Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA.
Biol Lett. 2013 Mar 27;9(3):20130104. doi: 10.1098/rsbl.2013.0104. Print 2013 Jun 23.
The constant darkness of caves and other subterranean habitats imposes sensory constraints that offer a unique opportunity to examine evolution of sensory modalities. Hearing in cavefishes has not been well explored, and here we show that cavefishes in the family Amblyopsidae are not only blind but have also lost a significant portion of their hearing range. Our results showed that cave and surface amblyopsids shared the same audiogram profile at low frequencies but only surface amblyopsids were able to hear frequencies higher than 800 Hz and up to 2 kHz. We measured ambient noise in aquatic cave and surface habitats and found high intensity peaks near 1 kHz for streams underground, suggesting no adaptive advantage in hearing in those frequencies. In addition, cave amblyopsids had lower hair cell densities compared with their surface relative. These traits may have evolved in response to the loud high-frequency background noise found in subterranean pools and streams. This study represents the first report of auditory regression in a subterranean organism.
洞穴和其他地下栖息地的持续黑暗带来了感官限制，为研究感官模态的进化提供了独特的机会。洞穴鱼类的听觉功能尚未得到充分探索，而我们的研究表明，棘鳍鱼科的洞穴鱼类不仅是盲的，而且听觉范围也显著缩小。我们的研究结果表明，洞穴和地表棘鳍鱼类在低频段具有相同的听力图，但只有地表棘鳍鱼类能够听到高于 800 Hz 且高达 2 kHz 的频率。我们测量了水生洞穴和地表栖息地的环境噪声，发现地下溪流的噪声在 1 kHz 附近存在高强度峰值，表明在这些频率下听觉没有适应优势。此外，洞穴棘鳍鱼类的毛细胞密度相对于其地表同类要低。这些特征可能是对地下水池和溪流中高频背景噪声的适应进化。本研究首次报道了地下生物听觉功能的退化。
