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

Here, using an automated device able to quantify CO2-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 CO2 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".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.Mosquitoes transmit pathogens of diseases such as malaria, filariasis, yellow fever, and dengue fever. Malaria, killing nearly one million people annually [1], is caused by infection with parasites of the genus Plasmodium that is transmitted by female anopheline mosquitoes. Anopheles stephensi mosquitoes are the leading vector of malaria in India, parts of Asia and the Middle East. Despite these control efforts using mosquito nets [2], repellents [3], and insecticide [4,5], malaria remains a leading cause of worldwide morbidity and mortality [1,6]. The rate of contact between vertebrate hosts and mosquito Anopheles vectors has long been recognized as a crucial determinant of malaria transmission [7-9], and successful malaria control depends on understanding the interactions between mosquitoes and humans [10-13]. In order for transmission to occur, however, a female mosquito must be able to find potential hosts. In general, it is known that mosquitoes are remarkable for their ability to locate blood meal using human body emanations such as CO2, lactic acid, 1-octen-3-