Department of Neuroscience, Faculty of Medicine, and Cluster of Excellence "Hearing for All", University of Oldenburg, 26129 Oldenburg, Germany.
University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, Groningen, The Netherlands.
Hear Res. 2024 Apr;445:108994. doi: 10.1016/j.heares.2024.108994. Epub 2024 Mar 19.
African mole-rats display highly derived hearing that is characterized by low sensitivity and a narrow auditory range restricted to low frequencies < 10 kHz. Recently, it has been suggested that two species of these rodents do not exhibit distortion product otoacoustic emissions (DPOAE), which was interpreted as evidence for a lack of cochlear amplification. If true, this would make them unique among mammals. However, both theoretical considerations on the generation of DPOAE as well as previously published experimental evidence challenge this assumption. We measured DPOAE and stimulus-frequency otoacoustic emissions (SFOAE) in three species of African mole-rats (Ansell's mole-rat - Fukomys anselli; Mashona mole-rat - Fukomys darlingi; naked mole-rat - Heterocephalus glaber) and found unexceptional otoacoustic emission values. Measurements were complicated by the remarkably long, narrow and curved external ear canals of these animals, for which we provide a morphological description. Both DPOAE and SFOAE displayed the highest amplitudes near 1 kHz, which corresponds to the region of best hearing in all tested species, as well as to the frequency region of the low-frequency acoustic fovea previously described in Ansell's mole-rat. Thus, the cochlea in African mole-rats shares the ability to generate evoked otoacoustic emission with other mammals.
非洲鼹鼠表现出高度特化的听力，其特征为敏感性低且听觉范围狭窄，仅限于低频<10 kHz。最近，有研究表明，这两种啮齿动物不表现出畸变产物耳声发射（DPOAE），这被解释为耳蜗放大缺失的证据。如果这是真的，那么它们将在哺乳动物中独一无二。然而，DPOAE 的产生的理论考虑以及之前发表的实验证据都对这一假设提出了挑战。我们在三种非洲鼹鼠（安塞尔鼹鼠 - Fukomys anselli；马绍纳兰鼹鼠 - Fukomys darlingi；裸鼹鼠 - Heterocephalus glaber）中测量了畸变产物耳声发射（DPOAE）和刺激频率耳声发射（SFOAE），并发现了异常的耳声发射值。这些动物的外耳道非常长、窄且弯曲，这使得测量变得复杂，我们为此提供了形态描述。DPOAE 和 SFOAE 的振幅在 1 kHz 附近都达到了最大值，这与所有测试物种的最佳听力区域相对应，也与之前在安塞尔鼹鼠中描述的低频声凹的频率区域相对应。因此，非洲鼹鼠的耳蜗与其他哺乳动物一样，具有产生诱发耳声发射的能力。
