An olfactory recognition system in the ferret Mustela furo L. (Carnivora: Mustelidae)

This study demonstrates that ferrets can use variations in odours from anal sac secretions as a communication system. Odour preference tests showed that ferrets can discriminate between male and female ferret anal sac odours, between strange and familiar, familiar and their own, and fresh and 1-day-old odours. They did not discriminate between fresh and 2-h-old odours, nor did male ferrets discriminate between the odours of oestrous and anoestrous females. Ferrets were more attracted to the odours of the opposite sex than to those of their own sex. When faced by an opponent, male ferrets were more aggressive in the presence of their own rather than their opponent's odour, and less aggressive with their opponent's odour than with that of a known, dominant animal's odour. These results are consistent with both a sex attraction role and a territorial defence role for anal sac odours. A scent-matching mechanism for territorial defence is supported, although a neighbour-neighbour recognition/avoidance mechanism cannot be rejected. Gas chromatography revealed sexually and individually distinct profiles of volatile compounds in anal sac extracts, but no consistent seasonal trends. Females had high concentrations of 2,3-dimethylthietane and/or 3,4-dimethyl-1,2-dithiolane. Males usually had high concentrations of indole. 2-Propylthietane was an important constituent in most individuals. These differences in concentration were significant and could provide an olfactory recognition system of sex and individual identity.     

Olfactory discrimination of anal sac secretions in the domestic cat and the chemical profiles of the volatile compounds

Scent emitted from anal sac secretions provides important signals for most Carnivora. Their secretions emit a variety of volatile compounds, some of which function as chemical signals with information about the scent owners. The domestic cat has a pair of anal sac glands to secrete a pungent liquid. Their anal sac secretions may give information about sex, reproductive state, and recognition of individuals. However, little is known about the volatile compounds emitted from anal sac secretions and their biological functions in cats. In this study, we examined the volatile chemical profiles of anal sac secretions in cats and their olfactory ability to discriminate intraspecific anal sac secretions. Analysis with gas chromatography–mass spectrometry showed that the major volatile compounds were short-chain free fatty acids, whose contents varied among individuals, as well as other carnivores. There was no sex difference in the volatile profiles. In temporal analyses of individual anal sac secretions performed 2 months apart, the profiles were highly conserved within individuals. Habituation–dishabituation tests showed that cats can distinguish individual differences in the odor of anal sac secretions. These results suggest that cats utilize short-chain free fatty acids emitted from anal sac secretions to obtain scent information for individual recognition rather than species or sex recognition.     

Pheromones exchanged during mating: a mechanism for mate assessment in Drosophila

Many insect species are sexually dimorphic for volatile compounds associated with the cuticle. In these species, females may acquire volatile compounds from males through direct contact with males during mating. In some cases, these compounds function as antiaphrodisiacs, which inhibit subsequent male precopulatory behaviour. During mating, males may also acquire female compounds, which normally stimulate males to court. Contact during mating thus results in a mutual exchange of compounds usually found primarily, or exclusively, on one or the other sex. Drosophila melanogaster is a sexually dimorphic dipteran species in which predominant male and female cuticular hydrocarbons are mutually exchanged during mating. Using synthetic compounds, the effect of this exchange on the post-mating sexual attractiveness of both males and females was tested. The sex-predominant hydrocarbons acquired during mating decreased the attractiveness of both males and females to members of the other sex. Mated females are courted less actively than virgins, and are usually unwilling to re-mate. Similarly, recently mated males are less attractive to females than virgin males are, and may be less fertile. Thus, cuticular hydrocarbons acquired by the other sex during mating could allow both males and females to assess the immediate reproductive potential of prospective mates.     

