College of Marine Science, University of South Florida, St Petersburg, Florida, United States of America.
PLoS One. 2013 Jul 26;8(7):e69872. doi: 10.1371/journal.pone.0069872. Print 2013.
Two types of vibrissal surface structures, undulated and smooth, exist among pinnipeds. Most Phocidae have vibrissae with undulated surfaces, while Otariidae, Odobenidae, and a few phocid species possess vibrissae with smooth surfaces. Variations in cross-sectional profile and orientation of the vibrissae also exist between pinniped species. These factors may influence the way that the vibrissae behave when exposed to water flow. This study investigated the effect that vibrissal surface structure and orientation have on flow-induced vibrations of pinniped vibrissae. Laser vibrometry was used to record vibrations along the whisker shaft from the undulated vibrissae of harbor seals (Phoca vitulina) and northern elephant seals (Mirounga angustirostris) and the smooth vibrissae of California sea lions (Zalophus californianus). Vibrations along the whisker shaft were measured in a flume tank, at three orientations (0°, 45°, 90°) to the water flow. The results show that vibration frequency and velocity ranges were similar for both undulated and smooth vibrissae. Angle of orientation, rather than surface structure, had the greatest effect on flow-induced vibrations. Vibration velocity was up to 60 times higher when the wide, flat aspect of the whisker faced into the flow (90°), compared to when the thin edge faced into the flow (0°). Vibration frequency was also dependent on angle of orientation. Peak frequencies were measured up to 270 Hz and were highest at the 0° orientation for all whiskers. Furthermore, CT scanning was used to quantify the three-dimensional structure of pinniped vibrissae that may influence flow interactions. The CT data provide evidence that all vibrissae are flattened in cross-section to some extent and that differences exist in the orientation of this profile with respect to the major curvature of the hair shaft. These data support the hypothesis that a compressed cross-sectional profile may play a key role in reducing self-noise of the vibrissae.
两种类型的触须表面结构，波纹状和光滑状，存在于鳍足类动物中。大多数 Phocidae 具有波纹状表面的触须，而 Otariidae、Odobenidae 和少数 Phocid 物种则具有光滑表面的触须。鳍足类动物之间的触须横截面轮廓和方向也存在差异。这些因素可能会影响触须在暴露于水流时的行为方式。本研究调查了触须表面结构和方向对鳍足类触须的流致振动的影响。激光测振仪用于记录来自港海豹（Phoca vitulina）和北象海豹（Mirounga angustirostris）的波纹状触须以及加利福尼亚海狮（Zalophus californianus）的光滑触须的沿触须轴的振动。在水槽中，在三个方向（0°、45°、90°）对水流测量沿触须轴的振动。结果表明，波纹状和光滑状触须的振动频率和速度范围相似。定向角度而不是表面结构对流致振动的影响最大。当触须宽而平的一面朝向水流（90°）时，振动速度高达 60 倍，而当触须的薄边朝向水流（0°）时，振动速度高达 60 倍。振动频率也依赖于定向角度。所有触须的峰值频率测量高达 270 Hz，在所有触须中，0°方向的峰值频率最高。此外，CT 扫描用于量化可能影响流相互作用的鳍足类触须的三维结构。CT 数据提供的证据表明，所有触须在横截面中都在一定程度上被压扁，并且该轮廓相对于毛发轴的主要曲率的方向存在差异。这些数据支持了一个假设，即压缩的横截面形状可能在降低触须的自噪声方面发挥关键作用。
