Studies on the nature of chemical signals in scent marks and urine ofSaguinus fuscicollis (Callitricidae,primates)

The circumgenital scent marks ofSaguinus fuscicollis are mixtures of skin gland secretions, urine, and perhaps vaginal discharge. One of their ingredients, urine, is readily investigated by conspecifics. Female tamarins are able to utilize urine to discriminate between the sexes, but it appears that urine, unlike the scent marks, offers no clues for individual discrimination. Moreover, urine is less attractive to conspecifics than complete scent marks, which signal sex and individuality. The sexual identity of marks is recognized even if the tamarins are prevented from contacting the material directly and seems to be retained in a mixture of scent from both sexes.     

Floral Odors of Silene otites: Their Variability and Attractiveness to Mosquitoes

Inflorescence scent samples from nine populations of dioecious Silene otites, a plant pollinated by moths and mosquitoes, were collected by dynamic headspace extraction. Sixty-three scent samples were analyzed by gas chromatography–mass spectrometry. Out of 38 found, 35 compounds were identified, most of which were monoterpenoids, fatty acid derivatives, and benzenoids. Phenyl acetaldehyde was the most dominant compound in the majority of samples. The variability in scent composition was high, and population and sex differences were found. Nevertheless, wind tunnel experiments proved similar attraction of Culex pipiens pipiens biotype molestus mosquitoes to the inflorescence odor of S. otites of different populations, indicating that different blends are similarly attractive to mosquitoes. The electrophysiological responses of mosquitoes to the 12 most common and abundant odor compounds of S. otites differed. Linalool oxide (furanoid) and linalool evoked the strongest responses in male and female mosquitoes, and (Z)-3-hexenyl acetate was strongly active in females. Medium responses were evoked in males by (Z)-3-hexenyl acetate, in females by benzaldehyde and methyl salicylate, and in both sexes by lilac aldehyde, lilac alcohol, and linalool oxide (pyranoid).     

Olfactory responses ofIps plastographus maritimus lanier (coleoptera: Scolytidae) to insect and host-associated volatiles in the laboratory

Attraction of both sexes ofIps plastographus maritimus Lanier to bark-phloem-xylem discs of Monterey pine,Pinus radiata D. Don, was demonstrated in the laboratory. Increasing concentrations of male and female volatiles trapped separately and released in a one-to-one ratio decreased attraction for both sexes combined. Attraction of both sexes to volatiles derived from males and females tunneling together in a one-to-one ratio increased with increasing concentration of extract. Attraction of males and females to male-infested discs and to trapped male volatiles increased with increasing dose of males or male extract. Attraction of males and females to female-infested discs and to trapped female volatiles was also demonstrated. The presence of females in male galleries reduced the attractiveness of infested disks to both sexes combined. Increasing numbers of females, tunneling separately from males in the same disc, reduced attraction of males, but not females. When a constant attractive dose of male volatiles was released with increasing doses of female volatiles, there was no difference in response of either sex when female volatiles were present compared with the response to male volatiles alone. When a constant attractive dose of male volatiles was released with increasing concentrations of volatiles derived from males and females tunneling together in a one-to-one ratio, attraction ofI. p. maritimus decreased. Response of females was frequently higher than that of males to the same attractant source. Hence, both sexes produce an attractant, and both sexes tunneling together in the same gallery reduce attraction of males and females to an attractive dose of male attractant.     

Some communicatory functions of scent marking in the cotton-top tamarin (Saguinus oedipus oedipus)

The ability of cotton-top tamarins to discriminate between scents from conspecifics and those from other tamarin species, and between scents from conspecific individuals was tested. Cotton-tops scent mark with specialized skin glands in the circumgenital area. Females possess larger glands than males and show more scent-marking behavior. In the first experiment, subjects were presented with a glass rod scented with either material collected from the surface of the scent glands of a conspecific female, with scent material from a female of a related species, or with an unscented rod. Glass rods carrying scent from conspecifics were sniffed more frequently than rods carrying scent from related tamarin species or unscented rods. A second experiment offered a choice between two glass rods, one scent marked by aSaguinus o. oedipus female, the second one scent marked by aSaguinus fusdcollis female. Shelves carrying rods that had been scent marked by conspecifics were contacted more frequently than those carrying rods marked by heterospecific females. Scent marks from conspecific females were also sniffed more frequently. A third experiment compared the level of responses to rods carrying material collected from the scent glands of female individuals to which the subjects had been habituated with their responses to rods carrying scent from females to which they had not been habituated. Contacting and sniffing responses to the scents of novel females were higher than those to the scents of females to which the subjects had been habituated.     

