Population Variation in Salamander Courtship Pheromones

We examined intraand interspecific chemical variation in salamander courtship pheromones. The extent to which plethodontid receptivity factor (PRF) and other glandular components vary among populations of Plethodon jordani was analyzed by reverse-phase HPLC. Gland extracts from individuals revealed that males within a population differ in the relative amounts of the glandular components as well as in the presence and absence of components, including PRF. Comparisons between populations showed that each population had a unique elution profile and differed significantly in the relative amounts of PRF and the other extract components. Knowledge about the nature of geographic variation in the courtship pheromone, combined with behavioral tests of female response, will contribute towards understanding how the pheromone evolved.     

Chemical Communication in Chagas Disease Vectors. Source, Identity, and Potential Function of Volatiles Released by the Metasternal and Brindley's Glands of Triatoma infestans Adults

Compounds from the metasternal and Brindley's glands of the blood-sucking bug, Triatoma infestans, were identified by solid phase microextraction (SPME) and gas chromatography-mass spectrometry. Volatile compounds released by adult bugs during copulation or after mechanical disturbance were also characterized. Six compounds were identified and found consistently in all samples from metasternal glands. The most abundant were 3-pentanone, 2-methylbutanol, 3-pentanol, and an unidentified compound. The metasternal gland blends did not differ qualitatively between sexes. Compounds found in Brindley's glands were short chain acids, alcohols, esters, and a ketone with no qualitative differences between sexes. Isobutyric acid was the main component of this blend, and two new confirmed compounds were described as products of these glands: 2-butanone and 2-methylbutyric acid. 3-Pentanone was collected from the headspace over 33% of the copulating pairs of T. infestans. Volatiles found in the headspace of disturbed T. infestans adults included short-chain fatty acids, alcohols, esters, and ketones, with no qualitative differences between sexes. Both types of glands apparently discharge their contents after disturbance. However, most of the volatiles released by bugs after disturbance came from Brindley's glands. The locomotor activity of fourth instars increased significantly after stimulation with the odors emitted by disturbed adults, as compared with larvae stimulated by the odor of undisturbed adults or by clean air. We also studied the directional behavioral response of fifth instars to the disturbance scent in a locomotion compensator. Larvae exposed to volatiles released by disturbed adults walked away from the direction of the odor. The results suggest that this blend or part of it functions as an alarm pheromone for T. infestans. We suggest that the metasternal glands of this species are involved both in the sexual and the alarm contexts, and that the Brindley's glands probably have both alarm and defensive roles.     

Periodical and Age-related Variation in Chemical Communication System of Black Cutworm Moth, Agrotis ipsilon

Periodical and age-related changes in sex pheromone signaling and response were studied in the black cutworm moth, Agrotis ipsilon. Females began to call on the first night after eclosion and called mainly during the second half of the scotophase. The percentage of females calling increased from 1- to 3-day-old females and decreased from 3- to 6-day-old females (P < 0.001). One-day-old females called later in the scotophase than 2- and 3-day-old females (P = 0.016). The quantity of Z7–12:Ac, Z9–14:Ac, and Z11–16:Ac in pheromone gland extracts of 1- to 6-day-old females varied with time of the photoregime, increasing during scotophase and decreasing during photophase (P 0.001). These oscillations were described by using equations containing angular terms with a period of 24 hr. The quantities of Z7–12:Ac and Z9–14:Ac, but not of Z11–16:Ac, varied with female age during the calling period (P < 0.001, P = 0.021, and P = 0.529, respectively). The ratios of Z9–14:Ac and Z11–16:Ac to Z7–12:Ac did not change with age or time during calling period. Male response to female pheromone in a wind tunnel increased with age and time of the scotophase. The type of response exhibited by the males (taking flight, oriented flight, and pheromone source contact) was affected by both age and time of the scotophase (P < 0.001).     

