Van Wassenbergh Sam, Lieben Tim, Herrel Anthony, Huysentruyt Frank, Geerinckx Tom, Adriaens Dominique, Aerts Peter
Department of Biology, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium.
J Exp Biol. 2009 Jan;212(Pt 1):116-25. doi: 10.1242/jeb.023929.
Food scraping has independently evolved twice from suction feeding in the evolution of catfishes: within neotropical Loricarioidea and paleotropical Mochokidae. To gain insight in the evolutionary transitions associated with the evolution towards scraping, we analyzed prey capture kinematics in two species of benthic suction feeders which belong to taxa that are closely related to the scraper lineages (respectively, Corydoras splendens and Synodontis multipunctatus), and compared it to prey capture in a more distantly related, generalist suction feeder (Clarias gariepinus). Simultaneous ventral and lateral view high-speed videos were recorded to quantify the movements of the lower jaw, hyoid, pectoral girdle and neurocranium. Additionally, ellipse modeling was applied to relate head shape differences to buccal expansion kinematics. Similarly to what has been observed in scrapers, rotations of the neurocranium are minimal in the benthic suction feeders, and may consequently have facilitated the evolution of a scraping feeding mechanism. The hypothesis that fish with a more laterally compressed head rely more heavily on lateral expansion of the buccal cavity to generate suction, was confirmed in our sample of catfish species. Since an important contribution of lateral expansion of the head to suction may avoid the need for a strong, ventral depression of the mouth floor during feeding, we hypothesized that this may have allowed a closer association with the substrate in the ancestors of scrapers. However, our hypothesis was not supported by an ancestral state reconstruction, which suggests that scraping probably evolved from sub-terminal mouthed ancestors with dorsoventrally flattened heads.
在鲶鱼的进化过程中，刮食行为从吸食行为中独立进化了两次：分别在新热带区的甲鲶科和古热带区的蝌蚪鲶科。为了深入了解与向刮食进化相关的进化转变，我们分析了两种底栖吸食者的猎物捕获运动学，这两种吸食者属于与刮食者谱系密切相关的类群（分别是美丽兵鲶和多斑歧须鲶），并将其与一种亲缘关系更远的、杂食性的吸食者（埃及胡子鲶）的猎物捕获情况进行了比较。记录了同时从腹侧和侧面拍摄的高速视频，以量化下颌、舌骨、胸带和脑颅的运动。此外，应用椭圆模型将头部形状差异与口腔扩张运动学联系起来。与在刮食者中观察到的情况类似，底栖吸食者的脑颅旋转最小，因此可能促进了刮食摄食机制的进化。在我们的鲶鱼样本中，证实了头部更侧向压缩的鱼类更依赖口腔侧向扩张来产生吸力这一假设。由于头部侧向扩张对吸力的重要贡献可能避免了进食时口底强烈的腹侧凹陷的需要，我们推测这可能使刮食者的祖先与底物有更紧密的联系。然而，我们的假设没有得到祖先状态重建的支持，这表明刮食可能从具有背腹扁平头部的亚端口祖先进化而来。
