The role of water vapour in the orientation behaviour of the blood-sucking bug Triatoma infestans (Hemiptera, Reduviidae)

The gustatory system of animals is involved in food quality assessment and controls the feeding decision of an individual confronted with a potential alimentary source. Triatomines are haematophagous insects that feed on vertebrate blood. Once they reach a potential host, they walk over the host skin searching for an adequate site to pierce. Then, they insert their stylets and take a first sampling gorge to decide whether food is acceptable. Our work reveals that the presence of bitter compounds inhibits the feeding behavior of these bugs. Firstly, triatomines decreased their feeding behavior if substrates spread with quinine or caffeine were detected by external receptors localized exclusively in the antennae. Morphological inspections along with electrophysiological recordings revealed the existence of four gustatory sensilla located in the tip of the antenna that respond to both bitter tastants. The absence of these bitter detectors by antennal ablation reversed the observed feeding inhibition evoked by bitter compounds. Secondly, once triatomines pumped the first volume of food with bitter compounds (quinine, caffeine, berberine, salicin), a decrease in their feeding behavior was observed. Morphological inspections revealed the existence of eight gustatory sensilla located in the pharynx that might be responsible for the internal bitter detection. Finally, we found that a brief pre-exposure to bitter compounds negatively modulates the motivation of bugs to feed on an appetitive solution. Results presented here highlight the relevance of bitter taste perception in the modulation of the feeding behavior of a blood-sucking insect.

Section: Recognition Of An Adequate Substratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bitter stimuli modulates the feeding decision of a blood-sucking insect via two sensory inputs

Pontes

Minoli

Insaurralde

et al. 2014

“…After 1min of familiarisation, the door was opened. Led by its positive anemotaxis (Barrozo et al, 2003), the insect walked along the starting arm and, at the bifurcation, could choose to follow one of the two air streams, one bearing the stimulus and the other only clean air, by entering into one of the two choice arms. We considered the first choice made by bugs, when they crossed an arbitrary decision line at the entry of each arm.…”

Section: Testing Procedure: the Olfactometermentioning

confidence: 99%

Learning the way to blood: first evidence of dual olfactory conditioning in a blood-sucking insect, Rhodnius prolixus. I. Appetitive learning

Vinauger

Buratti

Lazzari

2011

a major role in host-seeking behaviour in haematophagous insects (Lazzari, 2009;Guerenstein and Lazzari, 2009 Accepted 28 June 2011 SUMMARY It has been largely assumed that the individual experience of insects that are disease vectors might not only contribute to animal fitness, but also have an important influence on parasite transmission. Nevertheless, despite the invested efforts in testing the capacity to learn and remember information in blood-sucking insects, only little conclusive information has been obtained to date. Adapting a classical conditioning approach to our haematophagous model, we trained larvae of Rhodnius prolixus to associate Llactic-acid, an odour perceived by these bugs but behaviourally neutral when presented alone, with food (i.e. positive reinforcement). Naive bugs -those exposed either to a conditioned stimulus (CS, L-lactic acid), unconditioned stimulus (US, heat) and reward (blood) alone or CS, US and reward in the absence of contingency -remained indifferent to the presence of an air stream loaded with L-lactic acid when tested in an olfactometer (random orientation), whereas the groups previously exposed to the contingency CS-US-reward (blood) were significantly attracted by L-lactic-acid. In a companion paper, the opposite, i.e. repellence, was induced in bugs exposed to the contingency of the same odour with a negative reinforcement. This constitutes the first evidence of olfactory conditioning in triatomine bugs, vectors of Chagas disease, and one of the few substantiations available to date of olfactory conditioning in haematophagous insects.

“…Because triatomines exhibit spontaneous anemotaxis to odourless air-streams under these conditions (Barrozo et al, 2003), a simultaneous-discrimination bioassay was conducted, similar to that previously used by us (Barrozo et al, 2004;Barrozo and Lazzari, 2004a;Barrozo and Lazzari, 2004b;Bodin et al, 2008;Bodin et al, 2009). Individual insects were exposed to two opposite horizontal charcoal-filtered air-streams (180 deg.…”

Section: The Response To Comentioning

confidence: 99%

Behavioural and physiological state dependency of host seeking in the blood-sucking insectRhodnius prolixus

Bodin

Vinauger

Lazzari

2009

SUMMARYVertebrate blood is essential for the growth and the reproduction of haematophagous insects. Provided that hosts play the double role of food sources and predators, feeding on their blood exposes these insects to a high predation risk. Therefore, it is expected that host seeking occurs only when insects need to feed. In the present study, we analyse how the feeding status affects the response to host-associated cues in the blood-sucking insect Rhodnius prolixus. We show that the responsiveness to hostassociated cues, such as CO 2 and heat, and that the motivation to feed depend on the time elapsed since a blood meal. Depending on the time elapsed after feeding, the same concentration of CO 2 may attract or repel the insects. As far as we know, this is the first time that a host signal has been shown to be repellent for a haematophagous insect. The response to heat is also modulated but no repellence was observed. When blood was replaced by saline solution as food, a significant reduction of the response to both signals was evinced but repellence was not observed. The injection of haemolymph from fed insects into starved insects inhibited the response of the receiver insects to both signals but this was not observed after the injection of saline solution or of haemolymph from non-fed insects. This is the first time that the modulation of feeding behaviour by the feeding status has been analysed in a hemimetabolous blood-sucking insect, fully excluding any effect of other processes, such as reproduction.