Attractant volatiles released by female and male Triatoma infestans (Hemiptera: Reduviidae), a vector of chagas disease: chemical analysis and behavioral bioassay

Abstract

Volatiles emitted by male and female T infestans before and during copula were collected on Porapak-Q filters, desorbed with dichloromethane, and analyzed by gas chromotography and gas chromatography-mass spectrometry after confirmation of attractiveness in an arena bioassay. Chemical analysis confirmed the presence of (R,S) -2- and 3-methylbutan-1-ol in a 2:1 ratio; short chain acids (ethanoic to nonanoic acid); long chains acids decanoic to (Z)-9-octadecenoic acid; aliphatic aldehydes (hexanal to nonanal), benzaldehyde and dipropylsulphide from insects in copula. Electroantennographic studies conducted with a homologous series of aliphatic aldehydes on female and male T infestans showed that, for a given dose, EAG responses elicited from both sexes increased with increased chain length up to nonanal, after which EAG-activity declined. Attractiveness of non-acidic trace components identified in the volatiles were tested on male and female T. infestans, in an arena bioassay using a video tracking method. Aliphatic C6 to C10 aldehydes were tested: hexanal (1-100 microg) and heptanal (10 microg) were attractive to female T. infestans, high doses of octanal and nonanal (1-100 microg) were Unattractive to male and female T. infestans but low doses of nonanal (0.01-0.1 microg) were attractive to male T infestans. Benzaldehyde was highly attractive to female T. infestans at low doses (0.05- 0.1 microg). 3-methylbutan-1-ol was attractive to male T infestans at high dose (1,000 microg). (S) or (S,R) 2-methyl-butan-1-ol were attractive to males or females (1-1,000 microg). Blends of hexanal and benzaldehyde (20:1 and 40:1) showed an additive effect on attraction compared with hexanal alone, when tested on female T. infestans. The study has demonstrated the presence of a number of electrophysiologically and behaviorally active compounds in volatiles emitted by T. infestans in copula that may have a role in the postulated copulation pheromone.