Raimondas Mozūraitis

The roles of kairomones, synomones and pheromones in the chemically-mediated behaviour of male mosquitoes

Despite decades of intensive study of the chemical ecology of female mosquitoes, relatively little is known about the chemical ecology of males. This short review summarizes the current state of knowledge of the chemicals that mediate male mosquito behaviour. Various trophic interactions including insect-plant, insect-host, and insect-insect responses are emphasized. The relevance of the chemical ecology of male mosquitoes in the context of vector control programmes is discussed.

p-Cresol: A Sex Pheromone Component Identified from the Estrous Urine of Mares

Previously it was shown that m- and p-cresols in the urine of mares exhibits a temporally reproducible pattern that is dependent on ovarian activity and, thus, provides information about the timing of ovulation. New behavioral data demonstrate 1) that stallions spend significantly more time sniffing p-cresol as compared to o-, and m-cresols, and, 2) that the extent of stallions’ erections differ significantly in response to different types of samples. The lowest erection level was recorded for the pure-water control, a moderate erection level was elicited by the urine of diestrous mares, and the highest erection level was elicited by urine of a diestrous mare containing synthetic p-cresol at a quantity equivalent to half of the amount of p-cresol found in the urine of estrous mares. Consequently, p-cresol is at least one of the components of a horse sex pheromone.

p- and m-Cresols emitted from estrous urine are reliable volatile chemical markers of ovulation in mares

Urine samples from 14 mares, belonging to five breeds, were collected at estrus and diestrus to search for estrous specific volatile compounds which could be used to determine ovulation time. Around 150 volatiles were collected from urine head-space samples by solid phase micro extraction technique, and analyses were conducted by gas chromatography-mass spectrometry methods. Comparison of chromatographic profiles of volatile substances revealed that concentrations of m- and p-cresols were significantly greater during estrus while diethylphthalate was more abundant at diestrus. Monitoring of m- and p-cresols during the period of estrus and a few days before and after estrus revealed irregular changes in amounts of cresols until 3-4 days before ovulation when the concentration of the compounds began to increase with peaks 1 day before ovulation. On the day when ovulation occurred, amounts of the metabolites decreased sharply, almost to basal concentrations, and remained at these concentrations for 6 days - when sampling was finished. In four of the mares changes in the concentration of diethylphthalate were less pronounced and more temporally variable compared with those of cresols. Based on reproducible temporal changes in concentrations of m- and p-cresols, with respect to the time of ovulation, a noninvasive test to determine a precise insemination time could occur. This would save time, reduce costs and simplify the procedure.

Chemocommunication in Phyllonorycter ulmifoliella (HBN.) (Lepidoptera : Gracillariidae) : Periodicity, sex pheromone, and inhibitors

Abstract(Z)-10-Tetradecenyl acetate (Z10-14:OAc) from abdominal tip extracts of virgin females of the tentiform leafminer moth Phyllonorycter ulmifoliella (Lepidoptera: Gracillariidae) was identified by gas chromatography and mass spectrometry. The biological activity of the component was confirmed by field tests with synthetic compounds. As a sex pheromone component this ester is novel both in the family Gracillariidae and in the superfamily Gracillarioidea. Field trapping of P. ulmifoliella with synthetic Z10-14: OAc at dosages of 1 and 0.2 mg/dispenser led to catches of approximately 9000 and 3000 male moths, respectively. The attractivity of the Z10-14:OAc was strongly inhibited by a 10% admixture of either (Z)-9-tetradecenyl acetate (Z9-14:OAc), (E)-9-tetradecenyl acetate (E9-14:OAc), or (E)-11-tetradecenyl acetate (E11-14:OAc). Addition of 10% (E)-10-tetradecenyl acetate (E10-14:OAc) to the sex pheromone reduced attractivity, but significantly less than the inhibitors previously mentioned. The pheromone releasing (or “calling”) behavior of virgin P. ulmifoliella females was recorded under laboratory conditions. Calling activity started about half an hour before lightson and the maximum number of calling females was registered half an hour after the start of photophase. A high level of pheromone releasing activity lasted for about 2 hr and ceased about 5 hr after the start of photophase. Chemocommunication activity in the light period of day is assumed to be an adaptation which allows this phyllonoryctid to avoid inhibitors emitted as pheromones by many other species. A scheme of probable interactions by means of semiochemicals between P. ulmifoliella and other lepidopterans is presented and the appearance of Z10-14: OAc as a sex pheromone component in Lepidoptera during evolution of the order is discussed.