Putative chemosignals of the ferret (Mustela furo) associated with individual and gender recognition

Quantitative stir bar sorptive extraction methods, both in the aqueous and headspace modes, followed by thermal desorption gas chromatography-mass spectrometry were used to investigate individual variations in the volatile components of male and female ferret (Mustela furo) urine. The urinary profiles were further compared with volatile profiles of anal gland secretions of breeding male and female ferrets. Thirty volatile compounds were quantified in male and female urine. Among them, 2-methylquinoline was unique to male urine. Four ketones (4-heptanone, 2-heptanone, o-aminoacetophenone, and a dimethoxyacetophenone) and several nitrogen compounds (e.g., 2,5-dimethylpyrazine, quinoline, 4-methylquinazoline) and low levels of three unidentified nonsulfur compounds were significantly more abundant in males than in females. Quantitative comparison of 30 volatile urinary compounds showed several statistically significant differences between the sexes and individuals of the same sex. These findings suggest that ferrets may use urine marking for sex and individual recognitions. Ten of the 26 compounds identified in anal gland secretions from females and males were also found in urine. However, most of the major compounds (thietanes, dithiolanes, and indole) in anal glands were not present in urine. This suggests that urine may convey specific signals that differ from those of anal glands. Additionally, 10 volatiles (two aldehydes, five ketones, benzothiazole, 2-methylquinoline, and 4-methylquinazoline), not previously identified, were found in ferret anal gland secretions. Among the new compounds, o-aminoacetophenone was found only in males, while only traces of this compound were found in females. Similar results were previously obtained in anal glands of three other Mustela species. These findings provide new information about the constituents of urine and volatile components of anal gland secretions in ferrets.     

Host odours enhance the responses of adult Rhyzopertha dominica to male-produced aggregation pheromone

The behavioural responses of adult male and female Rhyzopertha dominica (Coleoptera, Bostrichidae) to blends of host volatiles and male-produced aggregation pheromone were observed in a four-arm airflow olfactometer. The odour sources used were five pheromone-releasing males each on a single maize grain (lower maize-volatiles blend), five pheromone-releasing males on 500 g of maize (higher maize-volatiles blend) or the host volatiles emanating from 500g of maize (maize volatiles alone). Multiple-choice tests, in which volatiles from all three odour sources were presented in the exposure chamber at the same time, were used to study odour preferences of the males and females. Both sexes showed strongest attraction to the higher maize volatile blend but there were significant sex differences in response to the odour sources. Males spent significantly more time than females in the zone with only maize volatiles, and females spent significantly more time in the higher maize-volatiles zone. However, when odour sources were offered singly, females gave numerically greater responses than males to all sources although this difference was statistically significant for only the lower maize-volatiles blend. As males are more attracted than females to host odours alone it is suggested that they may be more highly adapted to seek out new hosts while females are more inclined to locate a food source by following the pheromone signals produced by males. However, both sexes responded most strongly to the odour source comprising aggregation pheromone with the higher proportion of maize volatiles.     

Olfactory Discrimination of Individual Scents in the Subterranean Rodent Ctenomys talarum (tuco-tuco)

Biological odours that convey cues regarding individual identity can provide valuable information mediating many aspects of mammalian social relationships such us dominance hierarchies, group memberships, territorial and mating activities. The ability of the subterranean rodent, tuco‐tuco (Ctenomys talarum), to discriminate between soiled shavings, urine and faeces from different individuals was investigated using the habituation–discrimination paradigm. Discrimination by both males and females was tested using scents obtained from same‐ and opposite‐sex individuals. Each test subject was habituated for three consecutive days to odour samples from the same individual; on the fourth day a scent from a novel individual was provided. For all odour sources, animals spent significantly less time investigating the habituation scent over successive trials, indicating that animals perceived the stimulus as familiar. For all stimuli, test subjects spent more time investigating the novel odour, rather than the familiar one. Animals spent more time investigating soiled shavings than urine or faeces. Both males and females discriminated novel from familiar odours in shavings and urine regardless of the gender of the odour donors. In contrast, test animals discriminated between familiar and novel odours in feces only when the fecal donors were of different sex from subjects. Possible territorial and reproductive functions of individual scent discrimination are discussed.     

