Micro- and nano-scale ultrastructure of cell walls in Cryogenian microfossils: revealing their biological affinity

Authors

  • MAŁGORZATA MOCZYDŁOWSKA,

    1. Małgorzata Moczydłowska [malgo.vidal@pal.uu.se], Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden; J. William Schopf [schopf@ess.ucla.edu], Department of Earth and Space Sciences, Center for the Study of Evolution and the Origin of Life (Institute of Geophysics and Planetary Physics), Molecular Biology Institute, and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095, USA; Sebastian Willman [sebastian.willman@geo.uu.se]; Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
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  • J. WILLIAM SCHOPF,

    1. Małgorzata Moczydłowska [malgo.vidal@pal.uu.se], Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden; J. William Schopf [schopf@ess.ucla.edu], Department of Earth and Space Sciences, Center for the Study of Evolution and the Origin of Life (Institute of Geophysics and Planetary Physics), Molecular Biology Institute, and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095, USA; Sebastian Willman [sebastian.willman@geo.uu.se]; Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
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  • SEBASTIAN WILLMAN

    1. Małgorzata Moczydłowska [malgo.vidal@pal.uu.se], Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden; J. William Schopf [schopf@ess.ucla.edu], Department of Earth and Space Sciences, Center for the Study of Evolution and the Origin of Life (Institute of Geophysics and Planetary Physics), Molecular Biology Institute, and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095, USA; Sebastian Willman [sebastian.willman@geo.uu.se]; Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
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Abstract

Moczydłowska, M., Schopf, J.W. & Willman, S. 2009: Micro- and nano-scale ultrastructure of cell walls in Cryogenian microfossils: revealing their biological affinity. Lethaia, Vol. 43, pp. 129–136.

Recently established protocols and methods in advanced microscopy and spectrometry applied to studies of ancient unicellular organic-walled microfossils of uncertain biological affinities (acritarchs) provide new evidence of the fine ultrastructure of cell walls and their biochemistry that support the interpretation of some such microfossils as photosynthesizing microalgae. The micro-scale and nanoscale ultrastructure of the cell walls of late Cryogenian sphaeromorphic acritarchs from the Chichkan Formation (Kazakhstan) revealed by the advanced techniques and studied originally by Kempe et al. (2005) is here further analysed and compared with that of modern microalgal analogues. On the basis of such comparison, we interpret the preserved cell wall ultrastructure to reflect original layering and lamination within sub-layers of the fossil wall, rather than being a result of taphonomic and diagenetic alteration. The outer thick layer represents the primary wall and the inner layer the secondary wall of the cell, whereas the laminated amorphous sub-layers, 10–20 nm in thickness and revealed by transmission electron and atomic force microscopy, are recognized as trilaminar sheath structure. Because two-layered cell walls, trilaminar sheaths and the position of the TLS within the fossil cell wall are characteristic of the mature developmental state in cyst morphogenesis in modern microalgae, we infer that the Chichkan sphaeromorphs are probably resting cells (aplanospores) of chlorophyceaen green microalgae from the order Volvocales. □Biological affinity, cell wall, Cryogenian, microfossils, ultrastructure.

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