Geurten Bart R H, Niesterok Benedikt, Dehnhardt Guido, Hanke Frederike D
Georg-August-University of Göttingen, Department of Cellular Neurobiology, Schwann-Schleiden Research Center, Julia-Lermontowa-Weg 3, Göttingen 37007, Germany.
University of Rostock, Institute for Biosciences, Sensory and Cognitive Ecology, Albert-Einstein-Str. 3, Rostock 18059, Germany.
J Exp Biol. 2017 Apr 15;220(Pt 8):1503-1508. doi: 10.1242/jeb.150763. Epub 2017 Feb 6.
Moving animals can estimate the distance of visual objects from image shift on their retina (optic flow) created during translational, but not rotational movements. To facilitate this distance estimation, many terrestrial and flying animals perform saccadic movements, thereby temporally separating translational and rotational movements, keeping rotation times short. In this study, we analysed whether a semiaquatic mammal, the harbour seal, also adopts a saccadic movement strategy. We recorded the seals' normal swimming pattern with video cameras and analysed head and body movements. The swimming seals indeed minimized rotation times by saccadic head and body turns, with top rotation speeds exceeding 350 deg s which leads to an increase of translational movements. Saccades occurred during both types of locomotion of the seals' intermittent swimming mode: active propulsion and gliding. In conclusion, harbour seals share the saccadic movement strategy of terrestrial animals. Whether this movement strategy is adopted to facilitate distance estimation from optic flow or serves a different function will be a topic of future research.
移动中的动物可以根据平移运动（而非旋转运动）过程中在其视网膜上产生的图像移动（光流）来估计视觉物体的距离。为了便于这种距离估计，许多陆生和飞行动物会进行扫视运动，从而在时间上分离平移运动和旋转运动，使旋转时间保持较短。在本研究中，我们分析了一种半水生哺乳动物——港海豹是否也采用扫视运动策略。我们用摄像机记录了海豹的正常游泳模式，并分析了其头部和身体的运动。游泳的海豹确实通过快速的头部和身体转动将旋转时间减到了最短，最高旋转速度超过350度/秒，这导致了平移运动的增加。扫视运动发生在海豹间歇性游泳模式的两种运动类型中：主动推进和滑行。总之，港海豹具有陆生动物的扫视运动策略。这种运动策略是为了便于根据光流估计距离，还是具有其他功能，将是未来研究的一个课题。