Evidence for a female‐produced,long range pheromone of Anoplophora glabripennis (Coleoptera: Cerambycidae)

Abstract Volatiles from female Asian longhorned beetle (ALB), Anoplophora glabripennis, were evaluated as candidate sex pheromone components. Previous studies on ALB have revealed several antennally active compounds from virgin females; however the origins and activity of these compounds were not apparent and require further investigation. We tested the hypothesis that one or more of the ALB contact sex pheromones is a precursor that undergoes abiotic oxidation to yield volatile pheromone components, and evaluated the activity of these compounds using laboratory and field bioassays. Gas chromatography coupled electroantennography detection (GC‐EAD) analysis indicated the presence of three antennally active aldehydes (heptanal, nonanal, and hexadecanal) in female cuticular extracts exposed to ozone or UV and visible light. In laboratory bioassays using a Y‐tube olfactometer, males were preferentially attracted to ozonized female body washes over crude body washes. Similarly, synthetic formulations of these compounds were preferred over controls in the olfactometer. Field trapping experiments conducted from 2006 to 2008 in Ningxia, China showed that synthetic lures of the three aldehydes formulated in a ratio simulating that of virgin females attracted more beetles compared to controls, and that combinations of these aldehydes, linalool oxide, and host kairomones captured more beetles than controls, and captured significantly more males.     

The Coolidge effect, individual recognition and selection for distinctive cuticular signatures in a burying beetle

The ability to recognize individuals is an important aspect of social interactions, but it can also be useful to avoid repeated matings with the same individual. The Coolidge effect is the progressive decline in a male's propensity to mate with the same female combined with a heightened sexual interest in new females. Although males that recognize previous partners and show a preference for novel females should have a selective advantage as they can distribute sperm evenly among the females they encounter, there are few invertebrate examples of the Coolidge effect. Here we present evidence for this effect in the burying beetle Nicrophorus vespilloides and examine the mechanism underlying the discrimination between familiar and novel mates. Burying beetles feed and reproduce on vertebrate carcasses, where they regularly encounter conspecifics. Males showed greater sexual interest in novel females (virgin or mated) than in females they had inseminated before. The application of identical cuticular extracts allowed us to experimentally create females with similar odours, and male responses to such females demonstrated that they use female cuticular patterns for discrimination. The chemical analysis of the cuticular profile revealed greater inter-individual variation in female than in male cuticular patterns, which might be due to greater selection on females to signal their individual identity.     

Benzoquinone levels as a function of age and gender of the red flour beetle, Tribolium castaneum

Liquid chromatography with both photodiode array and electrochemical detection was used to analyze as a function of age and gender the levels of two ρ-quinones, methyl-1,4-benzoquinone (MBQ) and ethyl-1,4-benzoquinone (EBQ), which are found in defensive secretions of the red flour beetle, Tribolium castaneum. We developed a method to simultaneously analyze quinones and hydroquinones excreted from or in homogenates of individual beetles. The major components present in beetle extracts were the benzoquinones and not free or conjugated forms of the hydroquinones. Greater than 95% of the quinone/hydroquinone mixture in extracts was present in the oxidized form. Because of their lability, however, the quinones were quantified indirectly as their hydroquinone derivatives after extraction in dilute acid supplemented with ascorbic acid as a reducing agent. Comparisons of whole body rinses and homogenates revealed that rinses recovered only up to 60% of the total quinones that were extracted after homogenization. The levels recovered also depended on the age and sex of the individual beetles sampled. ρ-Benzoquinones in both male and female beetles increased after adult eclosion and cuticle sclerotization for 40–50 days and then remained at their highest levels (15–21 μg MBQ and 22–32 μg EBQ per beetle) through 80 days posteclosion. Virgin females that were collected 40–80 days after eclosion contained approximately 40% more of these compounds than males of the same age. The build-up of ρ-benzoquinones subsequent to cuticle sclerotization apparently reflects the need for an adequate cuticular barrier for self-protection from these defensive compounds.     

