Abstract The thorny catfish (Doradidae; order Siluriforme), has characteristic barbed pectoral fin spines and mid-lateral scutes that work in concert to provide an active mechanical defense mechanism. The pectoral spines can be locked into several fixed positions at angles between 0° and 90° to the longitudinal axis. Upon deployment they provide a formidable barrier to deglutition by a predator. Additionally, each spine contains two rows of sharp serrations which are inclined to its axis and can slice through tissue. We characterize the internal structure of the rotation joint of the pectoral spines and unravel the locking mechanism which is ensured by dual sources of friction generated from the dorsal and anterior components on the spine base. In addition to the lockable spines, thorny catfish also possess two arrays of mid-lateral dermal scutes with a sharp hook shape and gradient inner structure, which also have potential cutting capability and are part of the fish’s active defense, since they can injure the predator through rapid motions of the catfish body. The structural design of these two weapons is very impressive, including a hollow structure, porous components, and gradient transitions, leading to outstanding performance by maintaining strength, toughness and light weight synergistically. These designs may provide inspiration for the development of novel structural materials or new armor materials.

中文翻译：

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刺鲶的主动防御机制

摘要 多刺鲶鱼 (Doradidae; order Siluriforme) 具有特征性的带刺胸鳍刺和中外侧盾，它们协同工作以提供积极的机械防御机制。胸椎可以与纵轴呈 0° 到 90° 之间的角度锁定在几个固定位置。部署后，它们为捕食者的吞食提供了强大的屏障。此外，每个脊椎包含两排锋利的锯齿，这些锯齿与其轴倾斜，可以切穿组织。我们描述了胸椎旋转关节的内部结构，并解开了锁定机制，这是由脊柱底部的背部和前部组件产生的双重摩擦源确保的。除了可锁定的刺，多刺鲶鱼还拥有两排中外侧的鳞片，具有锋利的钩状和渐变的内部结构，也具有潜在的切割能力，是鱼类主动防御的一部分，因为它们可以通过鲶鱼身体的快速运动伤害捕食者. 这两种武器的结构设计非常令人印象深刻，包括中空结构、多孔部件和梯度过渡，通过协同保持强度、韧性和轻量化来实现出色的性能。这些设计可能为开发新型结构材料或新型装甲材料提供灵感。这两种武器的结构设计非常令人印象深刻，包括中空结构、多孔部件和梯度过渡，通过协同保持强度、韧性和轻量化来实现出色的性能。这些设计可能为开发新型结构材料或新型装甲材料提供灵感。这两种武器的结构设计非常令人印象深刻，包括中空结构、多孔部件和梯度过渡，通过协同保持强度、韧性和轻量化来实现出色的性能。这些设计可能为开发新型结构材料或新型装甲材料提供灵感。