Heffner R S, Heffner H E
Department of Psychology, University of Toledo, Ohio 43606.
Hear Res. 1992 Oct;62(2):206-16. doi: 10.1016/0378-5955(92)90188-s.
Two blind mole rats were tested for their ability to detect and localize sound. The results indicate that blind mole rats have severely limited, and probably degenerate, auditory abilities. Although their 60-dB low-frequency hearing limit of 54 Hz is within the range for other rodents, the highest frequency they can hear at a level of 60 dB SPL is only 5.9 kHz, giving them the poorest high-frequency sensitivity yet observed in any mammal. In addition they have poor sensitivity as indicated by the fact that their lowest threshold is only 32 dB SPL (at 1 kHz). Finally, they are unable to localize brief sounds but retain a rudimentary ability to localize sounds of 0.5 s or longer. These results, combined with those of previous studies of subterranean species (i.e., blind mole rats, naked mole rats, and pocket gophers), suggest that poor auditory sensitivity, the loss of high-frequency hearing, and an inability to localize brief sounds is a degenerate state which may be characteristic of subterranean mammals. Thus it appears that an exclusive adaptation to a subterranean lifestyle (where airborne sound propagates poorly and where directional responses are limited by the tunnels) can result in vestigial auditory abilities just as the absence of light results in vestigial vision.
对两只盲鼹鼠进行了检测，以评估它们探测声音并确定声音位置的能力。结果表明，盲鼹鼠的听觉能力严重受限，可能已经退化。尽管它们54赫兹的60分贝低频听力极限在其他啮齿动物的范围内，但在60分贝声压级下它们能听到的最高频率仅为5.9千赫，这使它们成为迄今在任何哺乳动物中观察到的高频敏感度最差的。此外，它们的敏感度也很差，因为它们的最低阈值仅为32分贝声压级（在1千赫时）。最后，它们无法确定短暂声音的位置，但仍保留了确定持续0.5秒或更长时间声音位置的基本能力。这些结果，结合之前对地下物种（即盲鼹鼠、裸鼹鼠和囊鼠）的研究结果，表明听觉敏感度差、高频听力丧失以及无法确定短暂声音的位置是一种退化状态，可能是地下哺乳动物的特征。因此，似乎对地下生活方式的完全适应（在这种环境中，空气传播的声音传播不佳，定向反应受隧道限制）会导致听觉能力退化，就像没有光线会导致视觉退化一样。