Attraction of male winterform pear psylla to female-produced volatiles and to female extracts and evidence of male–male repellency

Pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae), is a major pest of commercial pears in North America and Europe. Olfactometer trials have shown that males of both the summer and winter morphotype are attracted to female-infested host material. Additional work with the summer morphotype has shown that males are attracted to females even in the absence of the host plant, which is evidence that female C. pyricola produce a volatile sex attractant. Here, we describe similar results with the winterform, confirming for this morphotype that the female psylla rather than the infested host material is the source of the attractant. Male winterforms displayed attraction to odors from live females in the absence of the host plant, freshly killed females, and female whole body extracts. The female whole body extracts were at least as attractive as a comparable number of live females, suggesting that we were successful at extracting the components of the attractant with this procedure. All previous olfactometer trials with C. pyricola used the insect as the attractant source; the current study is the first to demonstrate that volatile chemicals isolated from the female insect were attractive to male conspecifics. Winterform males were also assayed to odors produced by conspecific males. We found that male psylla avoided volatile odors from live males, freshly killed males, or whole body extracts of males. To our knowledge, these results are the first indication that males of any member of the Psyllidae avoid odors associated with conspecific males.     

Recognition of social parasites as nest-mates: adoption of colony-specific host cuticular odours by the paper wasp parasite Polistes sulcifer.

Colonies of the polistine wasp Polistes dominulus are parasitized by the permanent worker-less social parasite Polistes sulcifer. After usurpation of the host colony, parasite females are characterized by a change in the relative proportions of their cuticular hydrocarbons to match those of the host species. In this paper we present evidence from field data and laboratory experiments that P. sulcifer females adopt a colony-specific host odour that facilitates their acceptance by host females of the usurped colony. Presentation experiments demonstrate that parasite females are recognized as foreign individuals by workers of other parasitized nests. We show that the modification of parasite cuticular compounds is sufficient for this recognition. This provides evidence that, after invasion, P. sulcifer queens do not require appeasement or propaganda substances for their acceptance by host colonies. Furthermore, multivariate discriminant analysis of the cuticular hydrocarbon proportions of the parasites after usurpation assigns the parasites together with P. dominulus females of their own host colony. To the authors' knowledge, this is the first confirmation that social parasites adopt colony-specific host odours.     

Sex attraction in Bactericera cockerelli (Hemiptera: Triozidae)

The potato psyllid, Bactericera (=Paratrioza) cockerelli (?ulc) (Hemiptera: Triozidae), is a major pest of potato. We examined the role of chemical signals in sex attraction, assessing male and female response to male- and female-produced volatile chemicals. In laboratory olfactometer assays, potato psyllid males were attracted to odorants emitted from live females and from solvent extract of females. These results indicate that the female-produced chemicals responsible for attracting males may be isolated by means of insect extractions. Males were also attracted to volatile chemicals from males and extracts of males, providing the first example of male-male attraction in the Psylloidea. Males exposed simultaneously to odorants from conspecific females and males were preferentially attracted to female odorants, suggesting the presence of a female-specific sex attractant for males. Potato psyllid females avoided volatile chemicals emitted by females and extracts of females and by volatile chemicals emitted by males and extracts of males. Possible explanations for avoidance of conspecifics by females are discussed. This study is the first report of male attraction to volatile chemicals emitted by females and female extracts in the Triozidae and more specifically in the potato psyllid.     

The role of cuticular hydrocarbons in mating and conspecific recognition in the closely related longicorn beetles Pidonia grallatrix and P. takechii

The role of cuticular chemicals in mating behavior and their chemical components were studied in two sympatric flower-visiting longicorn beetles, Pidonia grallatrix and P. takechii. Mating experiments revealed that female cuticular chemicals elicit male mating behavior and that males can discriminate between conspecific and heterospecific females on the basis of contact chemicals. GC-MS analyses of whole-body extracts in the two species and both sexes determined that extracts contained a series of hydrocarbons including n-alkanes, n-alkenes, and methylalkanes. The relative abundance of some hydrocarbons differed between species and sexes, and canonical discriminant analysis showed discrimination of species and sex could be made unambiguously with several compounds. These results imply that the difference in cuticular hydrocarbons facilitates the premating isolation of sympatric Pidonia species.     

