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Subcellular structures in Ediacaran cleavage embryos
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2008 (English)In: The 33rd International Geology Congress, Olso 2008 6–14 August, 2008Conference paper (Refereed)
Abstract [en]

The Ediacaran Doushantuo phosphoritic deposits in southern China hold exquisitely preserved embryos of early animals and during the past ten years, a large number of papers have been published regarding these investigations. Recent studies, in which fossil embryos were analysed with synchrotron-based X-ray tomographic microscopy (srXTM), have shown that with this technique it is possible not only to distinguish between taphonomic and diagenetic features (Donoghue et al. 2006, Nature 442: 680–683), but also to depict cellular and subcellular details of the internal embryonic structures (Hagadorn et al. 2006, Science 314: 291–294). The Ediacaran cleavage embryos, preserved as diagenetically phosphatized replacements and encrustations, are of uncertain affinity, and no co-occurring adult forms have been identified. The cleavage embryos generally seem to be restricted to early cleavage stages, with up to some hundred cells. In this study, I describe the diversity of internal morphological features found in early-stage cleavage embryos by use of srXTM. For example, a few exceptionally preserved 4-cell stage specimens exhibit subcellular structures indicative of eukaryotic affinity, such as complex nucleus-like structures, which are centrally located in each cell. Other specimens display spheroidal and ovoidal structures interpreted as lipid vesicles or yolk granules. Recently, Bailey and colleagues (2007, Nature 445: 198–201) published an alternative interpretation of these fossils, in which they propose that they represent giant sulphur bacteria. However, the discoveries of likely eukaryotic subcellular features, augmented by decay studies of modern animal embryos by Raff et al. (2006, Proc. Natl. Acad. Sci. USA 103: 5846–5851) and Gostling et al. (2008, Evol Dev. 10:3, 339–349), support the interpretation that these fossils from the Doushantuo Formation are of embryonic nature.

Place, publisher, year, edition, pages
URN: urn:nbn:se:su:diva-16235OAI: diva2:182755
Available from: 2008-12-15 Created: 2008-12-15Bibliographically approved

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