Dekker Teun, Geier Martin, Cardé Ring T
Department of Entomology, University of California, Riverside, CA 92521, USA.
J Exp Biol. 2005 Aug;208(Pt 15):2963-72. doi: 10.1242/jeb.01736.
Female mosquitoes are noted for their ability to use odours to locate a host for a blood meal. Two sensory organs contribute to their sense of smell: the maxillary palps, which measure the level of CO2, and the antennae, which detect other host-released odours. To establish the relative importance and interactions of CO2 and other body emissions in freely flying mosquitoes, we presented female yellow fever mosquitoes Aedes aegypti L. with broad plumes of human skin odour and CO2 at natural concentrations and dilutions thereof in a wind tunnel. 3-D video-recorded flight tracks were reconstructed. Activation, flight velocity, upwind turning and source finding waned quickly as skin odours were diluted, whereas in the presence of CO2 these parameters remained unchanged over more than a 100-fold dilution from exhaled concentrations. Although mosquitoes were behaviourally less sensitive to skin odours than to CO2, their sensitivity to skin odours increased transiently by at least fivefold immediately following a brief encounter with a filament of CO2. This sensitization was reflected in flight velocity, track angle, turning rate upon entering and exiting the broad odour plume and, ultimately, in the source-finding rate. In Ae. aegypti, CO2 thus functions as a ;releaser' for a higher sensitivity and responsiveness to skin odours. The initially low responsiveness of mosquitoes to skin odours, their high sensitivity to CO2, and the sensitization of the olfactory circuitry by CO2 are ecologically relevant, because rapidly fluctuating CO2 levels reliably signal a potential host. Possible mechanisms of the instantaneous sensitization are considered.
雌性蚊子以其利用气味定位宿主以获取血餐的能力而闻名。有两个感觉器官有助于它们的嗅觉：下颚须，用于测量二氧化碳水平；触角，用于检测宿主释放的其他气味。为了确定二氧化碳和其他身体排放物在自由飞行的蚊子中的相对重要性及相互作用，我们在风洞中向雌性埃及伊蚊呈现了自然浓度及其稀释度的人类皮肤气味和二氧化碳的宽羽流。对三维视频记录的飞行轨迹进行了重建。随着皮肤气味被稀释，激活、飞行速度、逆风转向和寻找源头的能力迅速减弱，而在有二氧化碳的情况下，从呼出浓度稀释超过100倍时，这些参数仍保持不变。尽管蚊子对皮肤气味的行为敏感性低于对二氧化碳的敏感性，但在与一缕二氧化碳短暂接触后，它们对皮肤气味的敏感性会瞬间增加至少五倍。这种致敏作用体现在飞行速度、轨迹角度、进入和离开宽气味羽流时的转向率上，最终体现在寻找源头的速率上。因此，在埃及伊蚊中，二氧化碳起到了一种“释放剂”的作用，可提高对皮肤气味的敏感性和反应性。蚊子最初对皮肤气味的低反应性、对二氧化碳的高敏感性以及二氧化碳对嗅觉回路的致敏作用在生态上具有相关性，因为快速波动的二氧化碳水平可靠地表明了潜在宿主的存在。文中还考虑了瞬时致敏的可能机制。