C18 Dienes as attractants for eighteen clearwing (Sesiidae), tineid (Tineidae), and choreutid (Choreutidae) moth species

By screening singly and binary mixed 2,13- and 3,13-octadecadien-yl acetates and alcohols (2,13- and 3,13-18: Ac/OH)in Lithuania, Armenia, Azerbaijan, Turkmenistan, Ukraine, and the far east of Russia, sex attractants were discovered for 12 Sesiidae, four Tineidae, and one Choreutidae moth species. Males ofSesia yezoensis andBembecia puella as well asNemapogon flavifrons were attracted by mixture ofZ3,Z13-18:Ac/OH in a ratio of 9∶1,Pyropteron sp. n. by the same mixture (ratio 1∶9),Bembecia romanovi andB. zuwandica byZ3,Z13-18:Ac andE3,Z13-18:Ac (9∶1),Synanthedon caucasicum by the same mixture in the opposite ratio (1∶9),B. scopigera by 23,213-18:Ac andE2,Z13-18:OH in a ratio 9∶1,Synasphecia triannuliformis byZ3,Z13-18:OH andE3,Z13-18:OH (9∶1),Similipepsis takizawai andArchimeessia sp. n. byE3,Z13-18:OH andE2,Z13-18:Ac (1∶1),Prochoreutis sechestediana by a mixture ofE3,Z13-18:Ac plusE2,Z13-18:OH (1∶),Microsphecia brosiformis byE3,Z13-18:Ac,Synanthedon conopiformis by the analogous alcohol,Synanthedon scoliaeformis andNemaxera betulinella byE2,Z13-18:Ac,Triaxomera fulvimitrella byZ3,Z13-18:Ac. An analogous alcohol component is essential for the attraction ofB. ichneumoniformis males. Inhibitors forB. romanovi, B. scopigera andB. zuwandica attraction were discovered. Preliminary data on attractants for six other species as well as on the diurnal rhythm of sexual activity of three species are presented. A new method for the stereoselective synthesis of 3,13–18:Ac/OH andE2,Z13-18:Ac/OH is described.

Syntheses, characterizations, and biological activities of tetradeca-4,8-dien-1-yl acetates as sex attractants of leaf-mining moth of the genus Phyllonorycter (Lepidoptera: Gracillariidae).

The four possible isomers of tetradeca‐4,8‐dien‐1‐yl acetate and corresponding alcohols were synthesized stereoselectively by synthetic routes employing Wittig coupling reaction for the preparation of (Z,E)‐ and (Z,Z)‐isomers, and alkylation of terminal alkynes for the preparation of (E,E)‐ and (E,Z)‐isomers as the key steps. Synthetic products were characterized by 13C‐ and 1H‐NMR spectroscopy as well as mass‐spectrometric methods. All four isomers gave distinctive mass spectra where m/z 81 fragments clearly dominated. Elution order, followed by retention index presented in parenthesis, of tetradeca‐4,8‐dien‐1‐ols was determined as (Z,Z) (2082.1), (Z,E) (2082.8), (E,E) (2083.1), and (E,Z) (2083.2) from unpolar SPB‐1 column, and as (E,E) (2210.2), (Z,E) (2222.1), (E,Z) (2223.4), and (Z,Z) (2224.7) from polar DB‐WAX column. The isomers of tetradeca‐4,8‐dien‐1‐yl acetates eluted in the order of (Z,Z) (2176.1), (Z,E) (2178.4), (E,Z) (2185.9), and (E,E) (2186.4) from SPB‐1, and (Z,E) (2124.3), (E,E) (2157.7), (Z,Z) (2128.9), and (E,Z) (2135.9) from DB‐WAX columns. Field‐screening tests for attractiveness of tetradeca‐4,8‐dien‐1‐yl acetates revealed that (4Z,8E)‐tetradeca‐4,8‐dien‐1‐yl acetate significantly attracted Phyllonorycter coryli and Chrysoesthia drurella males. (4E,8E)‐Tetradeca‐4,8‐dien‐1‐yl acetate was the most efficient attractant for Ph. esperella and Ph. saportella males, and (4E,8Z)‐tetradeca‐4,8‐dien‐1‐yl acetate was attractive to Ph. cerasicolella males.

