Chemical Communication in Chagas Disease Vectors. Source, Identity, and Potential Function of Volatiles Released by the Metasternal and Brindley's Glands of Triatoma infestans Adults

Abstract

Compounds from the metasternal and Brindley's glands of the blood-sucking bug, Triatoma infestans, were identified by solid phase microextraction (SPME) and gas chromatography-mass spectrometry. Volatile compounds released by adult bugs during copulation or after mechanical disturbance were also characterized. Six compounds were identified and found consistently in all samples from metasternal glands. The most abundant were 3-pentanone, 2-methylbutanol, 3-pentanol, and an unidentified compound. The metasternal gland blends did not differ qualitatively between sexes. Compounds found in Brindley's glands were short chain acids, alcohols, esters, and a ketone with no qualitative differences between sexes. Isobutyric acid was the main component of this blend, and two new confirmed compounds were described as products of these glands: 2-butanone and 2-methylbutyric acid. 3-Pentanone was collected from the headspace over 33% of the copulating pairs of T. infestans. Volatiles found in the headspace of disturbed T. infestans adults included short-chain fatty acids, alcohols, esters, and ketones, with no qualitative differences between sexes. Both types of glands apparently discharge their contents after disturbance. However, most of the volatiles released by bugs after disturbance came from Brindley's glands. The locomotor activity of fourth instars increased significantly after stimulation with the odors emitted by disturbed adults, as compared with larvae stimulated by the odor of undisturbed adults or by clean air. We also studied the directional behavioral response of fifth instars to the disturbance scent in a locomotion compensator. Larvae exposed to volatiles released by disturbed adults walked away from the direction of the odor. The results suggest that this blend or part of it functions as an alarm pheromone for T. infestans. We suggest that the metasternal glands of this species are involved both in the sexual and the alarm contexts, and that the Brindley's glands probably have both alarm and defensive roles.

Olfaction in vector-host interactions

“…It should be mentioned that isobutyric acid has also been identified as a main constituent of the alarm pheromone of triatomines (e.g. Cruz López et al 1995, Guerenstein and Guerin 2004, Manrique et al 2006, Rojas et al 2002, Schofield 1979a. Thus, a parsimonious use of this odorant by these insects has been proposed (Guerenstein and Guerin 2001, Guerenstein and Lazzari 2009) because it is used by triatomines as, at least, host attractant and alarm signal depending on its concentration, sensory (in particular odour blend) context and the physiological state of the perceiving bug.…”

Biology, diversity and strategies for the monitoring and control of triatomines - Chagas disease vectors

“…This ample knowledge reported by the authors indicates that the development of sampling or detection devices can be based on solid information. Other aspects of triatomine behaviour, such as aggregation and sexual signals, are being studied and may generate further alternatives for interfering with insect communication processes and manipulating their behaviour (Lorenzo et al 2000, Manrique et al 2006, Pontes et al 2008.…”

Insect pheromone research in South America

“…92 Behavioral studies suggested both an alarm and defensive role of these compounds. 91,92 Several short-chain ketones and alcohols were also detected in the metasternal glands of adult female R. prolixus, and a possible role in sexual communication of the species was suggested. …”

“…The role of Brindley's and metasternal glands in chemical communication of T. infestans has been studied 90 and it has been suggested that volatiles released from the metasternal glands are involved in sexual and alarm behavior of this species. 90,91 Several compounds have been identified from metasternal glands, including 3-pentanone, 2-methylbutanol, and 3-pentanol. 91 Major volatiles released from Brindley's glands include isobutyric acid, 2-methylbutanol, 3-methylbutanol 91 as well as the isobutanoates of the latter alcohols.…”

“…90,91 Several compounds have been identified from metasternal glands, including 3-pentanone, 2-methylbutanol, and 3-pentanol. 91 Major volatiles released from Brindley's glands include isobutyric acid, 2-methylbutanol, 3-methylbutanol 91 as well as the isobutanoates of the latter alcohols. 92 Behavioral studies suggested both an alarm and defensive role of these compounds.…”