Responses to inter- and intraspecific scent marks in pine martens (Martes martes)

In order to analyze intra and interspecific olfactory discrimination, behavioral responses (sniffing and marking) towards various odors were observed in pine martens (Manes martes). Two adult males and two adult females were tested for intraspecific discrimination of abdominal gland odors and urine. Both sexes sniffed and marked objects carrying their own scent less than unscented objects. There were no differences in sniffing or marking objects impregnated with odors from known and unknown conspecifics of the opposite sex or objects carrying the odor of an unknown male or female. A second experiment with two adult females gave no evidence for interspecific discrimination: no differences emerged when comparing reactions towards marks of pine martens, stone martens (a closely related species), or genets. The most obvious result of this study is the reduced response of pine martens towards their own mark. It is suggested that scent marking in martens may reflect autocommunication, the primary effect being to familiarize an animal with its environment.     

Sexual Dimorphism in Territorial Scent Marking by Adult Eurasian Beavers (Castor fiber)

Mammalian scent marking is often associated with territorial defense. However, males and females may demonstrate different activity patterns and play different roles. Female mammals nurture the young during lactation, while males purportedly perform other tasks more frequently, such as territorial maintenance and defense. This paper investigates the contribution made by mated pairs of adult males and females to territorial scent-marking in the obligate monogamous Eurasian beavers (Castor fiber). We hypothesized that both sexes should show territorial behavior, and predicted that they deposit a higher proportion of scent marks at borders. We also hypothesized that a sexual dimorphism exists due to reproductive constraints on the females, and predicted that males should invest significantly more in scent-marking behavior than females during summer. We obtained behavioral data by radio tracking six mated pairs of Eurasian beavers during spring and summer 2000–2001 on two rivers in southeastern Norway. Our results showed that both males and females clustered their scent marks near territorial borders, but males deposited a larger number of scent marks than females and spent more time at borders. Males were also found to have a higher scent marking rate and scent marks per night than females during summer, but not during spring. Overall, scent marks per night were higher in males than females. We conclude that both males and females Eurasian beavers carry out territorial behavior by scent marking, but males carry a larger part of the territorial defense during summer when females lactate. Our results are discussed in the light of the codefense hypothesis.     

Scent marks as social signals inGalago crassicaudatus II. Discrimination between individuals by scent

Thick-tailed galagos,Galago crassicaudatus argentatus, which had been habituated to the scent marks of a conspecific through repeated presentations, increased their sniffing when presented with scent marks from a second conspecific of the same sex. Thus, they discriminated between the scents of individual conspecifics. This result was obtained using naturally scent-marked perches and perches carrying only chest gland scent—the latter even two weeks after the marking. When urine, the prevalent scent signal among most other galago species, was tested, it elicited little interest and discriminations were not clearly made. It is suggested that the use of more specialized scents is related to the social characteristics ofGalago crassicaudatus.     

Partial chemical characterization of urinary signaling pheromone in tree shrews (Tupaia belangen)

Tree shrews of both sexes exhibit marking behavior (chinning) in response to scent marks made by the urine of fertile male conspecifics. To isolate the effective odor components, the urine was fractionated by liquid-liquid extraction and TLC, and the fractions were tested by bioassay. The results show that chinning is elicited by several lipophilic urine fractions, which are more effective in combination than alone. To characterize the complex scent signal, the lipophilic extracts from urine of the two sexes were analyzed by GC-MS and compared. The GC profile of the males is distinguished by pyrazine compounds not detected in the profile of the females. The profiles of the sexes also differ with regard to several volatile monocarboxylic acids, which are present at higher concentrations in male than in female urine. More than 30 urine components have been identified. Synthetic equivalents of these urine components were bioassayed for effectiveness in eliciting chinning and compared with one another as well as with scent substances not normally present in tree-shrew urine. Strong chinning responses were elicited by (1) certain pyrazine compounds and (2) some monocarboxylic acids, when presented at the high concentrations specific to male urine. Marking behavior is usually not elicited by scent substances not contained in tree-shrew urine or by urine components common to mammals in general. The data so far available indicate that the male-specific scent signal of tree shrews is based less on a single unique component than on the qualitative and quantitative characteristics of a multicomponent mixture. In the bioassay, tree shrews of both sexes respond equally to the male specific substances by chinning. As the scent signal represented by these substances has a different meaning to males and females (rival or potential mate, respectively), chinning probably serves several different functions.     

