Triatomine Sexual Behaviour is Mediated by Chemical Communication Mechanisms

GINA B. PONTES; ANA C.R. DE VITTA; BJÖRN BOHMAN; CLAUDIA A. ZACHARIAS; GABRIEL MANRIQUE; C. RIKARD UNELIUS; MARCELO G. LORENZO

Vicosa, MG

Otro; VI Encontro Brasileiro de Ecologia Química; 2009

Universidade de Vicosa

Triatomine bugs are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease, an illness that affects ca.16 million people in the Americas. To facilitate the development of control tools, our work intends to clarify whether their sexual behavior is based on chemical communication mechanisms. For this, we have developed assays to characterize several phases of the sequence of behaviours that mediate encounters between individuals of both sexes. Furthermore, we developed experiments in order to identify chemical compounds produced by the metasternal glands (MG) of Triatoma infestans, Triatoma brasiliensis and Rhodnius prolixus. Finally, we evaluated the potential role of these substances as sexual communication signals. We have demonstrated that R. prolixus males present oriented take-off towards airstreams laden with female odour. Moreover, we have shown that MGodours are responsible for triggering this behaviour. In addition, SPME experiments have demonstrated that MG odours are emitted preferentially by R. prolixus females mostly during the dark phase of the daily cycle. Olfactometer experiments have allowed us to show that walking T. brasiliensis males are attracted by airstreams laden with female odour and that MG secretions mediate this behaviour. Additionally, similar results were obtained with R. prolixus males walking on a locomotion compensator. Mating pairs of T. infestans and R. prolixus, which are known to promote the aggregation of other males around them, also emitted MG odours. In fact, experiments with pairs of T. infestans and R. prolixus showed that mating success is drastically affected by the occlusion of MGs. Moreover, the occlusion of female MGs abolished male aggregation in T. infestans and R. prolixus. We have established that triatomine males detect the presence of competitors and can respond exhibiting postcopulatory associations. Moreover, the duration of the copula may vary depending on the presence of signals of sperm precedence by competitors or by the occlusion of female MGs. For the first time, the complex volatile products produced by the MGs of triatomine vectors were identified. We performed GC-EAD studies and determined that different MG compounds are able to promote responses in the antennae of T. brasiliensis males. Finally, we intend to evaluate the potential of MG odours as baits for the detection or capture of these vectors of Chagas disease.