Using Generic Pheromone Lures to Expedite Identification of Aggregation Pheromones for the Cerambycid Beetles Xylotrechus nauticus, Phymatodes lecontei, and Neoclytus modestus modestus

Males of several species of longhorned beetles in the subfamily Cerambycinae produce sex or aggregation pheromones consisting of 2,3-hexanediols and/or hydroxyhexanones. We tested the hypothesis that this diol/hydroxyketone pheromone motif is highly conserved within the subfamily, and the resulting prediction that multiple cerambycine species will be attracted to compounds of this type. We also tested the concept that live traps baited with generic blends of these compounds could be used as a source of live insects from which pheromones could be collected and identified. Traps placed in a mature oak woodland and baited with generic blends of racemic 2-hydroxyhexan-3-one and 3-hydroxyhexan-2-one captured adults of both sexes of three cerambycine species: Xylotrechus nauticus (Mannerheim), Phymatodes lecontei Linsley, and Phymatodes decussatus decussatus (LeConte). Odors collected from male X. nauticus contained a 9:1 ratio of two male-specific compounds, (R)- and (S)-3-hydroxyhexan-2-one. Field trials with synthetic compounds determined that traps baited with (R)-3-hydroxyhexan-2-one (94% ee), alone or in blends with other isomers, attracted similar numbers of X. nauticus of both sexes, whereas (S)-3-hydroxyhexan-2-one (94% ee) attracted significantly fewer beetles. Phymatodes lecontei and P. d. decussatus also were caught in traps baited with hydroxyhexanones, as well as a few specimens of two other cerambycine species, Neoclytus modestus modestus Fall (both sexes) and Brothylus gemmulatus LeConte (only females). Male N. m. modestus produced (R)-3-hydroxyhexan-2-one, which was not present in extracts from females. Neoclytus m. modestus of both sexes also responded to lures that included (R)-3-hydroxyhexan-2-one as one of the components. The only male-specific compound found in extracts from P. lecontei was (R)-2-methylbutan-1-ol, and adults of both sexes were attracted to racemic 2-methylbutan-1-ol in field bioassays. Surprisingly, P. lecontei of both sexes also were attracted to (R)- and (S)-3-hydroxyhexan-2-ones, although neither compound was detected in extracts from this species. Males of all five beetle species had gland pores on their prothoraces that were similar in structure to those that have been associated with volatile pheromone production in other cerambycine species. The attraction of multiple cerambycine species of two tribes to (R)-3-hydroxyhexan-2-one in this study, and in earlier studies with other cerambycine species, suggests that this compound is a widespread aggregation pheromone component in this large and diverse subfamily. Overall, the attraction of multiple species from different cerambycine tribes to this compound at a single field site supports the hypothesis that the hydroxyketone pheromone structural motif is highly conserved within this subfamily.     

Discrimination Between Self-Produced Pheromones and Those Produced by Individuals of the Same Sex in the Lizard Cordylus cordylus

Male and female Cordylus cordylus can discriminate between tiles labeled by their own pheromones and tiles labeled by individuals of the same sex, as shown by elevated tongue-flick rates in which the tongue contacts only air above the tiles labeled by other individuals and tongue-flicks in which the tongue contacts the tiles themselves. Potential pheromone sources for these discriminations are the femoral glands, cloacal glands, generation glands, ventral skin, and excretory products. Although studied in few species, pheromonal discriminations between self and other individuals, familiar and unfamiliar individuals, and kin and unrelated individuals appear to be broadly distributed in lizards, occurring in Iguania and in both Gekkonoidea and Scincomorpha within Scleroglossa. Both sexes of C. cordylus defend territories against both sexes. An ability to distinguish pheromones of other individuals of the same sex from self-produced pheromones would allow detection of intruders, but pheromonal discriminations among individuals would be more useful. Adaptive functions of pheromonal discriminations for residents and nonresidents and discriminatory abilities required are discussed. Tongue-flicks touching labeled tiles differed between experimental conditions, suggesting vomerolfactory discrimination, but the interpretation of a similar difference for tongue-flicks that contacted no substrate is problematical. Such air tongue-flicks might indicate sampling of volatile molecules for delivery to the vomeronasal organs. Experiments are needed to conclusively determine the sensory bases of the discriminations and the role of air tongue-flicks.     