Pheromone Release Behaviour in Females of Phyllonorycter junoniella (Z.) (Lepidoptera, Gracillariidae) Under Constant and Cycling Temperatures

The calling activity of virgin Phyllonorycter junoniella (Z.) females under a cycling thermal regime differed from that under constant temperature in the following ways: the percentage of females calling at the morning activity peak was increased; the morning period of calling activity was prolonged; the total period of calling activity of an individual female was increased; an extra peak of activity occurred at the end of the photophase, and females changed the calling pattern during the active period. We assume that the occurrence of two calling peaks and the extension of the calling period might be adaptive for a Ph. junoniella species with a sex ratio strongly shifted towards females (8:1 females:males), as it could lead to an increased proportion of females mated.

Natal origin affects host preference and larval performance relationships in a tritrophic system

Abstract Many insects face the challenge to select oviposition sites in heterogeneous environments where biotic and abiotic factors can change over time. One way to deal with this complexity is to use sensory experiences made during developmental stages to locate similar habitats or hosts in which larval development can be maximized. While various studies have investigated oviposition preference and larval performance relationships in insects, they have largely overlooked that sensory experiences made during the larval stage can affect such relationships. We addressed this issue by determining the role of natal experience on oviposition preference and larval performance relationships in a tritrophic system consisting of Galerucella sagittariae, feeding on the two host plants Potentilla palustris and Lysimachia thyrsiflora, and its larval parasitoid Asecodes lucens. We firstly determined whether differences in host‐derived olfactory information could lead to divergent host selection, and secondly, whether host preference could result in higher larval performance based on the natal origin of the insects. Our results showed that the natal origin and the quality of the current host are both important aspects in oviposition preference and larval performance relationships. While we found a positive relationship between preference and performance for natal Lysimachia beetles, natal Potentilla larvae showed no such relationship and developed better on L. thyrsiflora. Additionally, the host selection by the parasitoid was mainly affected by the natal origin, while its performance was higher on Lysimachia larvae. With this study, we showed that the relationship between oviposition preference and larval performance depends on the interplay between the natal origin of the female and the quality of the current host. However, without incorporating the full tritrophic context of these interactions, their implication in insect fitness and potential adaptation cannot be fully understood.

Electrophysiological and behavioural responses of Ips typographus (L.) to trans-4-thujanol—a host tree volatile compound

Key messageSpruce trees emit significant amounts of trans-4-thujanol, but the amount of this compound in bark decreases with tree age. Trans-4-thujanol acts as an efficient repellent for the bark beetle Ips typographus.ContextThe spruce bark beetle, Ips typographus, is an economically significant pest of Norway spruce (Picea abies) that preferentially infests and kills old trees.AimsWe looked for spruce volatiles that were perceivable by I. typographus and that differed as the host tree aged.MethodsBark beetles were collected in the wild. Bark samples from spruce trees of different age were hydrodistilled. Gas chromatography–electroantennogram detection (GC-EAD) was used to identify which compounds induced beetle olfactory responses. These were identified by gas chromatography–mass spectrometry (GC-MS). Behavioural responses of bark beetles were tested using a Y-tube olfactometer.ResultsSeveral EAD peaks were recorded, of which trans-4-thujanol was consistently active and could be identified chemically unequivocally. The antennae of I. typographus females responded to a lower dosage of the compound than males, but both sexes were repelled by it. The bark of 10-year-old spruce trees contained 3 times more trans-4-thujanol than that of 35- 40-year-old trees, 27 times more than that of 70- to 80-year-old trees, and 200 times more than that of 120-year-old trees.ConclusionsTrans-4-thujanol is a bioactive compound in Norway spruce bark that varies in amount with tree age and affects spruce bark beetle behaviour under laboratory conditions. It is suggested that trans-4-thujanol might play a role in both spruce tree defence and tree choice by beetles.

Nonvolatile chemical cues affect host-plant ranking by gravid Polygonia c-album females.

In a multiple-choice test, the preference of egg-laying Polygonia c-album (comma butterfly) females was studied for oviposition on plants bearing surrogate leaves treated with crude methanol extracts obtained from leaves of seven host-plant species: Humulus lupulus, Urtica dioica, Ulmus glabra, Salix caprea, Ribes nigrum, Corylus avellana, and Betula pubescens. The ranking order of surrogate leaves treated with host-plant extracts corresponded well to that reported on natural foliage, except R. nigrum. Thus, host-plant choice in P. c-album seems to be highly dependent on chemical cues. Moreover, after two subsequent fractionations using reversed-phase chromatography the nonvolatile chemical cues residing in the most polar water-soluble fractions evidently provided sufficient information for egg-laying females to discriminate and rank between the samples of more and less preferred plants, since the ranking in these assays was similar to that for natural foliage or whole methanol extracts, while the physical traits of the surrogate leaves remained uniform.