Kissing bugs can generalize and discriminate between different bitter compounds

ASPARCH, YAMILA; PONTES, GINA; MASAGUÉ, SANTIAGO; MINOLI, SEBASTIAN; BARROZO, ROMINA

Physiology of Paris

ELSEVIER

Año: 2016

1769-7115

Animals make use of contact chemoreception structures to examine the quality ofpotential food sources. During this evaluation they can detect nutritious compounds thatpromote feeding and recognize toxins that trigger evasive behaviors. Although animals caneasily distinguish between stimuli of different gustatory qualities (bitter, salty, sweet, etc.),their ability to discriminate between compounds of the same quality may be limited.Numerous plants produce alkaloids, compounds that elicit aversive behaviors inphytophagous insects and almost uniformly evoke a bitter taste for man. Inhematophagous insects, however, the effect of feeding deterrent molecules has beenbarely studied. Recent studies showed that feeding in Rhodnius prolixus can be negativelymodulated by the presence of alkaloids such as quinine (QUI) and caffeine (CAF),compounds that elicit similar aversive responses. Here, we applied associative and nonassociativelearning paradigms to examine under two behavioral contexts the ability of R.prolixus to distinguish, discriminate and/or generalize between these two bittercompounds, QUI and CAF.Our results show that bugs innately repelled by bitter compounds can changetheir behavior from avoidance to indifference or even to preference according to theirprevious experiences. After an aversive operant conditioning with QUI or CAF, R. prolixusmodified its behavior in a direct but also in a cross-compound manner, suggesting theoccurrence of a generalization process between these two alkaloids. Conversely, after along pre-exposure to each alkaloid, bugs decreased their avoidance to the compoundused during pre-exposure but still expressed an avoidance of the novel compound, provingthat QUI and CAF are detected separately. Our results suggest that R. prolixus is able todiscriminate between QUI and CAF, although after an associative conditioning theyexpress a symmetrical cross-generalization. This kind of studies adds insight into the gustatory sense of a blood-sucking model but also into the learning abilities ofhematophagous insects.