Data from: A fish that uses its hydrodynamic tongue to feed on land

To capture and swallow food on land, a sticky tongue supported by the hyoid and gill arch skeleton has evolved in land vertebrates from aquatic ancestors that used mouth-cavity-expanding actions of the hyoid to suck food into the mouth. However, the evolutionary pathway bridging this drastic shift in feeding mechanism and associated hyoid motions remains unknown. Modern fish that feed on land may help to unravel the physical constraints and biomechanical solutions that led to terrestrialization of fish-feeding systems. Here, we show that the mudskipper emerges onto land with its mouth cavity filled with water, which it uses as a protruding and retracting ‘hydrodynamic tongue’ during the initial capture and subsequent intra-oral transport of food. Our analyses link this hydrodynamic action of the intra-oral water to a sequence of compressive and expansive cranial motions that diverge from the general pattern known for suction feeding in fishes. However, the hyoid motion pattern showed a remarkable resemblance to newts during tongue prehension. Consequently, although alternative scenarios cannot be excluded, hydrodynamic tongue usage may be a transitional step onto which the evolution of adhesive mucosa and intrinsic lingual muscles can be added to gain further independence from water for terrestrial foraging.

为实现在陆地的食物捕获与吞咽，由以舌骨扩张口腔、将食物吸入口中的水生祖先演化而来的陆生脊椎动物，进化出了由舌骨与鳃弓骨骼支撑的粘性舌。然而，衔接取食机制与相关舌骨运动这一剧烈转变的演化路径至今仍未明晰。以陆地为觅食生境的现生鱼类，或可帮助我们揭示推动鱼类取食系统陆生化的物理约束与生物力学解决方案。
本研究显示，弹涂鱼在登陆时口腔内会充满水分，并在初始食物捕获与后续口腔内食物转运过程中，将这些水作为可伸缩的流体动力舌（hydrodynamic tongue）使用。分析表明，口腔内水的这一流体力学作用，关联着一系列压缩与扩张的颅部运动——该运动模式不同于已知的鱼类抽吸进食通用范式，但舌骨的运动模式却与蝾螈的舌部攫取运动极为相似。
综上，尽管无法排除其他演化场景的可能性，使用流体动力舌或许是一个过渡性步骤：在此基础上，粘性黏膜与舌固有肌的演化可进一步摆脱水体限制，实现更为独立的陆生觅食行为。