Hale Melina E, Day Ryan D, Thorsen Dean H, Westneat Mark W
Department of Organismal Biology and Anatomy, The University of Chicago, 1027 E. 57th Street, Chicago, IL 60637, USA.
J Exp Biol. 2006 Oct;209(Pt 19):3708-18. doi: 10.1242/jeb.02449.
A common feature of animal locomotion is its organization into gaits with distinct patterns of movement and propulsor use for specific speeds. In terrestrial vertebrates, limb gaits have been extensively studied in diverse taxa and gait transitions have been shown to provide efficient locomotion across a wide range of speeds. In contrast, examination of gaits in fishes has focused on axial gaits and the transition between synchronous paired fin locomotion and axial propulsion. Because many fishes use their pectoral fins as their primary propulsors, we aimed to examine more broadly the use of pectoral fin gaits in locomotion. We used juvenile reef fishes in these experiments because their swimming could be recorded readily across a wide range of Reynolds numbers, which we thought would promote gait diversity. Based on previous work in larval fishes, we hypothesized that juveniles have alternating pectoral fin movements rather than the synchronous, or in-phase, coordination pattern of adults. In flow tank swim studies, we found that juvenile sapphire damselfish Pomacentrus pavo used two fin gaits during steady swimming. Below approximately 3 BL s(-1), P. pavo primarily swam with alternating fin strokes 180 degrees out of phase with one another. At speeds in the range of 3-4 BL s(-1), they performed a gait transition to synchronous fin coordination. Between approximately 4 and 8 BL s(-1), P. pavo primarily beat their fins synchronously. At around 8 BL s(-1) there was another gait transition to body-caudal fin swimming, in which the pectoral fins were tucked against the body. We suggest that the transition from alternating to synchronous fin coordination occurs due to mechanical limits of gait performance rather than to energy efficiency, stability or transitions in hydrodynamic regime. To determine whether this gait transition was species-specific, we surveyed pectoral fin locomotion in juveniles from 11 species in three reef fish families (Pomacentridae, Labridae and Scaridae). We found that this gait transition occurred in every species examined, suggesting that it may be a common behavior of juvenile reef fishes. Greater inclusion of early life history stages in the study of fin-based locomotion should significantly enhance and inform the growing body of work on these behaviors.
动物运动的一个共同特征是其运动组织成具有不同运动模式和用于特定速度的推进器使用方式的步态。在陆生脊椎动物中，肢体步态已在多种分类群中得到广泛研究，并且步态转换已被证明能在很宽的速度范围内提供高效运动。相比之下，对鱼类步态的研究主要集中在轴向步态以及同步成对鳍运动和轴向推进之间的转换。由于许多鱼类将胸鳍作为主要推进器，我们旨在更广泛地研究胸鳍步态在运动中的使用情况。我们在这些实验中使用了幼年珊瑚礁鱼类，因为它们的游泳可以在很宽的雷诺数范围内轻松记录，我们认为这会促进步态多样性。基于之前对幼体鱼类的研究工作，我们假设幼鱼的胸鳍运动是交替的，而不是成体的同步或同相协调模式。在流水槽游泳研究中，我们发现幼年蓝宝石雀鲷（Pomacentrus pavo）在稳定游泳时使用两种鳍步态。在大约3体长/秒以下，蓝宝石雀鲷主要通过相互相位差180度的交替鳍划水来游泳。在3 - 4体长/秒的速度范围内，它们会进行步态转换，变为同步鳍协调。在大约4到8体长/秒之间，蓝宝石雀鲷主要同步摆动它们的鳍。在大约8体长/秒时，会发生另一种步态转换，变为身体 - 尾鳍游泳，此时胸鳍贴靠身体收起。我们认为从交替鳍协调到同步鳍协调的转换是由于步态表现的机械限制，而不是能量效率、稳定性或流体动力学状态的转变。为了确定这种步态转换是否具有物种特异性，我们调查了三个珊瑚礁鱼类科（雀鲷科、隆头鱼科和鹦嘴鱼科）中11个物种幼鱼的胸鳍运动。我们发现这种步态转换在每个被检查的物种中都发生了，这表明它可能是幼年珊瑚礁鱼类的一种常见行为。在基于鳍的运动研究中更多地纳入生命早期阶段，应该会显著加强并为关于这些行为的不断增长的研究工作提供信息。
