.     

Intra- and interindividual variation in flank gland secretions of free-ranging shrewsCrocidura russula

Individual differences in flank gland secretions were examined among males of the monogamous shrewCrocidura russula during the breeding and nonbreeding seasons. Gas chromatography was used to measure intra- and interindividual variation of flank gland secretions of free-ranging shrews from different populations. The number of compounds detected by gas Chromatographic analyses was correlated with body mass, flank gland size, and the presence of blood parasites in individual shrews. Very few compounds were detected from the flank gland area of juvenile males. After they reached sexual maturity, however, the number of compounds detected from the flank gland secretions increased significantly. At the beginning of the reproductive season 48 different compounds were detected from male flank gland secretions. In the middle of the breeding season 70 compounds were detected, while only 11 compounds were detected during the nonbreeding season. Few compounds were common to all males. There were more volatile compounds in the flank gland secretions of males in the beginning of the breeding season than later in the breeding season. Males from the same population had fewer differences in the elution profile of compounds than males from different populations indicating that individuals from a distinct population have similar elution profiles of compounds and that each population has its own type of elution profile. No correlations were found between the number of compounds detected by gas chromatography for each male and the male's body mass or flank gland size. Blood parasites (trypanosomes,Trypanosoma crocidurae) were found in only three of 30 males investigated.     

Repellency to two-spotted spider mite,Tetranychus urticae Koch,as related to leaf surface chemistry ofLycopersicon hirsutum accessions

Bioassays employingTetranychus urticae Koch were used to examine repellency of leaves and trichome secretions of one cultivar of tomato,Lycopersicon esculentum, and 11 accessions ofL. hirsutum consisting of seven accessions ofL. hirsutum f.typicum and four accessions ofL. hirsutum f.glabratum. Leaves of f.typicum were more repellent to mites than were those of f.glabratum orL. esculentum. Removal of trichomes and their secretions by wiping leaves of f.typicum accessions with 95% ethanol rendered them less repellent, indicating that trichomes or their secretions were potentially responsible for repellency. Gas and thin-layer chromatography of leaflet washes obtained by steeping leaflets in hexane indicated that the chemical composition of the washes differed among accessions. The main difference between botanical forms was the presence in leaflet washes from f.typicum accessions of compounds eluting late on the gas Chromatograph and migrating further on reverse-phase thin-layer chromatography; compounds having these characteristics were absent in washes of f.glabratum andL. esculentum. The compositions of secretions taken directly from type I, type IV, and type VI trichomes were similar to that of the leaflet wash obtained from the same f.typicum plant, indicating that leaflet washes contained mainly compounds of trichomal origin. Leaflet washes from f.typicum plants were generally more repellent toT. urticae than were washes from f.glabratum when tested by choice and nonchoice bioassays. Taken together, the data indicate that trichome secretions of f.typicum are likely responsible for potent repellency to two-spotted spider mites observed in this taxon; the likely active compounds are sesquiterpene acids or other polar constituents of trichome secretions.     

Chemistry of fruit flies: Nature of glandular secretion and volatile emission ofBactrocera (bactrocera) cacuminatus (Héring)

The major component of the rectal glandular extract and volatile emission of maleBactrocera cacuminatus is racemic 1,7-dioxaspiro[5.5]undecane. l-Hydroxy-5-nonanone as its open chain form, together with 6-n-butyl-3,4-dihydro-2H-pyran are minor components. 1,7-Dioxaspiro[5.5]undecan-4-ol is present at a low level and is shown to be exclusively the diastereomer with an equatorial hydroxy group by comparison with synthesized samples of both epimers. Examination of the trifiuoroacetate by chiral gas chromatography has established the (4S,6S) stereochemistry (ca. 80% ee). The presence of 1,7-dioxaspiro[5.5]undecan-3-ol, or its isomerization product, 1,6-dioxaspiro[4.5]decan-2-ylmethanol, could not be confirmed. Trapping of the volatiles released by sexually mature male flies at dusk revealed that a number of the glandular components described above are released at mating time. Reexamination of the glandular secretion of sexually mature female olive flies (B. oleae) has failed to confirm the presence of any 1,7-dioxaspiro[5.5]undecanols, with the only volatile component (other than fatty acids) being 1,7-dioxaspiro[5.5]undecane.     

Chemical composition of precloacal secretions of Liolaemus lizards

Interspecific chemical variation of precloacal pore secretions of Liolaemus lizards was characterized in 20 species, and intraspecific chemical variation was characterized using nine individuals of L. bellii. The latitude (Chile, 18° to 33° South latitude) and altitude (100 to 4350 m.a.s.l.) of the capture sites were recorded, as well as the number of precloacal pores of each lizard. Secretions were analyzed by GC-MS. A total of 49 compounds were found distributed among the 20 species of Liolaemus. Different chemical patterns occurred at intra- and interspecific levels. Compounds belonged to three main families: n-alkanes, long chain carboxylic acids, and steroids. Cholesterol and five carboxylic acids (tetradecanoic, hexadecanoic, hexadecenoic, octadecanoic, and Z-9-octadecenoic) appeared in all species. The number of precloacal pores correlated positively with altitude and negatively with latitude, suggesting that lizards produce more secretions under harsh environments.     

