What does heat tell a mosquito?

P. ZERMOGLIO; E. ROBUCHON; M.S. LEONARDI; F. CHANDRE; C. LAZZARI

Congreso; International Congress of Neuroethology; 2016

Orientation of haematophagous insects towards their hot-blooded hosts using heat as a cue has been acknowledged for many decades. In mosquitoes, heat has been recently studied, along with other cues which allow these insects to locate and approach their human hosts, in multimodal perception contexts. However, a direct characterization of how they evaluate thermal sources is still lacking. In this study we characterize Aedes aegypti thermal sense using simple dual choice assays, providing direct evidence on how distinct traits of heat sources affect mosquitoes choices. We found that female mosquitoes, but not males, are able to discriminate among heat sources that are at ambient (25°C), host-range (34°C) and deleterious (50°C) temperatures when no other stimuli are present, eliciting a positive response towards host-range and an avoidance response towards deleterious temperatures. We also tested the orientation of females according to the size and position of the sources. We found that females do not discriminate between heat sources of different sizes, but actively orientate towards closer sources at the host temperature. Furthermore, we show that females cannot use IR radiation as an orientation cue. Our results constitute the first behavioural characterization of the thermal sense of mosquitoes. Orientation towards a host involves the integration of cues of different nature in distinct phases of the orientation. Although such integration might be decisive in the success of the host encounter, we show that heat alone is sufficient to elicit orientation behaviour. We discuss the performance of mosquitoes thermal behaviour, as compared to other blood-sucking insects.