Fox C H, Gibb A C, Summers A P, Bemis W E
Department of Ecology and Evolutionary Biology, Corson Hall, 215 Tower Rd., Cornell University, Ithaca, NY, 14853, USA.
Friday Harbor Laboratories, 614-698 University Rd., University of Washington, Friday Harbor, WA, 98250, USA.
Zoology (Jena). 2018 Oct;130:19-29. doi: 10.1016/j.zool.2018.07.002. Epub 2018 Jul 17.
Video-based observations of voluntary movements reveal that six species of pleuronectid flatfishes use sequential portions of long-based dorsal and anal fins as "feet" (hereafter, fin-feet) to move on the substrate. All six species used a gait that we term "walking," which produced constant forward movement, and several of these species also used a second gait that we call "bounding" for intermittent movements over the substrate. We selected Pacific Sand Sole, Psettichthys melanostictus, and English Sole, Parophrys vetulus, for kinematic analyses of these two gaits. Psettichthys melanostictus consistently used walking for benthic locomotion; Parophrys vetulus primarily used a bounding gait. During forward walking, a fin ray swings up off the substrate, protracts and converges with neighboring fin rays to contribute to a fin-foot. The fin-foot pushes down on the substrate and rotates posteriorly by sequential recruitment of fin rays, a pattern known as a metachronal wave. As one fin-foot passes off the posterior end of the fin, a new fin-foot forms anteriorly. During bounding, undulations of the body and tail assist one or two waves of fin-feet, producing rapid but intermittent forward acceleration of the body. Flatfishes also use fin-feet to maneuver on the substrate. The Starry Flounder, Platichthys stellatus, performs near zero displacement rotation by running waves of fin-feet in opposing directions along the dorsal and anal fins. Although other teleosts use specialized pectoral fin rays for bottom walking (e.g., Sea Robins: Triglidae), the duplication of structures and patterns of movement in the median fins of flatfishes more closely resembles metachronal motions of millipede feet or the parapodia of polychaete worms. Sequential use of median fin rays in flatfishes resembles that of other teleosts that swim with elongate median fins, including Amiiformes, Gymnotiformes, and some Tetraodontiformes, but flatfishes offer a novel form of substrate locomotion based on dorsal and anal fins.
基于视频对自主运动的观察发现，六种鲽形目比目鱼利用长基部背鳍和臀鳍的连续部分作为“脚”（以下简称鳍脚）在基质上移动。所有六种比目鱼都采用了一种我们称为“行走”的步态，这种步态能产生持续向前的运动，其中几种比目鱼还采用了第二种步态，我们称之为“跳跃”，用于在基质上进行间歇性运动。我们选择了太平洋沙鳎（Psettichthys melanostictus）和英国鳎（Parophrys vetulus）对这两种步态进行运动学分析。太平洋沙鳎在底栖运动中始终采用行走步态；英国鳎主要采用跳跃步态。在向前行走时，一根鳍条从基质上摆动起来，伸展并与相邻的鳍条汇聚形成一个鳍脚。鳍脚向下压在基质上，并通过鳍条的顺序募集向后旋转，这种模式称为顺序波。当一个鳍脚从鳍的后端离开时，一个新的鳍脚在前端形成。在跳跃时，身体和尾巴的波动辅助一到两波鳍脚运动，使身体产生快速但间歇性的向前加速。比目鱼还利用鳍脚在基质上进行机动。星斑川鲽（Platichthys stellatus）通过沿着背鳍和臀鳍以相反方向运行鳍脚波来进行近零位移旋转。尽管其他硬骨鱼利用特化的胸鳍条进行底栖行走（如：鲂鮄科），但比目鱼中鳍的结构和运动模式的重复更类似于千足虫脚的顺序运动或多毛纲蠕虫类的疣足。比目鱼中鳍条的顺序使用类似于其他利用细长中鳍游泳的硬骨鱼，包括弓鳍鱼目、裸背电鳗目和一些鲀形目，但比目鱼提供了一种基于背鳍和臀鳍的新型基质运动形式。
