Cuticular lipids mediate mate recognition in Triatomines

JUÁREZ M.P.; LORENZO FIGUIRAS A.; CALDERÓN FERNÁNDEZ G.M. ; COCCHIARARO BASTÍAS L.M.

Colonia del Sacramento, Uruguay

Congreso; 1st Latin American Meeting of Chemical Ecology.; 2010

Asociación Latino Americana de Ecología Química

Triatomine bugs (Hemiptera, Reduviidae) are vectors of the parasite Trypanosoma cruzi, the causative agent of Chagas disease. Cuticular lipids (CL) are known to participate in insect intraspecific chemical communication as contact cues; e.g. in aggregation and sexual behavior. In triatomines, CL include a blend of hydrocarbons, free and esterified fatty acids and fatty alcohols, together with minor components. CL extracts or selected fatty acid components of Triatoma infestans -a major Chagas disease vector- were shown to trigger aggregation and arrestment behavior [1]; however no reports on their role in sex-related events are yet available in triatomines. Here we report CL contribution to contact sex recognition both in T. infestans and in secondary vector species of T. sordida subcomplex.   Chemical composition: Male and female CL were solvent-extracted and analyzed by capillary gas chromatography (CGC) coupled to mass spectrometry (MS). Alternatively, CL were extracted by solid phase microextraction (SPME) either by direct contact with a fiber, or from the head space of heated intact insects. The hydrocarbon fractions were analyzed by CGC-MS. Bioassays: CL were evaluated for their role on the copulatory behavior. Male copulation attempts were quantizated in the presence of freeze-killed females, either intact, deprived of their CL, or reconstituted with a female extract; the response of males of T. sordida subcomplex against heptacosane (n-C27) was also evaluated. T. sordida, T. garciabesi and T. guasayana showed significantly larger amounts of n-C27 in females compared to males (2-6 times), with smaller variation in other hydrocarbon components. On the contrary, no sex dimorphism was evident in the major lipid fractions of T. infestans. Contact cues are necessary in mate recognition by males of all the species tested; the cuticular recognition cues are removed by hexane wash. Males contact females with their antenna and legs prior to elicit mating attempts. Recently freeze-killed females were attractive to males (80-100% mating attemps); no response was detected when males were exposed to hexane-washed females. The attraction was partially recovered when the lipid extract was reloaded on the female dorsal surface. In the species of T. sordida subcomplex, the hydrocarbon fraction elicited similar response than that of the whole lipid extract; a like response was also obtained with 5 equivalents of n-C27, suggesting the participation of other hydrocarbon components. We conclude that cuticular lipids trigger mate recognition in triatomines, probably involving the participation of contact chemoreceptors. The identity of the sex chemical signal seems to be species specific in triatomines. Further studies are ongoing to detect sex dimorphism in minor cuticle lipid fractions in T. infestans.     [1] Parasites & Vectors 2009, 2:8