Animal Physiology, Institute for Neurobiology, Faculty of Science, University of Tübingen, 72076 Tübingen, Germany.
J Exp Biol. 2022 Feb 1;225(3). doi: 10.1242/jeb.243569. Epub 2022 Feb 3.
Doppler shift (DS) compensating bats adjust in flight the second harmonic of the constant-frequency component (CF2) of their echolocation signals so that the frequency of the Doppler-shifted echoes returning from ahead is kept constant with high precision (0.1-0.2%) at the so-called reference frequency (fref). This feedback adjustment is mediated by an audio-vocal control system that correlates with a maximal activation of the foveal resonance area in the cochlea. Stationary bats adjust the average CF2 with similar precision at the resting frequency (frest), which is slightly below the fref. Over a range of time periods (from minutes up to years), variations of the coupled fref and frest have been observed, and were attributed to age, social influences and behavioural situations in rhinolophids and hipposiderids, and to body temperature effects and flight activity in Pteronotus parnellii. We assume that, for all DS-compensating bats, a change in body temperature has a strong effect on the activation state of the foveal resonance area in the cochlea, which leads to a concomitant change in emission frequency. We tested our hypothesis in a hipposiderid bat, Hipposideros armiger, and measured how the circadian variation of body temperature at activation phases affected frest. With a miniature temperature logger, we recorded the skin temperature on the back of the bats simultaneously with echolocation signals produced. During warm-up from torpor, strong temperature increases were accompanied by an increase in frest, of up to 1.44 kHz. We discuss the implications of our results for the organization and function of the audio-vocal control systems of all DS-compensating bats.
Doppler 频移补偿蝙蝠在飞行中调整它们回声定位信号的恒定频率分量 (CF2) 的二次谐波，以使从前方返回的多普勒频移回波的频率以高精度（0.1-0.2%）保持在所谓的参考频率 (fref)。这种反馈调节是由一个音频-声音控制系统介导的，该系统与耳蜗中焦点共振区域的最大激活相关。静止的蝙蝠以类似的精度在静止频率 (frest) 下调整平均 CF2，该频率略低于 fref。在一段时间范围内（从几分钟到几年），观察到耦合的 fref 和 frest 的变化，并归因于天蝠科和蹄蝠科的年龄、社会影响和行为情况，以及皮氏果蝠的体温效应和飞行活动。我们假设，对于所有的 Doppler 频移补偿蝙蝠，体温的变化对耳蜗中焦点共振区域的激活状态有强烈的影响，这导致发射频率的相应变化。我们在一种蹄蝠 Hipposideros armiger 中检验了我们的假设，并测量了激活阶段体温的昼夜变化如何影响 frest。我们使用微型温度记录仪同时记录蝙蝠背部的皮肤温度和产生的回声定位信号。在从休眠中暖身时，强烈的温度升高伴随着 frest 的增加，最高可达 1.44 kHz。我们讨论了我们的结果对所有 Doppler 频移补偿蝙蝠的音频-声音控制系统的组织和功能的影响。
