Zoology Department, University of British Columbia, Vancouver, Canada.
Laboratori d'Aplicacions Bioacústiques, Universitat Politècnica de Catalunya, BarcelonaTech (UPC), Vilanova i la Geltrú, Spain.
Sci Rep. 2017 Feb 6;7:41848. doi: 10.1038/srep41848.
Assessment of the impact of noise over-exposure in stranded cetaceans is challenging, as the lesions that lead to hearing loss occur at the cellular level and inner ear cells are very sensitive to autolysis. Distinguishing ante-mortem pathology from post-mortem change has been a major constraint in diagnosing potential impact. Here, we outline a methodology applicable to the detection of noise-induced hearing loss in stranded cetaceans. Inner ears from two mass strandings of long-finned pilot whales in Scotland were processed for scanning electron microscopy observation. In one case, a juvenile animal, whose ears were fixed within 4 hours of death, revealed that many sensory cells at the apex of the cochlear spiral were missing. In this case, the absence of outer hair cells would be compatible with overexposure to underwater noise, affecting the region which transduces the lowest frequencies of the pilot whales hearing spectrum. Perfusion of cochlea with fixative greatly improved preservation and enabled diagnostic imaging of the organ of Corti, even 30 hours after death. This finding supports adopting a routine protocol to detect the pathological legacy of noise overexposure in mass stranded cetaceans as a key to understanding the complex processes and implications that lie behind such stranding events.
评估搁浅鲸目动物因噪声过度暴露而受到的影响具有挑战性，因为导致听力损失的病变发生在细胞水平，内耳细胞对自溶非常敏感。将生前病变与死后变化区分开来一直是诊断潜在影响的主要限制。在这里，我们概述了一种适用于检测搁浅鲸目动物噪声诱导性听力损失的方法。来自苏格兰两次长鳍领航鲸大规模搁浅事件的内耳被用于扫描电子显微镜观察。在一个案例中，一只幼年动物的耳朵在死亡后 4 小时内被固定，显示耳蜗螺旋顶点的许多感觉细胞缺失。在这种情况下，外毛细胞的缺失可能与水下噪声过度暴露有关，影响了领航鲸听力频谱中最低频率的转换区域。在死后 30 小时，用固定剂对耳蜗进行灌注极大地改善了保存效果，并能够对 Corti 器官进行诊断成像。这一发现支持采用常规方案来检测大规模搁浅鲸目动物中因噪声过度暴露而产生的病理遗留问题，这是理解此类搁浅事件背后复杂过程和影响的关键。
