Scent Gland Secretions Research Articles

Bioactivities of scent gland chemicals from Mictis fuscipes Hsiao (Hemiptera: Coreidae) on Solenopsis invicta Buren (Hymenoptera: Formicidae).

Given the chemical diversity within stink bugs scent glands, they can be convenient models for bioprospecting novel pest control products. Preliminary behaviour observations indicated that adult Mictis fuscipes stink bugs secrete liquid droplets when defending against Solenopsis invicta fire ants, killing them within minutes. Hence, this study aimed to analyse the chemical composition of the metathoracic scent gland secretions of M. fuscipes adults, as well as assess their biological activities against fire ants. Bioassaying fire ants against secretions of several local stink bugs confirmed that the defensive secretions of two Mictis species are significantly more lethal, where M. fuscipes was the most lethal. Volatiles chromatography analysis indicated the secretions of female and male M. fuscipes stink bugs contains 20 and 26 components, respectively, chiefly hexanoic acid and hexyl hexanoate. Five compounds were consistently present in the secretion of female adults: hexyl hexanoate, hexanoic acid, hexyl acetate, hexyl butyrate, and eugenol. These yielded a strong electrophysiological antennal (EAD) response from S. invicta workers, female alates and males, where hexyl acetate showed the strongest response. The combination of these five compounds proved strongly repellent to S. invicta. When tested singly, hexanoic acid, hexyl butyrate, hexyl hexanoate, and eugenol were repellent to S. invicta, but hexyl acetate seemed slightly attractive. Additionally, the same mixture of five components exhibited strong contact and fumigant toxicity towards S. invicta workers, eugenol being the strongest. Defensive chemicals of M. fuscipes exhibit robust biological activity against S. invicta and could inspire the development of biopesticides. © 2024 Society of Chemical Industry.

Sexual discrimination and attraction through scents in the water vole, Arvicola terrestris.

In mammals, especially rodents, social behaviours, such as parenting, territoriality or mate attraction, are largely based on olfactory communication through chemosignals. These behaviours are mediated by species-specific chemosignals, including small organic molecules and proteins that are secreted in the urine or in various fluids from exocrine glands. Chemosignal detection is mainly ensured by olfactory neurons in two specific sensory organs, the vomeronasal organ (VNO) and the main olfactory epithelium (MOE). This study aimed to characterise the olfactory communication in the fossorial ecotype of the water voles, Arvicola terrestris. We first measured the olfactory investigation of urine and lateral scent gland secretions from conspecifics. Our results showed that water voles can discriminate the sex of conspecifics based on the smell of urine, and that urinary male odour is attractive for female voles. Then, we demonstrated the ability of the VNO and MOE to detect volatile organic compounds (VOCs) found in water vole secretions using live-cell calcium imaging in dissociated cells. Finally, we evaluated the attractiveness of two mixtures of VOCs from urine or lateral scent glands in the field during a cyclical outbreak of vole populations.

Short-chain carboxylic acids in the scent gland secretions of the eastern small-scaled burrowing asp (Atractaspis fallax: Lamprophiidae, Serpentes, Reptilia)

Embedded in the tail base of all snakes is a pair of scent glands that open through ducts at the margin of the cloaca. Scent gland secretions (SGS), which typically are discharged when snakes are disturbed, are thought to deter predators. Previous chemical analyses have indicated carboxylic acids as the chief lipid constituents of SGS. We examined by GC-MS the SGS of the eastern small-scaled burrowing asp (Atractaspis fallax), a venomous, fossorial species in the Lamprophiidae, a diverse family containing more than 60 genera of mostly non-venomous African snakes. Our results confirm that acetic, propionic, 2-methylpropanoic, n-butanoic, and 3-methylbutanoic acids are the major constituents in the SGS samples of A. fallax. These compounds are widespread in the SGS of the Alethinophidia (‘typical snakes’). Some of these short-chain acids also occur in the anal glands of mammals and the uropygial (preen) glands of birds, where they arise via microbial activity. Whether these compounds in SGS have a similar origin is unknown.

