Kolmann Matthew A, Welch Kenneth C, Summers Adam P, Lovejoy Nathan R
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada.
Proc Biol Sci. 2016 Sep 14;283(1838). doi: 10.1098/rspb.2016.1392.
Chewing, characterized by shearing jaw motions and high-crowned molar teeth, is considered an evolutionary innovation that spurred dietary diversification and evolutionary radiation of mammals. Complex prey-processing behaviours have been thought to be lacking in fishes and other vertebrates, despite the fact that many of these animals feed on tough prey, like insects or even grasses. We investigated prey capture and processing in the insect-feeding freshwater stingray Potamotrygon motoro using high-speed videography. We find that Potamotrygon motoro uses asymmetrical motion of the jaws, effectively chewing, to dismantle insect prey. However, CT scanning suggests that this species has simple teeth. These findings suggest that in contrast to mammalian chewing, asymmetrical jaw action is sufficient for mastication in other vertebrates. We also determined that prey capture in these rays occurs through rapid uplift of the pectoral fins, sucking prey beneath the ray's body, thereby dissociating the jaws from a prey capture role. We suggest that the decoupling of prey capture and processing facilitated the evolution of a highly kinetic feeding apparatus in batoid fishes, giving these animals an ability to consume a wide variety of prey, including molluscs, fishes, aquatic insect larvae and crustaceans. We propose Potamotrygon as a model system for understanding evolutionary convergence of prey processing and chewing in vertebrates.
咀嚼以颌骨的剪切运动和高冠磨牙为特征，被认为是一种进化创新，它推动了哺乳动物的饮食多样化和进化辐射。尽管许多鱼类和其他脊椎动物以昆虫甚至草类等坚硬猎物为食，但人们一直认为它们缺乏复杂的猎物处理行为。我们使用高速摄像技术研究了以昆虫为食的淡水黄貂鱼——麦氏河魟的猎物捕获和处理过程。我们发现，麦氏河魟利用颌骨的不对称运动有效地咀嚼，来拆解昆虫猎物。然而，CT扫描显示该物种的牙齿很简单。这些发现表明，与哺乳动物的咀嚼不同，不对称的颌骨动作足以满足其他脊椎动物的咀嚼需求。我们还确定，这些魟类通过胸鳍的快速上抬来捕获猎物，将猎物吸到魟类身体下方，从而使颌骨不再承担猎物捕获的角色。我们认为，猎物捕获和处理的分离促进了鲼形目鱼类高度灵活的摄食器官的进化，使这些动物有能力食用各种猎物，包括软体动物、鱼类、水生昆虫幼虫和甲壳类动物。我们提议将麦氏河魟作为一个模型系统，用于理解脊椎动物猎物处理和咀嚼的进化趋同现象。
