Laboratory of Paper Coating and Converting, Centre for Functional Materials, Abo Akademi University, Porthaninkatu 3, 20500, Turku, Finland; Division of Biotechnology, Generasi Biologi Indonesia (Genbinesia) Foundation, Jl. Swadaya Barat no. 4, Gresik Regency, 61171, Indonesia.
Department of Biology Education, Faculty of Science and Technology, Universitas Islam Negeri Walisongo, Jl. Prof. Dr. Hamka No.2 Km, Semarang, 50185, Indonesia.
Zoology (Jena). 2020 Apr;139:125750. doi: 10.1016/j.zool.2020.125750. Epub 2020 Jan 24.
In this communication, we describe the water-hopping kinematics of the dusky-gilled mudskipper (Periophthalmus variabilis), and by doing so elucidate an entirely new form of fish locomotion that has yet to be reported in the public domain. Water-hopping is defined herein as an ability to hop once, or in succession, on the surface of water without full submergence and without a fin-guided glide. We find that taxiing on the water surface is the predominating kinematic movement used for the execution of successful water-hops. We observe that an initial concentric ripple forms as the mudskipper impacts the water, and that subsequent taxiing on the water surface generates a sinusoid-like ripple pattern in the water prior to take off. Interestingly whilst airborne, the pectoral fins of P. variabilis appear to remain stationary, only to be deployed upon contact with the water. When landing back onto the surface of the water, P. variabilis makes the initial contact via its pelvic region, occasionally extending its pectoral fins during its descent. The reasons for pectoral and pelvic fin extension are unclear, however, there may be either aerodynamic or hydrodynamic benefits in its doing so. This motion furthermore prepares the mudskipper for either, a follow-on water-hop, or a discontinuation of movement altogether, as the body of the mudskipper becomes aligned in a way conducive to either. P. variabilis will launch and land using both, horizontal surfaces such as littorals, and inclined-to-vertical surfaces such as rocks and trees.
在本通讯中，我们描述了沙塘鳢（Periophthalmus variabilis）的水上跳跃运动学，并借此阐明了一种全新的鱼类运动形式，这在公开文献中尚未有报道。本文将水上跳跃定义为一种无需完全潜入水中、无需鳍引导滑行即可在水面上单次或连续跳跃的能力。我们发现，在水面上滑行是成功进行水上跳跃的主要运动方式。我们观察到，沙塘鳢撞击水面时会形成一个初始的同心波纹，随后在起飞前，在水面上滑行会产生类似于正弦波的波纹图案。有趣的是，在空中时，沙塘鳢的胸鳍似乎保持静止，只有在接触水面时才会展开。当回到水面上时，沙塘鳢最初通过其骨盆区域接触水面，偶尔在下降过程中伸展胸鳍。伸展胸鳍和骨盆鳍的原因尚不清楚，但这样做可能有空气动力学或水动力学方面的好处。这种运动进一步使沙塘鳢为随后的水上跳跃或完全停止运动做好准备，因为沙塘鳢的身体会以一种有利于跳跃或停止的方式对齐。沙塘鳢可以在水平表面（如滨岸带）和倾斜至垂直表面（如岩石和树木）上使用水平或垂直表面进行起飞和着陆。
