Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
J Exp Biol. 2010 Mar 1;213(5):831-41. doi: 10.1242/jeb.033084.
Contrary to the previous premise that pelvic fins lacked obvious function, recent work on three-dimensional fin motions suggests that pelvic fins actively control stability and speed in slowly swimming trout. This study used electromyography to measure pelvic fin muscle activity and particle imaging velocimetry to quantify flow along the ventral body region to test this hypothesis. Fish swam at slow speeds (0.13-1.36 BL s(-1)) while being filmed with three high speed cameras. Three-dimensional kinematics were captured for all trials. During EMG trials pelvic fin muscle activity was synchronized to kinematic motion, during particle imaging velocimetry trials, a laser light-sheet was used to visualize the flow surrounding the ventral aspect of the fish. Four main conclusions are reached: first, pelvic fins are actively oscillated during slow-speed swimming; antagonistic abductor and adductor muscles contracted simultaneously, their collective action producing a unique contralateral oscillating behaviour in the fins. Second, pelvic fins slow the flow along the ventral side affecting pitch and yaw instabilities; flow upstream of the pelvic fins is slowed by 0.02 m s(-1) and flow downstream of the pelvic fins is slowed by 0.034 m s(-1) compared with free stream flow. Third, pelvic fin wake influences anal fin angle of attack; flow angle in the wake of the pelvic fin was 33.84+/-2.4 deg. (max) and -11.83+/-11.2 deg. (min) compared with the free stream flow angle of 1.27+/-0.1 deg. Fourth, pelvic fins appear to actively damp body oscillation during slow-speed swimming, providing drag to help control speed and stabilize the body position during slow-speed swimming.
与之前认为骨盆鳍没有明显功能的前提相反，最近对三维鳍运动的研究表明，骨盆鳍在缓慢游动的鳟鱼中积极控制稳定性和速度。本研究使用肌电图测量骨盆鳍肌肉活动，并使用粒子图像测速法量化沿腹侧身体区域的流动，以检验这一假设。鱼以 0.13-1.36 BL s(-1) 的缓慢速度游泳，同时用三台高速摄像机拍摄。对所有试验进行三维运动学捕捉。在肌电图试验中，骨盆鳍肌肉活动与运动学运动同步，在粒子图像测速试验中，使用激光光片来可视化鱼腹侧周围的流动。得出了四个主要结论：第一，骨盆鳍在缓慢游动时主动摆动；拮抗的外展肌和内收肌同时收缩，它们的集体作用使鳍产生独特的对侧摆动行为。第二，骨盆鳍减缓了沿腹侧的流动，影响俯仰和偏航不稳定性；与自由流相比，骨盆鳍上游的流速减慢了 0.02 m s(-1)，骨盆鳍下游的流速减慢了 0.034 m s(-1)。第三，骨盆鳍尾流影响肛鳍迎角；骨盆鳍尾流中的流动角度为 33.84+/-2.4 度（最大值）和-11.83+/-11.2 度（最小值），而自由流的流动角度为 1.27+/-0.1 度。第四，骨盆鳍似乎在缓慢游动时主动抑制身体摆动，提供阻力以帮助控制速度并在缓慢游动时稳定身体位置。
