Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Humboldt University Berlin, Berlin, Germany.
Biol Lett. 2012 Jun 23;8(3):457-60. doi: 10.1098/rsbl.2011.0923. Epub 2011 Nov 9.
High-resolution phase-contrast X-ray computed tomography (CT) reveals the phoretic deutonymph of a fossil astigmatid mite (Acariformes: Astigmata) attached to a spider's carapace (Araneae: Dysderidae) in Eocene (44-49 Myr ago) Baltic amber. Details of appendages and a sucker plate were resolved, and the resulting three-dimensional model demonstrates the potential of tomography to recover morphological characters of systematic significance from even the tiniest amber inclusions without the need for a synchrotron. Astigmatids have an extremely sparse palaeontological record. We confirm one of the few convincing fossils, potentially the oldest record of Histiostomatidae. At 176 µm long, we believe this to be the smallest arthropod in amber to be CT-scanned as a complete body fossil, extending the boundaries for what can be recovered using this technique. We also demonstrate a minimum age for the evolution of phoretic behaviour among their deutonymphs, an ecological trait used by extant species to disperse into favourable environments. The occurrence of the fossil on a spider is noteworthy, as modern histiostomatids tend to favour other arthropods as carriers.
高分辨率相衬 X 射线计算机断层扫描（CT）揭示了附着在始新世波罗的海琥珀（44-49 百万年前）中一只蜘蛛甲壳（蜘蛛目：Dysderidae）上的化石畸形螨（蜱螨目：Astigmata）的游走幼体。我们解析了附肢和吸盘的细节，并生成了三维模型，展示了 CT 技术从最小的琥珀包裹体中恢复具有系统意义的形态特征的潜力，而无需同步加速器。畸形螨的化石记录非常稀少。我们确认了为数不多的几个有说服力的化石之一，可能是Histiostomatidae 最早的记录。这个标本长 176 微米，我们认为这是琥珀中作为完整体化石进行 CT 扫描的最小节肢动物，扩展了使用该技术可以恢复的范围。我们还证明了在它们的第二幼体中出现了寄生动为的最小年龄，这种生态特征被现存物种用于扩散到有利的环境中。该化石出现在蜘蛛上是值得注意的，因为现代 histiostomatids 往往更喜欢其他节肢动物作为载体。
