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Open Access Highly Accessed Open Badges Research article

Systematic comparison and reconstruction of sea urchin (Echinoidea) internal anatomy: a novel approach using magnetic resonance imaging

Alexander Ziegler1*, Cornelius Faber23, Susanne Mueller4 and Thomas Bartolomaeus1

Author Affiliations

1 Institut für Biologie, Freie Universität Berlin, Königin-Luise-Straße, 14195 Berlin, Germany

2 Experimentelle Physik 5, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

3 Institut für Klinische Radiologie, Universitätsklinikum Münster, Waldeyerstraße, 48149 Münster, Germany

4 Berlin NeuroImaging Center, Charité-Universitätsmedizin Berlin, Charitéplatz, 10117 Berlin, Germany

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BMC Biology 2008, 6:33  doi:10.1186/1741-7007-6-33

Published: 23 July 2008



Traditional comparative morphological analyses and subsequent three-dimensional reconstructions suffer from a number of drawbacks. This is particularly evident in the case of soft tissue studies that are technically demanding, time-consuming, and often prone to produce artefacts. These problems can partly be overcome by employing non-invasive, destruction-free imaging techniques, in particular micro-computed tomography or magnetic resonance imaging.


Here, we employed high-field magnetic resonance imaging techniques to gather numerous data from members of a major marine invertebrate taxon, the sea urchins (Echinoidea). For this model study, 13 of the 14 currently recognized high-ranking subtaxa (orders) of this group of animals were analyzed. Based on the acquired datasets, interactive three-dimensional models were assembled. Our analyses reveal that selected soft tissue characters can even be used for phylogenetic inferences in sea urchins, as exemplified by differences in the size and shape of the gastric caecum found in the Irregularia.


The main focus of our investigation was to explore the possibility to systematically visualize the internal anatomy of echinoids obtained from various museum collections. We show that, in contrast to classical preparative procedures, magnetic resonance imaging can give rapid, destruction-free access to morphological data from numerous specimens, thus extending the range of techniques available for comparative studies of invertebrate morphology.