More about the role of 2,6-dichlorophenol in tick courtship: identification and olfactometer bioassay in Amblyomma cajennense and Rhipicephalus sanguineus

This study aimed to identify 2,6-dichlorophenol (2,6-DCP) in Amblyomma cajennense and to evaluate its role in A. cajennense and Rhipicephalus sanguineus courtship. Hexanic extract from attractive females was purified by solid phase extraction and the phenol was identified by the single ion monitoring method using GC/MS. In an olfactometer, the responses of A. cajennense and R. sanguineus males to females, control rubber septa or rubber septa impregnated with 2,6-DCP at 50, 500, and 5000 ng, respectively, were studied. 2,6-DCP was identified in A. cajennense extract and the males oriented themselves toward the concentration of 500 ng. These septa and the females were recognized as copula partners. The septa treated with 2,6-DCP did not attract and were not even recognized by the R. sanguineus males, whereas the females were recognized. Due to the presence of 2,6-DCP in A. cajennense and the results of biological bioassays, it was concluded that this compound acts as an attractant and mounting sex pheromone in this tick, but it does not play any role in R. sanguineus courtship.

Towards the identification and synthesis of the sex pheromone of the citrus leafminer, Phyllocnistis citrella Stainton ( Lepidoptera: Gracillariidae )

O objetivo desta pesquisa foi caracterizar o comportamento sexual do minador-dos-citros, Phyllocnistis citrella Stainton, como suporte para o isolamento, identificação e síntese do seu feromônio sexual. O acasalamento de P. citrella ocorre no intervalo entre 1h antes do início da fotofase e 1h após o término da escotofase, entre adultos de um e dois dias de idade. O comportamento de corte e cópula foi descrito para essa espécie, sendo a duração média da cópula de 49,6 min. Estudos conduzidos em olfatômetro tipo Y demonstraram que os machos foram fortemente atraídos pelas fêmeas virgens bem como pelo extrato natural de glândulas de feromônio sexual das fêmeas.

Evidence for presence of female produced pheromone components in male scent brush extract of castor semi-looper moth Achaea janata L.

Hexane extract of male terminalia (along with scent brushes) of castor semi-looper moth, Achaea janata L, elicited significant olfactory responses in both male and female insects by electroantennogram recording technique. However, male extract in the wind tunnel evoked noticeable behaviour responses in the female insects only. Orientation response of the males to the male extract was not evident in wind tunnel experiments. Two electrophysiologically-active compounds were identified from the male extract. Based on GC retention times and mass spectrometry the two compounds were confirmed as (Z,Z)-9,12-octadecadienal and (Z,Z,Z)-3,6,9-heneicosatriene. These two compounds are also constituents of female produced four-component blend of A. janata.

Identification of glandular (preputial and clitoral) proteins in house rat (Rattus rattus) involved in pheromonal communication.

Proteins (18-20 kDa) belonging to lipocalin family have been reported to act as carriers for ligands binding to pheromones in mouse urine, pig saliva, hamster vaginal fluid and human sweat, that are involved in pheromonal communication. As the preputial gland is a major pheromonal source, the present study was aimed to detect the specific protein bands (around 18-20 kDa) in the preputial and clitoral glands of the house rat, R. rattus. The amount of protein was higher in preputial gland of the male than that of female (clitoral) gland. A 20 kDa protein was noted in male and female glands; however, the intensity of the band was much higher in male than in female. In addition, 70, 60, 35 kDa bands, identified in male preputial gland, were absent in females. The presence of higher concentration of glandular proteins in the male preputial gland suggests that male rats may depend more on these glandular proteins for the maintenance of reproductive and dominance behaviours. The results further suggest that these glandular proteins (20 kDa) may act as a carrier for ligand binding.

Oviposition attractancy of an infusion from a wood inhabiting fungus for vector mosquitoes.

BACKGROUND & OBJECTIVES: Review of literature indicates that none of the chemicals so far studied for oviposition attractancy was found to be promising for operational use. Efforts are being made to find an effective substance to corner a large number of ovipositing females to selective breeding sites for ease of control operation. This will reduce insecticidal consumption and will be cost-effective. This study is aimed to evaluate the oviposition attractancy of aqueous infusion from a wood inhabiting fungus (Polyporus spp.) for vector mosquitoes both in the laboratory and under field conditions. METHODS: An aqueous infusion (10%) was prepared by soaking 10 g of fungal powder in 100 ml of chlorine-free tap water. The mixture was shaken thoroughly and filtered through Whatman No. 1 filter paper. The filtered infusion was tested for oviposition attractancy against vector mosquitoes both in the laboratory and under field conditions. RESULTS: The laboratory study on the dose-effect relationship indicated that at an optimum concentration of 4 ppm, maximum attractancy was observed. Water treated with aqueous fungal infusion (AFI) at 4 ppm received significantly more egg rafts/eggs of vector mosquitoes than other substrates like rearing water, natural breeding water and tap water. Trials conducted in the field showed that mud pots treated with AFI placed in both indoor and outdoor locations received significantly more Aedes aegypti eggs than the control. Similarly, treated pots placed in paddy fields attracted significantly more gravid Anopheles subpictus for oviposition than untreated pots. In contrast, the number of egg rafts of Culex quinquefasciatus laid in AFI treated pots was significantly less than in the control ones owing to strong natural olfactory factors associated with the breeding habitat. INTERPRETATION & CONCLUSION: The results indicated that there is scope for developing a trap incorporating this oviposition attractant along with insect growth regulator(s) (IGR) for surveillance and/or control of Ae. aegypti and other vector mosquitoes breeding in paddy fields.