Developmental study of the Proboscis Extension Response to heat in Rhodnius prolixus along the life cycle

Triatominae are blood-sucking insects that localise their hosts using a range of sensory signals to find food, and among them, the heat emitted by the hosts. Heat is one of the main short-range cues in vertebrate hosts, able to trigger alone the Proboscis Extension Response (PER) that precedes the bite. Previous studies demonstrated that heat responsiveness of fifth-instar nymphs is maximum to moderate temperatures (30-35°C) compatible with those of their vertebrate host's body surface. This study investigated whether this thermal preference for biting is maintained along the life cycle of R. prolixus, from the first larval instar to male and female adults. The results showed that PER rates were at maximum around 30-35°C and decreased for a warmer temperature. The same thermal preference was maintained all along the life cycle, despite the increase in the size of the antennae linked to the growth. Interestingly, a decreased thermal responsiveness was stated in males as compared with larval instars and females. This decrease might reveal a lower motivation for host-seeking and might have an impact on males's vectorial competence.