Chemical communication in the primitive antAneuretus simoni: The role of the sternal and pygidial glands

Trail and alarm communication inAneuretus simoni are mediated by the secretions of the sternal and pygidial glands, respectively. The sternal gland is composed of a glandular epithelium and an associated reservoir located in the 7th sternum. This gland produces a relatively long-lived mass recruitment pheromone. The pygidial gland opens between the 6th and 7th tergites and produces a secretion that releases aggressive alarm. The evolution of glandular physiology in the Aneuretinae and Dolichoderinae are discussed in view of these findings.     

Characterization of and male adaptation to pheromone of femaleTrichostrongylus colubriformis (Nematoda)

Males of the ruminant nematodeTrichostrongylus colubriformis were significantly attracted to an incubate from their females during in vitro assay. Exposure of males to sera from uninfected and infected animals or selected neurotransmitters had no effect on their subsequent responsiveness to the female's pheromone. In contrast, exposure to 1500 female-hours of pheromone decreased male responsiveness after moderate rinsing prior to bioassay. Rinsing of the males with larger volumes of Tyrode's solution prior to in vitro assay increased their subsequent response to the female's pheromone. High-performance liquid chromatography yielded a presumptive pheromone peak with a fivefold increase in biological activity. This peak was soluble in alcohols and tetrahydrofuran, based on elution from reverse-phase Sep-Pak cartridges. Stability of the peak was increased by EDTA or ascorbic acid (10 mM). Storage for six weeks in ascorbic acid at 4 °C allowed recovery of 47.3% of the original material.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Chemical recognition of the mother by the young of the cichlid fish,Cichlasoma citrinellum

When placed in aY-maze, the 1–10-day-old free-swimming fry of the Midas cichlid can chemically distinguish between their mother and plain water and between another mother and plain water. They do not distinguish between the two mothers offered together or between their father and plain water. Predation pressures make these responses adaptive.     

The Yeast ATF1 Acetyltransferase Efficiently Acetylates Insect Pheromone Alcohols: Implications for the Biological Production of Moth Pheromones

Many moth pheromones are composed of mixtures of acetates of long‐chain (≥10 carbon) fatty alcohols. Moth pheromone precursors such as fatty acids and fatty alcohols can be produced in yeast by the heterologous expression of genes involved in insect pheromone production. Acetyltransferases that subsequently catalyze the formation of acetates by transfer of the acetate unit from acetyl‐CoA to a fatty alcohol have been postulated in pheromone biosynthesis. However, so far no fatty alcohol acetyltransferases responsible for the production of straight chain alkyl acetate pheromone components in insects have been identified. In search for a non‐insect acetyltransferase alternative, we expressed a plant‐derived diacylglycerol acetyltransferase (EaDAcT) (EC 2.3.1.20) cloned from the seed of the burning bush (Euonymus alatus) in a yeast system. EaDAcT transformed various fatty alcohol insect pheromone precursors into acetates but we also found high background acetylation activities. Only one enzyme in yeast was shown to be responsible for the majority of that background activity, the acetyltransferase ATF1 (EC 2.3.1.84). We further investigated the usefulness of ATF1 for the conversion of moth pheromone alcohols into acetates in comparison with EaDAcT. Overexpression of ATF1 revealed that it was capable of acetylating these fatty alcohols with chain lengths from 10 to 18 carbons with up to 27‐ and 10‐fold higher in vivo and in vitro efficiency, respectively, compared to EaDAcT. The ATF1 enzyme thus has the potential to serve as the missing enzyme in the reconstruction of the biosynthetic pathway of insect acetate pheromones from precursor fatty acids in yeast.     

Chemical Orientation of Brown Bullheads, Ameiurus nebulosus, Under Different Flow Conditions

The spatiotemporal information in chemical signals provides critical information for organisms during chemical orientation. Information in chemical signals is influenced by the hydrodynamic conditions of the environment. Hydrodynamically distinct environments will contain different types of information, which will influence how organisms orient. This study was designed to examine how the orientation behavior of the brown bullhead (Ameiurus nebulosus) is influenced by flow regime. The experiment was conducted in a flume under two different flow conditions. Treatments consisted of control (no odor) and plain gelatin (odor). Percent success, swimming speed, turning angle, heading angle, heading angle upstream, and net-to-gross ratio were analyzed. Brown bullheads were 100% successful in finding the odor source under no flow and 57% successful in flow. Bullheads swam differently in the no-flow condition when compared to the flow condition. Since, these fish did not orient the same under different flow conditions, it appears that hydrodynamics plays a role in shaping their behavior.     

