Raimondas Mozuraitis

Review : Improving our knowledge of male mosquito biology in relation to genetic control programmes

The enormous burden placed on populations worldwide by mosquito-borne diseases, most notably malaria and dengue, is currently being tackled by the use of insecticides sprayed in residences or applied to bednets, and in the case of dengue vectors through reduction of larval breeding sites or larviciding with insecticides thereof. However, these methods are under threat from, amongst other issues, the development of insecticide resistance and the practical difficulty of maintaining long-term community-wide efforts. The sterile insect technique (SIT), whose success hinges on having a good understanding of the biology and behaviour of the male mosquito, is an additional weapon in the limited arsenal against mosquito vectors. The successful production and release of sterile males, which is the mechanism of population suppression by SIT, relies on the release of mass-reared sterile males able to confer sterility in the target population by mating with wild females. A five year Joint FAO/IAEA Coordinated Research Project brought together researchers from around the world to investigate the pre-mating conditions of male mosquitoes (physiology and behaviour, resource acquisition and allocation, and dispersal), the mosquito mating systems and the contribution of molecular or chemical approaches to the understanding of male mosquito mating behaviour. A summary of the existing knowledge and the main novel findings of this group is reviewed here, and further presented in the reviews and research articles that form this Acta Tropica special issue.

A key malaria metabolite modulates vector blood seeking, feeding, and susceptibility to infection

Siren molecule calls loudly to mosquitoes People infected by malaria become more attractive to the mosquito vectors of the disease, which facilitates the spread of malaria. Emami et al. found that red blood cells of the host respond to a parasite-derived isoprenoid called HMBPP by increasing the production of carbon dioxide and several monoterpenes and aldehydes. Mosquitoes fed HMBPP-spiked blood displayed malaria parasite–specific changes in gene transcription, which reinforced attractiveness for the mosquito. HMBPP also stimulates mosquito feeding and malaria parasite reproduction. Thus, the parasite manipulates its mammalian host to make it more attractive to the insect vectors and exploits the same molecule to amplify transmission. Science, this issue p. 1076 An isoprenoid released by Plasmodium-infected red blood cells has several functions in enhancing parasite transmission. Malaria infection renders humans more attractive to Anopheles gambiae sensu lato mosquitoes than uninfected people. The mechanisms remain unknown. We found that an isoprenoid precursor produced by Plasmodium falciparum, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), affects A. gambiae s.l. blood meal seeking and feeding behaviors as well as susceptibility to infection. HMBPP acts indirectly by triggering human red blood cells to increase the release of CO2, aldehydes, and monoterpenes, which together enhance vector attraction and stimulate vector feeding. When offered in a blood meal, HMBPP modulates neural, antimalarial, and oogenic gene transcription without affecting mosquito survival or fecundity; in a P. falciparum–infected blood meal, sporogony is increased.

Odour Maps in the Brain of Butterflies with Divergent Host-Plant Preferences

Butterflies are believed to use mainly visual cues when searching for food and oviposition sites despite that their olfactory system is morphologically similar to their nocturnal relatives, the moths. The olfactory ability in butterflies has, however, not been thoroughly investigated. Therefore, we performed the first study of odour representation in the primary olfactory centre, the antennal lobes, of butterflies. Host plant range is highly variable within the butterfly family Nymphalidae, with extreme specialists and wide generalists found even among closely related species. Here we measured odour evoked Ca2+ activity in the antennal lobes of two nymphalid species with diverging host plant preferences, the specialist Aglais urticae and the generalist Polygonia c-album. The butterflies responded with stimulus-specific combinations of activated glomeruli to single plant-related compounds and to extracts of host and non-host plants. In general, responses were similar between the species. However, the specialist A. urticae responded more specifically to its preferred host plant, stinging nettle, than P. c-album. In addition, we found a species-specific difference both in correlation between responses to two common green leaf volatiles and the sensitivity to these compounds. Our results indicate that these butterflies have the ability to detect and to discriminate between different plant-related odorants.