Polymorphic scent gland secretions in Nelima harvestmen: “Sclerosomatid compounds” but different chemical lineages

The scent glands of harvestmen (Opiliones) produce secretions of taxon-specific composition. One class of compounds, assumed to be a key group in opilionid chemosystematics and prevalent among sclerosomatid Eupnoi, was termed “sclerosomatid compounds” (SCs). Known compounds of this group comprise acyclic 4-methyl-branched ethyl-ketones and -alcohols as well as 2,4-dimethyl-branched primary alcohols and aldehydes, originally described from several species of North American Leiobuninae. We analyzed the scent gland secretions of Nelima ssp. (Sclerosomatidae, Leiobuninae) from two continents by gas chromatography-mass spectrometry, NMR, stereoselective synthesis, and chiral chromatography. We found a surprising chemical dichotomy: while North American N. paesserli produced typical acyclic SCs such as (E)-4-methyl-4-hexen-3-one, the secretions of European Nelima species exhibited a mixture of aromatic and aliphatic compounds, namely (R)-2-methyl-1-phenyl-pentan-3-one (MPP), 4-phenyl-2-butanone (PB), 2-phenylacetamide (PA), as well as (2R,4R)-2,4-dimethylhexanoic acid (DHA), all of which are new for the secretions of harvestmen. Remarkably, in N. sempronii, the secretions of juveniles (containing PB) differed from the secretions of adults (containing MPP and DHA). Though the chemistry of European Nelima species clearly diverged at first sight, all compounds detected either possess specific chemical motifs that allow an assignment to the class of SCs or appear to be biochemically/ontogenetically connected to SC-components. Thus, we here add novel compounds to the pool of SCs along with an extension of the definition of SCs to include aromatic compounds with SC-motifs. Furthermore, we describe a first case of juvenile-adult polymorphism for the exocrine secretions of harvestmen and provide a scheme of how secretions are regenerated.

The scent gland chemistry of Gagrellinae (Opiliones, Sclerosomatidae): evidence for sequestration of myrmicacin in a species of Prionostemma

The scent gland secretion of an undetermined species of Prionostemma from Costa Rica was analyzed by gas chromatography–mass spectrometry and shown to consist of medium-chain carboxylic acids (mainly octanoic acid) and a ß-hydroxy-carboxylic acid, eventually identified as myrmicacin (= (R)-3-hydroxydecanoic acid). While scent gland secretions in harvestmen have traditionally been considered to be products of de novo synthesis, we here provide evidence for the unusual case of sequestration-derived scent gland constituents: at least myrmicacin appears to be sequestered from leaf-cutter ants that constitute a part of the prey of the Prionostemma-species herein investigated. This is the first report on the scent gland chemistry of the sclerosomatid subfamily Gagrellinae as well as on a possible sequestration mechanism in harvestmen.

On the trail of primate scent signals: A field analysis of callitrichid scent-gland secretions by portable gas chromatography-mass spectrometry.

Chemosignals are mediators of social interactions in mammals, providing con- and hetero-specifics with information on fixed (e.g., species, sex, group, and individual identity) and variable (e.g., social, reproductive, and health status) features of the signaler. Yet, methodological difficulties of recording and quantifying odor signals, especially in field conditions, have hampered studies of natural systems. We present the first use of the Torion® portable gas chromatography-mass spectrometry (GC-MS) instrument for in situ chemical analysis of primate scents. We collected and analyzed swab samples from the scent glands and skin from 13 groups (57 individuals) of two sympatric species of wild emperor tamarins, Saguinus imperator, and Weddell's saddleback tamarins, Leontocebus weddelli (Callitrichidae). In total, 11 compounds of interest (i.e., probably derived from the animals) could be detected in the samples, with 31 of 215 samples containing at least one compound of interest. The composition of these 31 samples varied systematically with species, group, sex, and breeding status. Moreover, we tentatively identified seven of the compounds of interest as methyl hexanoate, benzaldehyde, ethyl hexanoate, acetophenone, a branched C15 alkane, 4-methoxybenzaldehyde, and hexadecan-1-ol. As the field of primate semiochemistry continues to grow, we believe that portable GC-MS instruments have the potential to help make progress in the study of primate chemosignaling in field conditions, despite limitations that we encountered. We further provide recommendations for future use of the Torion® portable GC-MS for in situ analyses.

