BACKGROUND AND AIMS The endangered aquatic carnivorous waterwheel plant (Aldrovanda vesiculosa) catches prey with 3-5 mm long underwater snap-traps. Trapping lasts 10-20 ms, which is 10-fold faster than in its famous sister, the terrestrial Venus flytrap (Dionaea muscipula). After successful capture, the trap narrows further and forms a 'stomach' for the digestion of prey, the so-called 'sickle-shaped cavity'. To date, our knowledge is very scarce regarding the deformation process during narrowing and consequent functional morphology of the trap. METHODS We performed comparative analyses of virtual 3D histology using Computed Tomography (CT) and conventional 2D histology. For 3D histology we established a contrasting agent-based preparation protocol tailored for delicate underwater plant tissues. KEY RESULTS Our analyses reveal new structural insights into the adaptive architecture of the complex A. vesiculosa snap-trap. Particularly, we discuss in detail the arrangement of sensitive trigger hairs inside the trap and present actual 3D representations of traps with prey. In addition, we provide trap volume calculations at different narrowing stages. Furthermore, the motile zone close to the trap midrib, which is thought to not only promote the fast trap closure by hydraulics but also the subsequent trap narrowing and trap reopening, is described and discussed for the first time in its entirety. CONCLUSIONS Our research contributes to the understanding of a complex, fast and reversible underwater plant movement and supplements preparation protocols for CT-analyses of other non-lignified and sensitive plant structures.

中文翻译：

---

利用 2D 和 3D 成像技术对水生肉食性水车植物 (Aldrovanda vesiculosa) 的精致捕捉器进行功能形态分析


背景和目的濒临灭绝的水生肉食性水车植物（Aldrovanda vesiculosa）用 3-5 毫米长的水下捕捉器捕获猎物。捕获持续 10-20 毫秒，比其著名的姐妹陆生捕蝇草 (Dionaea muscipula) 快 10 倍。成功捕获后，陷阱进一步缩小，形成消化猎物的“胃”，即所谓的“镰刀形腔”。迄今为止，我们对陷阱缩小过程中的变形过程以及随之而来的功能形态的了解非常缺乏。方法 我们使用计算机断层扫描 (CT) 和传统 2D 组织学对虚拟 3D 组织学进行比较分析。对于 3D 组织学，我们建立了一种基于造影剂的制备方案，专为脆弱的水下植物组织量身定制。主要结果 我们的分析揭示了对复杂 A. vesiculosa snap-trap 的适应性结构的新结构见解。特别是，我们详细讨论了陷阱内敏感触发毛的排列，并呈现了陷阱与猎物的实际 3D 表示。此外，我们还提供不同狭窄阶段的陷阱体积计算。此外，首次完整地描述和讨论了靠近疏水阀中脉的运动区，该区域被认为不仅可以通过液压促进疏水阀的快速关闭，而且还可以促进随后的疏水阀变窄和疏水阀的重新打开。结论我们的研究有助于理解复杂、快速和可逆的水下植物运动，并补充了其他非木质化和敏感植物结构的 CT 分析的准备方案。