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Myoanatomy of the velvet worm leg revealed by laboratory-based nanofocus X-ray source tomography

  1. Franz Pfeiffera,b,g,h,1
  1. aDepartment of Physics, Technical University of Munich, 85748 Garching, Germany;
  2. bMunich School of Bioengineering, Technical University of Munich, 85748 Garching, Germany;
  3. cDepartment of Zoology, Institute of Biology, University of Kassel, 34132 Kassel, Germany;
  4. dDepartamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, Brazil;
  5. eInstitute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany;
  6. fInstitut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universit?t Jena, 07743 Jena, Germany;
  7. gDepartment of Diagnostic and Interventional Radiology, Technical University of Munich, 81675 Munich, Germany;
  8. hInstitute for Advanced Study, Technical University of Munich, 85748 Garching, Germany
  1. Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved October 3, 2017 (received for review June 22, 2017)


X-ray computed tomography (CT) imaging has become popular for investigating, nondestructively and three-dimensionally, both external and internal structures of various specimens. However, the limited resolution of conventional laboratory-based CT systems (≥500 nm) still hampers the detailed visualization of features on the low nanometer level. We present a laboratory CT device and data processing pipeline to routinely and efficiently generate high-resolution 3D data (≈100 nm) without requiring synchrotron radiation facilities. Our setup is especially relevant for conducting detailed analysis of very small biological samples, as demonstrated for a walking appendage of a velvet worm. Comparative analyses of our CT data with those obtained from other popular imaging methods highlight the advantages and future applicability of the nanoCT setup.


X-ray computed tomography (CT) is a powerful noninvasive technique for investigating the inner structure of objects and organisms. However, the resolution of laboratory CT systems is typically limited to the micrometer range. In this paper, we present a table-top nanoCT system in conjunction with standard processing tools that is able to routinely reach resolutions down to 100 nm without using X-ray optics. We demonstrate its potential for biological investigations by imaging a walking appendage of Euperipatoides rowelli, a representative of Onychophora—an invertebrate group pivotal for understanding animal evolution. Comparative analyses proved that the nanoCT can depict the external morphology of the limb with an image quality similar to scanning electron microscopy, while simultaneously visualizing internal muscular structures at higher resolutions than confocal laser scanning microscopy. The obtained nanoCT data revealed hitherto unknown aspects of the onychophoran limb musculature, enabling the 3D reconstruction of individual muscle fibers, which was previously impossible using any laboratory-based imaging technique.


  • ?1To whom correspondence may be addressed. Email: mark.mueller{at}ph.tum.de or franz.pfeiffer{at}tum.de.
  • Author contributions: G.M. and F.P. designed research; M.M., I.d.S.O., S.A., S.F., P.B., K.M., A.F., L.H., M.D., K.A., and B.G. performed research; M.M., I.d.S.O., J.U.H., and H.J. analyzed data; and M.M., I.d.S.O., and F.P. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1710742114/-/DCSupplemental.

Published under the PNAS license.

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