*Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA; Department of Mechanical Engineering, Southern Methodist University, Dallas, TX 75275, USA; Department of Biology, Franklin and Marshall College, Lancaster, PA 17604, USA.
Integr Comp Biol. 2008 Dec;48(6):720-33. doi: 10.1093/icb/icn043. Epub 2008 May 20.
Squids encounter vastly different flow regimes throughout ontogeny as they undergo critical morphological changes to their two locomotive systems: the fins and jet. Squid hatchlings (paralarvae) operate at low and intermediate Reynolds numbers (Re) and typically have rounded bodies, small fins, and relatively large funnel apertures, whereas juveniles and adults operate at higher Re and generally have more streamlined bodies, larger fins, and relatively small funnel apertures. These morphological changes and varying flow conditions affect swimming performance in squids. To determine how swimming dynamics and propulsive efficiency change throughout ontogeny, digital particle image velocimetry (DPIV) and kinematic data were collected from an ontogenetic range of long-finned squid Doryteuthis pealeii and brief squid Lolliguncula brevis swimming in a holding chamber or water tunnel (Re = 20-20 000). Jet and fin wake bulk properties were quantified, and propulsive efficiency was computed based on measurements of impulse and excess kinetic energy in the wakes. Paralarvae relied predominantly on a vertically directed, high frequency, low velocity jet as they bobbed up and down in the water column. Although some spherical vortex rings were observed, most paralarval jets consisted of an elongated vortical region of variable length with no clear pinch-off of a vortex ring from the trailing tail component. Compared with paralarvae, juvenile and adult squid exhibited a more diverse range of swimming strategies, involving greater overall locomotive fin reliance and multiple fin and jet wake modes with better defined vortex rings. Despite greater locomotive flexibility, jet propulsive efficiency of juveniles/adults was significantly lower than that of paralarvae, even when juvenile/adults employed their highest efficiency jet mode involving the production of periodic isolated vortex rings with each jet pulse. When the fins were considered together with the jet for several juvenile/adult swimming sequences, overall propulsive efficiency increased, suggesting that fin contributions are important and should not be overlooked in analyses of the swimming performance of squids. The fins produced significant thrust and consistently had higher propulsive efficiency than did the jet. One particularly important area of future study is the determination of coordinated jet/fin wake modes that have the greatest impact on propulsive efficiency. Although such research would be technically challenging, requiring new, powerful, 3D approaches, it is necessary for a more comprehensive assessment of propulsive efficiency of the squid dual-mode locomotive system.
鳍和射流中经历关键的形态变化，从而在整个发育过程中遇到截然不同的流动状态。鱿鱼幼体（副幼虫）在低和中等雷诺数（Re）下运行，通常具有圆形身体、小鳍和相对较大的漏斗开口，而幼体和成年鱿鱼在较高的 Re 下运行，通常具有更流线型的身体、更大的鳍和相对较小的漏斗开口。这些形态变化和不同的流动条件会影响鱿鱼的游泳性能。为了确定游泳动力学和推进效率如何在整个发育过程中发生变化，我们从长鳍鱿鱼 Doryteuthis pealeii 和短鱿鱼 Lolliguncula brevis 的发育范围中收集了数字粒子图像测速（DPIV）和运动学数据，这些鱿鱼在保持室或水隧道中游泳（Re = 20-20 000）。量化了射流和鳍尾迹的整体性质，并根据尾迹中的冲量和过剩动能的测量计算了推进效率。副幼虫在水柱中上下跳动时，主要依赖于垂直定向、高频、低速射流。尽管观察到一些球形涡环，但大多数副幼虫射流由可变长度的拉长涡旋区域组成，没有明显的从尾部组件上切离涡环。与副幼虫相比，幼体和成年鱿鱼表现出更广泛的游泳策略，涉及更大程度的整体运动鳍依赖和多种鳍和射流尾迹模式，具有更好定义的涡环。尽管运动灵活性更大，但幼体/成体的射流推进效率明显低于副幼虫，即使幼体/成体采用了其最高效率的射流模式，即通过每次射流脉冲产生周期性的孤立涡环。当将鳍与几个幼体/成体游泳序列的射流一起考虑时，整体推进效率增加，这表明鳍的贡献很重要，在分析鱿鱼的游泳性能时不应忽视。鳍产生了显著的推力，并且始终比射流具有更高的推进效率。未来研究的一个特别重要的领域是确定对推进效率影响最大的协调射流/鳍尾迹模式。虽然这种研究在技术上具有挑战性，需要新的、强大的、3D 方法，但对于更全面地评估鱿鱼双模式运动系统的推进效率是必要的。