Mandibular gland secretions of two parasitoid wasps (Hymenoptera: Ichneumonidae)

Males ofRhyssa persuasoria andMegarhyssa nortoni nortoni exhibit marked aggregation behavior prior to and during the emergence of females from host trees, and this has been linked with the secretion of an odorous liquid from the mandibular glands. The volatile components of these secretions were examined by combined gas chromatography-mass spectrometry. While both species contained 6-methylhept-5-en-2-one,M. nortoni nortoni was characterized by a series of alkyl spiroacetals andR. persuasoria contained 3-hydroxy-3-methylbutan-2-one. The same spiroacetals have previously been isolated from the mandibular glands of other Hymenoptera and have been directly associated with aggregation behavior in some species. The chemical and behavioral aspects of the two species are discussed.     

Protected by Fumigants: Beetle Perfumes in Antimicrobial Defense

Beetles share with other eukaryotes an innate immune system that mediates endogenous defense against pathogens. In addition, larvae of some taxa produce fluid exocrine secretions that contain antimicrobial compounds. In this paper, we provide evidence that larvae of the brassy willow leaf beetle Phratora vitellinae constitutively release volatile glandular secretions that combat pathogens in their microenvironment. We identified salicylaldehyde as the major component of their enveloping perfume cloud, which is emitted by furrow-shaped openings of larval glandular reservoirs and which inhibits in vitro the growth of the bacterial entomopathogen Bacillus thuringiensis. The suggested role of salicylaldehyde as a fumigant in exogenous antimicrobial defense was confirmed in vivo by its removal from glandular reservoirs. This resulted in an enhanced susceptibility of the larvae to infection with the fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae. Consequently, we established the hypothesis that antimicrobial defense in beetles can be expanded beyond innate immunity to include external disinfection of their microenvironment, and we report for the first time the contribution of fumigants to antimicrobial defense in animals.     

Volatile secretions of old world army antAenictus rotundatus and chemotaxonomic implications of army ant dufour gland chemistry

The Dufour glands ofAenictus rotundatus contain a complex mixture of terpenoids with geranylgeraniol comprising over 50% of the secretion. Some novel compounds have been tentatively identified as higher homologs of 1,3,3-trimethyl-2,7-dioxabicyclo[2,2,1]heptane based on GC-MS data. The Dufour gland secretion ofA. rotundatus is more similar in composition to the secretions of members of the subfamily Ecitoninae than to its closer relatives from the tribe Dorylini, a result that further complicates studies on the phylogeny of army ants. The mandibular glands ofA. rotundatus contain a mixture of 4-methyl-3-heptanone and limonene in trace amounts, and the well-developed postpygidial glands contain methyl anthranilate only.     

Dermal gland secretions of tropical bont tick,Amblyomma variegatum (Acarina: Ixodidae): Biological activity on predators and pathogens

When they are mechanically disturbed, all instars of the tropical bont tickAmblyomma variegatum exude droplets of a liquid on the dorsal, lateral, and ventral cuticle. These spread out and quickly evaporate. In this study, the possible role of these secretions was investigated in relation to predators and pathogens. In laboratory bioassays, it was demonstrated that the secretions from engorged larvae, nymphs, and females have an antibiotic activity against the bacteria speciesBacillus thuringiensis andSerratia marcescens, combined with a repellent effect on a potential predator, the fire-antSolenopsis geminata.     

Dynamics of Algal Secondary Metabolites in Two Species of Sea Hare

The function of acquired algal secondary metabolites in sea hares is the subject of debate, in part because the dynamics/processing of metabolites by sea hares is poorly understood. This study investigates the dynamics of red algal secondary metabolites in two sea hares, Aplysia parvula and Aplysia dactylomela. Secondary metabolite levels were quantified for the dietary red algae Laurencia obtusa and Delisea pulchra and for sea hares collected from these seaweeds in the field. The patterns and dynamics of algal secondary metabolites were further investigated in the laboratory by quantitative analysis of secondary metabolites in sea hares grown on diets of L. obtusa, D. pulchra, or the green alga Ulva sp. Sea hares accumulated the most abundant metabolites from each red alga, the terpene palisadin A from L. obtusa, and the halogenated furanone 3 from D. pulchra, and stored a greater proportion of these metabolites than other algal metabolites. A. parvula accumulated D. pulchra metabolites at much higher levels than L. obtusa metabolites. A. dactylomela accumulated similar concentrations of L. obtusa metabolites to A. parvula. The loss of L. obtusa metabolites by A. dactylomela matched that expected for dilution of metabolites via growth of the sea hares. However, the loss of L. obtusa metabolites by A. parvula was faster than predicted for growth alone, suggesting that metabolites were actively metabolized or excreted. Data for the loss of D. pulchra metabolites by A. parvula was equivocal. The secretions of A. parvula fed D. pulchra or L. obtusa were analyzed for the presence of algal secondary metabolites to investigate one possible path of excretion. L. obtusa secondary metabolites were detected in the mucous and opaline secretions of A. parvula, but D. pulchra metabolites were not detected in any secretions. The deployment of L. obtusa secondary metabolites in secretions by A. parvula may explain the more rapid rate of loss of these compounds and is consistent with a possible defensive role for acquired metabolites.