Intersexual Differences in Chemical Composition of Precloacal Gland Secretions of the Amphisbaenian <Emphasis Type="Italic">Blanus cinereus</Emphasis>

Pheromonal communication seems to be especially important in amphisbaenians, a group of reptiles morphologically and functionally adapted to fossorial life. Both male and female amphisbaenians (Blanus cinereus) produce copious amounts of a secretion from the precloacal glands. Analysis by gas chromatography–mass spectrometry revealed that these secretions contain 29 major lipophilic compounds, including several steroids (mainly cholesterol and cholesteryl methyl ether), n-C₉ to n-C₁₈ carboxylic acids (more diverse in males), and methyl and long-chain (waxy)-type esters of carboxylic acids, along with squalene (mainly in males) and tocopherol (only in females). There were clear intersexual differences in the presence/absence of some compounds, such as some fatty acids, steroids, and tocopherol, and in the relative proportions of some shared compounds, such as squalene. These differences may explain how the sexes of this amphisbaenian discriminate one another based on scent alone. The abundance of steroids and waxy esters in secretions of both male and female amphisbaenians may be useful to scent mark underground tunnels to facilitate orientation by these organisms.     

An Antiaphrodisiac in Heliconius melpomene Butterflies

Gilbert (1976) suggested that male-contributed odors of mated females of Heliconius erato could enforce monogamy. We investigated the pheromone system of a relative, Heliconius melpomene, using chemical analysis, behavioral experiments, and feeding experiments with labeled biosynthetic pheromone precursors. The abdominal scent glands of males contained a complex odor bouquet, consisting of the volatile compound (E)-β-ocimene together with some trace components and a less volatile matrix made up predominately of esters of common C₁₆- and C₁₈-fatty acids with the alcohols ethanol, 2-propanol, 1-butanol, isobutanol, 1-hexanol, and (Z)-3-hexenol. This bouquet is formed during the first days after eclosion, and transferred during copulation to the females. Virgin female scent glands do not contain these compounds. The transfer of ocimene and the esters was shown by analysis of butterflies of both sexes before and after copulation. Additional proof was obtained by males fed with labeled D-¹³C₆– glucose. They produced ¹³C-labeled ocimene and transferred it to females during copulation. Behavioral tests with ocimene applied to unmated females showed its repellency to males. The esters did not show such activity, but they moderated the evaporation rate of ocimene. Our investigation showed that β-ocimene is an antiaphrodisiac pheromone of H. melpomene.     

Male bugs modulate pheromone emission in response to vibratory signals from conspecifics

Male Nezara viridula emit a volatile sex pheromone that acts as a long-range attractant to females. Both sexes communicate through vibrations once they are on the same plant. Males respond to the female calling song by emitting a male courtship song, and they orient to the female calling song on a plant. Simultaneity between vibratory and chemical communication during the last steps of mate finding suggests that pheromone emission might be modulated by signals from conspecifics. Male volatile emissions were collected with fibers for solid-phase microextraction, while male bugs were stimulated with natural and artificial signals. Percentages of males releasing pheromone and collected amounts of pheromone increased when males were stimulated with female calling song. Pheromone emission was stable in males stimulated with male rivalry songs, and it decreased in males stimulated with a 100-Hz artificial signal. The ability of male bugs to modulate their pheromone emission may reduce metabolic costs, reduce parasitism, and offer a better synchronization of sexual activity.     

Cuticular hydrocarbons regulate mate recognition,male aggression,and female choice of the rove beetle,Aleochara curtula

Immature, starved, or multiply mated males of the staphylinid beetle,Aleochara curtula, mimic their females chemically. The titer of the female sex pheromone components (Z)-7-heneicosene and (Z)-7-tricosene was quantified for various physiological types and both sexes by gas chromatography and correlated with the sexual response of males towards the cuticular hydrocarbon fractions. Modulation of intermale aggression by production of the female pheromone was shown by (1) reduction of the alkene titer of females kept at elevated temperatures, (2) treating live males with the synthetic female pheromone mixture, and (3) gradual amputation of male antennal segments.A. curtula males do not fight against members of otherAleochara species with a different hydrocarbon pattern. Contamination ofA. peschkei males with the hydrocarbon fraction ofA. curtula males, however, provoked the release of aggression. Choosy females reject mating attempts of males bearing the female sex pheromone.     

