Data from: Always chew your food: freshwater stingrays use mastication to process tough insect prey

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.以剪切式颌部运动和高冠臼齿为特征的咀嚼行为，被视为推动哺乳动物饮食多样化与演化辐射的演化创新。尽管诸多鱼类与其他脊椎动物会取食昆虫乃至草本植物等坚硬猎物，但过往学界曾认为此类动物并不具备复杂的猎物处理行为。本研究借助高速摄像技术，对以昆虫为食的淡水魟（Potamotrygon motoro）的猎物捕获与处理行为展开了研究。研究发现，该淡水魟通过颌部的不对称运动实现高效咀嚼，以此拆解昆虫猎物。然而，计算机断层扫描（CT）结果显示，该物种的牙齿结构十分简单。上述研究结果表明，与哺乳动物的咀嚼行为不同，其他脊椎动物仅需不对称的颌部运动即可完成咀嚼。本研究同时发现，此类魟鱼的猎物捕获依赖胸鳍快速抬升，将猎物吸至体腹侧，从而使颌部脱离了猎物捕获的功能职责。我们推测，猎物捕获与处理功能的解耦，推动了鳐形目鱼类高度动态化摄食器官的演化，使此类动物能够取食软体动物、鱼类、水生昆虫幼虫以及甲壳类等多样猎物。本研究提出，可将Potamotrygon属魟鱼作为研究脊椎动物猎物处理与咀嚼行为演化趋同的模式系统。