Trail-Following Pheromones in Basal Termites, with Special Reference to Mastotermes darwiniensis

In the framework of an evolutionary study, trail pheromones have been studied in the most basal extant termite, Mastotermes darwiniensis (Mastotermitidae), and two other basal termites, the Termopsidae Porotermes adamsoni (Porotermitinae) and Stolotermes victoriensis (Stolotermitinae). Although workers of M. darwiniensis do not walk in single file while exploring a new environment under experimental conditions and are unable to follow artificial trails in ‘open field’ experiments, they do secrete a trail-following pheromone from their sternal glands. This unique behavior might reflect a primitive function of communication of the sternal gland. The major component of the pheromone appears to be the same in the three basal species: the norsesquiterpene alcohol (E)-2,6,10-trimethyl-5,9-undecadien-1-ol. This represents a new chemical category of trail-following pheromones for termites. The quantity of pheromone was estimated as 20 pg/individual in M. darwiniensis, 700 pg/individual in P. adamsoni, and 4 pg/individual in S. victoriensis. The activity threshold was 1 ng/cm in M. darwiniensis and 10 pg/cm in P. adamsoni. In M. darwiniensis, the trail pheromone was secreted by sternal gland 4 and to a lesser degree by sternal gland 3, sternal gland 5 being almost inactive. This study highlighted phylogenetic relationships between the Mastotermitidae and two subfamilies of the Termopsidae, the Porotermitinae and the Stolotermitinae. Furthermore, it indicated a heterogeneity within the Termopsidae, with Porotermitinae and Stolotermitinae on one hand, and Termopsinae on the other. Finally, Mastotermitidae and Termopsidae, with C14 trail pheromones, are clearly separated from the Kalotermitidae, Rhinotermitidae, and Termitidae that secrete C12 or C20 trail pheromones.     

Chemical basis for asymmetric mating isolation between strains of screwworm fly,Cochliomyia hominivorax

Laboratory mating tests and bioassays for a contact, mating-stimulant pheromone were conducted within and between two strains of the screwworm fly,Cochliomyia hominivorax. No strain or sex difference in pheromone activity occurred at emergence. However, the pheromone activity of females increased with age in one strain but declined in the other. Activity also declined in males of both strains but more steeply than in the females. Thus, sexual dimorphism in pheromone activity developed with age in both strains but to differing degrees. The decline in female pheromone activity was partly compensated for within that strain by a higher male responsiveness to pheromone. Female pheromone activity and mating success were positively correlated. Virgin females and those inseminated 24–48 hr previously were equally stimulatory. It appears that the strain differences arose from selection for reduced pheromone activity during laboratory colonization.     

Chemical Identification, Emission Pattern and Function of Male-Specific Pheromones Released by a Rarely Swarming Locust, Schistocerca americana

Pheromones serve key functions in the biology of swarming locusts. However, research has focused largely on the mass-swarming desert locust, Schistocerca gregaria. We extended these investigations to the pheromonal profile of the rarely swarming American bird grasshopper, S. americana (Drury). The headspace of mature gregarious S. americana males contained three characteristic electroantennogram-active components: (Z)-3-nonen-1-ol, (Z)-2-octen-1-ol, and nonanal. These substances were accompanied by aromatics such as phenol that are also released by females and immatures. Male-specific pheromone components were released independently from epidermal gland cells, with the highest emission rate being for (Z)-3-nonen-1-ol from the abdomen and legs. The emission of the major compound, (Z)-3-nonen-1-ol, is stress-sensitive, and coincides with sexual maturity and crowding. The emission pattern strongly supports a role of (Z)-3-nonen-1-ol in the reproductive biology of S. americana. The pheromone is involved in courtship-inhibition and is used as mate assessment pheromone in cryptic female choice. In double mating experiments, females choose sperm of males with high (Z)-3-nonen-1-ol emission. Furthermore the pheromone accelerated maturation of immature adults and supports synchronization of sexual development.     

