Amblyomma cajennense (Acari: Ixodidae) é um carrapato de grande importância sócio-econômica no subcontinente Sul-Americano. Apesar disso, pouco se conhece acerca de sua ecologia química, cuja informação é crucial para o seu controle. Nesse estudo, 2,6-diclorofenol (2,6-DCP), o feromônio sexual de A. cajennense foi quantificado por cromatografia gasosa acoplada a espectrometria de massas no modo de análise por monitoramento seletivo de íons (CG/EM-MSI) a partir de fêmeas alimentadas em coelhos durante 6 dias. O extrato do feromônio sexual foi obtido pela exposição ao ultrassom de fêmeas virgens em hexano em duas amostras independentes. Nenhum pré-tratamento da amostra foi necessário. Os métodos de adição padrão (SA) e de curva de calibração com 5-bromo-4-hidróxi-3-metóxibenzaldeído (5-BrV) como padrão interno (IS) foram utilizados para a quantificação. O conteúdo de 2,6-DCP não apresentou diferença significativa entre os extratos e/ou métodos utilizados. Os resultados mostraram que as faixas de concentração de 2,6-DCP por fêmea foram de 2,03-2,27 ng mL -1 e de 2,06-2,24 ng mL -1 para os métodos SA e IS, respectivamente. Os métodos mostraram ser específicos, sensíveis e fidedignos na determinação de 2,6-DCP em carrapatos.Amblyomma cajennense (Acari: Ixodidae) is a tick of socioeconomic importance in the South American sub-continent. Nevertheless, little is known pertaining to its chemical ecology, information deemed crucial to its management. In this study, the tick sex pheromone 2,6-dichlorophenol (2,6-DCP) was quantified from A. cajennense fed on rabbits for 6 days by use of gas chromatography-mass spectrometry in the selected ion monitoring mode (GC/MS-SIM). The sex pheromone extract was obtained by the exposure of attractive females to hexane and ultrasound probe in two independent samples. Clean-up was not necessary. Standard addition method (SA) and calibration curve with 5-bromine-4-hydroxy-3-methoxybenzaldehyde (5-BrV) as an internal standard (IS) were employed in the quantification. 2,6-DCP contents did not show significant differences between extracts and/or methods. Results showed that the concentration range of sex pheromone per female were 2.03-2.27 ng mL -1 and 2.06-2.24 ng mL -1 for SA and IS methods, respectively. The methods provide a specific, sensitive and reliable technique for determining 2,6-DCP levels in ticks.Keywords: Amblyomma cajennense, tick sex pheromone, 2,6-dichlorophenol, GC/MS-SIM, internal standard, standard addition IntroductionAmblyomma cajennense Fabricius (Acari: Ixodidae) is a three-host tick of great socioeconomic importance. Though mainly a parasite of equines, A. cajennense attacks humans and a diverse range of other animals, both wild and domesticated. It is also a vector of the etiologic agent for Rocky Mountain spotted fever, Rickettsia rickettsii, in humans and animals living in the region.3 This tick species seems to expand continually in areas where it was Gachoka et al. 1643 Vol. 21, No. 9, 2010 previously unimportant, with recent reports of its spread from the ...
In order to clarify the role of 2,6-dichlorophenol (2,6-DCP) in the courtship of Amblyomma cajennense, sexually mature males that had previously fed on rabbits were tested in bioassays. The males were released onto dummies treated with whole female extract or synthetic 2,6-DCP at a concentration of two female equivalents, or with hexane (control), and their responses were observed. In the presence of both the extract and 2,6-DCP, excitation was observed among the males, expressed in the form of touching and probing the dummy, and mounting occurred readily. The percentages of mounting (73%) and tipping over (60%) were equal in the two treatments and higher than in the control group (27 and 20%, respectively). Relatively short durations of mounting were recorded, and these were statistically similar in all treatments. Almost all instances of mounting resulted in tipping-over behavior. A few isolated cases of males that went directly to ventral positioning without mounting were observed. It was confirmed that 2,6-DCP alone is capable of mediation of mounting behavior in A. cajennense.Keywords: 2,6-DCP, Amblyomma cajennense, mount, sex pheromone, tick. ResumoVisando elucidar o papel do 2,6-diclorofenol (2,6-DCF) no cortejo de Amblyomma cajennense, machos sexualmente maduros, previamente alimentados em coelhos, foram avaliados em testes biológicos. Os machos foram liberados sobre manequins tratados com um extrato de fêmeas, ou com 2,6-DCF sintético na concentração equivalente a duas fêmeas, ou com hexano (controle), e suas respostas foram observadas. Na presença do extrato e do 2,6-DCF, a excitação dos machos foi expressa na forma de toques e sondagens, e a monta ocorreu rapidamente. As porcentagens de respostas observadas nos dois tratamentos foram iguais, sendo a monta (73%) e retorno na superfície ventral (60%) mais altos que no controle (27 e 20%, respectivamente). Foram observados períodos de monta relativamente curtos, sendo esses estatisticamente iguais em todos os tratamentos, e quase todos resultando em posicionamento ventral. Alguns casos isolados de posicionamento ventral sem monta foram observados. Foi confirmado que o 2,6-DCP sozinho é capaz de mediar o comportamento de monta de A. cajennense. Palavras-chave: 2,6-DCF, Amblyomma cajennense, monta, feromônio sexual, carrapato.Amblyomma cajennense (Acari: Ixodidae) is a tick of great importance in relation to public health in South America, principally because of its capacity to transmit the causative agent of Brazilian spotted fever, Rickettsia rickettsii, to humans and animals (SUCEN, 2004;SANGIONI et al., 2005). The female sex attractant pheromone consists of 2,6-dichlorophenol (2,6-DCP), which is a highly volatile substance. This phenol has so far been reported from 18 species of Ixodidae in seven genera, and it has great potential for exploitation with the aim of controlling these species (SONENSHINE, 2006 LOULY et al., 2008). In two of these, it has been further associated with induction of mounting behavior (BORGES; RIBEIRO, 1999;BORGES et al...
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