Museum of Comparative Zoology, Harvard University, 26 Oxford St., Cambridge, Massachusetts 02138.
Integr Comp Biol. 2002 Nov;42(5):997-1008. doi: 10.1093/icb/42.5.997.
The great anatomical diversification of paired fins within the Actinopterygii (ray-finned fishes) can be understood as a suite of evolutionary transformations in design. At a broad taxonomic scale, two clear trends exist in the morphology of the anteriorly situated pectoral fins. In comparing basal to more derived clades, there are general patterns of (i) reorientation of the pectoral fin base from a nearly horizontal to more vertical inclination, and (ii) migration of the pectoral fin from a ventral to mid-dorsal body position. As yet, the functional significance of these historical trends in pectoral fin design remains largely untested by experiment. In this paper we test the proposal that variation in pectoral fin structure has an important influence on the magnitude and orientation of fluid forces generated during maneuvering locomotion. Using digital particle image velocimetry for quantitative wake visualization, we measure swimming forces in ray-finned fishes exhibiting the plesiomorphic and apomorphic pectoral fin anatomy. Our experiments focus on rainbow trout (Oncorhynchus mykiss), a lower teleost with pectoral fins positioned ventrally and with nearly horizontally inclined fin bases, and bluegill sunfish (Lepomis macrochirus), a relatively derived perciform fish with more vertically oriented pectoral fins positioned mid-dorsally on the body. In support of hypotheses arising from our prior wake studies and previously untested models in the literature, we find that the pectoral fins of sunfish generate significantly higher forces for turning and direct braking forces closer to the center of mass of the body than the pectoral fins of trout. These results provide insight into the hydrodynamic importance of major evolutionary transformations in pectoral fin morphology within the Actinopterygii.
硬骨鱼（条鳍鱼）中配对鳍的巨大解剖学多样化可以被理解为一系列设计上的进化转变。在广泛的分类尺度上，前位胸鳍的形态存在两种明显的趋势。在比较基础到更衍生的类群时，存在着胸鳍基部从几乎水平到更垂直倾斜的（i）重新定向和胸鳍从腹侧到中背身体位置的（ii）迁移的一般模式。然而，这些胸鳍设计历史趋势的功能意义在很大程度上仍然没有通过实验来检验。在本文中，我们检验了胸鳍结构的变化对操纵运动过程中产生的流体力的大小和方向有重要影响的假说。我们使用数字粒子图像测速法进行定量尾流可视化，测量了具有原始和特化胸鳍解剖结构的条鳍鱼类的游泳力。我们的实验集中在虹鳟（Oncorhynchus mykiss）上，这是一种下等硬骨鱼，胸鳍位于腹侧，基底几乎水平倾斜，以及蓝鳃太阳鱼（Lepomis macrochirus），这是一种相对衍生的鲈形目鱼类，胸鳍位于身体中背侧。支持了我们先前的尾流研究和文献中未经测试的模型提出的假设，我们发现太阳鱼的胸鳍产生的转向力和更接近身体质心的直接制动力明显高于虹鳟的胸鳍。这些结果为了解硬骨鱼中胸鳍形态的主要进化转变在水动力方面的重要性提供了线索。
