Meeting Abstract

17.5  Friday, Jan. 4  Mosquitoes do not track warm plumes in the absence of CO2 ZAMORE, S*; LAMARCA, E; DANIEL, TL; University of Washington; Roosevelt High School; University of Washington sharri@uw.edu

Mosquitoes track host prey at large distances using windborne signals such as CO₂ and odor emission. They are also equipped with a pair of thermosensory organs on the distal end of each antenna. The calculated radiative sensitivity and unbiased landing on surfaces of varying radiative emissivity suggest they are not sensitive to radiative (black body) heat, making convective (windborne) heat a likely navigation signal. Experiments suggest that thermosensation is gated by CO₂ detection, suggesting convective tracking may require the presence of CO₂. We seek to determine if mosquitoes can track a convective thermal signal, and how this behavior is modulated by a CO₂ background. To test mosquitoes’ ability to navigate using convective heat in the absence of CO₂, we flew female mosquitoes (Aedes aegypti) in a darkened wind tunnel (1 m long, 0.33 m wide) in clean air. Two gold-leafed stainless steel heating rods were placed upwind as a convective heat source with low radiative emissivity. Small changes in temperature (+2 C) were detectible in thermographic images. For all trials, one heater was kept at 40 ± 0.1 C. We used 200 fps video to track the flight path and landing selectivity between two heat sources. Our data suggest that, in the absence of CO2, A. aegypti do not exhibit bias toward the heated element. Of the animals flights analyzed, 5 of 9 of the mosquitoes flew predominantly downwind of the heated element, while 2 trials showed no side preference. All exhibited search behaviors, but none landed on the heated rods. Given the low radiation of the heat source and the falloff of radiant heat, it remains unlikely that the mosquitoes detect radiant heat at these distances. Our observations suggest thermal tracking requires CO₂ detection.