Kairomonal Response of Predators to Three Pine Bast Scale Sex Pheromones

The kairomonal activity of the sex pheromones of three pine bast scales, Matsucoccus feytaudi, Matsucoccus josephi, and Matsucoccus matsumurae, as well as a new analog of the M. feytaudi sex pheromone, were investigated in pine forests of France, Portugal, and Italy. The response of the maritime pine bast scale predators, Elatophilus spp. and Hemerobius stigma, was used to test the influence of trapping methods, kairomone composition, and dose. Both predators showed significant attraction to all compounds except to the sex pheromone of M. josephi. Significant increase in captures was observed as a function of dose, and within the studied dose range, up to 2200 μg, no threshold saturation limits were observed for any of the attractive compounds. Trap design and size did not significantly influence predator captures, except for high population levels of Elatophilus crassicornis, when plate traps were more efficient than delta traps. Geographic variations were found in the kairomonal responses patterns of both predators, with the M. matsumurae sex pheromone being more attractive to the oriental populations from Corsica and Italy, whereas the western populations in Aquitaine and Portugal were more attracted to the M. feytaudi sex pheromone.     

Enhancement of Attraction to Sex Pheromones of Spodoptera exigua by Volatile Compounds Produced by Host Plants

We measured the effects of exposure to volatile compounds produced by host plants on the rate of capture of male Spodoptera exigua using synthetic sex pheromones. Exposure to volatile compounds stimulated strong electroantennographic responses of male S. exigua. The behavioral responses of male moths to combinations of sex pheromone and volatile compounds were tested in wind tunnel experiments. When lures were baited with synthetic sex pheromone plus benzaldehyde, phenylacetaldehyde, (Z)-3-hexenyl acetate, or linalool, respectively, the landing rate of S. exigua males was increased by 101.4%, 79.6%, 60.6%, and 34.3%, respectively, compared to sex pheromone alone. In field tests, traps baited with either pheromone + (E)-2-hexenal, pheromone + phenylacetaldehyde, pheromone + (Z)-3-hexenyl acetate, or pheromone + (Z)-3-hexenol enhanced moth catches by 38.8%, 34.6%, 24.6%, and 20.8%, respectively compared to traps baited with pheromone alone. In a second field experiment, more S. exigua males were trapped with a combination of a synthetic sex pheromone blend and several individual host plant volatiles compared to synthetic sex pheromone alone. These results suggest that some host plant volatiles enhance the orientation response of S. exigua male moths to sex pheromone sources.     

Insect Pheromones and Precursors in Female African Elephant Urine

Using automated solid-phase dynamic extraction and gas chromatography-mass spectrometry, our search for urinary chemical signals from ovulatory female African elephants (Loxodonta africana) has revealed the bark beetle aggregation pheromones frontalin, exo-brevicomin, and endo-brevicomin, as well as their precursors and the aphid alarm pheromones (E,E)-alpha-farnesene and (E)-beta-farnesene. Enantiomeric ratios for brevicomins have been determined. Prior discovery of common insect/elephant pheromones in Asian elephants, namely, (Z)-7-dodecenyl acetate and frontalin, suggests that the present findings may yield valuable insights into chemical communication among African elephants.     

几种鳞翅目昆虫性信息素10和11－十二碳烯－1－醇乙酸酯的简便合成

从芥酸出发，经臭氧化还原，乙酰化及四乙酸铅脱羧三步反应合成了茶长卷峨性信息素组份（４），再经ＣｏＣｌ２／Ｐｈ３Ｐ／ＮａＢＨ４体系异构化合成桦广翅小卷峨、豆荚小卷娥等昆虫性信息素组份（５）。     

Ostariophysan Alarm Pheromones: Laboratory and Field Tests of the Functional Significance of Nitrogen Oxides