The hard task of a short-tailed mouse opossum (Monodelphis) to prey a harvestman (Arachnida: Opiliones)

ABSTRACT Despite the great diversity of small insectivorous mammals and the use of scent gland secretions as a defense mechanism by harvestmen, there is no observation about the effectiveness of scent glands against predators such as small mammals. We report a remarkable harvestman defense mechanism against a small-mammal attack. When a harvestman and a mouse opossum confronted each other inside a cage, the harvestman knocked out the mouse opossum two sequential times before it could attack the harvestman. Although it is a unique observation and there is no information about its frequency in nature, this report stimulates the study of agonistic behavior between small, cryptic species, which are difficult to observe in the field.

Reproductive and Somatic Senescence in the European Badger (Meles meles): Evidence from Lifetime Sex-Steroid Profiles

Among the Carnivora, there is sparse evidence for any substantive fitness benefits of post reproductive lifespan (PRLS, survival after reproductive cessation, RC). Using the European badger (Meles meles) as a model species, we analyzed sex-specific cross-sectional endocrinological and morphological data to investigate: 1) age-dependent reproductive decline in sex-steroid levels versus prime reproductive age; 2) age-dependent declines in somatic condition and reproductive advertisement (from subcaudal scent gland secretion); 3) changes in reproductive success with age due to somatic and endocrinological decline; 4) occurrence of RC, PRLS, and post reproductive representation (PrR) in the population with reference to pre-pubescent hormone levels and evidenced by fewer cub assignments from pedigree. We provide strong evidence for a gradual, not abrupt, decline in sex-steroid levels with age, with both sexes following a concave (down) quadratic trend. For both sexes, the onset of decline in somatic condition commenced at the age of 3 years. In contrast, decline in reproductive hormones started at age ca. 5.5 years in females and 6 years in males, with similar rates of decline thereafter. Subcaudal gland secretion volume also decreased in both sexes, especially after age 5, suggesting less investment in reproductive advertisement. After age 3, fewer (surviving) females were assigned cubs. This coincided with the onset of somatic decline but came earlier than hormonal decline (5.5 years onwards). The decrease in offspring assignments commenced later in males at age 5-6 years; concomitant with onset of testosterone decline at 6 years. This suggests that, contrary to females, in males declining body condition does not preclude reproductive success (no ‘restraint’) in advance of hormonal senescence (‘constraint’). There was evidence of female PRLS, with very old adults living up to 2.59 ± 1.29 years after RC; although in males this evidence was weaker. We discuss the implications of these findings for RC and PRLS in the context of adaptive and non-adaptive hypotheses. There was evidence of over 2 years of Post Reproductive Life Span in both sexes.

Analysis of defensive secretion of a milkweed bug Lygaeus equestris by 1D GC-MS and GC\xd7GC-MS: sex differences and host-plant effect

The composition of defensive secretion produced by metathoracic scent glands was analysed in males and females of the milkweed bug Lygaeus equestris (Heteroptera) using gas chromatography with mass spectrometric detection (GC-MS). The bugs were raised either on cardenolide-containing Adonis vernalis or on control sunflower seeds in order to determine whether the possibility to sequester cardenolides from their host plants would affect the composition of defensive scent-gland secretion. Profiles of the composition of defensive secretions of males and females raised on sunflower were closely similar, with predominant presence of (E)-2-octenal, (E)-2-octen-1-ol, decanal and 3-octen-1-ol acetate. The secretion of bugs raised on A. vernalis was more sexually dimorphic, and some chemicals e.g. (E,E)-2,4-hexadienyl acetate and 2-phenylethyl acetate were dominant in males, but absent in females. Compared to bugs from sunflower, the scent-gland secretion of bugs raised on A. vernalis was characterized by lower overall intensity of the peaks obtained for detected chemicals and by absence of some chemicals that have supposedly antipredatory function ((E)-2-hexenal, (E)-4-oxo-hex-2-enal, 2,4-octadienal). The results suggest that there might be a trade-off between the sequestration of defensive chemicals from host plants and their synthesis in metathoracic scent-glands.