Sex-Related Perception of Insect and Plant Volatiles in Lygocoris pabulinus

We recorded electroantennograms of male and female Lygocoris pabulinus antennae to 63 insect and plant volatiles. EAGs were between 100 and 500 V. Overall, male EAGs were about twice the size of female EAGs. In both sexes, largest EAGs were recorded to (E)-2-hexenyl butanoate and (E)-2-hexen-1-ol. Response profiles were similar in both sexes. However, male antennae were more sensitive to a number of esters, especially the butanoates and pentanoates. Female antennae were more sensitive to nine of the 19 plant volatiles, i.e., to hexan-1-ol, heptan-1-ol, 1-octen-3-ol, 2-heptanone, (R)-carvone, linalool, geraniol, nerol, and methyl salicylate. Sexual differences in responses suggest that males are more sensitive to insect-produced pheromone-type compounds, whereas females are more sensitive to plant compounds for their orientation towards oviposition sites.     

Potential use of chemical cues for colony-mate recognition in the big brown bat,Eptesicus fuscus

Bats should benefit from recognition of their roost-mates when colonies form stable social units that persist over time. We used Y-maze experiments and gas chromatography–olfactometry (GC-O) to evaluate whether female big brown bats Eptesicus fuscus (Chiroptera: Vespertilionidae) use chemical cues to distinguish among conspecifics. In dual-choice Y-maze experiments, females chose the scent of another female from their own roost over a conspecific female from a different roost in a majority of trials. Analysis of total body odors using GC-O suggests that individuals from a given colony may share a more common odor signature with roost-mates than with non-roost-mate conspecifics. Using four principle components derived from 15 odor variables, discriminant function analysis correctly assigned most individuals to the correct colony.     

Chemical signals involved in spacing behavior of breeding female bank voles (Clethrionomys glareolus Schreber 1780, Microtidae,Rodentia)

In order to study the mechanism involved in the seasonal territoriality of breeding bank voles, the social behavior and scent marking of paired females were observed throughout a reproductive cycle. Initially unfamiliar females were kept in large laboratory pens provided with individual burrows. After a brief period of hostility, females behaved in a friendly manner towards each other, sharing the same nest even in the presence of a male and until the middle of pregnancy. They scarcely marked with urine. Continuous olfactory assessment appeared to play an important role in maintaining the friendly interactions. In late pregnant and lactating females, on the contrary, the odor of a familiar female triggered aggressiveness and scent marking with urine and probably with flank glands. These reactions may be interpreted as spacing behavior. Moreover, the interaction between females may inhibit reproduction in one of them. These results are discussed in relation with the available ecological data.     

Factors Accounting for the Variability in the Behavioral Response of the Onion Fly (Delia antiqua) to n-Dipropyl Disulfide

The onion fly Delia antiqua is a specialist herbivore attacking only onions and closely related Allium species. n-Dipropyl disulfide (Pr₂S₂) has long been known to be attractive to onion flies in the laboratory and in the field. However, the insect's response is highly variable. Using behavioral bioassays we found that Pr₂S₂ was highly attractive to gravid, mated female onion flies, but did not stimulate oviposition. The response of female onion flies was concentration dependent. The physiological state of the flies (i.e., age, mating status, egg load/oviposition experience) also affected their responsiveness. The response of both sexes of onion flies varied with age, but females were always more strongly attracted than males. Responsiveness of females increased during the first 10 days after emergence. It stayed at a high level until 21 days after which the experiment was terminated. The responsiveness of males reached a maximum at 6–7 days after which it declined. Mated, gravid females responded more strongly to Pr₂S₂ than unmated, gravid females. Females deprived of the opportunity to oviposit were more attracted compared to females that had oviposited on cut onions prior to the experiment. Electroantennograms (EAG) of females revealed a higher response to stimulation compared to males. The EAG-response of females was not affected by mating status.     

1,4-Dimethoxybenzene,a Floral Scent Compound in Willows that Attracts an Oligolectic Bee

Many bees are oligolectic and collect pollen for their larvae only from one particular plant family or genus. Here, we identified flower scent compounds of two Salix species important for the attraction of the oligolectic bee Andrena vaga, which collects pollen only from Salix. Flower scent was collected by using dynamic-headspace methods from Salix caprea and S. atrocinerea, and the samples were subsequently analyzed by coupled gas chromatographic–electroantennographic detection (GC-EAD) to detect possible attractants of A. vaga. EAD active compounds were identified by gas chromatography coupled to mass spectrometry. Both Salix species had relatively similar scent profiles, and the antennae of male and female bees responded to at least 16 compounds, among them different benzenoids as well as oxygenated monoterpenoids and sesquiterpenoids. The strongest antennal responses were triggered by 1,4-dimethoxybenzene, and in field bioassays, this benzenoid attracted females of A. vaga at the beginning of its flight period, but not at the end.     

