Aiello Brett R, Hardy Adam R, Cherian Chery, Olsen Aaron M, Orsbon Courtney P, Hale Melina E, Westneat Mark W
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois.
The College, University of Chicago, Chicago, Illinois.
J Morphol. 2018 Aug;279(8):1031-1044. doi: 10.1002/jmor.20830. Epub 2018 Apr 25.
The organization of tissues in appendages often affects their mechanical properties and function. In the fish family Labridae, swimming behavior is associated with pectoral fin flexural stiffness and morphology, where fins range on a continuum from stiff to relatively flexible fins. Across this diversity, pectoral fin flexural stiffness decreases exponentially along the length of any given fin ray, and ray stiffness decreases along the chord of the fin from the leading to trailing edge. In this study, we examine the morphological properties of fin rays, including the effective modulus in bending (E), second moment of area (I), segmentation, and branching patterns, and their impact on fin ray stiffness. We quantify intrinsic pectoral fin ray stiffness in similarly sized fins of two closely related species that employ fins of divergent mechanics, the flapping Gomphosus varius and the rowing Halichoeres bivittatus. While segmentation patterns and E were similar between species, measurements of I and the number of fin ray branch nodes were greater in G. varius than in H. bivittatus. A multiple regression model found that of these variables, I was always significantly correlated with fin ray flexural stiffness and that variation in I always explained the majority of the variation in flexural stiffness. Thus, while most of the morphological variables quantified in this study correlate with fin ray flexural stiffness, second moment of area is the greatest factor contributing to variation in flexural stiffness. Further, interspecific variation in fin ray branching pattern could be used as a means of tuning the effective stiffness of the fin webbing to differences in swimming behavior and hydrodynamics. The comparison of these results to other systems begins to unveil fundamental morphological features of biological beams and yields insight into the role of mechanical properties in fin deformation for aquatic locomotion.
附肢中组织的结构通常会影响其力学性能和功能。在隆头鱼科鱼类中，游泳行为与胸鳍的弯曲刚度和形态相关，其鳍在从硬鳍到相对软鳍的连续范围内变化。在这种多样性中，胸鳍的弯曲刚度沿任何给定鳍条的长度呈指数下降，并且鳍条刚度从鳍的前缘到后缘沿鳍的弦长方向降低。在本研究中，我们研究了鳍条的形态学特性，包括弯曲有效模量（E）、截面惯性矩（I）、分段和分支模式，以及它们对鳍条刚度的影响。我们量化了两种亲缘关系密切、采用不同力学方式使用鳍的物种的相似大小鳍中胸鳍鳍条的固有刚度，即拍打型的杂色烟管鱼和划水型的双带海猪鱼。虽然物种之间的分段模式和E相似，但杂色烟管鱼的I测量值和鳍条分支节点数量比双带海猪鱼的更大。多元回归模型发现，在这些变量中，I始终与鳍条弯曲刚度显著相关，并且I的变化始终解释了弯曲刚度变化的大部分。因此，虽然本研究中量化的大多数形态学变量与鳍条弯曲刚度相关，但截面惯性矩是导致弯曲刚度变化的最大因素。此外，鳍条分支模式的种间差异可作为一种手段，根据游泳行为和流体动力学的差异来调整鳍膜的有效刚度。将这些结果与其他系统进行比较，开始揭示生物梁的基本形态特征，并深入了解力学性能在水生运动中鳍变形中的作用。