The scent gland chemistry of neogoveid cyphophthalmids (Opiliones): an unusual methyljuglone from Metasiro savannahensis

While the chemistries of scent gland secretions from a few selected species of three families of Cyphophthalmi, namely Sironidae, Pettalidae, and Stylocellidae, have already been reported and found to consist of complex blends of naphthoquinones and methyl ketones, nothing is known about the other families. We here report on the secretions of Metasiro savannahensis Clouse and Wheeler (Zootaxa 3814:177–201, 2014), a first representative of the family Neogoveidae. The secretions from males, females and one juvenile were extracted and analyzed by gas chromatography–mass spectrometry. Twenty-five compounds were identified, all of which belong to the chemical classes of naphthoquinones and methyl ketones, confirming a hypothesized chemical uniformity of cyphophthalmid exudates. One major naphthoquinone compound, however, was new for cyphophthalmids and for arthropod exocrine secretions in general: a methyljuglone isomer, 6-methyljuglone (= 6-MJ; iupac name: 5-hydroxy-6-methyl-1,4-naphthoquinone), amounted for about 20% of the secretion and was eventually identified by synthesis. Hydroxy-naphthoquinones and their derivatives are known to possess a variety of antibiotic effects, probably enhancing the antimicrobial/antifungal potential of the Metasiro-secretion. Currently, without further data on neogoveids, the compound represents a chemical autapomorphy of M. savannahensis, and—just as the strange chloro-naphthoquinones of Sironidae and Pettalidae—adds to the repertoire of unusual naphthoquinone compounds across the Cyphophthalmi.

Interspecific, ontogenetic, and sexual variation in ozopore morphology among cosmetid harvestmen (Arachnida, Opiliones, Laniatores).

The ozopores of cosmetid harvestmen rest upon lateral projections of the carapace, have simple or highly reduced channels, and are partially obscured by enlarged dorsal processes associated with coxae I and II. Rather than use scent gland secretions to form a chemical shield on the dorsum, the cosmetid harvestman exhibits a unique defensive behavior known as "leg dabbing" in which the distal tip of tarsus I or II is dipped into fluid that accumulate at the base of coxa II and the droplet on the tarsus is pointed toward the predator. Relatively little is known about interspecific variation in ozopore morphology among cosmetid harvestmen. In this study, we used scanning electron microscopy to examine the ozopores of males and females of nine species as well as those of antepenultimate nymphs for two species. Among adults, we found differences between species in the shapes of the ozopores (round or subtriangular), the morphology of the dorsal and lateral channels (if present), and the relative size, shape and armature of the dorsal posterior process (dpp) of coxa I and the dorsal anterior process (dap) of coxa II. Our observations suggest that the morphology of dpp I and dap II could be sources for systematic characters in future phylogenetic studies of the Cosmetidae. We observed ontogenetic differences but relatively little intersexual variation in the morphology of the ozopore. The ozopores of nymphs are generally more oval than those of adults and the opening of the ozopore of the nymph is less obstructed, if at all, by the dorsal coxal processes of legs I-II. These morphological differences suggest that nymphs may use scent gland secretions in a manner different from that of adults.

Intraspecific Variation in the Secretion and Morphology of the Scent Glands of a Neotropical Harvestman (Opiliones, Cosmetidae)

Relatively little is known about intraspecific variation in the use of chemical defenses by cosmetid harvestmen. In this study, we investigated sexual and ontogenetic variation in the emission of secretions from the scent glands and the morphology of the ozopores of Erginulus clavotibialis, a Neotropical species from Belize. Most individuals (> 94%) did not secrete when seized by leg IV, however, when the body was subsequently grasped firmly with forceps, 76% of the harvestmen (n = 96) responded by releasing enteric fluid (clear, no odor) or secretions from the scent glands (reddish-brown, distinct odor), most commonly in the form of globules near the ozopores. Adults and penultimate nymphs rarely (less than 5% of all trials) exhibited leg dabbing, an unusual behavior generally associated with cosmetid harvestmen. Males released enteric fluid (without scent gland secretions) significantly more than females or nymphs. Nymphs emitted secretions from scent glands at a significantly greater frequency than males or females. Using SEM, we examined the ozopores and the dorsal processes of coxae I and II and found that the morphology of these structures varies between adults and nymphs but not between males and females. The openings of the ozopores of nymphs are circular and are not obscured by the dorsal posterior process of coxa I and the dorsal anterior process of coxa II. In contrast, adults have subtriangular ozopores that are difficult to observe without dissection because they are partially blocked by the dorsal processes of coxae I and II.

Anal scent gland secretions inform on sexual maturity, sex and social status in the Alpine marmot, Marmota marmota (Rodentia: Sciuridae): a role in intrasexual competition in cooperative breeders?

