Behavioural and electrophysiological responses of Triatoma dimidiata nymphs to conspecific faecal volatiles

Abstract

Abstract. The behavioural and electrophysiological (electroantennography) responses of the first two instars of Triatoma dimidiata (Hemiptera: Reduviidae) Latreille to fresh and dry faecal headspace volatile extracts from fifth instar conspecific nymphs and synthetic compounds were analysed in this study. Recently emerged nymphs (3-5 days) aggregated around filter paper impregnated with dry faeces and around filter paper impregnated with extracts from both fresh and dry faeces. Older first instars (10-15 days) and second instars aggregated around filter paper impregnated with fresh and dry faeces, and their respective headspace extracts. Dry faecal volatile extracts elicited the strongest antennal responses, followed by fresh faecal extracts. Gas chromatography−mass spectrometry analysis of dried faecal headspace volatiles demonstrated the presence of 12 compounds: 2-ethyl-1-hexanol, 1,2,4-trimethylbenzene, n-octadecane, n-nonadecane, n-eicosane, n-heneicosane, n-tricosane, n-pentaeicosane, n-hexaeicosane, n-octaeicosane, nonanal, and 4-methyl quinazoline. In fresh faecal headspace extracts, only nonanal was clearly detected, although there were other trace compounds, including several unidentified sesquiterpenes. Four of the 11 compounds tested individually elicited aggregation behaviour at concentrations of 100 ng/μL and 1 μg/μL. A blend containing these four components also mediated the aggregation of nymphs. These volatiles may be valuable for developing monitoring methods and designing sensitive strategies to detect and measure T. dimidiata infestation.

Lessons to be popular: the chemical basis of aggregation pheromone in Trypanosoma cruzi- infected and non-infected Chagasic bugs

“…This suggest that these compounds are not properly a signal (pheromone), but that serve as cues that communicate the presence of the kissing bugs (aldehydes) or host (amino acid derivatives). This idea is supported by recent ndings of short chain aldehydes found in faeces of other triatomines 12,19,22 , and studies that demonstrate that faeces attract insects from the same as well as different species 13,15 .…”

“…Faeces from 100 fth instar nymphs were collected as previously described with slight modi cations 12 . Bugs were placed in a plastic bottle with a lter paper at the bottom.…”

“…These bugs are gregarious and nocturnal insects that feed mostly on bird and mammal blood 10 . During daylight hours, these insects use different physical and chemical cues to orient towards refuges 11,12 . As for the chemical cues, triatomines are attracted to conspeci c and heterospeci c faeces [13][14][15] , cuticular lipids 16,17 , and footprints [18][19][20] .…”

“…There is some background information for aggregation pheromones in triatomines. First, short chain aldehydes (C 6 -C 10 ) have been found in faeces or in volatiles of aggregated insects which work as attractants 12,21,24 . Second, alkanes (C 18 -C 25 ) have been found in faeces of T. dimidiata and T. infestans 12 .…”

Isolation and identification of attractants from the pupae of three lepidopteran species for the parasitoid Chouioia cunea Yang

“…Nonadecane is fairly common in insects and plants. It has been detected in volatiles from a variety of plants, such as Epipogium aphyllum and Acacia cyclops (Fabaccae), as well as the fecal headspace volatiles of Triatoma dimidiata and the Dufour's gland secretions of some ants . Sun et al .…”