Triatomine cuticle lipids participate in chemical communication. Application to ecological vector control.

JUÁREZ M.P.; MIJAILOVSKY S; COCCHIARARO BASTÍAS L.; CALDERÓN G.M; GIROTTI J

La Plata

Workshop; Triatomine Genomics and Biology III; 2012

INTRODUCTION Insect cuticular lipids are known to participate in chemical communication as contact pheromones, either in aggregation or sexual behavior. In triatomines (Hemiptera: Reduviidae), cuticular lipids include a blend of hydrocarbons, free and esterified fatty acids and fatty alcohols, together with minor components [1]. This lipid layer is known to protect insects against desiccation, as well as from chemical and biological attack [2]. Here we report cuticular lipid contribution to aggregation behavior and sex recognition both in T. infestans and in secondary vector species of T. sordida complex. MATERIALS AND METHODS Extraction of cuticular lipids: cuticular lipids (CL) from adults (virgin males and females) and fifth-stage nymphs were extracted by immersing insect bodies in hexane (6 ml/g x 3) for 5 minutes each. Chemical analyses: T. infestans CL were sampled by head space solid phase microextraction (HS-SPME) at 150°C for 20 min., using a 65 μm polydimethylsiloxane/divinylbenzene fiber (PDMS/DVB). T. sordida and T. garciabesi CL were fractioned by column chromatography, cuticular hydrocarbons (CHC) were eluted with hexane. CL and CHC were analyzed by capillary gas chromatography (CGC) coupled to mass spectrometry (MS) [3]. T. infestans CL were also fractioned by preparative thin layer chromatography (TLC) for behavior studies. Bioassays: Aggregation behavior: T. infestans lipid fractions or separate free fatty acids were applied to the surface of filter paper strips; control papers were treated with same volume of hexane. Treated papers were placed on a Petri dish arena (12 cm diameter). Bugs were released in the arena for 1 h; then, the number of insects on each sector was counted. Sex behavior: Male response to dead females either intact, hexane-washed, or lipid-reconstituted was evaluated. Specific T. infestans female components (docosanol and eicosanol) were tested either individually or combined. T. garciabesi males were exposed to a synthetic hydrocarbon (heptacosane, n-C27). Statistical analyses: Differences in the CL or CHC profiles were tested by Student “t” test. Behavior bioassays were tested by Fisher exact test (sex pheromone) or G test (aggregation pheromone). CONCLUSIONS Triatomine cuticular lipids trigger both contact aggregation behavior and mate recognition. Male antennae contact is critical for sex discrimination. Olfactory cues do not seem to be involved in mate recognition. Components eliciting contact sex communication are species-specific: T. infestans female fatty alcohols trigger male copulatory response [4]. A female hydrocarbon (heptacosane) is attractive to T. sordida and T. garciabesi males. - The aggregation behavior of T. infestans is mediated by fatty acids and other lipid components [5]. - Cuticle lipids incorporated into trap-and-kill devices were shown to improve the performance of entomopathogenic fungi against domestic T. infestans [6].