Data from: Metamorphosis revealed: time-lapse three-dimensional imaging inside a living chrysalis

Studies of model insects have greatly increased our understanding our animal development. Yet they are limited in scope to this small pool of model species: a small number of representatives for a hyperdiverse group with highly varied developmental processes. One factor behind this narrow scope is the challenging nature of traditional methods of study, such as histology and dissection, which can preclude quantitative analysis and do not allow the development of a single individual to be followed. Here we use high resolution computed tomography to overcome these issues to 3D image numerous lepidopteran pupae throughout their development. The resulting models are presented in figures and supplementary videos taken for a single individual throughout development. They provide new insight and details of lepidotperan metamorphosis, and allow the measurement of tracheal and gut volume. Furthermore, this study demonstrates early and rapid development of the tracheal system – while unresolved in the caterpillar, tracheae become visible in scans just 12 hours after pupation. This suggests that there is less remodelling of the tracheal system than previously expected, and is methodologically important because the tracheal system is an often-understudied character systems in development. In the future this form of CT-scanning could allow faster and detailed developmental studies on a wider range of taxa than is presently possible.

对模式昆虫的研究极大地增进了我们对动物发育的认知。然而此类研究的范围始终局限于一小批模式物种：仅选取了高度多样化类群中的寥寥数个代表物种，而该类群的发育过程存在极高异质性。造成这一研究范围狭窄的核心原因之一，是传统研究方法存在诸多难点：例如组织学（histology）与解剖（dissection）技术既无法开展定量分析，也无法追踪单个个体的完整发育历程。本研究采用高分辨率计算机断层扫描（computed tomography, CT）技术攻克上述局限，对大量鳞翅目（Lepidoptera）蛹的整个发育过程开展三维成像。所获得的三维模型以图片及补充视频的形式呈现，所有素材均取自同一只个体的完整发育过程。这些模型为鳞翅目变态发育提供了全新的认知维度与细节信息，同时可用于气管系统（tracheal system）与肠道的体积定量测量。此外，本研究揭示了气管系统早期且快速的发育过程：尽管幼虫阶段气管系统难以分辨，但蛹化仅12小时后，扫描图像中即可观测到气管结构。这一发现表明气管系统的重塑程度较此前预期更低，同时该方法学成果具有重要意义——因为气管系统在发育研究中常属于被忽视的性状系统（character systems）。未来，此类CT扫描技术可实现对更广范围类群的快速、精细发育研究，远超当前研究的可行范畴。