Temporal and sexual variation of leaf-produced pollinator-attracting odours in the dwarf palm

Information on intra-specific variation in pollinator-attracting floral traits provides clues to selective pressures imposed by pollinators. However, these traits also reflect constraints related to floral phenology or morphology. The specific weevil pollinator Derelomus chamaeropsis of the dioecious Mediterranean dwarf palm Chamaerops humilis is attracted by volatile compounds that leaves, and not flowers, release during anthesis. Production of these olfactory cues is thus probably not constrained by any other floral function. This provides the opportunity to study variation of a floral trait that is not produced by a floral organ. We studied volatile compounds emitted by leaves of 12 individual C. humilis over the whole flowering season. The quantity of volatile compounds emitted by leaves reached a maximum when plants required pollinator visits. The relationship between odour emission and floral phenology was slightly different between male and female plants, probably reflecting differences in the exact time at which females and males benefit from pollinator visitation. Male plants produced higher quantities of volatile compounds than females. Odour composition was highly variable among individuals but did not differ between male and female plants. In this system, female C. humilis are pollinated by deceit and pollinators should be selected to avoid visiting them. The absence of sexual difference in blend composition may thus prevent pollinators from discriminating between male and female plants.An erratum to this article can be found at     

Female marmoset monkeys (Callithrix jacchus) can be identified from the chemical composition of their scent marks.

The present study analyzed 42 organic solvent extracts of scent mark pools from five dominant female common marmosets by gas chromatography (GC) and combined GC and mass spectrometry. We determined whether there were qualitative or quantitative differences between the chemical composition of scent marks from individual females. Gas chromatography and mass spectral analysis detected the same 162 chemicals in 86% (36/42) of scent mark pools from five dominant females. This near identical chemical composition of scent marks suggested there were few, if any, qualitative differences between the chemical composition of scent marks from individual females. Instead, quantitative differences in scent may provide the key factor distinguishing individual females. Using the relative concentration of highly volatile chemicals detected by GC in scent marks, linear discriminant analysis classified scent mark pools to their correct donor approximately 91% of the time. Such highly reliable statistical matching of scent to donor suggested that each individual female common marmoset has a unique ratio of highly volatile chemicals in their scent marks which may permit individual identification of females from odors in their scent alone.     

Age-related changes in the surface pheromones of the wasp Mischocyttarus consimilis (Hymenoptera: Vespidae)

One of the most important attributes that allowed the evolution and maintenance of sociality in insects is their ability to distinguish members of their own colonies. The capacity for individual recognition in social insects is mediated by chemical signals that are acquired soon after the adult emerges, and vary according to the tasks performed by individuals in their colonies. We determined the time when adults of the wasp Mischocyttarus consimilis acquire the chemical signature of their colonies, as well as the variation in the cuticular hydrocarbon profiles of the exoskeleton of individuals, according to their functions in the colony. The method used was Fourier transform infrared photoacoustic spectroscopy directly on the gaster of each individual. Young wasps take three to four days to acquire the colony's chemical signature, with a small change on the fifth day, when the cuticular hydrocarbon profile of the workers is more similar to that of the queens than that of the males, probably because they are of the same sex, but primarily because of the similarity of tasks executed by these two groups of females in the colonies.     

Wearing a raincoat: exocrine secretions contain anti-wetting agents in the oribatid mite, <Emphasis Type="Italic">Liacarus subterraneus</Emphasis> (Acari: Oribatida)

