Volatile compound diversity and conserved alarm behaviour in Triatoma dimidiata

Abstract

BackgroundTriatoma dimidiata (Latreille) is a key vector complex of Trypanosoma cruzi, etiologic agent of Chagas disease, as it spans North, Central, and South America. Although morphological and genetic studies clearly indicate existence of at least five clades within the species, there has been no robust or systematic revision, or appropriate nomenclature change for species within the complex. Three of the clades (haplogroups) are distributed in Mexico, and recent evidence attests to dispersal of clades across previously “presumed” monotypic geographic regions. Evidence of niche conservatism among sister species of this complex suggests that geographic dispersal is possible for non-sympatric populations, although no information is available on the behavioural aspects of potential interclade interactions, for instance whether differentiation of chemical signaling or response to these signals could impede communication among the haplogroups.MethodsVolatiles emitted by disturbed bugs, Brindley’s (BGs), and metasternal (MGs) glands were identified using solid-phase micro-extraction (SPME) and gas chromatography coupled mass spectrometry (GC-MS). Volatile compounds emitted by BGs and MGs, and those secreted by disturbed nymphs and adults, of the three Mexican T. dimidiata haplogroups were tested for avoidance behaviour by conspecific nymphs and adults using an olfactometer.ResultsTriatoma dimidiata haplogroups all have three age-related alarm responses: absence of response by early stage nymphs, stage-specific response by 4-5th stage nymphs, and a shared 4-5th nymph and adult response to adult compounds. Disturbed bugs released 15 to 24 compounds depending on the haplogroup, among which were three pyrazines, the first report of these organoleptics in Triatominae. Isobutyric acid from BGs was the most abundant molecule in the response in all haplogroups, in addition to 15 (h1) to 21 (h2 and h3) MG compounds. Avoidance behaviour of disturbed bugs and volatiles emitted by BGs were haplogroup specific, while those from the MG were not.ConclusionsDiscriminant and cluster analysis of BG + MG compounds indicate significant separation among the three haplogroups, while alarm response compounds were similar between h2 and h3, both distinct from h1. This latter haplogroup is ancestral phylogenetically to the other two. Our results suggest that alarm responses are a conserved behaviour in the Triatoma dimidiata complex.

Landscape ecology of Trypanosoma cruzi in the southern Yucatan Peninsula

“…These studies may benefit from recent information regarding aggregation molecules in T. dimidiata (May-Concha et al, 2015), which will hopefully now allow us, without the need for tracker dogs (Rolon et al, 2011), to develop traps for more effective and representative collections of all haplogroups, and more importantly, the parasite populations they contain. Parasite detection from bug faeces, although representing infective populations, may not be the only population in the vector.…”

Synthesis and secretion of volatile short‐chain fatty acids in Triatoma infestans infected with Beauveria bassiana

“…This compound is released by aphids and some coleopterans and is known to be repellent to grain storage weevils (Germinara et al ., ). In triatomines, propionic acid was previously reported to be a part of their volatile blend (May‐Concha et al ., , , ).The role of some synthetic components forming the volatile blend was tested by Palottini & Manrique () in order to detect any escape response of T. infestans ; however, no activity was reported for propionic acid, suggesting that it has no effect as an alarm pheromone.…”

“Sweeter than a rose”, at least to Triatoma phyllosoma complex males (Triatominae: Reduviidae)

“…Triatomine bugs have two principal exocrine glands: the Brindley’s (BGs) and the metasternal (MGs) glands [ 8 ]. Previous studies demonstrated that these glands in some triatomines produce and release VOCs for alarm and sexual behaviour [ 9 – 12 ]. BGs of most triatomines primarily release isobutyric acid, a highly conserved compound in both North and South American sub-clades of the Triatomini [ 13 ].…”

“…BGs of most triatomines primarily release isobutyric acid, a highly conserved compound in both North and South American sub-clades of the Triatomini [ 13 ]. In contrast, MGs produce multiple ketones and alcohols, most of which are species-specific [ 10 – 12 , 14 , 15 ]. A recent study comparing exocrine volatiles among the three primary dimidiata complex haplogroups demonstrated subtle but specific differences in production and secretion of VOCs between sister species [ 12 ].…”