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. 2013 Dec 13:3:3497.
doi: 10.1038/srep03497.

Discovery of 505-million-year old chitin in the basal demosponge Vauxia gracilenta

H Ehrlich  1 , J Keith Rigby  2 , J P Botting  3 , M V Tsurkan  4 , C Werner  4 , P Schwille  5 , Z Petrášek  5 , A Pisera  6 , P Simon  7 , V N Sivkov  8 , D V Vyalikh  9 , S L Molodtsov  10 , D Kurek  11 , M Kammer  12 , S Hunoldt  12 , R Born  13 , D Stawski  14 , A Steinhof  15 , V V Bazhenov  1 , T Geisler  16
Affiliations

Discovery of 505-million-year old chitin in the basal demosponge Vauxia gracilenta

H Ehrlich et al. Sci Rep. .

Abstract

Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of the early evolution of metazoans. Here, we present the discovery of 505-million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.

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Figures

Figure 1
Figure 1. Optical micrographs from the studied sample.
Burgess Shale sample with the fossil demosponge V. gracilenta (a) with detail of the exceptionally preserved skeleton (b).
Figure 2
Figure 2. Preliminary identification of chitin.
Calcofluor white staining of the cleaned surface of V. gracilenta with fluorescence, indicating the presence of polysaccharide-based compounds (a, b). Isolated and HF-demineralized fibers were identified as chitin using NEXAFS spectroscopy (c).
Figure 3
Figure 3. Structural features of the fossil sponge skeleton.
A selectively isolated fragment (b) of the aspiculate fibrous skeleton of V. gracilenta (a) shows autofluorescence (c) that is characteristic for chitin. The non-homogenous fluorescence can be explained by the presence of a residual mineral phase observed using SEM (d, e).
Figure 4
Figure 4. Identification of D-glucosamine as the final step in supporting the presence of chitin in the fossil V. gracilenta.
HPCE chromatograms as well as ESI-MS results give unambiguous evidence that D-glucosamine is present in the investigated samples (b) when compared with results from a chitin standard (a).
See this image and copyright information in PMC

References

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