Liacarus subterraneus is a large, soil-dwelling oribatid mite species that possesses a conspicuously shiny, clean and not wettable cuticular surface. The exocrine cuticular chemistry of this species was investigated by means of gas chromatography–mass spectrometry. Besides a fraction of hydrocarbons and a terpene, hexane extracts of whole mite bodies exhibited free carboxylic acids and their glycerides as main components. The compounds were arranged in three distinct extract profiles. Based on data from individual extracts, (1) the majority (more than 3/4) of specimens showed large amounts of 1,2-dioctanoyl-glycerol (and three other related esters) but no (or only traces of) free carboxylic acids. (2) In about 1/8 of extracts, free acids (mainly octanoic (caprylic) acid) and glycerides were detected. This second type of profile highly varied with respect to the relative abundance of acids and esters. (3) The third profile (in about 7% of specimens) exclusively exhibited free acids and no (or only traces of) glycerides. In addition, a few extracts exhibited no components at all. The extract compounds most likely originate from the lipid layer of the cerotegument of L. subterraneus. The cuticle of individuals that possessed extractable cerotegumental compounds (profile I, II, III) exhibited strong water repellent properties, while the cuticle of individuals that possessed no components in their extract did not. After hexane extraction, water repellent properties got lost. The distinct extract profiles detected most likely portray the stepwise generation of an anti-wetting, exocrine surface lipid layer of glycerides: If this layer is lost, fatty acids may be discharged again (profile III) and may subsequently esterify (profile II) to larger and more stable esters (diacyl-glycerols), eventually building up the “raincoat” (mainly profile I) of L. subterraneus.     

Field and laboratory evidence for a volatile pheromone produced by parous females of the Scottish biting midge, Culicoides impunctatus

Abstract. Electrophysiological, behavioural and field evidence is presented for a volatile attractant produced by host-seeking, parous female Culicoides impunctatus Goetghebuer. Attraction of host-seeking females to other live parous females or to extracts of parous females was demonstrated in Y-tube bioassays, as well as in field trials using baited sticky traps. Threshold numbers were 100–200 females, both in the laboratory and field. Antennal receptors to this pheromone were revealed by recording electroantennograms (EAGs) in response to odour from live parous females and to the extracts of female midges. The female-produced attractant did not alter field catches of male C. impunctatus.     

Kin recognition in a subsocial treehopper (Hemiptera: Membracidae)

1. Insects exhibiting parental care usually can discriminate between kin and non‐kin individuals, allowing parents to avoid investment in foreign offspring. 2. This study investigated the occurrence of kin recognition in the sap‐feeding insect Alchisme grossa Fairmaire (Membracidae) through bioassays assessing median female distance to nymphs and degree of nymphal aggregation. Each bioassay involved groups consisting of a female and a cohort of kin or non‐kin nymphs (mother and non‐mother treatments, respectively). Furthermore, cuticular non‐volatile compounds were extracted from nymphal cohorts, analysed by gas chromatography‐mass spectrometry and compared between cohorts. 3. In both treatments, nymphs performed a ‘rocking behaviour’ which appears to be correlated with aggregation. Temporal patterns of degree of nymphal aggregation and median female–nymph distance differed between treatments, the former parameter being higher in the mother treatment and the latter being higher in the non‐mother treatment. 4. A total of 40 compounds were found in the extracts. The composition of cuticular non‐volatile compounds differed between nymphal cohorts. 5. These results support the notion that kin recognition in A. grossa is possibly mediated by nymphal rocking behaviour and/or cuticular non‐volatile compounds (i.e. visual and/or chemical cues).     

Odour-genes eovariance and differential investigation of individual odours in the Mus species complex

Previous research using habituation techniques has demonstrated that greater genetic similarity between two individuals is associated with more similarity in the qualities of their individual odours ('odour-genes eovariance'). We assessed odour similarities across species in two pairs of genetically close species within the Mus species complex (M. musculus and M. domesticus; M. spicilegus and M. macedonicus). Subjects treated odours within each species pair as similar compared with an odour from the other species pair. Subjects also treated odours of M. spicilegus males from the same population as similar compared with the odour of M. spicilegus males from a different population. This confirms odour-genes eovariance across species and within populations and also supports previous findings that odour similarities are more salient than specific odour markers. When adult males were presented with odours of females from two different heterospecific species, subjects spent more time investigating the odour from his own species pair than the other species pair, indicating greater interest in the odour of the closer heterospecific and demonstrating that odour-genes eovariance is reflected in behavioural responses to odours. Implications of odour-genes eovariance as a basis for identifying degrees of genetic relatedness of unfamiliar individuals through similarities in individual odours are discussed.