听力在动物界已经独立进化了很多次,并且在各种昆虫和脊椎动物中对于特定的交流和捕食者的检测都很突出。在昆虫中,katydid(直翅目:Tettigoniidae)耳朵是独特的,当它们进化到外部时,中间,和内耳组件,类似于哺乳动物耳朵的生物物理原理。katydid耳由位于每个前腿的两个配对鼓膜组成。这些鼓膜在鼓膜表面的外部(通常通过耳廓)或在内部通过耳道(EC)接收声音。EC的功能是捕获特定的呼叫和低频,而耳廓被动放大包括蝙蝠回声定位在内的高频超声波。一起,这些外耳组件在超过100kHz的动态范围内提供增强的听觉灵敏度。然而,尽管人们越来越了解katydid耳的生物物理学和功能,它的精确出现和进化史仍然难以捉摸。这里,使用显微计算机断层扫描(μCT)扫描,Werecoveredgeometryoftheouterearcomponentsandwingsofanexcelllywell-preservedkatydidfollizedinBalticamber(jo.44millionyears[Ma]).使用机翼的数值和理论建模,我们表明该物种以31.62(±2.27)kHz的峰值频率进行通信,我们证明了耳朵被生物物理调谐到这个信号,并在更高频率的超声波(>80kHz)下提供听力,可能用于增强捕食者检测。结果表明,katydid独特的耳朵的进化,具有宽带超声灵敏度和类似哺乳动物耳朵的生物物理特性,出现在始新世。
Hearing has evolved independently many times in the animal kingdom and is prominent in various insects and vertebrates for conspecific communication and predator detection. Among insects, katydid (Orthoptera: Tettigoniidae) ears are unique, as they have evolved outer, middle, and inner ear components, analogous in their biophysical principles to the mammalian ear. The katydid ear consists of two paired tympana located in each foreleg. These tympana receive sound externally on the tympanum surface (usually via pinnae) or internally via an ear canal (EC). The EC functions to capture conspecific calls and low frequencies, while the pinnae passively amplify higher-frequency ultrasounds including bat echolocation. Together, these outer ear components provide enhanced hearing sensitivity across a dynamic range of over 100 kHz. However, despite a growing understanding of the biophysics and function of the katydid ear, its precise emergence and evolutionary history remains elusive. Here, using microcomputed tomography (μCT) scanning, we recovered geometries of the outer ear components and wings of an exceptionally well-preserved katydid fossilized in Baltic amber (∼44 million years [Ma]). Using numerical and theoretical modeling of the wings, we show that this species was communicating at a peak frequency of 31.62 (± 2.27) kHz, and we demonstrate that the ear was biophysically tuned to this signal and to providing hearing at higher-frequency ultrasounds (>80 kHz), likely for enhanced predator detection. The results indicate that the evolution of the unique ear of the katydid, with its broadband ultrasonic sensitivity and analogous biophysical properties to the ears of mammals, emerged in the Eocene.