Dabiri John O, Colin Sean P, Costello John H
Graduate Aeronautical Laboratories and Bioengineering, California Institute of Technology, Pasadena, CA 91125, USA.
J Exp Biol. 2007 Jun;210(Pt 11):1868-73. doi: 10.1242/jeb.003772.
Cnidarian medusae, commonly known as jellyfish, represent the earliest known animal taxa to achieve locomotion using muscle power. Propulsion by medusae requires the force of bell contraction to generate forward thrust. However, thrust production is limited in medusae by the primitive structure of their epitheliomuscular cells. This paper demonstrates that constraints in available locomotor muscular force result in a trade-off between high-thrust swimming via jet propulsion and high-efficiency swimming via a combined jet-paddling propulsion. This trade-off is reflected in the morphological diversity of medusae, which exhibit a range of fineness ratios (i.e. the ratio between bell height and diameter) and small body size in the high-thrust regime, and low fineness ratios and large body size in the high-efficiency regime. A quantitative model of the animal-fluid interactions that dictate this trade-off is developed and validated by comparison with morphological data collected from 660 extant medusan species ranging in size from 300 microm to over 2 m. These results demonstrate a biomechanical basis linking fluid dynamics and the evolution of medusan bell morphology. We believe these to be the organising principles for muscle-driven motility in Cnidaria.
刺胞动物门的水母体，通常被称为水母，是已知最早利用肌肉力量实现运动的动物类群。水母体的推进需要钟形身体收缩产生向前的推力。然而，水母体的上皮肌细胞结构原始，限制了推力的产生。本文表明，可用运动肌肉力量的限制导致了通过喷气推进实现高推力游泳和通过喷气-划水组合推进实现高效率游泳之间的权衡。这种权衡体现在水母体的形态多样性上，在高推力状态下，水母体呈现出一系列的细长比（即钟形身体高度与直径之比）且体型较小，而在高效率状态下，细长比低且体型较大。通过与从660种现存水母体物种收集的形态数据进行比较，建立并验证了决定这种权衡的动物-流体相互作用的定量模型，这些水母体物种的大小从300微米到超过2米不等。这些结果证明了流体动力学与水母体钟形形态演化之间的生物力学基础。我们认为这些是刺胞动物门中肌肉驱动运动的组织原则。