Anal scent gland secretions inform on sexual maturity, sex and social status in the Alpine marmot, Marmota marmota (Rodentia: Sciuridae): a role in intrasexual competition in cooperative breeders?

Methyl-ketones in the scent glands of Opiliones: a chemical trait of cyphophthalmi retrieved in the dyspnoan Nemastoma triste

The homologous and phylogenetically old scent glands of harvestmen—also called defensive or repugnatorial glands—represent an ideal system for a model reconstruction of the evolutionary history of exocrine secretion chemistry (“phylogenetic chemosystematics”). While the secretions of Laniatores (mainly phenols, benzoquinones), Cyphophthalmi (naphthoquinones, chloro-naphthoquinones, methyl-ketones) and some Eupnoi (naphthoquinones, ethyl-ketones) are fairly well studied, one open question refers to the still largely enigmatic scent gland chemistry of representatives of the suborder Dyspnoi and the relation of dyspnoan chemistry to the remaining suborders. We here report on the secretion of a nemastomatid Dyspnoi, Nemastoma triste, which is composed of straight-chain methyl-ketones (heptan-2-one, nonan-2-one, 6-tridecen-2-one, 8-tridecen-2-one), methyl-branched methyl-ketones (5-methyl-heptan-2-one, 6-methyl-nonan-2-one), naphthoquinones (1,4-naphthoquinone, 6-methyl-1,4-naphthoquinone) and chloro-naphthoquinones (4-chloro-1,2-naphthoquinone, 4-chloro-6-methyl-1,2-naphthoquinone). Chemically, the secretions of N. triste are remarkably reminiscent of those found in Cyphophthalmi. While naphthoquinones are widely distributed across the scent gland secretions of harvestmen (all suborders except Laniatores), methyl-ketones and chloro-naphthoquinones arise as linking elements between cyphophthalmid and dyspnoan scent gland chemistry.

A Model for Phylogenetic Chemosystematics: Evolutionary History of Quinones in the Scent Gland Secretions of Harvestmen.

By the possession of unique exocrine scent glands, Opiliones (harvestmen) arise as a perfect model for studies on the evolutionary history of secretion chemistry. Among gland compounds of harvestmen, it is the quinones that represent recurring elements across the secretions of all suborders. Reliable data on quinone-distribution, however, is only known for Laniatores (benzoquinones) and Cyphophthalmi (naphthoquinones). We here unraveled the quinone-distribution across scent gland secretions of the third large harvestman suborder, the Palpatores (= Eu- and Dyspnoi): Naphthoquinones were found in phalangiid Eupnoi across all subfamilies as well as in nemastomatid (and at least one ischyropsalid) Dyspnoi. Benzoquinones (1,4-benzoquinone) were restricted to a small entity within Eupnoi, namely platybunine Phalangiidae, probably misplaced Gyantinae (currently Sclerosomatidae) and Amilenus (incertae sedis). Our findings, combined with data from Laniatores and Cyphophthalmi, allow evaluation of a comprehensive chemosystematic model for Opiliones for the first time. Evolutionary scenarios imply naphthoquinones as scent gland compounds of common ancestry, having evolved in an early harvestman ancestor and present in cyphophthalmids and palpatoreans, but lost in laniatoreans. Benzoquinones evolved later and independently at least twice: once in the secretions of gonyleptoid Laniatores (alkylated benzoquinones), and a second time in a lineage of phalangiid Eupnoi (1,4-benzoquinone).

Scent gland constituents of the Middle American burrowing python, Loxocemus bicolor (Serpentes: Loxocemidae).

Analysis by gas chromatography/mass spectrometry of the scent gland secretions of male and female Middle American burrowing pythons (Loxocemus bicolor) revealed the presence of over 300 components including cholesterol, fatty acids, glyceryl monoalkyl ethers, and alcohols. The fatty acids, over 100 of which were identified, constitute most of the compounds in the secretions and show the greatest structural diversity. They include saturated and unsaturated, unbranched and mono-, di-, and trimethyl-branched compounds ranging in carbon-chain length from 13 to 24. The glyceryl monoethers possess saturated or unsaturated, straight or methyl-branched alkyl chains ranging in carbon-chain length from 13 to 24. Alcohols, which have not previously been reported from the scent glands, possess straight, chiefly saturated carbon chains ranging in length from 13 to 24. Sex or individual differences in secretion composition were not observed. Compounds in the scent gland secretions of L. bicolor may deter offending arthropods, such as ants.