Parthenogenesis, calling behavior, and insect-released volatiles of leafminer moth Phyllonorycter emberizaepenella

We proved that the leafminer moth Phyllonorycter emberizaepenella (Lepidoptera: Gracillariidae) reproduces by parthenogenesis of the thelytoky type. Despite a complete absence of males, parthenogenetically reproducing females diurnally demonstrated the calling posture normally used for releasing signaling compounds. Two compounds, which we collected from a calling female, were identified as potential sex pheromone components: (8E,10E)-8,10-tetradecadienyl acetate and (8E,10E)-8,10-tetradecadienol, the latter occurring only in trace amounts. In field experiments, no males were attracted to traps baited with either the potential sex pheromone or with virgin females. Both the pattern of behavior and the chemical characteristics of the pheromone of Ph. emberizaepenella species were similar to those known for Lepidoptera with the usual amphimictic mode of reproduction. Theoretical speculations that in thelytoky, where there is no need to find a sexual partner, the individuals would obtain certain advantages due to reduction in their sexual behavior, were, thus, not confirmed for Ph. emberizaepenella.

Sex pheromones of Phyllonorycter acerifoliella and Ph. heegerella and communication peculiarities in three species of leafmining moths

Females of the leaf miner moth Phyllonorycter acerifoliella (Z.) [=Ph. sylvella (Hw.)] and Ph. heegerella (Z.) (Lepidoptera: Gracillariidae: Lithocolletinae) release their sex pheromone at the beginning of photophase. The periodicity of the ‘calling’ behaviour of Ph. acerifoliella females was established. Three compounds from calling virgin Ph. heegerella females were collected by the Solid Phase Micro Extraction (SPME) technique and identified as (Z)‐8‐tetradecenyl acetate (Z8‐14:OAc), tetradecyl acetate (14:OAc) and (Z)‐8‐tetradecenol (Z8‐14:OH) in the ratio (88±3):(2±0.6):(10±5) by capillary gas chromatography and mass spectrometry. Field trapping experiments demonstrated that the first two compounds are important for the attraction of conspecific males. Z8‐14:OAc was found to be attractive when tested separately, while 14:OAc acted as synergist. The attractivity of the three component blend was reduced by 10% admixture of either (E)‐10‐dodecenyl acetate (E10‐12:OAc) or (Z)‐10‐tetradecenyl acetate (Z10‐14:OAc).

Sex pheromone of the spotted tentiform leafminer moth Phyllonorycter blancardella (Fabr.) (Lep., Gracillariidae)

Dodecyl acetate (12:OAc) (E)‐10‐dodecenyl acetate (E10‐12:OAc) and (E)‐10‐dodecenol (E10‐12:OH) in the ratio 8 : 80 : 12 were collected by solid phase micro‐extraction of the volatiles emitted by virgin signalling females of the spotted tentiform leafminer moth, Phyllonorycter blancardella. The same compounds in the ratio 8 : 79 : 13 were extracted from the sex pheromone glands of virgin signalling females of the same species. The chemical structures of the compounds were identified by gas chromatography and mass spectrometry. Trapping results obtained from field tests using synthetic components of the sex pheromone demonstrated that only one component, E10–12:OAc, was essential for the attraction of conspecific males and should be considered as a sex pheromone.

BOVINOSE: Pheromone-Based Sensor System for Detecting Estrus in Dairy Cows

The BOVINOSE project (www.bovinose.eu) aims to develop an electronic nose to detect estrus in a dairy cow, and thus to determine the optimal timing of artificial insemination. The physical principle is based on detection of sex pheromones that are secreted by the cow, exclusively during estrus. These pheromones are the natural olfactory signal for the bull that the cow is in heat. This technology aims to help the dairy farmers in the EU, the vast majority being micro-enterprises run as family businesses.

Sex pheromone of the Brazilian apple leafroller, Bonagota cranaodes Meyrick (Lepidoptera, Tortricidae)

Abstract The female sex pheromone of Bonagota (=Phthteochroa) cranaodes (Meyrick) is a blend of (E,Z)-3,5-dodecadienyl ajcetate (E3,Z5-12:Ac) and (Z)-9-hexadecenyl acetate (Z9-16:Ac) according to analysis of pheromone - gland extracts and field trapping in apple orchards. This is the first time that E3,Z5-12:Ac has been identified as a lepidopteran sex pheromone. Traps baited with 100 μg E3,Z5-12:Ac were attractive over 15 weeks in the field and were as effective as traps baited with virgin females. Addition of Z9-16:Ac to E3,Z5-12:Ac at ratio of 1:10 had a significantly increase of male moths. The addition of the Z,E and Z,Z isomers to rubber septa baited with E3,Z5-12:Ac did not modify B. cranaodes male attraction, but 10% of EE enhanced trap catch.