Close-range attraction in Lygocoris pabulinus (L.)

Males of the green capsid bug, Lygocoris pabulinus, exhibit a specific courtship behavior, i.e., a vibration of the abdomen. When both live and dead females were offered to males, this vibration behavior was elicited in most of the males tested. When females were dissected into separate body parts, heads, wings, and legs elicited equal responses, while thorax plus abdomen elicited a much lower response. When separate body parts were extracted, the leg extracts elicited significantly stronger responses than any other extract. This suggests that female L. pabulinuslegs are either the source of a close-range sex pheromone or that pheromone is accumulated on the legs due to grooming behavior. The leg extracts contained several hydrocarbons such as n-alkenes, n-alkanes, and some methylalkanes. Female extracts contained more (Z)-9-pentacosene and male extracts contained more (Z)-9-heptacosene. Substrates on which females had walked elicited similar responses as female legs, indicating that the pheromone is deposited on the substrate. This enlarges the functional range of low-volatility compounds, which are thought to function only when sexes are in close vicinity or in contact.     

Disease Status and Population Origin Effects on Floral Scent<Emphasis Type="SmallCaps">:</Emphasis> Potential Consequences for Oviposition and Fruit Predation in A Complex Interaction Between A Plant,Fungus, and Noctuid Moth

In the Silene latifolia–Hadena bicruris nursery pollination system, the Hadena moth is both pollinator and seed predator of its host plant. Floral scent, which differs among S. latifolia individuals and populations, is important for adult Hadena to locate its host. However, the success of moth larvae is strongly reduced if hosts are infected by the anther smut fungus Microbotryum violaceum, a pathogen that is transmitted by flower visitors. There were no qualitative differences between the scent of flowers from healthy and diseased plants. In addition, electroantennographic measurements showed that Hadena responded to the same subset of 19 compounds in samples collected from healthy and diseased plants. However, there were significant quantitative differences in scent profiles. Flowers from diseased plants emitted both a lower absolute amount of floral scent and had a different scent pattern, mainly due to their lower absolute amount of lilac aldehyde, whereas their amount of (E)-β-ocimene was similar to that in healthy flowers. Dual choice behavioral wind tunnel tests using differently scented flowers confirmed that moths respond to both qualitative and quantitative aspects of floral scent, suggesting that they could use differences in floral scent between healthy and infected plants to discriminate against diseased plants. Population mean fruit predation rates significantly increased with population mean levels of the emission rates of lilac aldehyde per flower, indicating that selection on floral scent compounds may not only be driven by effects on pollinator attraction but also by effects on fruit predation. However, variation in mean emission rates of scent compounds per flower generally could not explain the higher fruit predation in populations originating from the introduced North American range compared to populations native to Europe.     

Pheromone Components of the Wheat Stem Sawfly: Identification, Electrophysiology, and Field Bioassay

Volatiles collections and cuticular extracts of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), were analyzed by coupled gas chromatographic–electroantennographic detection (GC-EAD) in order to detect possible pheromone components of this species. Volatiles collections from male and female sawflies contained the same 13 GC-EAD-active compounds that stimulated both male and female antennae. GC-EAD-active compounds were identified by mass spectrometry, and the identities were verified by acquiring or synthesizing authentic standards with identical GC retention times and mass spectra. 9-Acetyloxynonanal gave the strongest EAD response. Additional GC-EAD-active compounds included 13-acetyloxytridecanal, aldehydes with 9–16 carbon chain lengths, acids with 8–10 carbon chain lengths, and phenylacetic acid. The last was instantly detectable by human nose when several males were allowed to interact, but not from isolated insects. On a per-insect basis, grouped males overall released higher amounts of the GC-EAD-active compounds than grouped females. Notable quantitative differences between the sexes were relatively higher amounts of 9-acetyloxynonanal, phenylacetic acid, and tetradecanal from males and hexadecanal from females. In the absence of an absolute, qualitative difference between sexes, these relative differences might be important for sex recognition. Field bioassay demonstrated the attractiveness of 9-acetyloxynonanal for male and female C. cinctus. The major compounds of male and female cuticular extracts showed no GC-EAD activity, but ozonolysis of extracts gave dramatically increased amounts of GC-EAD-active material. Hence, double-bond-containing cuticular compounds are suggested as precursors of the aldehydic pheromone components.