Blough Tasia, Colin Sean P, Costello John H, Marques Antonio C
Environmental Sciences and Marine Biology, Roger Williams University, Bristol, RI 02809, USA.
Biol Bull. 2011 Feb;220(1):6-14. doi: 10.1086/BBLv220n1p6.
Swimming animals may experience significant changes in the Reynolds number (Re) of their surrounding fluid flows throughout ontogeny. Many medusae experience Re environments with significant viscous forces as small juveniles but inertially dominated Re environments as adults. These different environments may affect their propulsive strategies. In particular, rowing, a propulsive strategy with ecological advantages for large adults, may be constrained by viscosity for small juvenile medusae. We examined changes in the bell morphology and swimming kinematics of the limnomedusa Liriope tetraphylla at different stages of development. L. tetraphylla maintained an oblate bell (fineness ratio ≈ 0.5-0.6), large velar aperture ratio (R(v) ≈ 0.5-0.8), and rapid bell kinematics throughout development. These traits enabled it to use rowing propulsion at all stages except the very smallest sizes observed (diameter = 0.14 cm). During the juvenile stage, very rapid bell kinematics served to increase Re sufficiently for rowing propulsion. Other taxa that use rowing propulsion as adults, such as leptomedusae and scyphomedusae, typically utilize different propulsive strategies as small juveniles to function in low Re environments. We compared the performance values of the different propulsive modes observed among juvenile medusae.
在整个个体发育过程中，水生动物周围流体流动的雷诺数（Re）可能会发生显著变化。许多水母在幼体阶段经历的Re环境中粘性力较大，但成年后则处于惯性主导的Re环境。这些不同的环境可能会影响它们的推进策略。特别是划水，这是一种对大型成年水母具有生态优势的推进策略，对于小型幼体水母来说，可能会受到粘性的限制。我们研究了四叶丽钵水母（Liriope tetraphylla）在不同发育阶段的钟形形态和游泳运动学变化。四叶丽钵水母在整个发育过程中保持扁平的钟形（长宽比≈0.5 - 0.6）、较大的缘膜孔径比（R(v)≈0.5 - 0.8）以及快速的钟形运动。这些特征使其能够在除观察到的最小尺寸（直径 = 0.14厘米）之外的所有阶段使用划水推进。在幼体阶段，非常快速的钟形运动有助于充分提高Re以实现划水推进。其他成年后使用划水推进的类群，如水螅水母和钵水母，在幼体较小时通常会采用不同的推进策略以在低Re环境中发挥作用。我们比较了在幼体水母中观察到的不同推进模式的性能值。
