The role of proboscis of the malaria vector mosquito Anopheles stephensi in host-seeking behavior.

BACKGROUND: The proboscis is an essential head appendage in insects that processes gustatory code during food intake, particularly useful considering that blood-sucking arthropods routinely reach vessels under the host skin using this proboscis as a probe. RESULTS: Here, using an automated device able to quantify CO(2)-activated thermo (35°C)-sensing behavior of the malaria vector Anopheles stephensi, we uncovered that the protruding proboscis of mosquitoes contributes unexpectedly to host identification from a distance. Ablation experiments indicated that not only antennae and maxillary palps, but also proboscis were required for the identification of pseudo-thermo targets. Furthermore, the function of the proboscis during this behavior can be segregated from CO(2) detection required to evoke mosquito activation, suggesting that the proboscis of mosquitoes divide the proboscis into a "thermo-antenna" in addition to a "thermo-probe". CONCLUSIONS: Our findings support an emerging view with a possible role of proboscis as important equipment during host-seeking, and give us an insight into how these appendages likely evolved from a common origin in order to function as antenna organs.