In laboratory and field-trapping studies, we exposed fathead minnows (Pimephales promelas) and finescale dace (Chrosomus neogaeus) to hypoxanthine-3-N-oxide and a suite of structurally and functionally similar compounds in order to determine if: (1) hypoxanthine-3-N-oxide functions as a chemical alarm signal in ostariophysan fishes and (2) the purine skeleton, a structural component, or the nitrogen oxide, a functional component, or both act as the molecular trigger in this chemical alarm signaling system. Minnows and dace exhibited significant antipredator responses when exposed to conspecific skin extract or hypoxanthine-3-N-oxide (increased shoaling and decreased area use) and the functionally similar pyridine-N-oxide (increased shoaling) but not to structurally similar molecules lacking a nitrogen oxide functional group or to a swordtail skin extract control. Field-trapping studies revealed similar results. Traps labeled with fathead minnows skin extract, hypoxanthine-3-N-oxide, or pyridine-N-oxide caught significantly fewer fish than did those labeled with distilled water. These data strongly suggest that the nitrogen oxide functional group acts as the chief molecular trigger in the Ostariophysan alarm pheromone system and that, contrary to previous research, hypoxanthine-3-N-oxide may be one of several possible molecules that function as a chemical alarm signal. Here we report the first example of a single functional group capable of eliciting a suite of behavioral responses.     

Specificity of Response to Sex Pheromones Among Sweetpotato Weevils, Cylas puncticollis and C. brunneus

Trapping experiments were carried out in Uganda and Indonesia with decyl (E)-2-butenoate and dodecyl (E)-2-butenoate, previously identified as components of the female sex pheromones of the African species of sweetpotato weevil, Cylas puncticollis and C. brunneus, respectively. In Uganda, decyl (E)-2-butenoate attracted only C. puncticollis males, but dodecyl (E)-2-butenoate attracted males of both C. brunneus and C. puncticollis. Catches of C. puncticollis with both compounds were higher when they were dispensed from polyethylene vials rather than rubber septa, while dodecyl (E)-2-butenoate dispensed from rubber septa gave higher catches of C. brunneus and was more selective for this species. Release rates of the two compounds from the two types of dispenser were measured in the laboratory and possible explanations for differences in dispenser performance considered. Lures containing decyl (E)-2-butenoate were as attactive to male C. puncticollis as 10 live virgin female C. puncticollis weevils, but lures containing dodecyl (E)-2-butenoate were not always as attractive to male C. brunneus as the conspecific virgin female weevils. Dose–response relationships with the synthetic pheromones varied between repeat experiments and with the type of dispenser. Addition of dodecyl (E)-2-butenoate to decyl (E)-2-butenoate either did not affect or increased catches of C. puncticollis males, but adding 1% or more of decyl (E)-2-butenoate to dodecyl (E)-2-butenoate significantly reduced attractiveness to C. brunneus. Traps baited with synthetic lures captured male C. brunneus weevils mostly early in the evening while the majority of male C. puncticollis were trapped between 01:00 hr and 03:00 hr. This clear temporal separation of activity of males of the two species helps to ensure species specificity of mating in these sympatric species. In Indonesia, dodecyl (E)-2-butenoate but not decyl (E)-2-butenoate attracted C. formicarius males, but this attractiveness was less than 0.4% that of the pheromone of C. formicarius, (Z)-3-dodecenyl (E)-2-butenoate.     

Pheromone Communication in the Honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Recent studies have demonstrated a remarkable and unexpected complexity in social insect pheromone communication, particularly for honeybees (Apis mellifera L.). The intricate interactions characteristic of social insects demand a complex language, based on specialized chemical signals that provide a syntax that is deeper in complexity and richer in nuance than previously imagined. Here, we discuss this rapidly evolving field for honeybees, the only social insect for which any primer pheromones have been identified. Novel research has demonstrated the importance of complexity, synergy, context, and dose, mediated through spatial and temporal pheromone distribution, and has revealed an unprecedented wealth of identified semiochemicals and functions. These new results demand fresh terminology, and we propose adding “colony pheromone” and “passenger pheromone” to the current terms sociochemical, releaser, and primer pheromone to better encompass our growing understanding of chemical communication in social insects.