New sex attractants for five Chamaesphecia species (Lepidoptera, Sesiidae) from the Ukraine and Turkmenistan

Abstract Field screening tests of (3Z,13Z)- and (3E,13Z)-octadecadienols, (2Z,13Z)-and (2E,13Z)-octadecadienols and their acetates as well as some binary mixtures of these compounds in dosages of 0.5 mg/dispenser were carried out in the Crimea, the Ukraine, and in the West Kopetdag mountains, Turkmenistan, in 1989-1993. New sex attractants for five clearwing moth species of the genus Chamaesphecia (Lepidoptera, Sesiidae) were discovered. Males of Ch. chalciformis were attracted by a 1:1 mixture of 3Z,13Z-18:OH and 2E,13Z-18:OAc, Ch. schmidtiformis by a 9:1 mixture of 3Z,13Z-18:OAc and 3Z,13Z-18:OH in the Ukraine as well as in the ratios 9:1 and 1:1 in Turkmenistan, Ch. mezentzevi by a 9:1 mixture of 3Z,13Z-18:OAc and the corresponding alcohol, Ch. zimmermanni by a 1:9 mixture of 3Z,13Z-18:OAc and 3.E,13Z-18:OH, and Ch. specia nova in Turkmenistan by a 1:1 mixture of 3Z,13Z-18:OH and 3E,13Z-18:OAc. Two inhibitors, 3Z,13Z-18:OH and 3E,13Z-18:OAc, of the sex attractant were found for Ch. zimmermanni. The periods of attraction to the traps were registered for males of Ch. zimmermanni and Ch. specia nova and were found to occur at 1900-2100 and 1430-1700 local time, respectively. Males of Ch. chalciformis and Ch. schmidtiform is were attracted to the traps in the afternoon.

New sex attractants and inhibitors for 17 moth species from the families Gracillariidae, Tortricidae, Yponomeutidae, Oecophoridae, Pyralidae and Gelechiidae

Abstract: Field screening tests of 21 saturated and monounsaturated straight chain C12 and C14 alcohols and their acetates as well as some binary mixtures in dosages of 1 and 0.2 mg/dispenser were carried out in Lithuanian in 1993 and 1994. New sex attractants were determined for males of five moth species of the family Gracillariidae (E10–12:OH for Phyllonorycter sorbi, E10–12Ac for Ph. cydoniella and Ph. oxyacanthae, Z10–12:OAc for Ph. junoniella, and a mixture of Z10–14:OAc with E9–14:OAc in a 1:10 for Ph. sylvella), for four species of the family Tortricidae (E10–14:OAc for Endothenia ericetana, Z10–14:OAc in a 10:1 mixture with E11–14:OAc for Eudemis pozphyrana, E11–14:OAc in a 10:1 mixture with E11–14:OH for Dichrorampha petiverella and Cochylis dubitana), for two species of Gelechiidae (Z9–14:OAc in a mixture with either Z10–14:OAc in a ratio 1:1, E9–14:OAc in a ratio 1:10 or E10–14:OAc in a ratio 10:1 for Bryotropha galhanella, Z10–14:OAc and E9–14:OAc in a ratio 10:1 for B. mundella), as well as for one species of each of the families Yponomeutidae (Z7–14:OAc for Paraswammerdamia lutarea) and Oecophoridae (Z10–14:OAc and E9–14:OAc in a ratio 10:1 for Pseudatemelia josephinae). Preliminary composition of sex attractants was established for three moth species of the family Gracillariidae (Z10–14:OAc in a 1:10 mixture with E9–14:OAc for Phyllonorycter heegerella, Ph. coryli and Ph. dubitella) and for one species of the family Gelechiidae (Z9–14:OAc for Bryotropha terella). Inhibitors of the sex attractants were found for four leafminer species of the family Gracillariidae (Z7‐, Z9‐ and Z10–12:OAc for Phyllonorycter sorbi, Z10‐, E10–12:OH and E10–14:OH for Ph. mespilella, E10–12:OH for Ph. cydoniella, Z10–12:OH and E10–14:OH for Ph. oxyacanthae), for three species of Tortricidae (E9‐, Z11‐ and E11–14:OAc for Endothenia ericetana, E11–14:OAc for Gypsonoma minutana, E10‐ and E11–14:OAc for Epagoge grotiana), and for one species from the family Pyralidae (Z10‐, E10‐ and E11–14:OAc for Pyrausta aurata). Data from male behaviour tests in tube olfactometers are presented for Phyllonorycter blancardella, Ph. sorbi, Ph. dubitella and Ph. strigulatella and active compounds revealed.