Chemosensory discrimination of identity and familiarity in koalas

Despite numerous descriptive accounts of scent marking in marsupials, rigorous experimentation is rare, and relatively little evidence exists to show that conspecifics use chemical signals to distinguish between individuals or different social groups. In this study a series of olfactory discrimination tests sought to determine whether: (1) male koala sternal scent gland secretions are individually distinctive; and (2) male koalas can differentiate between the scent of familiar and unfamiliar individuals. In the first experiment a habituation–discrimination trial demonstrated that male koalas discriminate between the scent gland secretions of different unfamiliar individuals. In a second experiment male koalas spent significantly more time investigating scent from unfamiliar males than familiar males, supporting the hypothesis that they differentiate between conspecifics based on their familiarity. Taken together these results suggest that male koalas are able to discriminate the identity and familiarity of conspecifics using chemical cues, and provide a platform for further studies investigating the functional role of olfactory communication in this species.

Benzoquinones from scent glands of phalangiid harvestmen (Arachnida, Opiliones, Eupnoi): a lesson from Rilaena triangularis.

In case of disturbance, the phalangiine harvestman Rilaena triangularis (Eupnoi, Phalangiidae) emits a directed jet from large prosomal scent (“defensive”) glands. The pungent-smelling secretion was analyzed by gas chromatography–mass spectrometry and found to contain mainly 1,4-benzoquinone along with 1,4-naphthoquinone and caprylic (=octanoic) acid. While various alkylated benzoquinones are characteristic for the scent gland secretions of many grassatorean Laniatores, this is the first incidence of benzoquinone-based chemical defense in palpatorean harvestmen.

Chemosystematics in the Opiliones (Arachnida): a comment on the evolutionary history of alkylphenols and benzoquinones in the scent gland secretions of Laniatores.

Large prosomal scent glands constitute a major synapomorphic character of the arachnid order Opiliones. These glands produce a variety of chemicals very specific to opilionid taxa of different taxonomic levels, and thus represent a model system to investigate the evolutionary traits in exocrine secretion chemistry across a phylogenetically old group of animals. The chemically best-studied opilionid group is certainly Laniatores, and currently available chemical data allow first hypotheses linking the phylogeny of this group to the evolution of major chemical classes of secretion chemistry. Such hypotheses are essential to decide upon a best-fitting explanation of the distribution of scent-gland secretion compounds across extant laniatorean taxa, and hence represent a key toward a well-founded opilionid chemosystematics.

Chemical signals in the echidna: differences between seasons, sexes, individuals and gland types

AbstractSeasonally reproducing animals show many behavioural and physiological changes during the mating period, including increased signalling for mate attraction. Mammals often rely on chemical signals for communication and coordination of mating and other social behaviours, but our understanding of the subtleties and functions of mammalian signalling could be increased with more input from non‐model systems. We used gas chromatography–mass spectrometry and non‐parametric statistics to investigate the volatile and non‐volatile composition of odorous secretions in an egg‐laying mammal (monotreme), the short‐beaked echidna Tachyglossus aculeatus. We collected a total of 778 odorant samples from 69 wild, sexually mature individuals over 3 years at our field site in southern Tasmania. Animals were sampled during the breeding and non‐breeding seasons, as well as during hibernation. Odorants included swabs from the cloaca and ‘waxy’ secretions from putative scent glands in the cloacal wall and at the base of the spurs. Chemical profiles varied between different gland secretions and by sex and season. Female spur and cloacal wax secretion profiles had higher relative abundances of sterols, whereas male wax secretion profiles had more long chain fatty acids. Male spur secretions changed significantly during the mating season and could function in intra‐sexual competition or female mate choice. Echidna scent gland secretions also varied between individuals, suggesting olfactory cues could be used for individual recognition. Our results indicate that echidna secretions contain information that could be used by individuals to attract and locate mates during the breeding season. We also provide evidence for the potential importance of compounds traditionally classified as ‘non‐volatile’, including sterols and fatty acids, as cues for individual recognition or mate assessment.