Data from: Masking of an auditory behaviour reveals how male mosquitoes use distortion to detect females

The mating behaviour of many mosquito species is mediated essentially by sound: males follow and mate with a female mid-flight by detecting and tracking the whine of her flight-tones. The stereotypical rapid frequency modulation (RFM) male behaviour, initiated in response to the detection of the female's flight-tones, has provided a means of investigating these auditory mechanisms while males are free-flying. Mosquitoes hear with their antennae, which vibrate to near-field acoustic excitation. The antennae generate nonlinear vibrations (distortion products, DPs) at frequencies that are equal to the difference between the two simultaneously presented tones, e.g. the male and female flight-tones, which are detected by mechanoreceptors in the auditory Johnston's organ (JO) at the base of the antenna. Recent studies indicated the male mosquito's JO is tuned not to the female flight-tone, but to the frequency difference between the male and female flight-tones. To test the hypothesis that mosquitoes detect this frequency difference, Culex quinquefasciatus males were presented simultaneously with a female flight-tone and a masking tone, which should suppress the male's RFM response to sound. The free-flight behavioural and in vivo electrophysiological experiments revealed that acoustic masking suppresses the RFM response to the female's flight-tones by attenuating the DPs generated in the nonlinear vibration of the antennae. These findings provide direct evidence in support of the hypothesis that male mosquitoes detect females when both are in flight through difference tones generated in the vibrations of their antennae owing to the interaction between their own flight-tones and those of a female.

多数蚊类的交配行为本质上以声音作为介导信号：雄性蚊子可通过检测并追踪雌性的飞行鸣声，在飞行过程中尾随并完成交配。这种由检测雌性飞行鸣声触发的典型快速频率调制（rapid frequency modulation, RFM）雄性行为，为自由飞行状态下的雄性听觉机制研究提供了有效途径。蚊子依靠触角实现听觉，触角会在近场声学刺激下产生振动。当同时存在两种音调（例如雄性与雌性飞行鸣声）时，触角会产生等于二者频率差的非线性畸变产物（distortion products, DPs），这类振动信号会被触角基部听觉器官江氏器（Johnston's organ, JO）中的机械感受器所捕捉。近期研究显示，雄性蚊子的江氏器并非调谐至雌性飞行鸣声的频率，而是响应雌雄飞行鸣声的频率差。为验证“蚊子可检测该频率差”这一假说，研究人员向尖音库蚊（Culex quinquefasciatus）雄性同时施加雌性飞行鸣声与掩蔽音调，该掩蔽音调可抑制雄性对声音的RFM响应。自由飞行行为学与体内电生理实验结果表明，声学掩蔽通过削弱触角非线性振动产生的畸变产物，抑制了雄性对雌性飞行鸣声的RFM响应。上述发现为以下假说提供了直接证据：当雌雄双方均处于飞行状态时，雄性蚊子可通过自身飞行鸣声与雌性飞行鸣声相互作用所引发的触角振动差频，完成对雌性配偶的检测。